The evaluation of RO membrane performance with pretreatment membrane on municipal sewage treatment

In this research, to investigate totally the phenomenon of concentration and dilution in microfiltration membrane (MF)- reverse osmosis membrane (RO) hybrid process, it was operated for sewage with the change of variables such as temperature and TMP (trans-membrane pressure). MF modules were used directly without pretreatment and then MF permeate was sent to RO module. For evaluation of membrane fouling at a point of time, continuous process was conducted at a fixed temperature and TMP. With physical cleaning by air-stripping, permeate flux of MF module was decreased by the lapse of time. After 11 h, permeate flux in RO was decreased drastically and it implied the cleaning period of RO module. The removal efficiency of chemical oxygen demand (COD), T-N, T-P, total dissolved solid (TDS) and turbidity in RO module was observed high values over 94% regardless of the variations of temperature and TMP. It suggests that this system is very suitable for the treatment of sewage and the treated water is satisfied on environment standard. Turbidity was removed sufficiently in microfiltration modules and pH values were maintained under 6.5–8.1 range. In RO module, degree of concentration (DC) of COD, T-N, T-P and TDS was shown high values. T-N, T-P and TDS were shown very high DC values because of low removal efficiency in microfiltration modules.