In recent years, with the overuse of traditional fossil fuels, humanity is facing multiple crises of global warming, water pollution and energy shortages. On March 23, 2021, the United Nations released the World Water Development Report warning that climate change will affect the availability, quality and volume of water needed to meet basic human needs, thereby undermining the basic rights of billions of people to safe drinking water and sanitation, calling on countries to make more concrete commitments to address this challenge. In order to reduce environmental and energy stress, the search for a pollutant-to-energy conversion technology that allows for clean energy production alongside wastewater treatment is urgent. [1]
With the rapid development of China's economy after the reform and opening up, the level of urbanization has been increasing, and the amount of domestic wastewater, industrial wastewater and runoff wastewater discharged within China's cities has increased, and its composition is complex, containing not only a large amount of N, P and other nutrients in domestic wastewater, but also a small amount of toxic and harmful substances in industrial wastewater.
(1) If wastewater is discharged directly into canals, rivers, lakes, oceans and ground without treatment, it will not only pollute the fresh water in these waters, but also contaminate surface water and groundwater.
(2) Some highly toxic and polluting pollutants can directly lead to the death or even extinction of fish or aquatic plants.
(3) Wastewater will also infiltrate into the ground, polluting groundwater and surface water, and even directly polluting people's drinking water, posing a threat to human health and causing various human diseases and deaths in serious cases.
(4) Wastewater infiltration into the soil will contaminate the soil, resulting in excessive soil metals, affecting the growth of crops, plants, microorganisms, chemical wastewater also carries a certain irritating odor, polluting the air.
(5) The toxic and harmful substances in the wastewater stay in animals, organisms and plant bodies, which will be absorbed by them as nutrients and eventually enter the human body through the food chain, posing a threat to human health. [2]
Traditional municipal wastewater treatment mostly uses two independent processes to remove nitrogen and phosphorus. Nitrogen and phosphorus emissions often exceed the standard, and the eutrophication of water bodies has increased. At present, the conventional secondary wastewater treatment process can remove most of the organic pollutants, but the removal of nitrogen and phosphorus is poor; chemical methods can form precipitation with pollutants through aluminum or iron salts to achieve better removal efficiency, but the cost of chemicals is high, and the formation of a large number of chemical sludge is difficult to deal with.
Unlike traditional wastewater treatment, microalgae can absorb nitrogen and phosphorus nutrients from wastewater during growth, which has great advantages in wastewater nitrogen and phosphorus removal. Although the high cost of recovering microalgae after wastewater culture greatly limits the application of this technology, we designed the alginate nanoalgae sphere encapsulation technology to largely reduce the recovery cost and the risk of microalgae leakage. At the same time, microalgae fix inorganic carbon and reproduce rapidly by themselves to convert inorganic carbon into organic matter, and the harvested algae can be used to produce high-value products such as biodiesel and algal protein, which has a promising utilization. [3] Based on microalgae treatment of wastewater, not only can we realize the harmless treatment of wastewater, but also consider the resourcefulness property of wastewater and use the nutrient elements in wastewater to produce high-value products of microalgae.
Hoping to take care of our common environment through this small but subtle system, we are committed to making the world a better place！
