Advanced treatment of real grey water by SBR followed by ultrafiltration-performance and fouling behavior

Grey water has been identified as a potential source of water in a number of applications e.g., toilet flushing, laundering in first rinsing, floor cleaning, and irrigation. The major obstacle to the reuse of grey water relates to pathogens, nutrients, and organic matter found in grey water. Therefore, much effort has been put to treat grey water, in order to yield high-quality water deprived of bacteria and with an appropriate value in a wide range of quality parameters (Total Organic Carbon (TOC), nitrate, phosphate, ammonium, pH, and absorbance), similar to the values for tap water. The aim of this study was to treat the real grey water, and turn it into high-quality, safe water. For this purpose, the real grey water was treated by means of a sequential biological reactor (SBR) followed by ultrafiltration. Initially, grey water was treated in a laboratory SBR reactor with a capacity of 3 L, operated in a 24 h cycle. Then, SBR effluent was purified in a cross-flow ultrafiltration setup. Treatment efficiency in SBR and ultrafiltration was assessed using extended physicochemical and microbiological analyses (pH, conductivity, color, absorbance, Chemical Oxygen Demand (COD), Biological Oxygen Demand (BOD₅), nitrate, phosphate, ammonium, total nitrogen, phenol index, nonionic and anionic surfactants, TOC, Escherichia coli, and enterococci). Additionally, ultrafiltration was evaluated in terms of fouling behavior for three polymer membranes with different MWCO (molecular weight cut-off). The values of quality parameters (pH, conductivity, COD, BOD₅, TOC, N-NH₄⁺, N-NO₃^-, N_tot, and P-PO₄^3-) measured in SBR effluent did not exceed permissible values for wastewater discharged to soil and water. Ultrafiltration provided the high-quality water with very low values of COD (5.8-18.1 mg/L), TOC (0.47-2.19 mg/L), absorbanceUV254 (0.015-0.048 1/cm), color (10-29 mgPt/L) and concentration of nitrate (0.18-0.56 mg/L), phosphate (0.9-2.1 mg/L), ammonium (0.03-0.11 mg/L), and total nitrogen (3.3-4.7 mg/L) as well as lack of E. coli and enterococci. Membrane structural and surface properties did not affect the treatment efficiency, but did influence the fouling behavior.