Startup And Operation Of A~2/O Process For Municipal Wastewater Treatment

Rapid and high efficient startup of activated sludge process is the important content in operation and management of Waste Water Treatment Plant. Raw sewage was introduced then allowing sludge to develop naturally, which was studied in a pilot plant with anaerobic-anoxic-oxic (A2/O) process. The influent used in this study is that with and without sedimentation of municipal wastewater. The startup conditions and effects have been investigated. Then the removal of carbon, nitrogen and phosphorus was discussed when some parameters (the volume ratio of anaerobic tank, the ratio of Hydraulic Retention Time (HRT) in anoxic tank, oxic tank and anaerobic tank.) changed in A2/O system. The main results and conclusions are as follows.(1) After 20 days, the concentration of Mixed Liquor Suspended Solid (MLSS) in aeration tank was 500mg/L less than that in aeration tank of conventional activated sludge system when pre-settled municipal wastewater was used as the influent. However, the concentration of MLSS was above 3000mg/L in aeration tank after the system had been cultivated by without sedimentation for 15 days. The rapid startup of activated sludge system can be achieved by without sedimentation of municipal wastewater.(2) The concentration of MLSS was less than 1000mg/L at the beginning of the cultivation stage. However, cultivation process could be accelerated when 30～50mg/L PAC and 3mg/L PAM were added, which stimulate the sludge flocculation and sedimentation in aeration tank. This strategy can avoid the sludge loss with supernatant at the beginning of startup.(3) When the volume ratio of A/A/O was changed from 1:2:7 to 2:3:4, at the same time, the HRT of anaerobic tank prolonged from one hour to 2.1 hours. The concentration of PO43--P raised from 4.45mg/l to 8.47mg/L, the amount of denitrifying phosphorus accumulation raised from 0.93mg/L to 4.87mg/L. The amount of denitrifying phosphorus accumulation accounted for 64.2% of the total phosphorus accumulation. The removal rate of total phosphorus (TP) increased from 33.6% to 56%. It showed that the biological phosphorus removal was enhanced with this volume adjustment.