Characterization of membrane fouling in a microfiltration ceramic membrane system treating secondary effluent

Membrane filtration is one of the most promising technologies used for the advanced treatment of secondary effluents. Despite the number of fouling-control studies that have been conducted, membrane fouling remains a problem of utmost importance. In this study, pilot-scale ceramic microfiltration equipment was used to treat real secondary effluents from a wastewater treatment plant. Reversible fouling and irreversible fouling, which are defined based on backwashing, were characterized, and the effects of coagulation and membrane pore sizes on fouling evolution, as well as the composition of foulants, were also studied. The results showed that coagulation is an effective pretreatment for the control of microfiltration fouling, and that 5 mg aluminum per liter feed water is a cost-effective dosage for treatment. In terms of stable operating time and recovered water volume, the performance of the 0.1 μm ceramic membrane was the best. Results of pure water filtration experiments revealed that sodium hypochlorite solution washing recovered more flux than citric acid solution. The concept of a “trans-membrane pressure (TMP for short) turning point” was suggested as an operational signal for conducting membrane off-line chemical washing. After this point, both reversible and irreversible fouling increased drastically to maximum levels within a short span of time, resulting in difficulties in thoroughly cleaning the membrane.

► A pilot ceramic MF equipment was used to treat real secondary effluent from a wastewater treatment plant of Beijing.
► Effects of coagulation and membrane pore sizes on fouling evolution, and the composition of foulant were studied.
► Reversible fouling, irreversible fouling, and their interaction are characterized when treating real secondary effluent.
► A “TMP turning point” concept was suggested as an operational signal to conduct the membrane off-line chemical washing.