A water purification technology using pollutant-consuming alga shows the world a green way out of the water crisis.
According to UNICEF, around 4 billion people experience severe water scarcity for at least one month each year and over 2 billion people are living in countries where water supply is inadequate. At our current rate of water consumption, nearly half of the world’s population is projected to face water shortages by 2025. Without proper and stable access to safe and clean freshwater, inadequate sanitation can lead to the outbreak of various diseases including cholera and typhoid fever, among many other health threats.
Given these dire circumstances, scientists have been innovating water purification strategies in hopes of accommodating our ever-growing demand for freshwater. Presently, the most common methods to treat wastewater involve the use of chemicals or ultraviolet radiation to kill microorganisms or remove pollutants. However, these conventional techniques are limited in practice as the addition of chemical substances can be toxic to our health and most treatment facilities run on high energy. Fortunately, the rise of green technology in recent years has inspired the scientific community to devise cheaper, sustainable technologies.
In a collaborative study between researchers from India (Algae Research and Bioenergy Lab, Uttaranchal University; Faculty of Applied Sciences and Biotechnology, Shoolini University; and Department of Biotechnology, Dolphin (P.G.) Institute of Biomedical and Natural Sciences), Korea (Department of Environmental Engineering, The University of Seoul), and Russia (Joint Institute for High Temperatures of the Russian Academy of Sciences and Department of Environmental Monitoring and Forecasting, RUDN University), they have developed a new wastewater treatment technology based on algal bioremediation that can purify wastewater in an eco-friendly, self-sustaining, and cost-effective manner.
Algae has long been recognised as a promising agent to purify wastewater due to their ability to feed on nitrogen, carbon, phosphorous, and even heavy metals in water. When a high algal load is present in water bodies, other microorganisms, including bacteria, are forced to compete for nutrients and sunlight to survive, thus naturally lowering the number of bacteria present in the water.
With this in mind, the researchers led by Dr. Pankaj Kumar Chauhan from Shoolini University conducted a pilot-scale study to investigate a novel microalgal strain called Pseudochlorella pringsheimii. The team collected the algae from a natural pond and cultivated it in artificial tanks of raw urban wastewater which contained various heavy metal pollutants and antibiotic-resistant bacteria.
“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,” explained Dr. Chauhan.
After 14 days of cultivating the algae, the team proceeded to assess the water quality, the growth, and biochemical composition of Pseudochlorella pringsheimii, as well as the possibility of using the microalgae-treated water for fish farming. The team found extremely encouraging results as the cultivation of Pseudochlorella pringsheimii successfully improved the water quality by eradicating the heavy metals and harmful microorganisms.
According to Dr. Chauhan, “After the treatment, we observed that the levels of water pollution indicators such as chemical oxygen demand (COD), alkalinity, and hardness reduced by 83.2 per cent, 66.7 per cent, and 69.6 per cent, respectively. 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 these algae can be recycled for biofuel synthesis.”
To determine whether the treated wastewater could be used for fish farms, the team cultivated sucker fish in raw and treated wastewater and compared their growth rates through bodyweight measurements. In raw wastewater, no sucker fish was able to survive. In contrast, 84 per cent of the fish cultivated in the treated wastewater not only survived but also grew 47 per cent in bodyweight.
The remarkable success of this new technology has opened a new door in eco-friendly wastewater treatment research. Besides its powerful ability to reduce micropollutants and bacteria from urban wastewater, it also offers a platform for the reuse of treated water to cultivate fish with low cost. Dr. Chauhan believes that their microalgae-based bioremediation technique will pave the way for a greener and more sustainable future.
Source: Kumar et al. (2021). Algae-based sustainable approach for simultaneous removal of micropollutants, and bacteria from urban wastewater and its real-time reuse for aquaculture. Science of The Total Environment, 774, 14556.