Based on the fascinating potential of algae to remove a large number of chemical pollutants and various bacteria from water, scientists have recently developed a new eco-friendly, sustainable, and cost-effective solution for urban wastewater treatment, and tested the utility of such treated water for pisciculture.

Our ever-growing demand for freshwater has caused its sources to diminish rapidly and scientists have been attempting to find strategies to purify wastewater for reuse to meet future demands. At present, the most common wastewater treatment techniques involve the use of chemicals or ultraviolet radiation to kill microorganisms or remove pollutants. But these conventional techniques have several drawbacks, such as the toxic effects of chemical substances on our health or the high energy requirements to run treatment facilities. To create a sustainable system of wastewater treatment, the focus has shifted to eco-friendly and cost-effective technologies.

One such technology under exploration involves using aquatic microorganisms, such as algae, which are known to be able to degrade complex molecules. Recently, a team of scientists led by Pankaj Kumar Chauhan from Shoolini University, India, have developed wastewater treatment technology based on algal bioremediation. Their study is published in Science of the Total Environment.

Algae rapidly cover water bodies with a green film or cause red tides, using the nitrogen, carbon, phosphorous or heavy metals present in water as nutrition. A high algal load in the water then creates competition for nutrients and sunlight with other microorganisms, causing a reduction in the number of bacteria present in the water. These are some of the properties that make algae promising wastewater purification agents. Added to these is the fact that they’re are eco-friendly, self-sustaining, and cost-effective as a wastewater treatment agent.

Chauhan explains the basis of the technology developed by his team. “We selected a novel microalgal strain Pseudochlorella pringsheimii because it can tolerate high pollutant load and can grow over a wide range of temperatures. Moreover, under conditions of stress, Pseudochlorella is known to accumulate high amounts of lipids in their cells, opening up the possibility of using this algal biomass for biofuel synthesis.”

For their experiments, the researchers collected the Pseudochlorella pringsheimii microalgae strain from a natural pond and cultivated it in artificial tanks of raw urban wastewater which contained various heavy metal pollutants and antibiotic-resistant bacteria. After 14 days of cultivation, they measured three parameters in these tanks: the water quality, and growth and biochemical composition of P. pringsheimii. They also assessed the possibility of using the microalgae-treated water for fish farming.

The findings of this pilot-scale study were encouraging. P. pringsheimii cultivation significantly improved the water quality by removing heavy metals and harmful microorganisms.

“After the treatment, we observed that the levels of water pollution indicators such as chemical oxygen demand, alkalinity and hardness reduced by 83.2%, 66.7% and 69.6%, respectively,:” says Chauhan. “Moreover, the algal growth naturally nearly eliminated the total bacteria and coliform in the water. We also saw a significant increase in the lipid content in wastewater-grown algal biomass in comparison to the algae grown in the control medium. This means that this algae can be recycled for biofuel synthesis.”

In addition, while no suckerfish survived in raw wastewater, in treated wastewater, 84% of them not only survived, but over 10 days, their bodyweight also increased by 47%.

This new technology is a success in eco-friendly wastewater treatment research and highlights the suitability of using treated water for low-cost fish cultivation. Chauhan says he’s is hopeful that the microalgae-based bioremediation technique will pave the way for a greener and more sustainable future.