[Culture conditions for heterotrophic nitrification-aerobic granular formation sludge]

Heterotrophic nitrification-aerobic granular sludge was successfully formed by batch culture method, with the heterotrophic nitrification bacteria with aerobic denitrification abilities as inoculants, and activated carbon powder as pre-immobilizer. The granulation conditions were studied. Results show that organic loading rate, wastewater characteristics, aeration rate and settling time play important roles in the sludge granulation. Heterotrophic nitrification-aerobic granular sludge can grow on both synthetic wastewater and piggery wastewater. Granulation occurred under the conditions of COD loading rate was 4.0 g x (L x d)(-1), NH4+ -N loading rate was 0.212 g x (L x d)(-1), aeration rate was 200 L x h(-1) and settling time was 2.0-4.0 min. Filamentous bacteria overgrowth was observed when the organic loading rate increasing with synthetic wastewater using glucose as sole carbon resource. It resulted worse settling and denitrification of the aerobic granular sludge. When piggery wastewater was used as influent, the filamentous bacteria were disappeared, better settling and denitrification of the aerobic granular sludge was regained and the granular sludge was grown up. The grown-up granular sludge showed good stability. And its removal rate of TN, NH4+ -N and COD were 84.75%-88.33%, over 99.9% and 97.29%-98.62% respectively when the granular sludge treat piggery wastewater with glucose as additional carbon resource under the loading rates of TN, NH4+ -N and COD were 0.409-0.474 g x (L x d)(-1), 0.285-0.304 g'(L'd)-'and 6.6-8.6 g'(L'd)-' respectively.