Study of anaerobic co-digestion on wastewater treatment sludge and food waste leachate using BMP test

Abstract

The study conducted basic component analyses including three component analyses, elementary analysis and heavy metal content and BMP test according to the mixing ratio for food waste leachate and wastewater treatment sludge(from brewery, dairy factory, bread factory, sewage sludge), and calculated biogas production speed using mathematical models. According to the elementary analysis of organic wastes, the C/N ratio, a major condition for anaerobic digestion, is 5.40–9.23, except for food waste leachate (FWL). Defined by Tchobanoglous’ mathematical biogas prediction model, methane gas and biogas productions increased, depending on the mixing rate of FWL. Furthermore, anaerobic digestion of both wastewater sludge and food waste leachate based on the correct mixing ratio, increases methane gas productions compared to digesting wastewater sludge alone. In other words, co-anaerobic digestion is more likely to realize biogasification than single anaerobic digestion. We mixed food waste leachate and wastewater treatment sludge by proportion of 1:9, 3:7, and 5:5, respectively. It turns out that they produced 118, 175, 223 CH₄ mL/g VS with the dairy factory, 176, 233, 263 CH₄mL/g VS with the brewery, 268, 300, 314 CH₄ mL/g VS with the bread factory and 233, 298, 344 CH₄-mL/g VS with the sewage sludge of methane gas. The result proposes that as the mixing rate of food waste leachate rises, the methane gas production increases as well. In the case of co-digestion of wastewater treatment sludge and food waste leachate based on the mixing ratio, more methane gas is produced compared to single digestion of wastewater treatment sludge. Modified Gompertz and exponential models describe the BMP test results that show how methane gas is produced from organic waste. According to the test, the higher the mixing rate of food waste leachate is, the higher the methane gas production is. The mixing ratio of food waste leachate which produces the largest volume of methane gas is 1:9 for the dairy and bread facilities and 3:7 for brewery and sewage sludge. Modified Gompertz and exponential models describe the test results very well. The correlation values (R ²) that show how close the results of model prediction and experiment are 0.920–0.996.