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
  1. Shortage of resources/technology/field experts
  2. Fragmentation of operation (inappropriate data recording)
  3. 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:

1. 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.
2. 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.
3. 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.
4. 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.