城市污水处理厂污水处理工艺对VOCs挥发特征影响

对广州市某污水处理厂入厂原水进行了现场水样采集,用吹扫捕集-气相色谱质谱法测定了水样中VOCs含量.在污水处理厂入水口中共检出20种VOCs,浓度范围为0.1789~21.89μg/L.基于实测数据和构筑物结构参数,对该厂4种不同的污水处理工艺流程(包括A-B工艺,UNITANK工艺,改良A2/O脱氮除磷工艺和改良A2/O 高效沉淀工艺)利用WATER9模型计算了各工艺主要构筑物VOCs的挥发速率和挥发总量.挥发速率最大工艺为A-B工艺,其值为0.2318g/s;构筑物加盖的改良A2/O高效沉淀工艺挥发速率最小为0.0426g/s.各个工艺中挥发速率最大的单元有生物处理池和沉淀池,主要成分有苯、甲苯、三氯甲烷、四氯乙烯.根据VOCs挥发速率和污水处理量计算了VOCs在构筑物加盖和不加盖情况下的排放因子,并估算了珠江三角洲地区污水处理厂VOCs的总排放量,发现构筑物加盖可大大减少城市污水处理厂的排放率,削减率可达到74.72%.

Effects of treatment processes on the emission characteristics of volatile organic compounds(VOCs) in a municipal sewage treatment plant

Sewage treatment plant could be a potential exposure to volatile organic compounds (VOCs) in urban environment. Raw water samples were collected from the inlet of a municipal sewage treatment plant in Guangzhou and were analyzed by purge-trap concentrator and high-resolution gas chromatography coupled with mass spectrometry. 20individual compounds were discovered with a concentration ranged from approximately 0.1789 to 21.89mg/L in the inlet water. The emission rates and the total amount were calculated employing the model of WATER9 based on the measured data and units structural parameters. Among the four processes (A-B process, UNITANK processes, improved A2/O process concentrated on nitrogen and phosphorus removal, improved A2/O process with efficient sedimentation tank), A-B process had the highest emission rate of 0.2318g/s, while the covered A2/O process with efficient sedimentation tank had the lowest emission rate of 0.0426g/s. The biological tank and sedimentation tank were the two major units that contributed the largest VOCs emission in all the units and the most abundant VOCs consisted of Benzene, toluene, chloroform and tetrachloroethylene. The emission factors of covered and uncovered units were calculated by WATER9 model based on emission rates and sewage treatment amounts and VOCs emissions of sewage treatment plants in Pearl River Delta region were estimated as well, the results indicated that covered units will greatly reduce the amount of VOCs emissions with the reduction rate up to 74.72%.