| This dissertation is a component of the key project 'Study on the recycling and reuse of water resources for the arid and water-deficient area in west China' founded by National Natural Science Foundation of China (NSFC). A hybrid submerged membrane bioreactor (HSMBR) was devised for municipal wastewater treatment and reuse, combining both suspended growth-activated sludge and attached growth-biofilm in one bioreactor by adding suspended carriers into the mixed suspension, a submerged MF membrane module was equipped in the bioreactor for solid/liquid separation.The comparison of treated effects between hybrid bioreactor (HBR) and conventional activated sludge bioreactor (CAS) was analyzed. The properties of the HSMBR process for municipal wastewater treatment and reuse was studied, the coefficient of maintenance, E, and the theoretical conversion (sludge) yield, y, were therefore calculated on the basis of the maintenance energy of bacteria in growing cultures. In addition, the microorganism characteristics and these simultaneous nitrification and denitrification were studied, and the kinetics was described mathematically. The controlling parameters on membrane fouling were detected experimentally. Finally, the primary cost analysis of membrane bioreactor for wastewater treatment was evaluated. The main results of this study are as follows:1. The efficiencies of HBR and CAS for wastewater treatment were compared at parallel operational conditions. The experimental results showed that the color, COD, TOC and NH3-N of effluent in HBR system were lower than that in CAS system as well as increased organics removal and shock loading rate, marked nitrification. The attached growth-biofilm in HBR system can improved the disadvantages caused by sludge expansion and poor settlement, with the result of good operational stability in HBR process. According to the aerobic HBR system, the SOUR can reflects the extent of microbial viability and activity and the SOUR can be related to the equilibrium substrate concentration similar to the classical Monod equation. The biofilm plays a main role in biodegradation comparison with activated sludge.2. The HSMBR process was experimented for municipal wastewater treatment in Xi'an Beishiqiao Wastewater Purification Center. The results show that, the filtrate turbidity was always lower than 1 NTU (average turbidity as 0.59 NTU), showing a remarkable SS removal by the HSMBR. Regarding color, it ranged from 9 to 39 c.u. (average color as 30 c.u.) in the filtrate. The average COD removal by the HSMBR was as high as 95.5%, resulting in a residual COD in the filtrate from 6.0 to 22.8 mg/L (average as 14.5 mg/L). The disinfection of membrane achieved 3-4log removal of F. coliform. This meets the requirement for any reuse purpose with the post-disinfection process. Taking into account the particular conditions imposed by the HSMBR, the kinetics was inspired by works of Pirt's maintenance energy of bacteria, and help to arrive at two parameters, named E and y, which represent the coefficient of maintenance and the theoretical conversion yield, respectively. The calculated results indicated that E=0.0285mgCOD/mgTB.h and y=0.129mgTB/mgCOD. The conclusion can be obtained that the HSMBR process was able to adapt the changes of influent quality and quantity owing to the two smaller values than that of activated sludge MBR process.3. The characteristics of microorganism in HSMBR process were detected periodically by electronic microscope. It can be seen that the bacteria containing zoogloea and filamentous bacteria attached sludge and biofilm, and filamentous bacteria can inhabit on the biofilm prior to the sludge. The biofilm played a key role in the wastewater purification, which the microbial multiformity on attached growth was more rich than on suspended growth. The scanning electronic microscope (SEM) images showed that the biofilm flocs structures were dense compared with sludge flocs, and two flocs were consist of most micrococcus and bacterium. The quantity of micrococcus on biofilm was als...
|
PDF Full Text Request