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Study On Advanced Treatment Source Water In Shanghai By Combination Process Between PAC And Ultrafiltration

Posted on:2007-01-05Degree:DoctorType:Dissertation
Country:ChinaCandidate:M J FanFull Text:PDF
GTID:1102360242958283Subject:Municipal engineering
Abstract/Summary:PDF Full Text Request
With the serious pollution of drinking water resource, the conventional drinkingwater treatment processes can not meet the more stringent requirement of the drinkingwater quality standard. So it has been the most important research subject in thedrinking water treatment field to explore new drinking water treatment process.Ultra-filtration (UF) process was paid more and more attention because of the rapiddevelopment of membrane industry and its high removal efficiency to turbidity andvirus. UF technology was regarded as "water treatment technology in the 21stCentury". It was one of the optimal selections to alternate the conventional drinkingwater treatment processes. However, the dissolved organic matter removal efficiencywas very low in raw water by UF because of the high molecular weight cut-off of themembrane. So the UF membrane can be combined used with the coagulation orpowder activated carbon (PAC) to improve the organics removal effect. Theimprovement effect on organics removal by powder activated carbon and its influenceon the ultra-filtration membrane flux and resistance were the key research problems.The water from Huangpu River and Yangtze River, which were the twoimportant drinking water resources of shanghai, was used as the model samples in thispaper. The water purifying effect by conventional drinking water treatment processand PAC-UF combined process and the UF membrane flux variation were studied.The removal effect of the typical endocrine disruptors—atrazine by PAC-UFcombined process was also studied. The main conclusions were as follows accordingto the pilot-scale and small-scale experiments:To the raw water of Huangpu River, The removal ratio of CODMn,UV254 and TOCwas only 6.33%,4.1% and 8.0% respectively by UF membrane alone without thePAC dosage. The organic matter can be effectively removed by the dosage of PAC.The removal ratio of organics was increased with the increasing dosage of PAC, andthere was a liner relationship between them. When the PAC dosage was 22.0mg/L, theremoval ratio of CODMn and UV254 was 64.91%,49.27% respectively in the PAC-UFcombined process. The turbidity of effluent was below 0.15 NTU under all conditions in the combined process. When the PAC dosage was 20mg/L, the mutagenic activitywas greatly reduced.It was found for the first time to the raw water of Huangpu River that when thedosage of PAC was low(less than 10 mg/L), the increasing of PAC dosage did notcaused obvious reduction of the UF membrane flux. But when the dosage of PAC washigher than 20 mg/L, PAC would cause serious pollution to the membrane. Theadsorption resistance increased and the membrane flux decreased rapidly. So it wasnecessary to strengthen the pretreatment of the raw water in Huangpu River. Toguarantee the water quality of effluent and the stable running of the UF membrane,the concentration of organic matter must be decreased to some extent. However, itwas not the case with the raw water in Yangtze River. The optimal dosage of PAC wasthe 10 mg/L. There was no any influence of PAC on the UF membrane flux. ThePAC-UF combined process can be direly used without pretreatment.The PAC-UF combined process were firstly adopted in this paper to remove thetypical endocrine disruptors—atrazine. The removal effect,removal mechanism andinfluencing factors were studied. The removal ratio of atrazine in the pilot-scalePAC-UF system was very high. The concentration of biodegradable organic carbondecreased apparently. The biological characteristic was stable in the effluent. Theremoval ratio of atrazine in the small-scale PAC-UF system was also very high. Underthe PAC dosage of 20.0mg/L, the removal ratio of atrazine was 44.0%. Theconcentration of organic matter in the raw water would influence the removal effect ofatrazine.According to the raw water characteristic of Shanghai, the upper clarifier reactor(UCR) was used as the pretreatment process to the PAC-UF combined system. Tooptimize the removal effect and guarantee the stable running of the UF membrane,the running condition of UCR and the dosage point of PAC was altered. When thePAC dosage was 5.0mg/L in front of the UCR and the UF membrane, the ascendingflow velocity was of UCR was 4.0m/h and the sand filtration velocity was 8.0m/h, theoptimal organics removal effect was achieved. The removal ratio of CODMn andUV254 was 67.04 and 70.75% respectively.It was also found that the turbidity increased in the filtration effluent after the filtration backwashing. It is favorable to prevent the fouling of the UF membranewhen the PAC was dosed.The conventional drinking water treatment process was used with PAC-UFsystem in Wusong waterworks, which raw water came from Yangtze River. Thisprocess can effectively guarantee the quality of effluent water and the filtrationcharacteristic of UF membrane was quite stable. The concentration of organic matterin the effluent water decreased with the increasing of the PAC dosage. There was nooblivious influence of PAC on the UF membrane fooling. The increasing dosage ofPAC can make a better removal effect on CODMn,UV254 and DOC. However, whenthe dosage of PAC is higher than 10.0mg/L, the removal effect is not very good. Sothe optimal dosage of PAC should be 10.0mg/L.
Keywords/Search Tags:ultra-filtration, powder activated carbon, adsorption, membrane flux, drinking water, water source, atrazine
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