Fermentation Liquid Of Food-waste As The Carbon Source For Nitrogen Removal In Wastewater Treatment

Shortage of carbon source is prevalent in the sewage treatment process which lead to high nitrogen concentration in effluent, therefore many organics such as acetic, glucose and industrial wastewater were reported to be used as external carbon sources to enhance denitrification efficiency. Food-waste account for large proportion of municipal solid waste, and readily biodegradable substrates such as volatile fatty acids(VFA), and lactic acid produced in anaerobic fermentation of food-waste, but the application of fermentation liquid of food waste was rarely reported. So the selection of fermentation parameters and the application of fermentation liquid for nitrogen removal were studied in this paper. The main results are as follows:The effects of initial substrate concentration and temperature on fermentation products were studied, and the optimum operational conditions(TS=13%, 25℃) were selected due to the highest acidification rate. Carbohydrate, lactic acid, VFAs, protein are main components in fermentation liquid, which account 50%, 17%, 11%, 6% of SCOD(66.9g/L) respectively, afterwards the denitrification potential of complex carbon source was also proved.Nitrate uptake ratio(NUR) batch experiments were carried out to evaluate the denitrification performance of fermentation liquid and in comparison with sodium acetate and glucose, and find the optimum COD/N that fermentation liquid(6.5), glucose(10.7), acetate(4.0). Kinetic equations were used to simulate each phase of dinitrification with COD/N=5.0, results showed that NUR achieved to 7.44 mg NOX--N·(g VSS·h)-1 at the Ss metabolic phase for food-waste. And specific denitrification rate of food-waste was 0.77 times of sodium acetate and 2.1 times of glucose. So food-waste can be classified into readily organic substances.By comparison with sodium acetate, the influence of fermentation liquid of food-waste on nitrogen removal of SBR whose inflow was campus domestic sewage was investigated, and batch experiments were carried out to find the changes of KLa and OUR under different carbon source dosage. It was found that, NH4+-N concentration rose slightly when food-waste was added, and sodium acetate had no significant impact on NH4+-N remove rate; saturated DO and KLa declined with the increase of food-waste and acetate dosing quantity, food-waste had a less influence on oxygen transfer ability than acetate. DO could be maintained at 6mg/L which met the demand of nitrification when food-waste concentration was 300mg/L COD. OUR of food-waste was 25.1% smaller than acetate,while 52.3% smaller at the AOB Oxygen uptake phase. It indicated that the addition of food-waste affected the activity of nitrobacteria especially AOB.