A Pilot-scale Study Of Hybrid Membrane Bioreactor Applied To Municipal Wastewater Treatment

Aerobic MBR process, based on activated sludge process, with a high efficiency of biodegrade organic pollutants from wastewater and nitrification action but denitrification, so nitrogen and phosphor removal are not efficiently, in order to promote it, usually add pre-denitrification unit and wastewater and sludge refluence system, which result MBR purification system become complexity, long HRT and high power consumption. The research through increase fixed biomass by adding carrier into MBR to forming a particular Hybrid Membrane Bioreacter, which make suspended biomass and fixed biomass existed in the reactor simultaneously, both kinds of biomass play the roles of organic pollutant biodegradation and promote efficacy of phosphor and nitrogen removal, A pilot-scale study of HMBR was carried out in Xi'an Beishiqiao Wastewater Purification Center for municipal wastewater treatment, the performance of HMBR were mainly focused on biodegradation ability, the reuse feasibility of treated water and membrane fouling.Results showed that HMBR can enhance the efficiency of COD and NH3-N removal compare to CMBR with the same total biomass concentration; TN and TP removal rates were enhanced with the increasing of attach-biofilm concentration, In addition, to reduce TN and TP concentration of the effluent further, the thickness control of biolfilm is a key point.Long term experiment show that, the turbidity of filtrate was always lower than 0.5 NTU (average turbidity as 0.178 NTU), showing a remarkable SS removal by the HMBR. Regarding color, it ranged from 20 to 50 c.u. (average color as 28 c.u.) in the filtrate. The average COD removal by the HMBR was as high as 93.9%, resulting in a residual COD in the filtrate from 12.71 to 33.36 mg/L (average as 22.55 mg/L).These values of BOD, NH3-N, TN and TP are (96.95%,4.9-13.6mg/L,6.2mg/L), (98.8%,0.05-1.35mg/L,0.35mg/L), (56.05%,6.87-18.65mg/L,14.64mg/L) and (70.15%,0.13-3.26mg/L, 1.39mg/L) respectively. The removal efficiency of total coliform and total bacteria are 3-4 logs. With a post-disinfection process, it can meet the requirement of any municipal reuse purpose.With the detection of the HMBR system by electronic microscope periodically, a lot of zoogloea with filamentous bacteria as framework attached on sludge and biofilm, and filamentous bacteria can inhabit on the biofilm prior to the sludge, so the MLSS have a superior settle ability. The system also contains a lot of Protozoa and metazoa, by contrast, the species almost the same, but microbial multiformity and density in the biofilm is prior to MLSS, which can attribute to the biocarriers provide a harbor for the formation of biofilm, it elicit that biofilm played a key role in the wastewater biodegradation.Under the best operation conditions, the HMBR system worked 116 days in one cycle, it indicate that membrane fouling is slow in the system. Through the EPS detection and components of EPS analysis for MLSS, biofilm and sludge cake of membrane face, it is educed that HMBR system can retarding membrane fouling occurrence may be explained by the follwing reasons: the formation of attached-biofilm and its concentration increase reduced the concentration of suspended biomass relatively, so which can reduce the contact chance between membrane and EPS of MLSS.