Effect of solid-liquid separation on food waste fermentation products as external carbon source for denitrification

Food waste fermentation products could be one of cost-effective organic products to replace marketable carbon source for denitrification, whereas the effects of simple separation on food waste fermentation products and its denitrification performance are limited. In this study, the effect of gauze separation on production of food waste fermentation products, denitrification performance, effluent characteristics and activated sludge characteristics were investigated. The total chemical oxygen demand of separated and unseparated fermentation products were 48.0 ± 7.7 g/L and 105.0 ± 11.6 g/L, respectively, and 32% of organic matters in fermentation liquid was in the form of small particles. Lactate and polysaccharide were the dominant organic components in two products. The total nitrogen removal efficiencies with sodium acetate, unseparated fermentation slurry or separated fermentation liquid were 94.8 ± 3.4%, 72.7 ± 7.4% and 88.6 ± 8.1%, respectively. Protein and specific ultraviolet absorbance (SUVA₂₅₄) in the denitrification reactor with separated fermentation liquid was about 2–4 times lower than unseparated fermentation slurry. Furthermore, Proteobacteria, which is related to denitrification, obviously increased in the denitrification reactor with separated fermentation liquid as carbon source. Therefore, gauze separation can be used to separate food waste fermentation products, and obtain reliable alternative carbon source.