A/O-MBR在冷轧含油废水处理中的应用

Application of A/O-MBR in cold-rolling oil wastewater treatment

在轧钢生产过程中,会产生大量的废水,这些废水如果直接排放,不仅污染环境,而且造成水资源严重浪费。用厌氧/好氧膜生物反应器(A/O-MBR)中试装置和自制聚偏氟乙烯(PVDF)内衬膜帘式组件,在南京某钢铁股份有限公司进行轧钢废水处理中试试验,实现轧钢废水的达标排放。试验结果得到,废水的浊度去除率在99%以上,化学需氧量(COD)去除率在90%以上,矿物油去除率在80%以上,产水的浊度、COD、油含量分别可以达到0.2 NTU、50 mg/L、4.5 mg/L以下。膜组件在亚临界通量下长期稳定运行至250 h左右时,跨膜压差(TMP)快速升高并达到极限30 kPa,膜组件达到极限。膜污染阻力分析试验计算得出膜污染的主要类型为滤饼层污染,这部分污染物通过简单水洗即可去除,另外有较大比例的膜孔堵塞污染,这部分污染物是构成不可逆污染的主要成分,也是试验后期TMP快速升高的主要原因。轧钢废水内含的矿物油加剧了膜污染,用低浓度NaClO周期性反洗后收获了良好的效果。

In the steel rolling production process,a considerable amount of wastewater is generated.Direct discharge of them would not only pollute the environment,but also cause a substantial waste of water resources.This study employed an anaerobic/aerobic-membrane bioreactor(A/O-MBR)pilot equipment and custom-made braid reinforced polyvinylidene difluoride(PVDF)membrane modules for steel rolling wastewater treatment at a steel company in Nanjing.The objective is compliant discharge of steel rolling wastewater.The experiment showed that the waste water treatment achieved a turbidity removal rate above 99%,a chemical oxygen demand(COD)removal rate over 90%,and a mineral oil removal rate above 80%.The treated water s turbidity,COD and oil contents were reduced to below 0.2 NTU,50 mg/L,and 4.5 mg/L,respectively.When operated stably below subcritical flux for about 250 hours,the transmembrane pressure difference(TMP)of the membrane modules increased rapidly and reacheded the limit of 30 kPa,indicating the upper threshold of membrane capacity.The analysis of membrane fouling resistance showed that the main fouling type was filter cake layer fouling,which could be removed by simple water washing.In addition,a significant proportion of membrane pore blockage fouling,greatly contributing to irreversible fouling and the rapid TMP increase in the later stage of the pilot test,was identified.The mineral oil content in steel rolling wastewater aggravated membrane fouling and optimal results were obtained after periodic backwashing with low-concentration of sodium hypochlorite.