Research On Kitchen Waste Hydrolysis Products As External Carbon Source In The Treatment Of Domestic Wastewater

Nowadays, the treatment of food waste has become an importantenvironment issue. Food waste treated by anaerobic digestion generatesproducts full of volatile fatty acids (VFAs), and the food waste hydrolysisproducts can be applied as external carbon source for denitrification, whichcombines the disposal of food waste and nitrogen removal in the sewagetreatment plant. We investigated the denitrification efficiency of the food wastehydrolysis products and its applicability. The main achievements are as follows：Batch experiments were carried out to determine the denitrificationefficiency of2food waste hydrolysis products with various VFAs concentrationand component proportions. The VFAs concerntration, COD concerntration andammonia concerntration was34.6g/L,83.5g/L and505.5mg/L respectively forthe No.1food waste hydrolysis products, and45.0g/L,92.5g/L,1415mg/Lrespectively for the No.2food waste hydrolysis products. The results showedthat when the C/N ratio was4~6, the maximum specific denitrification rate was16.0~26.1mg NOx-N/(g VSS·h),13.1~25.0mg NOx-N/(g VSS·h) respectively，and the highest accumulation value12.76~15.50mg/L,14.43~18.01mg/Lrespectively for2hydrolysis products. Taking nitrogen and COD removal rateinto account, the suitable C/N was5~6for both of them. When using food wastehydrolysis products as external carbon source, the removal of nitrate occurred in2~3phases, and there were nitrite accumulation in the denitrifying process, withthe accumulated nitrite being reduced eventually. Food waste hydrolysisproducts brought some amount of ammonia into the reactor, but theconcentration was controllable. Compared with methanol, using food wastehydrolysis products as external carbon source had higer denitrification rate andneeded less C/N ratio, while the effluent COD were more likely to reachstandard. In comparison with sodium acetate, the denitrification rate of foodwaste hydrolysis products was a little bit low, but the cost could reducedsubstantially.Temperature was one of the main factors affecting the denitrification efficiency. The maximum specific denitrification rate was15.4~29.5mgNOx-N/(g VSS·h) when the temperature was15℃, C/N was4~7.5, and15.7~30.6mg NOx-N/(g VSS·h) for25℃, C/N was3~5.5. The resultsindicated that if the temperature dropped from25℃to15℃, in order to get thesame effect, the amount of hydrolysis products needed increased by36%~66%.Using food waste hydrolysis products as external carbon resource in thetreatment of domestic wastewater was proved, and C/N of4.3~8was the suitablerange. Compared with methanol, hydrolysis products denitrification efficiencyincreased by30%, and was in the same level with sodium acetate.Consequently, compared with traditional external carbon sources, foodwaste hydrolysis products has a good denitrification potential and economicperformance, showing great advantage in practical application.