污泥脱水液回流对引江水超滤处理工艺的影响分析

Analysis of Impact of Dewatered Sludge Filtrates on UF Treatment Process for River Raw Water

水厂排泥水处理过程中会产生较大量的污泥脱水液。为避免南水北调引江水资源的浪费,同时积极推进水厂的“零排放”建设目标,面向以引江水为水源的超滤处理工艺,评价了将污泥脱水液回流至原水池进行稀释回用的可行性。考察了不同污泥脱水液/引江原水混合比例下超滤系统的运行特性,发现当污泥脱水液适当稀释后,其对超滤净水效果和膜污染的影响急剧降低,当稀释比例达到1∶800时,出水水质与跨膜压增长曲线已接近引江原水直接超滤的情况。试验中引江原水的跨膜压增长速率为19.7 k Pa/d,而污泥脱水液原液则达到25.8 k Pa/d。当两者以1∶800比例稀释后,跨膜压增长速率下降为21.3 k Pa/d,接近于引江原水。膜表面微观表征结果显示随着稀释比例的提高,滤饼层厚度、溶解性有机物、特征官能团红外峰强、污染元素相对质量分数均显著降低,逐渐下降到与原水直接超滤相近的水平。引江原水组的超滤膜滤饼层厚度为1.77μm,而污泥脱水液原液组的滤饼层厚度为4.00μm,污染程度较重。两者按1∶800比例稀释后的滤饼层厚度降低至1.82μm,污染程度显著降低。研究结果可为南水北调受水城市超滤水厂的“零排放”建设提供参考。但值得注意的是,污泥脱水液的合理处置与利用问题目前仍处于起步和探索阶段,未来仍需从水质生物安全性和化学安全性的角度加以系统评估。同时可考虑氧化、吸附、微滤分离等预处理手段,以提高污泥脱水液回用过程的安全性。

A large amount of dewatered sludge filtrates is produced during the sludge treatment in water treatment plant(WTP).In order to avoid the waste of the river raw water in the South-to-North water diversion project,and actively promote the"zero discharge"construction goal of the WTP,the feasibility of recycling the sludge dewatering liquid to the raw water pool for dilution and reuse was evaluated towards the ultrafiltration(UF)using river water as the resource.The operation characteristics of the UF membrane under different sludge dewatering liquid/river raw water mixing ratio were investigated.It was found that when the sludge dewatering liquid was properly diluted,its influence on the UF effluent water qualities and membrane fouling was sharply reduced.When the dilution ratio reached to 1∶800,the effluent water quality and transmembrane pressure growth curve was close to the situation of direct UF of river raw water.In this test,transmembrane pressure growth rate of river raw water was 19.7 kPa/d,while the sludge dewatering liquid reached 25.8 kPa/d.When the two diluted at the ratio of 1∶800,the transmembrane pressure growth rate decreased to 21.3 kPa/d,which was close to river raw water were 21.3 kPa/d,which was close to river raw water.The characterization results of membrane surface showed that with the increase of dilution ratio,the thickness of cake layer,dissolved organic matter in cake layer,the infrared peak intensity of characteristic functional groups,and the relative mass fraction of fouling elements were decreased significantly,and gradually dropped to a level similar to that of direct UF of raw water.The thickness of ultrafiltration membrane cake layer in raw water group was 1.77μm,while the thickness of cake layer in sludge dewatering liquid group was 4.00μm,and the pollution degree was heavier.The thickness of the cake layer was reduced to 1.82μm after the two were diluted at the ratio of 1∶800,and the pollution degree was significantly reduced.The research results can provide reference for the"zero discharge"construction of ultrafiltration WTP in cities receiving water from the South-to-North water diversion project.However,it is worth noting that the rational disposal and utilization of sludge dewatering liquidis still in the initial and exploratory stage,and it needs to be systematically evaluated from the perspective of water quality biosafety and chemical safety in the future.At the same time,pretreatment methods such as oxidation,adsorption and microfiltration separation can be considered to improve the safety of sludge dewatering liquid reuse process.