Research On Start-up And Operation Of PVA Anaerobic Granular Sludge Reactor

Anaerobic microbial granulation and long-term retainment, considered as a key parameter for successful fast start-up and stable performance of anaerobic reactor. In order to solve the problem of fast cultivation of anaerobic granular sludge, whose self- immobilization is decided by many factors, lots of researches have been studied on facilitating anaerobic sludge granulation progress using bio-carriers.As PVA(Polyvinyl alcohol)-gel bead possesses the extremely similar physical property to that of natural granule, and meets the requirements of bio-carrier to promote the anaerobic granulation process. Therefore, promoting effect on formation of anaerobic granular sludge and operation performance of anaerobic reactor by PVA- gel bio-carriers with diameter of 5 mm was studied in this paper. The main research contents and conclusions are as follows:(1) Exploration of cultivation conditions of embryonic PVA granules: Inoculated with flocculent sludge, optimization of mixture volume ratio of sludge and PVA-gel bead was 2~2.5:1, and nutrients ratio of PVA granular sludge was 200:5:1.(2) Fast start- up and operation of PVA anaerobic granular sludge UASB reactor: During 14 days cultivation, embryonic PVA granules were obtained with mixture volume ratio of 2.5:1 and effluent recycling. 2#UASB reactor of 2.5 L was fast start- up inoculated with embryonic PVA granules. Over 26 days operation, well settling PVA granular sludge was obtained. Volume loading rate was reached up to 3.08 kg COD/(m3·d) with COD removal rate up to 93%. After 51 days operation, the volume loading rate was 24.00 kg COD/(m3·d), hydraulic retention time was reduced from 15.8 h to 4.8 h, COD removal rate kept stably at 94%. The formation time of anaerobic granular sludge was sharply shortened.(3) Fast start-up and operation of PVA anaerobic granular sludge EGSB reactor: EGSB reactor of 13.6 L was fast start- up inoculated with embryonic PVA granules. O ver 32 days cultivation, well settling PVA granular sludge was obtained. Volume loading rate was increased to 13.33 kg COD/(m3·d) with COD removal rate over 97%, and hydraulic retention time was reduced from 35 h to 8 h. After 42 days operation, volume loading rate reached up to 13.54 kg COD/(m3·d) with stable COD removal rate of 90%. Through SEM, filamentous, bacillus and coccus bacteria were found on the surface of PVA-gel beads, while filamentous bacteria in the interior.(4) Stable operation of EGSB reactor: PVA anaerobic granular sludge were inoculated, over 12 days operation, the COD removal rate reached up to 93%, volume loading rate was increased to 4.39 kg COD/(m3·d). Fast start- up of EGSB reactor was achieved. During 107 days continuous operation, hydraulic retention time was reduced from 21.3 h to 7.6 h, the volume loading rate, COD removal rate and gas production remained stably at 14.65 kg COD/(m3·d), 92%, 106.0 L/d, respectively.