中水回用装置膜污染分析与治理

Causes of Fouling of Membrane in Reclaimed Water Recycling Units and Countermeasures

大连石化公司中水回用装置采用"深度生化+混凝+气浮过滤(DAF)+超滤(UF)+二级反渗透(RO)+真空除气"的工艺路线,生产炼油化工装置使用的一级除盐水和循环冷却补充水。该中水回用装置随着运行周期延长,存在生化出水水质差、膜系统微生物污染严重、一级反渗透系统回收率高等问题。通过对预处理、有机物污染、微生物污染、颗粒和胶体污染、化学结垢等影响膜污堵的因素进行分析,提出了解决措施:对一期生化池进行改造,使其出水水质达到COD小于20mg/L、NH3-N小于3mg/L的要求;增加非氧化性杀菌剂投加设施,采取定期或连续地向膜系统投加非氧化性杀菌剂的措施;将一级反渗透系统阻垢剂(MDC151)的投加量控制在1～3mg/L,进水pH值控制在6.0～6.5,回收率从80%～82%降至75%～77%。

PetroChina Dalian Petrochemical Company adopts the process route of deep biochemical treatment＋ coagulation＋DAF＋UF＋secondary RO＋vacuum degassing for its reclaimed water recycling unit to produce primary desalting water and circulating cooling makeup water used in refining and chemical units.With the extension of its operational cycle,the reclaimed water recycling unit suffered some problems including deteriorated quality of effluent from biological treatment,serious microbe pollution in the membrane system and excessively high recycle rate of the primary RO system.By analyzing the factors affecting membrane fouling such as pretreatment,organic substance pollution,microbe pollution,granule and colloid pollution and chemical precipitation,the authors of the article propose solutions：upgrading the primary biochemical tank to reduce the concentration of COD in the effluent to below 20mg/L and that of NH3-N to below 3mg/L;adding non-oxidizing biocide dosing facilities to regularly or continuously feed non-oxidizing biocide to the membrane system ;con trolling the dosage of scale inhibitor（MDC151） to the primary RO system within the range of 1-3mg/L and the pH of feeding water within 6.0-6.5;reducing the recycle rate of the RO system to 75%-77% from 80%-82%.