Stabilizing the performance of ultrafiltration in filtering tertiary effluent—Technical choices and economic comparisons

The present study investigated technical choices controlling fouling development of a pressure-driven ultrafiltration (UF) pilot plant filtering tertiary effluent and its corresponding economical aspects. Experimental results showed that although fouling potential of tertiary effluent (treated by slow sand filtration) is much lower than that of secondary effluent, fouling is inevitable and is greatly impacted by the applied operational conditions. Under certain filtration flux and backwash interval the trans-membrane pressure (TMP) can be effectively controlled. Operated at high flux and extended backwash interval, a stable performance of UF can also be maintained using chemically enhanced backwash (CEBW). The test of three kinds of chemicals demonstrates that oxidants are suitable reagents with respect to present effluent quantity. Different reagents were used to clean the fouled membrane. Their effects on permeability recovery were compared in relation to fouling removal mechanisms. Based on the empirical results, the total cost of UF under suggested operational conditions was compared.

Research highlights▶ Fouling in ultrafiltration of tertiary effluent is inevitable. ▶ Sustainable operational condition mitigates fouling development. ▶ Chemically enhanced backwash is effective in fouling control. ▶ Effective cleaning of fouled membranes needs the cooperation effect of different chemicals. ▶ Economic comparisons are necessary in selecting operational conditions.