In the wastewater treatment system, nutrient (mainly dissolved nitrogen and phosphorus) removal is an important step in treating wastewater. These nutrients stimulate the growth of unwanted aquatic macrophytes and lead to eutrophication when discharged into the environment. In addition, excessive nitrate concentrations in drinking water can cause methemoglobinemia, also known as “blue baby” disease. On the other hand, nitrogen is an essential compound for biological microorganisms, such as microalgae. Microorganisms convert nitrogen into ammonium, then into proteins, as part of their growth process.
Microalgae are photosynthetic microorganisms which uses chlorophyll to convert light energy into energy sources such as carbohydrates. The inner cell walls of microalgae constitute mainly of hemicellulose and cellulose, which can be hydrolyzed into sugar monomers and further fermented into bioethanol. In addition, microalgae can accumulate a large mass of lipids which can be processed into biodiesel via transesterification. The use of ionic liquids (IL) are favorable pre-treatments for nutrient extraction as the ILs are able to dissolve the lipids; leaving a lipid-rich liquid and carbohydrate-solid. This allows for extraction of both components after a simple phase separation process.