Investigation of co-digestion of food waste and primary sludge at SNJ-wastewater treatment

Master's thesis in Environmental TechnologyAnaerobic co-digestion of different organic waste streams, has proven to be a viable solution for sustainable management of organic fraction of waste, with increased everyday application. Besides the environmentally sound management of organic waste, it enables increased economical performances of employed anaerobic digesters worldwide by increasing the energy recovery from the process itself. A full scale experiments were conducted at SNJ wastewater treatment plant to evaluate the effect of co-digestion of food waste and sewage sludge. The pulse feed resulted, in temporary overload of the system, with sharp increase in the concentrations of acetic acid and consequently 27% increased methane production rate from. During the overload period system remain its stability. Monitoring parameters used during the test were pH, VFA , Alkalinity, COD, TS and TVS. Laboratory scale, batch test experiments were undertaken, to determine the specific methane yield of different substrates and mixtures of substrates currently used in the co-digestion process at SNJ wastewater treatment plant, as well as to determine maximum food to biomass ratio (gVS substrate/gVS biomass) that can be used for enhanced methane production without causing process perturbations. The blends of sewage sludge and food waste in different ratio showed enhanced cumulative methane production for 36 and 57 % respectively. Organic loading experiment showed that the optimal organic load (food to biomass) is in the range from 1.73~2.1gVS substrate per gVS biomass