Research On Volatile Fatty Acid Production From Anaerobic Hydrolysis Of Food Waste

Recently, the amount of food waste in China has rapidly increased. The mostcommon disposal method for food waste is moving it to a sanitary landfill. Whilescholars tend to seek more cost-effective and environmentally friendly technologies forthe treatment of food waste due to the shortcomings of landfill such as the release ofgreenhouse gasses and the occupation of land. Food waste can be treated by anaerobicdigestion and volatile fatty acid (VFA) is produced, which can be used as a carbonsource in biological nutrient removal (BNR) processes. The influences of differentfactors on VFA production during the process of anaerobic hydrolysis and acidogenesisof food waste were studied. The main results are as follows:The effects of pH, temperature, and time on the VFA production have beendetermined in batch experiments. The change of VFA concentration, VFA composition,Soluble chemical oxygen demand (SCOD), ammonia nitrogen (NH4+-N), PO43--P,Volatile solids (VS) were investigated. The results showed that when the pH wascontrolled at6, the VFA concentration, VFA yield and VFA conversion rate were highestamong all the pHs, and were39.46g/L,0.316gVFA/gVSfedand0.471gVFA/gVSremoved,respectively. The anaerobic acidogenesis of food waste was best at45°C, but thedifferences compared to35°C were slight. Considering that more energy is consumed tocontrol the temperature at45°C, thus a more efficient and economical temperature forVFA production is35°C. The VFA concentration, VFA yield and VFA conversion ratewere highest at68thhour at pH6.0at35°C. The values of SCOD/NH4+-N andSCOD/PO43--P were70and493, were much higher than the corresponding values ofwaste water to be treated, thus it does not increase the burden of nitrogen andphosphorus removal system.Batch experiments were carried out to determine the effect of initial total solids(TS) concentration on the VFA production of food waste. The VFA concentrationincreased as initial TS increased, however, the change was very slight between TSconcentrations of100g/L to130g/L. The VFA yield and VFA conversion ratedecreased as initial TS increased. The optimum initial TS concentration was100g/L.The impact of inoculum amount on VFA production was very small. Experiments were carried out to determine the effect of organic loading rate (OLR)on the VFA production of food waste in a semi-continuous mode (once a day feedingand drawing off). The pH, temperatue and hydraulic retention time (HRT) were6.0,35°C and5d, respectively. The concentrations of VFA, SCOD, and NH4+-N increasedwith increasing OLR, while too high OLR will lead to the failure of the reactor.Therefore, an OLR of11gTS/(L d) is suitable for VFA production.The technology of “anaerobic acidogenesis of food waste” can be operated easilyand with a good treatment effect. The high concentration of VFA produced can be usedas a carbon source in BNR processes, and solves the problem of high operation cost andhigh high toxicity when methanol is used as carbon source. Meanwhile, it achieve thequantitative reduction, resources recovery and harmless of food waste.