ACID FERMENTATION OF FOOD WASTE LECAHTE FOR ON-SITE PRODUCTION OF DENITRIFICATION CARBON SOURCE

Abstract

Nowadays, climate change is globally faced crisis. Consequently, as a carbon neutral new renewable energy source has a lot of attention. Therefore, anaerobic digestion is caught renewed interest as the method of disposing organic waste and water and producing energy. Also, Acidogenic fermentation of organic waste (sewage sludge, food waste, animal manure and so on) can give a desirable selection for sustainable, eco-friendly and economic production of volatile fatty acids (VFAs), that have many industrial applications (bioplastic, biofuel, biochemical). This study investigated the simultaneous effects of hydraulic retention time (HRT) and pH on the fermentative production of VFA from food waste leachate using response surface analysis. The response surface approximations (R2 = 0.895, p < 0.05) revealed that pH has a dominant effect on the specific VFA production (PTVFA) within the explored space (1–4 day HRT, pH 4.5–6.5), with HRT being poorly correlated with the PTVFA response. The independent variables shared a weak interdependence, and the maximum response was estimated to be 0.26 g total VFAs/g COD at 2.14-day HRT and pH 6.44. The maximum response was experimentally validated by running triplicate reactors under the estimated optimum conditions, and a comparable PTVFA value (0.28 g total VFAs/g COD) to the model prediction was observed. The mixture of the filtrates recovered from these reactors was further tested as an alternative carbon source for denitrification, among the most practical applications of waste-derived VFAs. The fermentation filtrate demonstrated superior denitrification potential, in terms of reaction rate and lag length for nitrogen removal, to other carbon sources including acetate and methanol most commonly used in practice. Overall, the outcomes of this study provide useful information for better design and control of continuous fermentation processes for producing waste-derived VFAs. This potential may have practical implications, for example, in providing a sustainable alternative to expensive carbon sources conventionally used for denitrification.