Study On Treatment Of Polluted River Water With Continuous Flow A/O Biofilm

In this study, the suspended and combined packing （model NO.ZH） was addedinto the Pre-A/O process and become an A/O biofilm system, with the observation ofHRT、DO、C/N and temperature on the treatment effect of A/O biofilm systemtreating the polluted river water, also, several packing dosing rate and packing groupon the treatment efficiency. This study employs three sets of A/O biofilm systems, thefirst system （1^#） which dosing the combined packing and30%suspended packing intothe anoxic and aerobic reactors respectively; the second system （2^#） which bothadding the combined packing into the anoxic and aerobic reactors; the last one （3^#）which both adding50%suspended packing into the anoxic and aerobic reactors.Specific objectives of the research were to investigate the effect of changing theoperation conditions on the CODcrremoval, nitrate removal, ammonia nitrogen andtotal nitrogen removal.The conclusions can be summaried as follows:（1） A/O biofilm system forms the biofilm under the condition of inoculation sludge. Inthe early stage of biofilm formation, the combined packing has a better biofilmformation than the suspended packing, and obout operation of one month, the removalefficiency on CODcrand NH₄-N in the systems of1^#,2^#and3^#for aerobic operationwere91.0%,85%,96%and74.7%,82.2%,87.6%, respectively. After the formationof biofilm, combining the anoxic and aerobic reactors with the domestication ofpolluted river water, the removal efficiency of system was ups and downs, the seriousbiofilm drop and the bad effluent quality were achieved. After operation of two weeks,the systems operate stably（2） With the observation of the removal efficiency for nitrogen in the three sets ofsystems, we found that system of3^#achieved a better treatment effect for nitrogen,which observed80%removal on the ammonia nitrogen （NH₄-N） and84.5%removalon the nitrate nitrogen. （3） The nitrate nitrogen removal was greatly affected by hydraulic retention time（HRT）. When the HRT was9.98h, the three sets of systems achieved a bad nitratenitrogen effluent quality, which even observed outlet water had greater nitratenitrogen concentration. When the HRT dropped to the6.5h, the outlet water nitratenitrogen concentration was1mg/L below and achieved70%removal. There was nosimple trend of increase or decrease in three sets of systems on COD and ammoniaremoval rate, which could achieve60%ammonia nitrogen removal and80%CODcrremoval.（4） The adition of biological mass was achieved by adding suspended packing into theanaerobic reactor of3^#system, and the DO concentration range was1⁴mg/L and0.8¹.3mg/L respectively. DO concentration in the anoxic reator within system of3^#had great effect on the nitrate nitrogen and total nitrogen. When the DO concentrationvaried around1⁴mg/L, the average nitrate nitrogen and total nitrogen removals were25%and29.5%respectively. When the DO concentration decreased into range of0.8¹.3mg/L, the minimum effluent concentration of0.23mg/L was observed with the92%removal; also the total nitrogen removal was enhanced by135%and improved to69.2%.（5） The rate of carbon to nitrogen vary with the organic matter concentration whichwas increased by addition of glucose into the polluted river. The rate of COD to totalnitrogen had great effect on COD, the nitrate nitrogen and total nitrogen. With the rateof COD to total nitrogen increasing, the trend for COD removal first rise to be morestable. The COD removals in the three sets of systems were determined about80%,the minimum total nitrogen effluent concen-tration was achieved in the system of3^#with the total nitrogen removal of above85%.（6） Because of the variety of temperature with the season, the study was divided intothree sections for observation of temperature on the COD、ammonia nitrogen andnitrate nitrogen removals. The first section was from May22011to june2,2011andthe inlet temperature was22℃; the second section was from October1,2011toNovember7,2011and the inlet temperature was16℃; the last section was from November8,2011to December25,2011and the inlet temperature was4℃. The inlettemperature had little effect on the COD and ammonia nitrogen removals, when theinlet temperature dropped to4℃, above60%COD removal was also observed withinthe three sets of systems. In the temperature of4℃, the ammonia nitrogen removalswere around60%in the systems of1^#and2^#and70%in the system of3^#. Because ofthe very low organic matter concentration, the sets of systems achieved15%nitratenitrogen removal under the condition of higher temperature （16℃）. The nitratenitrogen removal was obviously improved by adding the glucose into the inlet waterfor increasing the C/N in the three sets of systems. In the low temperature condition of4℃, the nitrate nitrogen removal of52.9%,59.8%and73.1%were observed withinsystems of1^#,2^#and3^#respectively.（7）The nitrification activities are higher than the nitrosation activities withinsystems of1^#,2^#and3^#, which shows no obvious accumulation of nitrite nitrogen.The denitrification activities vary obviously with the change of pH value, and thedenitrification activities are the largest in system of1^#and3^#at pH value of7.5. Thedenitrification activity which is the best at pH value of6.5follows lower with risingin system of2^#.