Integrated wastewater management for sustainable agriculture operations using cyanobacteria

Abstract

Continuous rise in world population causes higher demands for food and agricultural resources in an unsustainable way. To ensure growth and access to safe food now and meet demands in future, sustainable and economically feasible measures are needed urgently. One of the major problems in agricultural operations is management of wastewater. Despite the enriched nutrient and embedded energy contents of agricultural wastewater, environmentally sound and economically feasible methods to reuse these sources are still not at desired levels. In this thesis research, cyanobacteria A. maxima was cultivated in chitosan pretreated manure wastewater in custom- made photobioreactors. With pretreatment, total nitrogen, total phosphorus, and chemical oxygen demand were removed by 84.8%, 92.7%, 64.1%, respectively, and with cyanobacteria by 14.6%, 5.6%, 28.8%, respectively. Overall removal of 99.4% of total nitrogen, 98.1% of total phosphorus, and 92.9% of chemical oxygen demand were achieved. For comprehensive evaluation of biofertilizer use of biomass, protein, carbohydrate, lipid, fatty acid methyl esters, vitamins, amino acids, and elemental composition were analyzed. Biomass had protein content of 41.8%, total carbohydrate of 27.3% and total lipid of 24.1%. Biomass also had significantly higher amounts of B vitamins and considerable amounts of free and bound amino acids, some of which are key indicators of biostimulant presence. The study aimed to evaluate the use of cyanobacteria for wastewater treatment and harvested biomass as biofertilizer for farm applications. Overall aim was to suggest a sustainable livestock and farm management option that can manage its waste and resources in a sustainable and economically feasible way.