某电厂废水零排放系统污堵分析

Membrane fouling analysis for zero liquid discharge treatment system in a power plant

某电厂采用“两级软化澄清+介质过滤+超滤+纳滤+反渗透”组合工艺处理循环水排污水,采用“化学软化+管式微滤+纳滤+海水淡化反渗透+电渗析+蒸发结晶”组合工艺处理末端废水,以实现全厂废水“零排放”。工程投运1年后,循环水处理系统出现纳滤出力不足,末端废水处理系统存在微滤膜有机污堵严重、电渗析硅结垢等问题。分析了膜污堵原因,对脱硫工艺用水进行了优化,从源头降低了脱硫废水化学需氧量(COD);同时优化了微滤运行方式,从而减缓了微滤有机污堵现象;此外,调整了循环水反渗透浓水处理方式,将全硅质量浓度降至1 mg/L以下后再进入电渗析设备,解决了电渗析硅结垢的问题。

In order to realize zero liquid discharge, a power plant treated circulating wastewater by the combination process of two stage softening and clarification, media filtration, ultrafiltration, nanofiltration(NF) and reverse osmosis(RO), and treated terminal wastewater by the combination process of chemical softening, tubular microfiltration(MF), NF, seawater desalination reverse osmosis, electrodialysis(ED) and evaporative crystallization. After the above measures were taken for 1 year, insufficient NF output was found in the circulating wastewater treatment system, and serious MF membrane organic fouling and ED silicon scaling was observed in the terminal wastewater treatment system. Thus, the causes of the membrane fouling was analyzed and the desulfurization process water was optimized to reduce the chemical oxygen demand(COD) of desulfurization wastewater from the source. Moreover, the MF operation mode was optimized, so as to slow down the MF organic pollution phenomenon. In addition, the RO concentrated water of circulating water treatment mode was adjusted,and the total silicon mass concentration was reduced to less than 1 mg/L before being fed into the ED equipment,to solve the problem of the ED silicon scaling.