Microalgae for Wastewater Treatment

What is Wastewater?

Any water that has been contaminated by human interventions is considered wastewater. Wastewater basically originates from domestic, industrial, commercial, or agricultural applications. It also includes surface runoff or stormwater and any sewer input or sewer infiltration is also referred to as wastewater.

Types of Wastewaters

Sewage: sewage is wastewater that develops and comes from domestically produced wastes like toilets, food, laundry, and other wastes. The contaminants that originated in sewage water are from domestic sewage and suspended and dissolved pollutants.

Non-sewage: Non-sewage refers to all other varieties of wastewater other than sewage. It contains wastewater originating from industrial washing applications, rainwater, stormwater, and industrial effluent. It doesn’t have any additional dangerous pathogens like sewage.

Water Pollutants and their Origin

Pollutants are materials, present in concentrations that could harm creatures (including people, plants, and animals) or exceed environmental quality standards.

Types of Pollutants:

• Organic and biological Pollutants: Organic pollution is a type of chemical pollution caused by persistent organic pollutants as they are difficult to remove or degrade once released into the environment, such as Dichlorodiphenyltrichloroethane (DDT). Other than organic pollutants biological pollutants originate from biological material that includes liquid manure, sewage treatment sludge, etc.
• Inorganic Pollutants: Inorganic pollutants are the compounds of inorganic by-products arising from various industrial applications that include, chemical, pharmaceutical, textiles and dyeing industries, paints, etc. Examples of inorganic metal pollutants are arsenic, cadmium, lead, mercury, chromium, aluminum, etc.

The major water pollutants are biological matter like feces, and human and animal body fluids containing bacteria, viruses, and parasites. And industrial pollutants include insecticides, pharmaceuticals, plastics, toxic chemicals, fertilizers, and pesticides.

Depending upon the application of industrial products their origin of water contamination can be categorized into centralized and distributed sources. Whereas a point-source contaminant, like a sewage discharge or outfall pipe, enters the water from a single conduit or channel.

So, whatever the source, all type of wastewater requires treatment before releasing it into the natural water body. Most commercial and industrial manufacturing plants strictly need to process their wastewater and recycle it, despite it many continuing to produce untreated wastewater. This leads to an issue of a rise in synthetic compounds in wastewater that is harmful to nature. To remove pollutants from wastewater, effective wastewater treatment solutions are mandatory.

What is Wastewater treatment?

The process of transforming wastewater or used water into water that may be safely released back into the environment is known as wastewater treatment. The methods and procedures utilized to clean up contaminated water are referred to as industrial wastewater treatment.

Conventional Ways of Wastewater Treatment

1. Primary (or Physical) Treatment: To remove any suspended sand particles from wastewater, a physical procedure (Sedimentation, Aeration, and Filtration) is used. Wastewater’s velocity is decreased to allow all of the suspended particles to fall to the ground as a result of gravity. The settling substance is referred to as sludge or bio soil.
2. Secondary (or Biological) Treatment: It is a biological process (Aerobic, Anaerobic, and Composing) that uses bacteria, algae, and microorganisms to take up the organic material in the wastewater. All of the organic contaminants are consumed by microbes, who then transform them into carbon dioxide, water, or energy for their further development or as byproducts.
3. Tertiary (or Chemical) Treatment: The pollutants or biological agents mostly pathogens that remain after secondary treatment are treated in tertiary treatment. Use of oxidizing agents like Chlorine liquid, Ozon gas, and UV rays, that kill most of the pathogen and make water free of pathogenic contamination. Through the employment of stronger and more sophisticated treatment systems, wastewater effluent is made even cleaner during this treatment process.

Conventional wastewater treatments eliminated major pollutants but they are unable to remove dissolved nutrients and toxic metals. This wastewater also contains nitrogen, phosphorus, ammonia, and bacteria. This often acts as a source of NPK contamination in a local water body. These pollutants lead to the eutrophication of waterbody once released into the environment which deteriorates the local water ecosystem.

Additionally, the traditional wastewater treatment method now has many drawbacks. Including increased chemical needs, high maintenance costs, sludge disposal issues, higher space and energy needs, and degradability issues. Therefore finding additional or even alternative options with conventional methods is very essential. 

Why Microalgae for Wastewater Treatment?

Credit: Euronews Next

In order to handle wastewater treatment ponds naturally and economically, natural methods like employing microalgae cultures are now being studied. In terms of its capacity to remove NPK nutrients, coliform bacteria, and heavy metals, the microalgal approach competes favorably with conventional treatments. Microalgae are so effective at absorbing pollutants that other bacterial species can’t do.  Microalgal species like Chlorella, Scenedesmus, Nannochloropsis, Phormedium, Botryococcus, Synechocystis, Spirogyra, etc., are well known for their effective wastewater treatment abilities.

Microalgae, serve as an indicator of water quality, with some strains proliferating in polluted water while others thrive in unpolluted water. Also, Algae can be used in wastewater treatment for a range of purposes. Some of these are used for the removal of coliform bacteria, reduction of both chemical and biochemical oxygen demand, and also removal of heavy metals.

Bio-treatment with microalgae is particularly attractive because of their photosynthetic capabilities, converting solar energy into useful biomasses and incorporating polluting NPK nutrients.   Wastewater treatment by microalgae generates biomass. It could be utilized for developing various other products, such as fertilizers and biofuels.