Study On The Treatment Efficiency Of Three Kinds Of Adsorbents Combined With MBR To Micro-pollutants

The pollution of surface water is worsening, conventional drinking water treatment processes can not satisfy people’s requirements to water quality. In order to deal with ammonia (NH3-N) and humic acid (HA) which are out of limits in micro-polluted water, the membrane bioreactor(MBR) with bentonite、 MBR with P-AC and MBR with anthracite are used to study the micro-polluted source water treatment. To find out the best dosage of bentonite/ P-AC /anthracite, these three combined processes were compared with the absorption of bentonite/ P-AC / anthracite to ammonia, UV254 and UV410. Under the best dosage of these three adsorbents, emphasis on analysising the waterquality indicators of three kinds of MBR combined processes in continuity test, such as ammonia, CODMn, UV254, UV410, membrane fouling situation and particle size distribution. The results are shown as followed:1. The adsorption capacity of three kinds of adsorbents to ammonia is weak. But the adsorption capacity of P-AC to UV254 and UV410 is rapid, stable and good. It can significantly improve the removal of MBR to UV254 and UV410. Both bentonite’s and anthracite’s adsorption to UV254, UV410 are not ideal. When they jointed the system of MBR, they can’t obviously enhance the removal capacity to UV254, UV410.2. In the running of MBR combined processes, the system achieved the best removal results to ammonia, CODMn, UV254, UV410, when the dosage were 1.5g/L bentonite,2g/L P-AC and 2g/L anthracite. The corresponding average removal rates were:92.00%,43.82%, 45.96%,47.45%; 93.21%,74.49%,86.25%,93.68%; 79.00%,47.31%,48.99%,68.27%. Their average particle sizes of residual contamination in treated water were 243.6nm, 122.8nm,284.6nm. Therefore, the P-AC+MBR combined process achieved the best removal result, the second one was bentonite+MBR combined process, and anthracite+MBR was the last one. The ultrafiltration membranes can effectively remove the the organisms whose size were bigger than 200nm.3. During the operation of bentonite+MBR, P-AC+MBR and anthracite+MBR, the fading period of MLSS were 25 days,27 days,21 days. Their corresponding average SVI in operation cycle were 6.65,6.84,6.62. The overall was at a low level. It meant the particles of activated sludge were fine, flocculation and sedimentation were poor. Poor nutrient hindered the growth of activated sludge, and caused the irreversible decline of MLS S.4. The membrane operation cycles of bentonite+MBR, P-AC+MBR, anthracite+MBR were 13d,18d,18d. P-AC and microbes can form a dense structure, a larger volume of microbial floc, so it can effectively delay membrane fouling and reduce the number of membrane cleaning. Dosing bentonite helped microbial particles size increase, but at the same time it also increased the risk of membrane clogging and the number of membrane cleaning. Anthracite and microorganisms didn’t improve the internal morphological structure of activated sludge, so there was no help to the delay membrane fouling.5. In the same running period, the degree of membrane fouling were:bentonite+ MBR> anthracite + MBR> P-AC + MBR. Physical cleaning, pickling, caustic made the membrane flux recover about 40%, 7.63%,10.45%. Organic pollution and cake layer were the main pollution source in the membrane module. In the running cycle prophase, small particulate matter was the main pollutant. With the extension of the running time, the membrane surface contaminants turned into massive particle. In the running cycle anaphase, the membrane surface accumulated a lot of massive dirt which made the membrane surface rough and formed a gel layer.