Study On Biofilm Reactor With SCMT Media Treating Municipal Sewage

Today, the main problems faced with water treatment technics are stillincreasing efficiency and decreasing consumption of energy. But one of the mostkey to resolve these problems is intensifying mass transfer efficiency in thewater treatment process. Therefore in this paper starting with improving masstransfer efficiency of biofilm reactor, a new type of biofilm reactor withSelf-Circumrotate-Mass-Transfer(SCMT) media was designed, which gatheredsubmerged biofilters and moving bed biofilm reactors'advantages to a suit,which utilized this kind of new type SCMT media unique configuration tochange sewage fluid state and intensify mass transfer process in biofilmreactors.Material of SCMT media was plastic, which diameter of external ring was110mm, height was 10mm and its thickness was 3mm,which diameter ofinternal ring was 15mm,height was 20mm and its thickness was 3mm. Therewere 20 blades which length was 45mm, width was 15mm and thickness was0.8mm between the two rings. A surface area of media in the reactors is237.6m2/m3. The blades were connected with internal ring vertically and withexternal ring horizontally, and everyone rotated 90°as the same direction fromexternal ring to internal ring radially. Media were installed layer upon layervertically, their centers crossed an axle,and there was a 15mm interval betweentwo media so as to be fixed properly. The advantages of this kind of media liedin lightness, innocuity, no solution, and abrasion resistance, compress resistance,corrosion resistance, and good machinery function. Surfaces of them werepolished so as to growth of biofilms easily, and made media good absorption,which contributed to improve biomass in the reactor. Configuration of mediawas reasonable, which formed bigger surface area easily, and interspaces amongspiral blades could avoid clogging of media for shedding and renovation ofbiofilms normally. Furthermore unique configuration of media made mediacircumrotate by gas and liquid flows driving. So because of configuration andanomalistic surface, fluid state of gas and liquid changed when they passed bymedia. At the same time of media circumrotation, around which high confusedextent gas and liquid flows were formed, which improved mass transfer of gas,liquid and solid greatly.Moreover, pilot experiments of biofilm reactor with new type SCMT mediatreating municipal sewage were carried out in this paper. During initial stage, themixture in aerating tank of Changchun Secondary Sewage Treatment Plant wereused to be basic microbe for start-up growth of biofilms. Microbes werecultivated and domesticated according to routine sewage biodegradation way. Inorder to intensify growth of biofilms'efficiency the cultivation anddomestication were directly carried in the bilfilm reactor, namely that theseprocesses finished at the same time. Two months later since start-up, thicknessof biofilm reached to 1~2mm, and which attached firmly under the scrubing ofgas and liquid flows. Maximum MLSS of reactor is 6500mg/L and averageMLSS is at the range of 4800~5200mg/L during steady stage.On the experiment 5 influent grades were selected, respectively is 120L/h,150L/h, 200L/h, 300L/h and 450L/h, corresponding hydraulic retentiontime(HRT) is 2.5h, 2h, 1.5h, 1h and 0.67h. Five ratioes of air to water (3:1~7:1)was carried at every HRT, adding up to 25 conditions, which were studied effectof biofilm reactor with new type SCMT media treating municipal sewage. It wasfound that removal effect of CODCr and NH4 —N was well. On the best technicsparameters conditions, namely ratio of air to water(4:1) and HRT (1.5h), at therange of influent CODCr concentration (97.41~866mg/L) , NH4 —N +concentration(25.45~65.78mg/L), these two average effluent concentrationswere respectively 79.16mg/L and 17.50mg/L, which reached to State SecondaryDischarge Standard of municipal sewage treatment plant pollutants. Furthermore,in this work the influencing factors of biofilm reactor with SCMT media treatingmunicipal sewage were researched, and the results showed that HRT and ratio ofair to water influenced apparently on the effect of biofilm reactor treatment.Namely on the constant ratio of air to water, effluent CODCr and NH4 —N +concentrations decreased gradually in company with HRT increasing, yet thetwo concentrations decreased slowly along with HRT extending, at the same...