In the realm of wastewater treatment, a green revolution is taking place, and it’s powered by algae. Phycoremediation, the use of algae for wastewater treatment, is gaining traction as a sustainable, cost-effective, and environmentally friendly approach. Recent advancements in phycoremediation technology and research are pushing the boundaries of what’s possible, offering innovative solutions to the global water pollution crisis. In this article, we will explore the latest breakthroughs in phycoremediation, their potential impact on the industry, and how these innovations are revolutionizing the way we treat wastewater.
The Algae Revolution: Why Phycoremediation Matters
Wastewater treatment is a pressing global challenge. Traditional methods often involve chemicals or energy-intensive processes, leading to high operational costs and environmental concerns. Phycoremediation, powered by the remarkable capabilities of algae, presents a compelling alternative.
Algae, including microalgae and macroalgae, are photosynthetic organisms that thrive in aquatic environments. They can absorb nutrients, heavy metals, and even certain organic pollutants, all while producing oxygen. This unique combination of capabilities makes algae ideal candidates for wastewater treatment. Here, we delve into recent innovations in phycoremediation that are reshaping the field.
Innovations in Algae Strain Selection
One of the fundamental aspects of phycoremediation is selecting the right algae species for the job. Recent advancements in strain selection are enhancing the efficiency and effectiveness of algae-based wastewater treatment.
Traditionally, researchers relied on naturally occurring algae strains for treatment. However, advancements in genetic engineering have allowed scientists to modify algae strains for enhanced pollutant removal. For example, researchers have created genetically modified algae strains with an increased capacity to absorb heavy metals or break down specific organic pollutants.
In addition to genetic engineering, advanced screening techniques are being used to identify native algae strains that possess exceptional pollutant-removal capabilities. These strains can then be cultivated and used for efficient and natural wastewater treatment.
The scalability of algae-based wastewater treatment has always been a concern. Recent innovations in algae cultivation techniques are addressing this challenge, making large-scale phycoremediation projects more feasible.
Photobioreactors: Photobioreactors are enclosed systems that provide controlled conditions for algae growth. Recent improvements in photobioreactor design have increased the productivity of algae cultivation. These systems allow for precise control of environmental variables like temperature, light intensity, and nutrient supply, resulting in higher biomass yields.
Algae Farming: Large-scale algae farming has become more practical due to innovations in pond and raceway designs. Advanced monitoring and automation systems now equip algae ponds, enabling efficient nutrient delivery and biomass harvesting. The development of floating algae platforms has also expanded the potential for algae farming in various water bodies.
Wastewater Integration: Researchers are exploring the integration of algae cultivation systems with existing wastewater treatment facilities. Incorporating algae ponds into the treatment process naturally treats wastewater while simultaneously generating valuable algal biomass for various applications.
Enhanced Nutrient Removal
Nutrient pollution, particularly excess nitrogen, and phosphorus, is a major concern in wastewater. Algae possess a renowned ability to assimilate and remove nutrients from water. Recent advancements are making this process even more efficient.
Algae-Bacteria Symbiosis: Researchers have discovered symbiotic relationships between algae and certain bacteria that enhance nutrient removal. These bacteria can convert ammonia into nitrate, a form of nitrogen that algae can more readily absorb. This synergy between algae and bacteria has the potential to significantly improve nutrient removal in phycoremediation systems.
Nutrient Recovery: Beyond removal, recent research has focused on nutrient recovery from algal biomass. Techniques like pyrolysis and hydrothermal liquefaction can convert algal biomass into nutrient-rich biochar or liquid fertilizers. In agriculture, people can use these products to close the nutrient cycle and reduce the need for synthetic fertilizers.
Algae-Based Biosensors for Monitoring
Effective monitoring is crucial for the success of phycoremediation projects. Recent innovations involve the development of algae-based biosensors that can provide real-time data on water quality.
Algae biosensors use changes in the fluorescence or growth of algae in response to specific pollutants as indicators of water quality. These biosensors are highly sensitive and can detect pollutants at low concentrations. They offer a cost-effective and eco-friendly solution for the continuous monitoring of water bodies, ensuring the efficiency of phycoremediation processes.
Algae for Value-Added Products
The potential of algae extends beyond wastewater treatment. Recent advancements are unlocking the possibilities of turning algal biomass into valuable products.
Biofuels: Algae are known for their high oil content, making them a promising source of biofuels. Advances in extraction and conversion technologies are improving the viability of algal biofuels as a sustainable energy source.
Food and Pharmaceuticals: Some algae species are rich in essential nutrients and bioactive compounds. Research is ongoing to develop algae-based products in the food and pharmaceutical industries. People can use algae for nutraceuticals, dietary supplements, and even plant-based proteins.
Bioplastics: Algae-derived bioplastics are gaining attention as an eco-friendly alternative to conventional plastics. Researchers are exploring ways to produce biodegradable plastics from algal biomass.
Implications for the Wastewater Industry
The innovations in phycoremediation are poised to have a profound impact on the wastewater treatment industry. Here are some key implications:
Sustainability: Algae-based wastewater treatment is inherently sustainable, as it relies on natural processes. As advancements continue, it’s likely to become an even more eco-friendly alternative to traditional treatment methods.
Cost-Effectiveness: The scalability and efficiency of modern algae cultivation techniques are making phycoremediation increasingly cost-effective. This could lead to reduced operational costs for wastewater treatment plants.
Resource Recovery: The ability to recover valuable resources from algal biomass, such as nutrients and biofuels, can create new revenue streams for wastewater treatment facilities.
Real-Time Monitoring: Algae-based biosensors offer a means of continuous monitoring, helping treatment plants respond rapidly to changes in water quality.
Versatility: Phycoremediation can be applied to a wide range of wastewater types, from municipal sewage to industrial effluents. Its versatility makes it a valuable tool in addressing various pollution challenges.
Challenges and Future Directions
While the recent innovations in phycoremediation are promising, several challenges remain:
Strain Optimization: Fine-tuning algae strains for specific contaminants and environmental conditions is an ongoing process.
Regulatory Frameworks: Regulations governing the use of genetically modified algae and the discharge of treated wastewater need to be developed and standardized.
Scale-Up: Scaling up phycoremediation projects for industrial use requires overcoming technical and logistical challenges.
Public Awareness: Raising public awareness about the benefits of algae-based wastewater treatment is essential for widespread adoption.
Long-Term Sustainability: Ensuring the long-term sustainability of phycoremediation projects, including the prevention of algal blooms, is critical.
Conclusion
Phycoremediation is at the forefront of sustainable wastewater treatment solutions, and recent innovations are pushing the boundaries of its potential. From enhanced algae strains and cultivation techniques to nutrient recovery and real-time monitoring, these breakthroughs are revolutionizing the field. The implications are far-reaching, offering a greener, more cost-effective, and versatile approach to addressing water pollution challenges. While challenges remain, the future of phycoremediation holds promise, transforming the way we treat and value our most precious resource — water. As society continues to grapple with water pollution and environmental sustainability, the algae revolution is a beacon of hope on the horizon.
Wastewater treatment is a pressing global concern, as the discharge of untreated or inadequately treated wastewater poses severe environmental and public health risks. While conventional wastewater treatment methods play a crucial role in addressing this issue, innovative and sustainable alternatives like bioremediation have gained prominence. In this article, we explore real-world case studies of successful wastewater treatment projects that have harnessed the power of bioremediation, shedding light on their outcomes and the valuable lessons learned.
One of the most iconic bioremediation projects took place along the Hudson River in the United States. The river had been contaminated with polychlorinated biphenyls (PCBs), a group of toxic industrial chemicals, released into the water by General Electric (GE) factories over several decades.
The Problem: PCBs had accumulated in the sediment, posing a significant threat to aquatic life and human health. Conventional dredging and disposal methods were considered, but they were costly and environmentally damaging.
Bioremediation Approach: GE collaborated with environmental scientists to implement a natural, environmentally friendly solution. They introduced a PCB-degrading bacterium called Dehalococcoides into the contaminated sediment. This bacterium had the unique ability to break down PCBs into harmless byproducts under anaerobic conditions.
Outcomes: Over time, the bioremediation approach significantly reduced PCB levels in the sediment. Native microorganisms also played a role in the cleanup. The project demonstrated that bioremediation could effectively remediate PCB-contaminated sites, offering a more sustainable alternative to traditional methods.
Lessons Learned: This case study emphasized the importance of selecting the right microorganisms for the specific contaminants present in the environment. It also highlighted the need for ongoing monitoring and adaptive management to ensure the success of bioremediation projects.
Case Study 2: The Tianjin Binhai New Area Oil Spill
In 2010, a catastrophic oil spill occurred in the Tianjin Binhai New Area in China, resulting in the release of thousands of tons of crude oil into the Bohai Sea. The spill posed a severe threat to marine ecosystems and coastal communities.
The Problem: Conventional cleanup methods, such as mechanical skimming and chemical dispersants, were insufficient to address the scale of the oil spill. The contamination persisted, endangering marine life and local economies.
Bioremediation Approach: Chinese authorities, in collaboration with environmental experts, decided to employ a bioremediation technique using naturally occurring oil-degrading bacteria. These microorganisms would break down the oil into less harmful substances.
Outcomes: Over time, the oil-degrading bacteria multiplied and effectively consumed the oil. This natural process significantly reduced the oil’s impact on the marine ecosystem. The success of the bioremediation approach minimized ecological damage and allowed for a quicker recovery of the affected areas.
Lessons Learned: The Tianjin Binhai New Area oil spill demonstrated the efficacy of bioremediation in addressing large-scale oil contamination. It highlighted the importance of promptly identifying and utilizing native oil-degrading bacteria to expedite the cleanup process.
Case Study 3: Rhizofiltration in Mining Wastewater
Mining operations often generate highly contaminated wastewater, particularly from metal and metalloid-rich ores. Rhizofiltration, a bioremediation technique that uses the roots of plants to absorb and accumulate contaminants, has shown promise in remediating mining wastewater.
The Problem: A gold mine in South Africa was facing a significant challenge with its wastewater, which contained elevated levels of heavy metals like arsenic, lead, and cadmium. Traditional treatment methods were expensive and generated chemical sludge.
Bioremediation Approach: Researchers introduced certain hyperaccumulator plants with a high affinity for heavy metals to the wastewater ponds. The plants absorbed the metals through their roots, effectively removing them from the water.
Outcomes: Over time, the plants accumulated substantial quantities of heavy metals, reducing the pollutant levels in the wastewater. The approach not only cleaned the water but also provided an opportunity to recover valuable metals from the plant biomass.
Lessons Learned: This case study highlighted the potential of rhizofiltration as a cost-effective and sustainable method for treating mining wastewater. It emphasized the importance of selecting appropriate plant species for specific contaminants and maintaining a balance to prevent overloading the plants.
Case Study 4: The Lake Washington Cleanup Project
Lake Washington in Seattle, Washington, USA, faced severe pollution problems in the mid-20th century due to untreated sewage discharges. The lake had become a cesspool, with low oxygen levels and high nutrient concentrations.
The Problem: Lake Washington was experiencing eutrophication, a process where excessive nutrients lead to harmful algal blooms and oxygen depletion, threatening aquatic life.
Bioremediation Approach: Authorities and scientists undertook an ambitious bioremediation effort, which involved diverting sewage to a wastewater treatment plant and allowing the lake’s natural ecosystem to recover. This process reduced nutrient inputs and allowed the lake to gradually cleanse itself.
Outcomes: Over several decades, the lake’s water quality improved significantly. Oxygen levels increased, harmful algal blooms diminished, and native fish populations rebounded. The project demonstrated that, in some cases, nature’s ability to self-cleanse can be harnessed through appropriate management.
Lessons Learned: The Lake Washington Cleanup Project showcased the importance of holistic, long-term approaches to bioremediation. It underscored the need for combining bioremediation techniques with prudent management practices to achieve lasting results.
Conclusion
These case studies exemplify the success and potential of bioremediation as a sustainable and effective approach to wastewater treatment. From remediating PCB-contaminated rivers to cleaning up oil spills and addressing mining wastewater challenges, bioremediation has proven its worth in diverse real-world scenarios. The lessons learned from these projects emphasize the importance of careful planning, monitoring, and adaptability when applying bioremediation techniques. As we continue to seek environmentally friendly solutions to our wastewater woes, these case studies provide valuable insights into the promising future of bioremediation.
The environmental impact of untreated or poorly treated wastewater is undeniable. Pollution of our water bodies, contamination of drinking water sources, and the destruction of aquatic ecosystems are just some of the dire consequences. In response to this growing crisis, we urgently need innovative and sustainable approaches to combat wastewater treatment. One such promising solution is phycoremediation, a process that harnesses the power of green algae to remove pollutants from wastewater. In this article, we will delve into the potential of green algae in wastewater treatment, highlighting its environmental advantages and diverse applications.
Green Algae for Wastewater Treatment
Understanding Phycoremediation
Phycoremediation, often referred to as algae-based wastewater treatment, is a natural and eco-friendly method that utilizes various species of green algae to purify wastewater. These algae, primarily belonging to the Chlorophyta division, are proficient in photosynthesis, enabling them to absorb nutrients and pollutants while releasing oxygen, making them nature’s own water purifiers.
The Environmental Advantages of Phycoremediation
Nutrient Uptake: One of the key environmental benefits of phycoremediation is its capacity to remove excess nutrients from wastewater. Algae are voracious consumers of nutrients such as nitrogen and phosphorus, which are often the culprits behind water pollution and harmful algal blooms. By absorbing these nutrients, algae help prevent eutrophication in receiving water bodies, thereby safeguarding aquatic ecosystems.
Carbon Sequestration: Green algae have a unique ability to remove carbon dioxide (CO2) from the atmosphere through photosynthesis. This not only reduces greenhouse gas emissions but also promotes carbon sequestration, aiding in the fight against climate change.
Toxic Metal Removal: Some species of green algae have demonstrated a remarkable capability to accumulate heavy metals and other toxic substances from wastewater. This feature makes them invaluable in the treatment of industrial effluents contaminated with heavy metals like lead, cadmium, and mercury.
Applications of Green Algae in Wastewater Treatment
Municipal Wastewater Treatment: Green algae-based systems are increasingly being incorporated into municipal wastewater treatment plants as an efficient and cost-effective means to reduce nutrient levels. These systems not only enhance the quality of treated effluent but also reduce the environmental impact of wastewater discharge.
Industrial Wastewater Treatment: Industries generating wastewater with high levels of nutrients or heavy metals can benefit from phycoremediation. Algae also can be cultivated in wastewater ponds or reactors, where they absorb pollutants, rendering the water suitable for safe discharge or even reuse in industrial processes.
Agricultural Runoff Remediation: Agricultural runoff laden with fertilizers and pesticides is a significant source of water pollution. Constructed wetlands also can deploy green algae to absorb excess nutrients, providing a natural buffer against pollution in agricultural areas.
Aquaculture Wastewater Treatment: In aquaculture, the buildup of nutrients and organic matter in water can be detrimental to fish health. Phycoremediation can be used to maintain optimal water quality in aquaculture systems, benefiting both fish health and the environment.
Challenges and Future Directions
While the potential of green algae in wastewater treatment is promising, there are challenges to address. These include optimizing algae cultivation methods, scaling up systems for larger applications, and ensuring the effective harvesting of algae biomass.
In the future, research into genetically modified algae strains with enhanced pollutant-uptake capabilities and increased resistance to adverse environmental conditions could further improve the efficiency of phycoremediation.
Conclusion
Green algae, with their remarkable ability to remove pollutants, sequester carbon, and promote water quality, hold immense promise in the realm of wastewater treatment. As we confront the pressing issues of water pollution and sustainability, phycoremediation emerges as a green, cost-effective, and also ecologically sound solution. Therefore, by harnessing the power of these microscopic organisms, we can work toward cleaner waterways, healthier ecosystems, and a more sustainable future for all. Phycoremediation is not just a rescue; it’s a step towards a brighter and cleaner tomorrow.
Global climate change has emerged as a pressing global issue in contemporary times. The primary contributors to this phenomenon are the rising levels of greenhouse gases, predominantly originating from human activities and the operations of power plants (Watanabe Y, et., al; 2017).
Human activities, such as fossil fuel usage and industrial production, as well as natural processes involving the Earth’s oceans, soil, plants, animals, and volcanoes, release greenhouse gases, including CO2, CH4, and N2O, into the atmosphere. However, since the Industrial Revolution, human activities have emerged as the primary contributors to greenhouse gas emissions (Baba Mohammad et al., 2015; Mirzaei et al., 2015).
Specific Sources of CO2 Emissions
According to Le Quere (Le Quere et al. 2013, 2015), the combustion of fossil fuels, namely coal, natural gas, and oil, is responsible for about 87% of human-produced CO2 emissions. Among these fuels, coal combustion contributes to 43% of CO2 emissions from fuel burning, followed by oil at 36% and natural gas at 20%. Power plants, vehicles, aircraft, and industrial facilities primarily use these fossil fuels to generate heat, electricity, and power. The largest share of man-made CO2 emissions, approximately 41%, originates from power generation and heating activities. Transportation ranks as the second largest source, accounting for around 22% of CO2 emissions resulting from fossil fuel burning. Industries contribute approximately 20% of CO2 emissions from fossil fuel combustion. Other human-related sources include deforestation and land-use changes, contributing to roughly 9%, and industrial processes like cement manufacturing, which account for around 4%.
The emission of CO2 into the atmosphere involves not only human activities but also natural processes. According to a study conducted by Denman et al. In 2007, researchers found that natural sources significantly contribute to CO2 emissions. The Earth’s oceans, through the exchange between the ocean and the atmosphere, account for a substantial 42.84% of these natural emissions. Additionally, sources like plant and animal respiration, soil respiration, and decomposition contribute to 28.56% of the total CO2 emissions generated naturally.
CO2: A major Green House Gas
Research efforts are ongoing and focused on tackling global warming by actively mitigating greenhouse gas emissions. While carbon dioxide naturally exists as a greenhouse gas, the concentration of CO2 in the atmosphere has undergone a substantial increase because of industrialization and human activities (National Research Council et al.,2011; Siegenthaler U et al., 2005; Chang EH et al, 2003).
According to a report by the French National Center for Scientific Research, atmospheric CO2 levels have soared to 380 parts per million (ppm), marking a twofold increase compared to the previous century (Morais and Costa, et al.,2007). The notable surge in CO2 concentration directly attributes to the combination of population growth and industrialization. Future projections indicate that by 2100, CO2 emissions in the atmosphere could reach a staggering 26 billion tons, surpassing the emissions recorded in the past century by 18.5 billion tons (Chiu et al., 2008).
Power plants play a significant role in releasing CO2 into the atmosphere through the combustion of fossil fuels (Benemann JR et al., 1993). To tackle the challenge of CO2 emissions from this source, it is imperative to prioritize efforts in enhancing the efficiency of power plant generation and transitioning towards cleaner and more sustainable alternatives.
In 1990, the Research Institute of Innovative Technology for the Earth (RITE) launched the Biological CO2 Fixation and Utilization Project under the sponsorship of the Ministry of International Trade and Industry (MITI). The New Energy and Industrial Technology Development Organization (NEDO) commissioned this pioneering initiative (Murakami, N, et al., 1996).
Among the array of available CO2 capture methods, the biological approach stands out as an attractive alternative. This approach harnesses the power of photosynthesis, which enables the conversion of carbon dioxide into organic matter, fueled by sunlight as an energy source. In this regard, photosynthetic microorganisms have emerged as a preferred choice, owing to their remarkable characteristics. These microorganisms possess the unique ability to assimilate CO2 into carbohydrates, lipids, and proteins using solar energy. They exhibit higher rates of CO2 fixation compared to land plants and offer better compatibility for integrating CO2 removal systems into industrial processes when compared to other photosynthetic systems involving higher plants.
Algae potential players for CO2 Sequestration.
Within the realm of photosynthesis, there are two fundamental processes at play: the light-dependent reaction, which entails a series of intricate steps reliant on the availability of light, and the light-independent reaction, also recognized as carbon fixation. In the context of microalgae, they have developed a specialized mechanism known as the CO2 concentrating mechanism (CCM) to secure an ample reservoir of inorganic carbon required to support cellular growth and proliferation during the process of photosynthesis (Brueggeman et al., 2012).
The CO2 concentrating mechanism (CCM) plays a crucial role in microalgae by effectively increasing the concentration of CO2 at the active site of the enzyme Rubisco (ribulose-1,5-bisphosphate carboxylase oxygenase). These microorganisms possess specialized inorganic carbon transporters located in the plasma membrane and thylakoid membrane, each with varying affinities and flux rates for HCO3 (bicarbonate) and CO2 (Beardall and Raven, 2017). Carbonic anhydrase (CA) is responsible for converting HCO3 into CO2, and the proper functioning of both CA and the CCM is highly dependent on the availability of CO2 (Zou et al., 2004; Zhou et al., 2016) See Fig 1.
As a result, the availability of CO2 intricately ties to the activity of these enzymes. While elevated CO2 levels can promote the growth of algae, they may also impede the activity of carbonic anhydrase (CA) and the functioning of the CO2 concentrating mechanism (CCM) (Xia and Gao, 2005).
Microalgae surpass terrestrial plants in their efficiency in converting CO2 into organic compounds. They exhibit approximately 10 times greater efficacy in CO2 fixation compared to land plants.
Algae cultivation in Wastewater an alternative approach for wastewater treatment & CO2 Sequestration.
The combination of biological CO2 fixation using microalgae and wastewater treatment presents significant advantages in terms of both economic feasibility and environmental sustainability. By cultivating microalgae in nutrient-rich wastewater, these microorganisms have ample access to the nutrients needed for their growth. As they flourish, microalgae absorb CO2 and convert it into biomass, which can be utilized as a valuable feedstock for biofuel production (Kannan DC et., 2022, Magar et al., 2022).
The integration of CO2 capture, wastewater treatment, and biofuel production creates a synergistic and compelling approach. It not only contributes to reducing CO2 emissions by capturing and utilizing CO2 but also addresses the crucial requirement for effective wastewater treatment. This combined strategy demonstrates a promising solution that not only helps mitigate climate change but also promotes the efficient utilization of resources while generating a valuable end product (Wang B et al., 2008).
The integration of microalgae in wastewater treatment presents a sustainable and eco-conscious solution that minimizes or eliminates the requirement for chemical treatments in wastewater plants. This groundbreaking technology utilizes the inherent abilities of microalgae to effectively extract nutrients, specifically nitrogen and phosphorus compounds, from wastewater. In addition to facilitating CO2 capture through photosynthesis, this approach successfully tackles the pressing challenge of nutrient removal in wastewater.
Mechanism of Microalgae-based Wastewater Treatment
Microalgae offer an invaluable solution to address the challenge of microcontaminants found in wastewater effluents, which can pose significant risks when they enter drinking water treatment processes (Beelen ES et al., 2007). By efficiently eliminating these microcontaminants, microalgae greatly improve the overall quality of water. Additionally, microalgae play a vital role in reducing nutrient levels, such as carbon, nitrogen, and phosphorus, while simultaneously releasing significant amounts of oxygen. This dual action not only aids in the decomposition of organic matter by bacteria but also helps mitigate odor-related issues commonly associated with wastewater (De Pauw N et al., 1983).
The abundant availability of nutrients in municipal wastewater makes it an ideal resource for harnessing the potential of microalgae. Furthermore, the close proximity of wastewater treatment plants to power plants, which generate significant amounts of CO2 in flue gases through the combustion of fossil fuels, further emphasizes the benefits of this approach. This strategic positioning enables the efficient utilization of readily available CO2 resources.
Microalgae cultivation in wastewater presents versatile opportunities, allowing for the use of either open or closed systems. These approaches enable precise control over the growth media, optimizing the removal of nutrients from wastewater and maximizing the production of valuable microalgae biomass. This customized approach ensures effective and sustainable wastewater treatment while generating valuable resources in the form of microalgae biomass.
Open ponds
High-rate algal ponds, commonly known as HRAPs or raceway ponds, are the prevailing large-scale production systems in practice. These open, shallow ponds have been employed since the 1950s and utilize a paddle wheel to ensure the circulation of algae and nutrients. While raceway ponds are relatively affordable to construct and operate, their productivity is often hindered by challenges such as contamination, inadequate mixing, the presence of dark zones, and inefficient utilization of CO2 (Chisti, 2007; Mata et al., 2010).
In theory, raceway ponds should achieve production levels of 50–60 g m−2 day−1, and there have been instances of reaching such levels in a single day (Sheehan et al., 1998). However, in practical applications, it proves difficult to attain even 10–20 g m−2 day−1 productivity (Shen et al., 2009). While the high evaporation rate of open ponds is often perceived as a limitation, it does provide some benefits by aiding in temperature regulation through evaporative cooling (U.S. DOE, 2010).
Moreover, the HRP system’s simplicity and symbiotic nature make it a perfect candidate for emulating natural ecosystems in laboratory and field settings, aligning harmoniously with the principles of ecological engineering (Cunningham M et al., 2010).
An important conclusion drawn from cost analysis studies conducted by the U.S. Department of Energy’s Aquatic Species Program was that there are limited prospects for alternative systems to replace the open pond approach, particularly when considering the need for low fuel costs (Sheehan et al., 1998).
Closed reactors
According to Chisti (2007), tubular photobioreactors are the exclusive type of closed systems used on a large scale. These reactors come in vertical, horizontal, and helical designs, with helical ones being regarded as the easiest to expand (Carvalho et al., 2006). In comparison to open ponds, tubular photobioreactors offer several advantages such as improved control over pH and temperature, better protection against contamination, enhanced mixing, reduced evaporation, and higher cell densities (Mata et al., 2010).
Reported productivities typically range from 20 to 40 grams per square meter per day (Shen et al., 2009). However, despite these benefits, tubular reactors have not gained significant usage due to various challenges. Issues such as the accumulation of toxic oxygen, unfavorable pH and CO2 gradients, overheating, bio-fouling, and high material and maintenance costs have limited their widespread adoption (Mata et al., 2010; Molina Grima et al., 1999). Among these challenges, the removal of oxygen is considered one of the most difficult problems to overcome, particularly when scaling up the system. It effectively imposes limitations on the length of tubes or panels and necessitates a more complex or modular design (Carvalho et al., 2006
How Algae CO2 Sequestration Potential is Calculated?
To tackle the challenge of reducing CO2 emissions, researchers have explored various avenues, which can be broadly divided into two groups: (i) methods based on chemical reactions and (ii) biological methods (Benemann JR et al., 1993, Wang B et al.,2008). Among these, biological processes have emerged as compelling solutions to combat global warming, attracting significant attention from the scientific community (Yun YS et al., 1997).
Chisti emphasizes that microalgal biomass typically consists of around 50% carbon, allowing for the capture of approximately 1.83 kg of CO2 per kilogram of biomass produced (Chisti et al., 2007). In the field of CO2 capture using microalgae, many studies rely on measuring CO2 concentrations at the inlet and outlet of cultivation reactors. However, this approach may pose challenges as it does not guarantee that all consumed CO2 is solely attributed to the growth of microalgae. Alternatively, estimating the carbon content can provide a more precise assessment of the CO2 consumption by microalgae cells, assuming that the culture medium does not contain carbon sources other than CO2 (Yun YS et al., 1997; Tang D et al., 2011).
Based on this premise, researchers can estimate the rate of CO2 capture (RCO2) using the following formula.
RCO2 = P·CCO2·MCO2/MC,
where P represents biomass productivity (g L-1 day-1), CCO2 denotes the carbon content of microalgae biomass obtained from CO2, and MCO2 and MC correspond to the molecular weights of carbon dioxide and carbon, respectively.
CO2 concentration and CO2 uptake efficiency of Microalgae
The cultivation of photoautotrophic microalgae relies on carbon dioxide (CO2) as the primary source of carbon. Despite the physiological significance of CO2 concentration on microalgae cell growth, researchers have conducted limited research to analyze CO2 uptake under relevant process conditions, indicating the need for further investigation (Cheng L et al., 2006). Atmospheric air contains minimal amounts of CO2, which cannot sufficiently support microalgae cell growth due to limited mass transfer driving forces. To overcome this challenge, researchers can obtain CO2 from pure sources or harness it from flue gases, thereby addressing the environmental concern associated with CO2 capture (Acién Fernández FG et al., 2012).
Microalgae and cyanobacteria have the ability to adapt their photosynthetic properties, including the carbon concentrating mechanism (CCM), to high concentrations of CO2 (Baba et al., 2011). Certain microalgae and cyanobacteria species, such as Chlamydomonas reinhardtii, can quickly acclimate to a CO2 concentration of 20% within a few days (Hanawa et al., 2007).
When developed at air-equilibrated CO2 levels, microalgae and cyanobacteria can effectively utilize low levels of dissolved inorganic carbon (DIC). Cyanobacteria actively increase calcite deposition at higher CO2 concentrations, which plays a crucial role in CO2 removal. This increase leads to a 1.5- to 2.5-fold enhancement in CO2 fixation rates (Ramanan et al., 2009, 2010; Badger and Price, 1994).
Enhancing CO2 Mass Transfer with Microbubbles
Some of the important physical factors that change the mass transfer rate of CO2 from the air to liquid are air bubble size, the pore size of the sparger, flow rate, air holding time of the liquid system, etc. Microbubble size is a very essential aspect to enhance the CO2 mass transfer rate (McGinn PJ et al., 2011). However, high CO2 concentrations hinder the growth of microalgae and cyanobacteria (Ramanan et al., 2010).
Previous research has reported that optimal CO2 fixation occurs at concentrations ranging from 2% to 5% CO2, with 3% CO2 being approximately 489 times higher than the atmospheric CO2concentration (Douskova et al., 2009; Ibn-Mohammed et al., 2013). These studies indicate that many algal strains may not require undermined haphazard high CO2 feeding. Excess-supplied CO2 mostly goes to waste, and it is necessary to determine the critical CO2 concentration required by each strain.(Chaitanya Magar et al. 2019, Rambhiya, S. J. et al 2021).
Conclusion
In summary, the utilization of microalgae cultures presents a promising solution for both CO2 capture and biomass production. By cultivating microalgae in wastewater media, it becomes possible to remove significant pollutants from the wastewater while efficiently capturing CO2 and converting it into valuable biomass feedstock. The selection of suitable algae strains and optimization of key parameters such as pH, temperature, and CO2 concentration is crucial in maximizing CO2 fixation efficiency in biological systems. Certain algae species, such as Scenedesmus dimorphus, Scenedesmus incrassatulus, Chlorella sp., and Scenedesmus obliquus, demonstrate remarkable CO2 fixation rates.
Moreover, integrating CO2 capture from flue gases with microalgae-based wastewater treatment holds immense potential for sustainable biofuel production. This integrated approach offers the opportunity to address environmental concerns by capturing CO2 emissions, treating wastewater, and producing valuable biofuel resources concurrently. To enhance the efficiency and effectiveness of microalgae cultivation, the development of comprehensive dynamic models becomes essential. These models should accurately depict the growth rates of microalgae under various limiting factors, enabling the design of optimized control systems and the identification of optimal operational conditions.
By advancing our understanding of the complex interactions and dynamics involved in microalgae-based systems, we can unlock the full potential of this technology. Ultimately, this will contribute to reducing reliance on fossil fuels, mitigating CO2 emissions, and promoting a more sustainable and environmentally friendly approach to energy and wastewater management.
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Utilities are actively working to decrease energy usage at wastewater treatment plants (WWTPs). They are increasingly interested in incorporating carbon diversion processes as a means to accomplish this goal. The market for carbon diversion is expanding, and in this regard, GWI (Global Water Intelligence) investigates the advantages and obstacles associated with its implementation.
Understand the carbon diversion in the context on WWTPs
Carbon diversion, also known as enhanced primary treatment, is gaining traction as a crucial tool in the water sector’s pursuit of energy efficiency. It offers utilities a means to maximize the value of their operations by simultaneously reducing aeration energy consumption and boosting biogas generation. Various carbon diversion methods are emerging in the market to achieve these dual benefits.
In wastewater treatment plants, aeration stands out as the most energy-intensive stage. It utilizes blowers to introduce air, creating optimal conditions for aerobic biological treatment processes. While crucial for effective wastewater treatment, this step offers significant potential for optimization to achieve strong results while minimizing energy usage.
Carbon diversion intervenes precisely at this point. It involves reducing the organic load on secondary treatment systems by diverting a higher portion of biochemical oxygen demand (BOD) towards the sludge line during primary treatment. Consequently, this reduces the aeration requirements for subsequent biological processes downstream.
Wastewater treatment plants, which employ anaerobic digestion, can capitalize on the additional benefit of carbon diversion by increasing biogas production by redirecting more organic matter to the sludge at an early stage of the treatment process. Depending on the operating conditions and the specific method of enhanced primary treatment employed, these plants could potentially achieve a 20-65% increase in biogas generation while simultaneously reducing aeration energy consumption by 10-30%.
How chemicals can important role in carbon diversion at WWTPs?
There are three types of carbon diversion methods: chemically enhanced, biologically enhanced, and filtration-based. Chemically-enhanced carbon diversion involves adding chemicals to clarifiers to promote faster settling of suspended solids. This process forms larger or heavier flocs that settle to the bottom of the tank, without requiring extensive infrastructure modifications.
However, the use of additional chemicals in chemically-enhanced carbon diversion incurs extra operational costs for utilities. These costs need to be carefully considered in relation to the benefits of reducing energy expenses for aeration. Another challenge with chemically-enhanced treatment is the difficulty of recovering chemically-bound phosphorus, which has become a significant concern for utilities, especially in Europe.
Ballasted clarification is a variation of chemically-enhanced primary treatment. It utilizes microsand or magnetic materials to enhance the settling of particles that would typically be too small to settle in traditional gravity-driven tanks. While chemical coagulants and flocculants are readily available, leading providers of ballasted clarification systems, such as Veolia Water Technologies, Evoqua, and WesTech Engineering, offer innovative solutions. These systems continuously reuse the materials that enhance the settling process, thereby reducing operational costs compared to purely chemical-based processes.
Infiltration technology to reduce chemical reliance
Utilities are increasingly seeking chemical-free solutions for carbon diversion. One emerging approach involves the use of filters to improve primary treatment by removing more suspended solids before biological processes. Researchers and wastewater treatment practitioners are employing various types and configurations of filters for this purpose, demonstrating promise in achieving desirable outcomes. Notably, cloth disc filters and compressible media filters have demonstrated effectiveness.
For instance, Aqua-Aerobic Systems has introduced the AquaPrime product, which is an adapted version of its tertiary disc filter. This innovative filter incorporates specially engineered cloth media and increased basin depth, making it well-suited for enhanced primary treatment applications.
Another technology addressing this need is the Proteus Primary filter developed by Tomorrow Water. This filter utilizes a cross-shaped media design that enhances the filtration surface area by 50%. Large-scale wastewater treatment plants in Korea have successfully implemented carbon diversion, as well as pilot projects in locations like Milwaukee in the United States. Additionally, Tomorrow Water offers the option of incorporating chemical enhancements into the filter to address the challenges posed by unpredictable peak flows resulting from climate change-induced wet weather events.
Advancements in biological processes – A potential alternative option.
Biological treatment processes for carbon diversion present a promising opportunity in the primary treatment market. Unlike physical and chemical processes that only eliminate suspended material, biological processes can also remove soluble matter, which constitutes a significant portion of municipal wastewater.
One prevalent configuration of biologically-enhanced primary treatment is the A-stage process. This approach involves establishing a small high-rate activated sludge system in the primary reactor. Bacteria within this system absorb soluble carbon from the wastewater without metabolizing it, ultimately settling into the waste sludge along with the excess carbon.
Another option is the A/B process, which represents a modification to the traditional activated sludge process. This method utilizes a combination of adsorption and bio-oxidation to divert carbon. The short retention time in the A/B process leads to reduced energy consumption for aeration, while soluble material is rapidly absorbed without being broken down.
Innovations within this market are focused on integrating treatment processes in novel ways. An exemplary instance is the alternating activated adsorption (AAA) clarifier, developed by NEWhub Corp. This technology combines the A-stage process with contact stabilization, directing the flow to the bacteria layer. Here, bacteria bind carbon to their surface and undergo biosorption. The AAA clarifier is particularly suitable for smaller treatment plants and has gained recognition in Europe, with plans to explore markets in the US and Australia.
Importance of the harmonization between different WWTPs processes for better results
Implementing enhanced primary treatment to reduce energy consumption is an attractive option, but utilities face a complex decision due to the crucial role of carbon in nutrient removal. If too much carbon is removed at the primary stage, additional carbon sources will be needed for biological processes to meet discharge standards.
The tightening of nutrient removal regulations worldwide highlights the importance of considering these standards. In Europe, for instance, the proposed updates to the Urban Waste Water Directive aim to significantly reduce total nitrogen and phosphorus limits. While utilities may prioritize efficiency and cost savings, their main focus will be on meeting these stringent regulatory limits.
Emerging methods of nutrient removal offer the potential to reduce carbon requirements in secondary treatment. One promising option is anaerobic ammonium oxidation, although widespread commercial adoption is still a distant goal. Nonetheless, it could eventually allow utilities to allocate more carbon to sludge. Currently, utilities must carefully balance the competing priorities of energy reduction and meeting strict nutrient removal requirements.
The immediate markets for carbon diversion are larger utilities in Europe, the US, and East Asia, where efforts to improve the sustainability and efficiency of wastewater treatment processes are gaining momentum. As more utilities adopt carbon diversion practices, they demonstrate how to harness the synergies that accelerate the development of energy-positive wastewater treatment plants with a smaller environmental footprint.
Reference: Original article (HOW COULD CARBON DIVERSION UNLOCK ENERGY SAVINGS FOR WWTPS? by AuqaTech) with Knowledge partner GWI published on Thursday, 11 May 2023.
Bioremediation technology utilizes the natural capabilities of living organisms such as plants, microbes, algae, and fungi to remove or degrade contaminants from the environment. This technology is gaining wide acceptance due to its potential to reduce anthropogenic pollutants and toxins from various environmental components. The technology can be applied in both in-situ and ex-situ conditions. Different biotechnological and genetic engineering strategies have been employed to improve the efficacy of this technique for the complete degradation of pollutants. Microbes and plants are used to achieve maximum removal of inorganic and organic contaminants. The process also enhances the potential of both plants and microbes for the successful remediation of one or more pollutants. The technology can be used to clean up contaminated sites, reduce the risk of health problems associated with pollution and ultimately improve the quality of the environment.
Bioremediation:
Bioremediation technology is primarily based on metabolic activities of microorganisms such as microbial degradation of organic pollutants, biosorption, binding of ions, molecules of pollutants, and transformation of pollutants to less toxic forms. In this technique, microbes, microalgae, fungi, plants, and enzymes are used to reduce the concentration of pollutants. Among the microbial species, bacteria, algae, yeasts, fungi, and actinomycetes are most commonly used in bioremediation processes. These microorganisms possess diverse metabolic capabilities and can degrade a wide variety of pollutants. In addition, certain plant species are also used to absorb pollutants from the environment and subsequently degrade them. The metabolic activities of microorganisms and plants are enhanced by the addition of various nutrients, enzymes, and other components. The bioremediation technology is also used to clean up spilled oil, reduce heavy metal contamination and treat wastewater. The bioremediation process is usually monitored by measuring the concentration of pollutants at regular intervals.
Categories of Bioremediation:
In Situ Bioremediation:
In situ bioremediation is a process that uses natural or engineered microorganisms to degrade, transform, or immobilize environmental pollutants in contaminated soil or groundwater. It is one of the most widely used methods of environmental remediation and treating a variety of contaminants. It includes petroleum hydrocarbons, chlorinated solvents, polychlorinated biphenyls (PCBs), and heavy metals. In situ bioremediation involves the introduction of microorganisms into the subsurface environment, where they are able to degrade or transform contaminants. This process can be or by stimulating the indigenous microorganisms in the contaminated area. In either case, the microorganisms are typically stimulated by the addition of nutrients and/or oxygen to the subsurface environment.
In Situ Bioremediation techniques
Bioventing:
Bioventing is an effective and efficient way to remediate contaminated soil. It has been used successfully to treat hydrocarbons, perchlorate, explosives, and propellants. Bioventing is most suitable for sites with low to moderate levels of contamination and is typically used in conjunction with other methods of remediation such as pump and treat systems or soil vapor extraction. The process can also be used to treat complex contaminants, including petroleum hydrocarbons, polyaromatic hydrocarbons, and phenols. Once the oxygen is introduced into the subsurface, bioventing can be used to stimulate the growth of naturally occurring microorganisms that degrade the target contaminants. Generally, bioventing is used to treat non-aqueous-phase liquids (NAPLs) such as gasoline, diesel, jet fuel, and petroleum products. But it can also be used to treat aqueous-phase contaminants such as chlorinated solvents and explosives.
Biostimulation:
Biostimulation has been used to reduce the toxicity of pollutants in contaminated soil, groundwater, and sediment. A variety of organisms such as bacteria, fungi, and algae have been used to promote the biodegradation of pollutants. Biostimulation is more effective when the pollutant is not very toxic and the environment is conducive to the growth of microorganisms. Biostimulation can be used to degrade persistent organic pollutants (POPs) such as polycyclic aromatic hydrocarbons (PAHs), chlorinated solvents, and polychlorinated biphenyls (PCBs). The addition of nitrogen and phosphorus can enhance the biodegradation of these pollutants by stimulating the growth of indigenous microorganisms. Biostimulation may also reduce the toxicity of pollutants by increasing the biodegradation rate of the pollutant. Thus, reducing the concentration of pollutants in the environment.
Bioattenuation:
Bioattenuation is a process by which contaminants are reduced in mass, toxicity, volume, or concentration. This can be done through a variety of means, including aerobic and anaerobic biodegradation, sorption, volatilization, and chemical or biological stabilization. Bioattenuation is often used on sites where other remedial techniques are not applicable, or where concentrations of contaminants are low.
Biosparging:
Volatile organic compounds (VOCs) can be a major problem for groundwater quality. Biosparging is an effective way to remove them. Biosparging works by injecting air into the aquifer below the zone of contamination. This oxygenates the aquifer and stimulates indigenous bacteria to degrade the VOCs. This process is relatively simple and can be quite effective in cleaning up groundwater contamination.
Ex Situ Bioremediation:
Ex-situ bioremediation is a biological process in which soil is excavated and placed in a lined above-ground treatment area. Where it is aerated to enhance the degradation of organic contaminants by the indigenous microbial population. This process is used to clean up contaminated sites, impacted by oil spills, hazardous waste, and agricultural chemicals.
Ex situ Bioremediation techniques:
Biopiles:
Biopile-mediated bioremediation is an effective way to clean up polluted soil. By excavating the soil and piling it above ground, and treatment bed is also created that is well-aerated and irrigated. This will encourage microbial activity and help to break down pollutants. The addition of nutrients to the soil may also be conducted to help speed up the process. Finally, a leachate collection system can be used to collect and treat any water that leaches from the soil.
Windrows:
Windrows can be used for bioremediation of soils contaminated with hydrocarbons, such as oil spills and refinery waste. Other contaminants include pesticides, heavy metals, and other persistent organic pollutants. The microbes in the windrows degrade the pollutants through oxidation, reduction, and hydrolysis. The pollutants are converted into harmless end products, such as carbon dioxide, water, and biomass. Moreover, windrows can also reduce odors associated with contaminated soils.
Landfarming:
Landfarming is a process through which pollutants are degraded in soil by manipulating its physical conditions. This is usually done by tilling or plowing the soil to create favorable conditions for microbial growth, which in turn would degrade the pollutants. The process of landfarming also includes the addition of certain amendments like organic matter, nitrogen, and phosphorous to stimulate microbial growth and enhance the pollutant degradation process. Land farming can also be used to treat a wide range of pollutants, including hydrocarbons, pesticides, dioxins, and metals. • The main advantage of land farming is that it is a cost-effective and relatively low-tech technique. Also, making it is suitable for small-scale operations. Furthermore, landfarming offers the possibility to treat a wide range of pollutants at the same time. It is not possible with other bioremediation techniques. Finally, landfarming can be used in a variety of soil types, including clay, loam, and sandy soils. • However, landfarming also has some drawbacks. For instance, it is a slow process, and it can be difficult to monitor the process and determine the degree of pollutant removal from the soil. Furthermore, landfarming is not suitable for treating pollutants with high concentrations. It may result in the redistribution of pollutants in the soil. Finally, landfarming can cause the release of pollutants into the air and water, which may result in environmental pollution.
Bioreactor:
A bioreactor is used to break down organic matter, reduce chemical oxygen demand (COD), and reduce suspended solids to levels deemed safe for discharge. Bioreactors also have applications in the biodegradation of pollutants, where the bioreactor is used to treat contaminated soils by bioremediation. Bioreactors are also used in industrial processes to produce chemicals, enzymes, and other products. They are designed to provide optimal conditions for the growth of microorganisms. And to control the process parameters (such as temperature, pH, nutrient supply, and oxygen supply) to yield the desired product.
Types of Bioremediation:
This is the classified basis on the type of microorganisms of living species used for bioremediation purposes.
Microbial Remediation
Microbial remediation is a form of bioremediation that utilizes microorganisms to transform, degrade, or remove contaminants from an environment. This process can occur naturally in the environment or be enhanced through the introduction of additional organisms or even nutrients.
Organic pollutants, such as petroleum hydrocarbons, polychlorinated biphenyls (PCBs), and polycyclic aromatic hydrocarbons (PAHs), are among the most common pollutants found in soil and groundwater. Microorganisms, including bacteria, fungi, and yeasts, in the presence of suitable environmental conditions and nutrients, break down the pollutants into less toxic compounds. For example, Pseudomonas bacterial strains have been shown to efficiently degrade petroleum hydrocarbons. While Trichoderma harzianum fungal species have been used to degrade PCBs and PAHs. In addition, various other species of bacteria and fungi have been successfully used for the bioremediation of organic pollutants.
Inorganic pollutants, such as heavy metals, are also of major environmental concern. Microorganisms can be used to reduce the bioavailability of heavy metals and reduce their toxicity. This can be achieved either directly, by binding the metal ions, or indirectly, by creating a complexing agent which reduces the metal’s solubility. In addition, some microorganisms are capable of transforming the metal ions into less toxic forms. For example, a consortium of bacteria, including Pseudomonas fluorescens, has been shown to efficiently reduce the bioavailability of lead ions. Microalgal species like Chlorella sorokiniana and Diatoms and some cyanobacterial species are scientifically proven to have bioremediation activity on many water-soluble pollutants. Moreover, blue-green algae like Rivularia and Phormidium species are rather the best biological indicators of pollution levels in the environment. (Mateo, P. et al. 2015)
Phytoremediation
Phytoremediation has several advantages over more traditional methods of environmental remediation such as incineration and landfills. It is relatively inexpensive, safe, and efficient. Additionally, it can be used in a wide range of environmental conditions and can be implemented rapidly. Furthermore, the process is relatively self-sustaining and can be used in areas where it may be difficult or impossible to use other methods.
The most common techniques used in phytoremediation include phytoextraction, phytodegradation, phytostabilization, and rhizofiltration. Phytoextraction involves the use of plants to extract metals from soils, sediments, and other matrices. These plants accumulate the metals in their tissues and can be harvested for removal and disposal. Phytodegradation involves the use of plants and their associated microorganisms to degrade organic contaminants. This is accomplished through a process known as biotransformation, in which the organisms transform the contaminants into less toxic or non-toxic forms. Phytostabilization involves the use of plants to immobilize or reduce the bioavailability of metals and other contaminants in soils and sediments. Finally, rhizofiltration involves the use of plants and their associated microorganisms to remove contaminants from water, such as heavy metals, pesticides, and other organic contaminants.
Phytoremediation may be applied to polluted soil or static water environment. This technology has been increasingly investigated and employed at sites with soils contaminated heavy metals like with cadmium, lead, aluminum, arsenic, and antimony. Many plants such as mustard plants, alpine pennycress, hemp, and pigweed have proven to be successful at hyper-accumulating contaminants at toxic waste sites. Not all plants are able to accumulate heavy metals or organic pollutants due to differences in the physiology of the plant.
Phycoremediation
Phycoremediation is a type of bioremediation process that uses algae and seaweed to clean up pollutants from a contaminated environment. In this process algae and seaweed help to naturally clean up pollutants, such as heavy metals and organic pollutants, from a contaminated environment. Algae and seaweed are naturally efficient at absorbing a wide range of pollutants and heavy metals.
The phycoremediation process begins with the selection of a suitable site for the algae or seaweed to be placed. The chosen site should have the right amount of light and nutrients, where either algae or seaweed or both are placed and allowed to grow. As the algae or seaweed grows, it absorbs the pollutants and heavy metals from the environment. The pollutants are then metabolized and converted into harmless compounds, which are then released back into the environment.
This process has been used to successfully remove heavy metals, such as lead, chromium, mercury, and arsenic, as well as organic pollutants, such as polycyclic aromatic hydrocarbons, from contaminated sites. Phycoremediation has been used to clean up polluted rivers, lakes, and oceans, as well as contaminated soils and sediments. In addition, it has also been used to treat wastewater from industrial and municipal sources.
The process of phycoremediation is both cost-effective and environmentally friendly. It is a much cheaper and faster method than other conventional remediation processes. Additionally, it does not produce any hazardous chemicals, so it does not contribute to air or water pollution. Phycoremediation is a viable option for cleaning up contaminated environments, and it has been successfully used in many locations around the world.
Mycoremediation
Mycoremediation is a form and a process of using organisms such as fungi, particularly white rot fungus like Phanerochaete chrysosporium, to degrade a multitude of persistent or toxic environmental contaminants. It has several advantages over other remediation methods including low cost, low energy requirement, minimal impact on the environment, and the potential for on-site treatment (Sylvestre et al. 2009). It is attractive for contaminated sites where the cost of excavating and disposing of the contaminated soil is prohibitively high. Mycoremediation is also attractive for sites with groundwater contamination, as the fungi can penetrate deep into the soils and contaminate the groundwater.
Conclusion:
In the current world scenario, bioremediation is being increasingly used to clean up contaminated sites. It is a cost-effective and environment-friendly way of dealing with pollution, as it uses natural organisms to break down hazardous materials. In recent years due to the scarcity of water resources and global warming government agencies are stressing policies for the reuse and reclamation of wastewater has promoted phycoremediation technology for wastewater treatment.
Algae and seaweed are being used extensively in bioremediation and phycoremediation processes, as they are capable of removing toxins and pollutants from the environment. Algae can absorb large amounts of nitrogen and phosphorus and can uptake heavy metals, such as arsenic and lead, from the environment. Seaweed is an important component of ocean ecosystems and is capable of sequestering carbon dioxide from the atmosphere. Algae are also known to utilize double the concentration of carbon dioxide for their biomass production as compared to terrestrial plants.
With advancements in bioremediation technologies and with emerging needs for these solutions in the world. Bioremediation is new hope for land, water resources, pollution control, and climate change.
References:
Sylvestre M., Macek T, Mackova M (2009) transgenic plants to improve rhizoremediation of polychlorinated biphenyls (PCBs). Curr Opin Biotechnol 20: 242–247
Mateo, P., Leganés, F., Perona, E., Loza, V., & Fernández-Piñas, F. (2015). Cyanobacteria as bioindicators and bioreporters of environmental analysis in aquatic ecosystems. Biodiversity and Conservation, 24(4), 909-948.
There are a number of issues in wastewater treatment plants, that are associated with the operational challenges to regulatory compliance issues. In order to address these problems, it is important to understand what they are and how they are impacting the plant. The below-given list is of some of the important challenges associated with wastewater treatment plants.
Exceeding the prescribed discharge limits of physicochemical parameters
Energy consumption
Sludge production
Environmental footprints
Issues under STP/ETP management
Shortage of resources/technology/field experts
Fragmentation of operation (inappropriate data recording)
Lack of real-time monitoring for precise output of the system
Seasonal variation
Microbial concentration/inoculum
Algal bloom
A. Exceeding the prescribed discharge limits of physicochemical parameters
Excess levels of suspended solids, biochemical oxygen demand (BOD), nitrogen, and phosphorus. These are the most common pollutants that are caused by exceeding the prescribed limits. These pollutants can lead to a decrease in the water quality of the treated water. And increase the amount of treatment necessary to meet the prescribed limits.
Suspended Solids:
Suspended solids are solid particles, such as dirt, debris, and other organic matter, that are suspended in the wastewater. These solids clog filters and pumps, as well as reduce the efficiency of the treatment process. Excessive amounts of suspended solids can also lead to the release of hazardous substances into the environment.
Biochemical Oxygen Demand (BOD):
BOD is a measure of the amount of oxygen that microorganisms require to completely break down organic matter in wastewater. If the BOD level is too high, it can disrupt the natural oxygen balance of the aquatic environment. High BOD wastewater is also highly contagious as it contains a high count of pathogenic microorganisms in its heavy load of organic waste. This can even lead to the death of fish and other aquatic organisms.
Mineral and Nutrients:
Chemical contaminants such as Nitrogen, Ammonia, Chlorine, Potassium, Trace metal nutrients, and Phosphorus. These can cause excessive growth of algae and aquatic plants in receiving water bodies. Excess nutrients can also lead to eutrophication, where a body of water becomes oversaturated with nutrients. It can cause a decrease in water quality. This leads to a decrease in dissolved oxygen levels, and the death of aquatic life.
Oil and Grease in ETP:
Oil and grease are both hydrophobic substances that can interfere with the performance of the plant. This is processed by blocking the flow of wastewater and causing anaerobic conditions. FOG-related blockages (due to foul odors and excess growth of bacteria) can result in sewer overflows due to reduced capacity or burst drains and sewer pipes.
Colorants and heavy and toxic metal ions from Metal industries:
Metals like Chromium (Cr), Lead (Pb), Cadmium (Cd), mercury, and Zinc (Zn). These metals come from textile, chemical industries, and other processes where metals are used as catalysts for oxidants. These are capable of causing severe health issues.
Emerging Contaminants:
A wide range of unregulated chemicals of synthetic origin or derived from natural sources, which may be a contender for future regulations are called Emerging Contaminants (ECs) (Xenobiotic, Pharmaceutical, and cosmetic products). The concentration of ECs ranges from ng/L to μg/L, which is comparatively smaller than other pollutants present in water and wastewater. Pharmaceutical active compounds (PhACs) or pharmaceutical contaminants (PCs) are one of the major groups of ECs which can cause inimical effects on living organisms even at very lower concentrations.
B. Energy Consumption:
Wastewater treatment plants consume large amounts of energy, estimated at between 1% and 3% of global energy output. And therefore, energy consumption is one of the prime problems in wastewater treatment plants. The main reasons are increasing energy costs, growing concern over climate change, and shrinking wastewater production resources. Energy-inefficient wastewater treatment processes lead to higher emissions of CO2 and other pollutants, which in turn pose serious environmental threats.
To reduce their energy bill, many wastewater treatment plants have started investing in new technologies. Also, retrofitting older facilities with more efficient systems. Some strategies include: using thermal conditioning instead of boiling; integrating MSW sludge digestion into existing biogas systems. And, increasing the use of containerized technologies such as activated carbon filters. However, even these measures will not be sufficient if plant operators don’t pay close attention to energy usage throughout the entire process chain from extraction to discharge, including grid energy usage as well as fuel and electricity costs.
One way to achieve significant reductions in sewage treatment plant energy demands would be to find ways to treat effluents more effectively. For example, optimizing process operation could result in significant reductions in wastewater temperature, which would reduce energy requirements for cooling systems. In addition, optimizing operations could also lead to reductions in drying time and emissions from organic solids disposal facilities.
C. Sludge Production
Sludge is the solid or semi-solid matter that settles to the bottom of a wastewater treatment facility. It can be a major problem for wastewater treatment plants. Because it often contains high levels of bacteria and other microorganisms.
The problem with sludge protection is that it can lead to serious issues such as clogging (leads to sewage overflow) pipes, damaging equipment, and releasing toxins into the environment. The production of sludge can be attributed to several factors such as high organic loading rates, low aeration rates, and high pH levels.
D. Environmental Footprints
Though wastewater treatment plants are made to restrict the pollution of environmental resources. They can lead to creating more hazardous effects on the environment if mismanaged. It has been studied and found that unregulated WTPs operations contribute to pollution in the environment through their own waste (Kumar et al., 2017). These plants release nearly 40% of their chemical emissions into the air and another 40% into surface water (Kumar et al., 2017 loc. cit.). This means that there are two ways that these plants are contributing to environmental pollution. That is through their own waste or through emissions released by them into surface water or air.
Environmental pollution due to emerging pollutants and modified pollutants at CETP plants realizing toxins, carcinogenic, mutagenic pollutants in nature. CETP effluent usually contains a wide range of pollutants including both emerging and modified pollutants. Emerging pollutants are substances that have only recently been identified as being harmful to the environment. As such, there is little to no regulation on these substances. Modified pollutants, on the other hand, are substances that have been altered by human activity. This can include everything from pesticides to pharmaceuticals. Both of these types of pollutants can be extremely harmful to the environment. Also, they are often found in high concentrations of CETP effluent. This has led to the degradation of water quality and has created serious health hazards for human beings as well as animals. This also causes a loss of biodiversity and ecological imbalance in the ecosystem.
E. Issues under STP/ETP Management
Shortage of Resources/Technology/Field Experts
The wastewater treatment plant is a critical component of wastewater management, responsible for the safe and efficient disposal of liquid waste. Unfortunately, many wastewater treatment plants are facing a major problem of inadequate resources, technology, and field experts to efficiently manage their operations. This shortage of resources is a major cause of concern for wastewater treatment plant operators, as it limits their ability to meet environmental standards and safeguard public health.
Funding
One of the primary causes of the resource shortage is the lack of available funding. Due to their relatively low operating costs, wastewater treatment plants are often overlooked when it comes to budget allocation. This means that the necessary resources, technology, and expertise are not available to the operators, resulting in a sub-standard level of operations.
Need for advanced Technology
There are some technologies to improve the shortage of machinery in Wastewater Treatment Plant:
Modern machinery for inline monitoring of the WTP activities is really necessary. This will efficiently help to understand the exact working conditions and changes happening in any WTP plant. Sensors and devices such as Dissolved O2, Dissolved CO2, pH, Temperature, Reactor embedded heat control systems, mechanical parts like baffles, mechanical/pneumatic agitators, efficient water/sludge transfer, etc. can be incorporated into advanced WTPs for enhanced working conditions.
Sludge thickening technology to produce sludge from wastewater: This will make it possible to use the sludge as fertilizer or fuel.
Membrane technology: Efficient membrane technology is required to reduce the BOD/COD of the wastewater at a fast rate. It also helps to reduce nutrients from water such as Carbon, Nitrogen, and Phosphate by allowing bacterial growth. Biomass produced on membrane filters is rich in nitrogen and can be utilized as a good quality fertilizer.
Bacteria-based technology: It can decompose a number of organic substances in wastewater, including cellulose and lignin wastes, into carbon dioxide and nutrients such as nitrogen and phosphate. Bioremediation technology for industrial effluents from Petroleum refineries and the petrochemical industry, Textile and Chemical companies, pharmaceutical industries, etc. requires a specialized microbial consortium for treatment. The generation of efficient microbial consortiums for such wastewater treatment activities is needed for the current WTPs.
Advancement in bioremediation technology – That involves the use of phytoremediation, phycoremediation, bioremediation, and utilization of nature-based processes like artificial wetlands, lagoons, algae ponds, and water streams. This help to clean the wastewater in the tertiary level of water treatment.
Utilize the mineralization of biomass: That is decomposed by bacteria into biochar, which can be used as an effective fertilizer.
Electricity
In a wastewater treatment plant, dropping power because of an energy outage is the maximum common disturbance. If a wastewater remedy facility loses energy, the filtration or purification structures will forestall working, until a backup generator or different power supply is available. If your facility loses electricity, the wastewater will hold amassing till you operate the wastewater treatment machine again.
Manpower (Field experts)
The lack of field experts can make it difficult for wastewater treatment plants to keep up with the latest developments in the industry. Technology is constantly evolving and field experts are necessary to ensure that wastewater treatment plants are able to make full use of the latest advances. Without the necessary expertise, wastewater treatment plants are unable to efficiently and effectively manage their operations. We can overcome this issue by technical or engineered methods. For example, we can use Artificial Intelligence-based simulation tools to build models of wastewater treatment plants and predict their performance.
Fragmentation of Operation (Inappropriate Data Recording)
The problem is that the operations of WTPs are fragmented due to the different levels of government involvement, which can lead to improper data recording. This can lead to a lack of understanding of how the system operates and what needs to be done in order to fix it. There are also issues of trade-offs and unintended consequences. For example, the use of chlorination in WTPs is an effective way to reduce pathogen levels, but it can also decrease the levels of different types of beneficial bacteria, which might lead to an increase in pathogens such as Escherichia coli. The study also highlights that there are few incentives for large industrial wastewater treatment plants to invest in innovation or generate new ideas without a clear understanding of how the system operates. To help address this, the study recommends:
Establishing public-private partnerships to foster innovation and encourage the use of high technology in wastewater treatment
Developing a market-based approach for incentivizing investment in innovation, including a new “wastewater innovation fund”.
Offering financial incentives for increased output from anaerobic digesters, which can generate energy and nutrient-rich biogas that can also be used as a renewable fuel source.
Lack of real-time monitoring for precise output of the system
The reasons for this are many: the complexity of the WTP system is one, but also that the issue is often seen as a “management problem” with little focus on technical solutions. As mentioned earlier in the section on the need for advanced technology real-time monitoring of the WTP would play a very effective role to improve their efficiency. Real-time WTPs monitoring can be done by designing and implementing an automated system in which sensors (such as flow meters, DO, DCO2) that measure processes and parameters (chemical oxygen demand, total suspended solids, pH levels, etc.) are installed at strategic locations within a WTP.
In order to prevent the exceeding of prescribed limits, it is important to have an effective monitoring system in place. This monitoring system should include regular laboratory testing of the wastewater, as well as the implementation of best management practices (BMPs), such as the installation of pre-treatment systems, to reduce the number of pollutants entering the plant. It is also important to ensure that the wastewater treatment plant has the capacity to treat the amount of wastewater that is being produced. If the plant does not have the capacity to treat the wastewater, then additional measures must be taken to reduce the amount of wastewater entering the plant.
F. Seasonal Variation
Seasonal temperature variations impact microbial population and their growth. Variations change the occurrence of specific types of microorganisms in a particular season. This alters the efficiency of WTPs. It has been observed that the sludge from domestic sewage treatment contains greater diversity than industrial wastewater treatment. The core genera in domestic wastewater treatment systems are usually Nitrospira, Caldilinea, Pseudomonas, and the fermentative function microbe-Lactococcus. (2)
Some of the research publications show that seasonal variation also impacts the concentration of the pollutants present in the wastewater. And obviously, if the microbial consortium is varying with seasonal variation the pollutant’s concentration would also change depending on the microbial community. (3)
F. Microbial Concentration/Inoculum
Microbial consortium plays a vital role in the efficient operation of the wastewater treatment plant. Biological treatments are regulated by the microbial community and lack of an adequate concentration of microbes or type of microbes leads to the failure of WTP’s operations. Sewage or domestic water brings an abundance of microbial flora along with it in STP. And, when secondary wastewater treatment begins the same microflora grows well with supplied adequate agitation and oxygenation. With further requirements, the activated sludge which is a very active form of microbial biomass. Also, it is retained in the STP’s secondary treatment units. This helps to provide a continuous supply of active microbial population for the treatment of freshly entering wastewater in STP.
The failure of STP’s secondary treatment unit is observed pertaining to the sudden degradation of activated sludge due to toxic water contaminants. When industrial water with a high concentration of toxic metal ions, and poisonous substances enter STP, oligodynamic actions kill microbial flora and lead to the failure of STP. In such cases finding and removal of industrial effluent sources entering STP water is essential. After which addition of activated sludge from another source or active commercial consortium of bacteria is also obtained as a source of efficient microflora for STP operations.
ETP influent of wastewater is mostly devoid of microorganisms. It requires a specially designed consortium of microorganisms to treat industry-specific wastewater. In many places activated sludge from STP, Cow dung like conventional sources of microorganisms is also tried. However, such a solution may or may not work efficiently due to the lack of potential bacterium to treat industrial effluents. In this case, a commercially derived consortium of potent microorganisms is necessary to utilize. Many commercial suppliers of industrial microorganisms offer effective solutions for a range of industrial effluents. (4)
G. Algae Bloom
Due to the high nutrient content of wastewater sometimes algae flourish in STP/ETP plants. Algae bloom creates problems for machinery and filter assemblies leading to blocking the air and water flow. To address this issue in WTPs, the most commonly used approach is algaecides. Algaecides are chemicals that are specifically designed to kill algae. They can be used to treat the water or effluent in the plant that is released from the plant. There are a number of advantages as well as drawbacks of using algaecides. But, algae bloom in wastewater itself is being termed by many researchers as a potential way of wastewater treatment solution.
In the environment, when water flows in wetlands, lagoons, estuaries, ponds, rivers even seas algae flourishes using available nutrient resources. Algae can consume many nutrients and pollutants including heavy metal ions. They have proved to be the best option to generate completely environment-friendly wastewater treatment solutions. However, this is not yet well explored due to the lack of development in the technology to utilize algae in large-scale wastewater treatment. This needs complete modification of the conventional STP/ETP plants to allow algae to grow along with microbial consortium. This would require separate provisions to be established in the vicinity of the plant for microalgae cultivation and wastewater remediation.
Conclusion
Worldwide with the increasing human population, the need for water resources is shooting higher year by year. Available freshwater resources are already scarce and with climate change issues, this question becoming more serious. Reducing, reusing, and recycling is the best solution to work with available water resources to make it sustainable. Therefore, WTPs play a very essential role in making the wastewater fit to reuse or recycle. However, as discussed in this article there are many problems ranging from operational issues to regulatory compliance making conventional WTP less efficient in their utility. Novel technological interventions are necessary to intervene for sustainable development in the sector of wastewater treatment. This can be achieved by applying environmental solutions with an available STP/ETP setup.
Use of novel bioremediation techniques (eg. phytoremediation, phycoremediation), wastewater lagoons, ponds, artificial wetlands, etc. are now given importance. Zero liquid discharge (ZLD) policy needs to be given importance to retain and reutilize wastewater in industrial, agricultural as well as domestic applications. In a country like India, National Green Tribunal (NGT) like lawmakers, making it mandatory to treat wastewater using various environment-friendly solutions to reduce the environmental impact of wastewater. Such activities will help to sustainably develop the wastewater treatment sector for a better tomorrow.
References:
Kumar, S., Smith, S. R., Fowler, G., Velis, C., Kumar, S. J., Arya, S., … & Cheeseman, C. (2017). Challenges and opportunities associated with waste management in India. Royal Society open science, 4(3), 160764.
Zhang, B., Yu, Q., Yan, G., Zhu, H., & Zhu, L. (2018). Seasonal bacterial community succession in four typical wastewater treatment plants: correlations between core microbes and process performance. Scientific reports, 8(1), 1-11.
Gao, D., Li, Z., Guan, J., & Liang, H. (2017). Seasonal variations in the concentration and removal of nonylphenol ethoxylates from the wastewater of a sewage treatment plant. Journal of Environmental Sciences, 54, 217-223.
Quraishi, T., Kenekar, A., Ranadive, P., & Kamath, G. (2018). Evaluation of Performance of cow dung as Microbial Inoculum in Industrial Wastewater Treatment and its Environmental Implications. Indian J. Sci. Technol, 11, 1-7.
Wastewater is a mixture of water and a variety of pollutants, including suspended solids, dissolved organic compounds, nutrients, and microorganisms. Domestic wastewater is typically composed of human waste, food waste, and paper products. Industrial wastewater may include toxic chemicals, heavy metals, oil and grease, and other pollutants.
Suspended solids are the largest component of wastewater and can include anything from toilet paper to food scraps. Dissolved organic compounds, such as detergents, food waste, and solvents, can also be found in wastewater. Heavy metals, salts, and nutrients are also present. Nutrients, such as nitrogen and phosphorus, are the primary sources of energy for microorganisms in wastewater. These microorganisms are responsible for breaking down organic matter, which in turn produces carbon dioxide and other gases. This decomposition is essential for the removal of some pollutants, such as ammonia and phosphorus from wastewater.
Health, Environment, and Social concerns associated with wastewater:
Health: Wastewater contains bacteria, viruses, and parasites that can cause diseases such as cholera, dysentery, hepatitis A, and typhoid. These diseases can spread through contaminated water. Wastewater also contains toxic chemicals, such as lead, arsenic, and mercury, which can cause serious health problems if ingested. Poorly treated wastewater leads to water pollution on its release, creating an even greater risk to public health.
Environment: Wastewater can have a damaging effect on the environment if it is not properly treated or disposed of. Untreated wastewater can pollute drinking water sources and contaminate soil, which can lead to water-borne diseases and the destruction of natural habitats. Wastewater can also cause algal blooms and oxygen depletion in water bodies, which can kill off fish and other aquatic life.
Social: Wastewater can have a significant impact on communities. Poorly treated or disposed wastewater can cause an increase in health risks to local residents. If wastewater is not managed properly, it can create an unpleasant living environment due to odor and the presence of vermin. Furthermore, wastewater has an adverse impact on the local economy, as it can contaminate agricultural land and decrease crop yields.
Precautionary measurements are taken to avoid wastewater-related issues
Precautionary measures are taken because untreated wastewater can cause a variety of negative environmental and health impacts.
To prevent these issues, precautionary measures are taken to ensure that wastewater is collected and disposed of properly. The collection of wastewater is usually done through sewer systems, septic tanks, or catchment basins. These systems allow for the safe collection and transport of wastewater to a treatment facility to remove pollutants and contaminants. Then water is released back into the environment.
Disposal of wastewater is also important in avoiding wastewater-related issues. Depending on the type of wastewater and the level of treatment it has undergone, it can be disposed of in various ways. Treated wastewater may be discharged into a local waterway, sprayed onto land, or recycled for use in industrial processes.
Wastewater collection
Wastewater collection systems typically include a network of pipes, manholes, and other structures such as pumping stations, treatment plants, and storage tanks. The collection systems are responsible for transporting wastewater from residences and businesses to a central drainage system.
Wastewater specific treatment
STP
A sewage treatment plant is a facility where wastewater is processed to remove pollutants and produce a treated effluent that is safe to return to the environment. Treatment processes may include physical, chemical, and biological processes to remove suspended solids, nutrients, and other pollutants. The treated effluent is typically discharged to a receiving water body such as a river, lake, or ocean.
Primary, Secondary, and Tertiary treatment process in STP:
Primary Treatment
It involves the physical removal of solids from wastewater. This is typically accomplished by screening, grit removal, and primary sedimentation. This is usually done by passing wastewater through large screens or grit channels to remove large debris, such as plastic, sticks, and rags. The wastewater is then pumped through a settling tank, which allows suspended solids to settle to the bottom and the clarified water to flow out of the tank. The settled sludge is usually sent to a secondary treatment process, such as anaerobic digestion or activated sludge. Primary treatment involves the addition of a coagulant and aims at removing grits, coarse solids, oil, and grease if any are present.
Secondary Treatment
This process uses bacteria and other microorganisms to break down organic matter from wastewater, such as food waste, soaps, and detergents, and convert it into a form to be released into the environment. The process usually involves aeration and clarification, using tanks, basins, and biological filters.
Membrane bioreactors (MBRs): Another wastewater treatment option is MBRs. These systems use membranes to separate suspended particles from the wastewater and then allow aerobic or anaerobic bacteria to break down the organic material. The end result is a stabilized effluent that meets environmental standards for safe discharge.
Sequential Batch Reactor (SBR): The SBR cycle is composed of several steps: fill, react, settle, decant, and idle. During the reaction stage, the wastewater is aerated and circulated to mix with the microbial population, allowing it to break off the organic matter. In the settling stage, the mixture is settled, allowing lighter biomass and organic matter to rise to the surface and be removed. In the idle phase, the tank is allowed to sit without any aeration or mixing, allowing the biomass to settle and the organisms to rest.
Moving Bed Biofilm Reactor (MBBR): MBBR is a type of wastewater treatment system that uses suspended carriers to provide a large surface area for the attached growth of biofilms. The carriers used in MBBRs provide a large surface area for biofilm growth, which helps to reduce the biomass size required for effective treatment.
Fluidized Bed Bioreactors (FBBR): FBBR is a type of secondary treatment for the removal of organic pollutants from wastewater. This allows microorganisms, such as bacteria and fungi, to colonize the particles and break down the organic pollutants. It is used in conjunction with primary treatment processes to achieve the highest level of pollutant removal possible.
Tertiary Treatment
The tertiary or chemical treatment process of sewage treatment plants typically involves the addition of chemicals such as calcium oxide, sodium hydroxide, and sodium carbonate to the wastewater. This process helps to break down organic matter and remove suspended solids and other contaminants. The process also helps to balance the pH of the water, reduce odors (Activated charcoal), and reduce the level of disease-causing organisms.
Activated charcoal is a carbon filtration that works to remove odor and color by adsorbing and trapping contaminants on the surface of its tiny pores. Activated carbon needs replacement as its capacity to work reduces gradually.
Chlorination: The process involves the addition of chlorine or chlorine-based compounds to the water to kill bacteria and other disease-causing microorganisms. The chlorine kills any disease-causing organisms, which helps to reduce the risk of water-borne diseases.
Ozonation is a form of the advanced oxidation process that produces extremely reactive oxygen species. Ozone is very reactive and readily oxidizes microorganisms, effectively killing them. Ozone oxidizes the cell wall, membrane, and internal components of microorganisms, damaging their structure and function. Ozone also disrupts the microorganism`s metabolic pathways, leading to cell death.
UV treatment – UV water disinfection technique disinfects by penetrating microorganisms and destroying their DNA. Chlorine and other disinfectants can produce toxic disinfection byproducts (THMs or Halo-acetic acids) as well as the dangers that come with their presence on site. Because UV light disinfection is a chemical-free method, it effectively eliminates any concerns about these byproducts.
The important water discharge parameters in STP are biochemical oxygen demand (BOD), chemical oxygen demand (COD), total suspended solids (TSS), total nitrogen (TN), total phosphorus (TP), and fecal coliform bacteria.
ETP
An effluent treatment plant (ETP) is a facility used to treat wastewater that is produced by industries and other sources. The treated wastewater (or effluent) is then released into the environment, usually a nearby river, lake, or ocean. ETP reduces the number of pollutants in the wastewater to the levels required by national and local environmental regulations.
In comparison with STP, ETP focuses more on reducing the number of chemical pollutants present in wastewater during its secondary treatment process.
Primary, Secondary, and Tertiary treatment process in ETP:
Primary Treatment
The primary treatment process in ETP typically involves the removal of suspended solids, oils, and other physical contaminants from wastewater. Wastewater is Treated by physical processes such as sedimentation, flocculation, clarification, and filtration.
Secondary Treatment
In secondary treatment, industrial effluent processes are modified as per the content and level of certain chemical pollutants. Following some of the industrial wastewater treatment processes will help to understand this concept better.
Oil and petroleum industry:
A vast amount of wastewater is generated from the extraction, refining, and transportation of petroleum products. This contains a variety of contaminants, including oil, grease, heavy metals, and other hazardous substances or pollutants. It helps to reduce the concentration of pollutants and contaminants in the effluent to a level that is safe for discharge into the environment. This is achieved through coagulation, flocculation, and biological treatment. The coagulation/flocculation process involves the addition of a coagulant, such as aluminum hydroxide chloride or aluminum sulfate, to the wastewater to remove suspended solids.
The biological treatment process utilizes microorganisms to break down organic material in the wastewater and reduce the concentration of pollutants. Finally, the N:P ratio is an important parameter for the treatment of oily wastewater by using oil-degrading bacteria. By using these techniques, secondary treatment can effectively reduce the contamination level of effluent and make it suitable for discharge into water bodies.
Example: Microorganisms to remove oil contaminants such as Bacteria, Pseudomonas aeruginosa: P. aeruginosa bacteria are able to break down oil and petroleum products due to their ability to produce enzymes that are specific to hydrocarbons. Pseudomonas bacteria are usually introduced into wastewater as slurry. This slurry is made up of a combination of Pseudomonas bacteria, nutrients, and a carbon source. The carbon source is important because it provides the bacteria with the energy they need to break down the oil and petroleum-based pollutants.
Other common microorganisms used in the oil and petroleum industry for wastewater treatment include bacteria such as Acinetobacter, and Bacillus, and fungi such as Aspergillus and Trichoderma.
Textile industry (Dyes and paints, colorants,):
The main purpose of secondary treatment is to provide BOD removal beyond what is achievable by simple sedimentation. It also removes appreciable amounts of oil and phenol. The dissolved and colloidal organic compounds and color present in wastewater are removed or reduced to stabilize the organic matter. Textile processing effluents are amenable to biological treatments.
Textile waste also contains significant quantities of non-biodegradable chemical polymers. For non-biodegradable pollutants, filtration technologies are utilized in the textile industry to clean wastewater. Traditional membrane processes in textile wastewater treatment include the use of ultrafiltration (UF), nanofiltration (NF), and reverse osmosis (RO) membranes. The selection of membrane technologies for textile effluent relies on costs based on the balance between water flux and solute retention. RO also becomes less effective when osmotic pressure, is caused by high salt concentration in the feed wastewater. Becomes too high to obtain a reasonable transmembrane permeate flux without applying excess transmembrane hydraulic pressure.
The membrane filtration system typically consists of a series of membranes with differing pore sizes and compositions that are used to remove particles from the wastewater. The membranes are typically made from polymeric materials such as polyvinylidene fluoride (PVDF), polysulfone, or polypropylene.
Metallurgic, chemical, and Fertilizer industry:
This is usually done through the application of an activated sludge process, trickling filter, rotating biological contactors, and oxidation ponds. The activated sludge process is used to remove organic pollutants from wastewater by using a variety of microorganisms. Trickling filters use a bed of media on which microorganisms grow to degrade the organic pollutants. Rotating biological contactors use a series of rotating plastic disks on which microorganisms grow and degrade organic pollutants. Finally, oxidation ponds are used to provide long-term biological treatment.
Tertiary Treatment
The tertiary treatment or biological treatment process in an ETP is designed to remove organic and inorganic pollutants from wastewater. This process is typically used in applications where the effluent needs to be treated to a high level of purity. The water is then treated with chlorine, ultraviolet light, or ozone to kill any remaining bacteria, viruses, and other pathogens before it is released into the environment. Primary and secondary treatment typically gets wastewater only clean enough to discharge safely into the environment. Tertiary treatment can achieve levels of water purification that make the water safe for reuse in water-intensive processes or even as drinking water.
Tertiary wastewater treatment often works by using a combination of physical and chemical processes to remove harmful microbiological contaminants. The process usually involves filtration followed by additional disinfecting treatment. In some cases, tertiary treatment may also use other specialized treatments like lagoon storage, biological nutrient removal, and nitrogen and phosphorus removal.
Final water disposal activities:
All water either from STP or ETP is finally safely disposed into the environment or reused depending upon the quality of wastewater as follows.
Filters: Tertiary filtration components can contain a few different materials. Sand and activated carbon filters are common, and filters can also contain fine woven cloth. The filters come in a few types, including bag filters, drum filters, and disc filters. Backwash cleans the media components to ensure their continual functioning.
Disinfecting: The process of tertiary disinfection may take a few different forms. Chlorine is one of the most commonly used disinfectants in wastewater treatment. Ultraviolet light is a common disinfectant in tertiary treatment. Ozone is highly reactive and can destroy most microorganisms it comes into contact with.
Discharge: Once the wastewater has undergone tertiary treatment, it is ready for discharge back into the environment. Many municipalities have specific requirements for the discharge of treated water. Tertiary treatment should be sufficient to meet those standards, keep the environment clean and preserve human health, experts say.
Reuse: Many treatment plants use tertiary treatment specifically to make the water safe for human ingestion. Water that has received tertiary treatment is also suitable for numerous operations that require clean water. These include industrial and manufacturing processes, oil and gas extraction and refining, utilities cooling, and agricultural practices like irrigation.
The drainage systems and wastewater collection are important components of proper collection and disposal of the city’s infrastructure. They are responsible for maintaining a safe and healthy environment by preventing the spread of diseases and pollutants. The drainage systems and wastewater collection are most often divided into two main components. The collection system includes sewers and pipes, and the treatment system, which includes wastewater treatment plants. The drainage system collects rainwater runoff and sewage from homes, businesses, and other sources. Then transports the collected wastewater to a treatment plant, where it is treated, cleaned, and released back into the environment.
Drainage System:
The drainage system is a network of pipes, drains and other structures used to collect and remove surplus water and waste from buildings, roads, and other areas. It is an integral part of modern life, allowing for the removal of rainwater, sewage, and other waste materials.
The drainage system is typically composed of two components. A surface drainage system collects and disposes of rainwater and surface runoff. A subsurface drainage system collects and removes waste water from buildings.
Surface drainage systems are designed to collect and convey excess water away from roads, buildings, and other areas. They usually consist of a series of underground pipes and channels that collect runoff from rooftops, driveways, and other surfaces. The collected water is then directed to a storm sewer, which carries it away from the area. In some cases, the water is directed to a nearby water body or a natural wetland.
Subsurface drainage systems are designed to collect and remove wastewater from buildings. These systems are typically comprised of a series of pipes and drains that collect wastewater from plumbing fixtures, such as toilets and sinks. It is then directed to a septic tank or a public sewer system, where it is treated before being discharged into a nearby water body.
Wastewater Collection:
Wastewater collection systems typically include a network of pipes, manholes, and other structures such as pumping stations, treatment plants, and storage tanks. The pipes are usually constructed from PVC, concrete, or iron and they come in a variety of sizes and shapes to accommodate different types of wastewater. The manholes are used to allow access to the pipes for cleaning and maintenance, and they are usually equipped with safety equipment such as gas detectors and airflow monitors.
Wastewater collection systems are responsible for transporting wastewater from residences and businesses to a central drainage system. In most cases, wastewater is collected through a network of underground pipes that lead to a sewage treatment facility. The drainage system works in conjunction with the wastewater collection system by receiving wastewater from the collection system and then distributing it to the treatment facility. The drainage system removes excess water from the surrounding area and provides a safe and efficient disposal of wastewater.
Wastewater Collection Categories:
Wastewater collection systems can be divided into two categories: sanitary sewers and combined sewers. Sanitary sewers are wastewater systems that collect it from homes and businesses and transport it to a wastewater treatment plant, while combined sewers collect both stormwater and wastewater and transport them to a wastewater treatment plant. The drainage flow rate is the amount of water that is discharged from a drainage system over a given period of time. This rate is usually expressed in cubic feet per second (CFS). The drainage flow rate can be affected by factors such as the size of the drainage system, the slope of the terrain, the amount of rainfall or snowmelt, and any obstructions in the flow.
The volume of water collected in wastewater treatment plants (WTPs) is determined by the size of the plant and its capacity. Normally, the size and type of treatment process used will determine the volume of water that can be processed in a given period of time. The capacity of WTPs can range from 1.9 million liters per day to over 80 million liters per day. Water collected by WTPs depends on the amount of wastewater generated by the community and precipitation in the area.
Treatment and Discharge:
Pumping stations are used to move wastewater from low-lying areas to higher points where it can be more easily transported. Treatment plants used to clean and treat wastewater involves a combination of physical, chemical, and biological processes.
Physical processes involve the removal of large suspended solids, such as sand, gravel, and other debris. This is usually done through sedimentation, filtration, or centrifugation. Chemical processes involve the addition of chemicals, such as chlorine or alum, to break down organic matter and other pollutants. Biological processes involve the use of microorganisms, such as bacteria, to break down organic matter in wastewater.
The treated wastewater is then discharged into a receiving water body, such as a river, lake, or ocean.
By tabulating general wastewater parameters, Population Control Board is able to understand the impact of wastewater on the environment. This information can then be used to develop measures to reduce the negative impacts of wastewater on the environment.
Wastewater management systems must be designed and operated to ensure that they adequately collect, and treat the wastewater and prevent environmental contamination.
Wastewater management systems should also be designed to prevent flooding and maintain an acceptable level of water quality. This may include the installation of pumps, detention basins, and other structures to reduce the effects of flooding. It may also include the use of stormwater management systems to prevent soil erosion and runoff of polluted wastewater.
Similarly, when these natural phenomena are applied for wastewater treatment by artificial means, both natural, as well as artificial resources are utilized. At the beginning of the process, wastewater is allowed to stabilize and remove suspended solids particles by aggregation, flocculation, and sedimentation in waste stabilization ponds. Then the water slowly flows to artificial wetlands where the plantation of diverse phytoremediation plants sequesters many pollutants and clears water to the maximum extent by phytoremediation process. Furthermore, in natural processes, the wastewater from wetlands enters the natural water bodies and water streams.
Constructed wetlands:
Constructed wetlands are artificial wetlands that are specifically designed to treat wastewater. They consist of a shallow body of water with a bed of gravel or sand and vegetation planted in them. As wastewater is pumped into the wetland, it flows slowly through the gravel or sand and is filtered by the plants, soil, and microorganisms. The microorganisms break down organic matter and suspended solids, while the plants and soil filter out pollutants and heavy metals.
Water Lagoons:
Lagoons are made up of a series of interconnected ponds, which are designed to capture, store, and treat wastewater. Each lagoon is filled with wastewater that is circulated and aerated, allowing beneficial bacteria and enzymes to break down harmful contaminants. This process helps to reduce the amount of organic matter, toxins, and other pollutants in the water, making it safe for reuse or discharge. As the water moves through the lagoons, suspended solids settle to the bottom, providing a nutrient-rich environment for beneficial bacteria and other organisms to thrive. The bacteria and other organisms help to further break down the contaminants and create a clean, safe effluent.
Importance of Wastewater management
Conservation of Resources: It helps to conserve valuable resources, such as energy and water, by recycling.
Preservation of Human Health: Wastewater management reduces the risk of water-borne diseases and helps in preserving public health.
Reduced Pollution: It helps to reduce the pollutant level in water sources and helps to protect aquatic ecosystems and wildlife.
Improved Water Quality: Water quality in rivers and lakes can be improved and making them safer for human use.
Reduced Contamination: It helps to reduce contamination of drinking water sources and ensure that they are safe for human consumption.
Economic Benefits: Proper wastewater management can help to reduce the costs of water treatment and disposal, providing economic benefits.
Conclusion:
Wastewater management is a complex process to manage. The infrastructure of a drainage system in wastewater management is a basic requirement. Improper drainage and wastewater management lead to wastewater-related issues in society that affects the quality of life. Poorly designed drainage systems can lead to poor sanitation, water pollution, and various serious water-related health hazards. Impotent drainage system flooding during rainy seasons may occur due to water logging which causes life and economic losses. Proper management is essential to avoid above mentioned damages. By investing in an efficient infrastructure and technology, wastewater can be well managed and we can enjoy a hygienic life.
Bio Remediation/ Phycoremediation
