Application of nonwoven microfiltration membrane on activated sludge final effluent: improving wastewater quality for re-use

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Masala, Murendeni Shonisani
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Vaal University of Technology
Water scarcity is one of the biggest problems that South Africa is facing currently, as a results it limits economic and social development. The application of membrane technology in wastewater treatment for re-use is one of the alternatives to reduce the demand of water in domestic, agricultural and industrial sectors. The primary aim of this study was to improve effluent wastewater quality prior to disinfection for re-use. This was done by diverting biological nutrient removal (BNR) clarifier effluent to a pilot nonwoven membrane filtration unit. The physical barrier provided by this unit, together with the effect of aeration within this system, provided particulate, physicochemical, and microbial removal. Monitoring of water quality was attained from the BNR clarifier effluent, and the nonwoven membrane permeate. Water quality trends against the standards were analysed for compliance with a water use license (WUL), and the removal efficiency for the permeate was also determined. The Single Factor Pollution Index (Pi) was used to determine the extent of pollution in the BNR clarifier effluent and the permeate, while the Water Quality Index (WQI) was utilised to determine the suitability of water derived from the BNR clarifier effluent and the permeate for re-use. Water Use Licence standards were utilised to determine the Water Quality Index of the BNR clarifier effluent and the permeate. Results for the BNR clarifier effluent showed that the physicochemical water quality parameters comply with the limits however, electrical conductivity (EC) and microbial water quality Escherichia coli (E. coli) were exceeded. Permeate results indicated that physicochemical and microbial parameters were compliant with the limits of the WUL. E. coli reduction was the highest with a removal efficiency of 90%, followed by chemical oxygen demand (COD) at 25%, NH4N at 22%, NO3 at 12.6%, PO4 at 7.8%, suspended solids (SS) at 6.3%, and the lowest was EC at 5.2%. The Single Factor Pollution Index has revealed that the BNR clarifier effluent water quality is medium polluted and the permeate water quality is slightly polluted. The WQI results for the BNR clarifier effluent showed good water quality and the water can be re-used for domestic, irrigation, and industrial purposes, while permeate WQI results indicated excellent water quality and the water can be re-used for drinking, domestic, irrigation, and industrial purposes. Outstanding permeate water quality improvement was observed on E. coli counts improving from 4974.48 counts/L to 294.33 counts/L. The standard of E. coli according to the WUL at Waterval WCW is 500 counts/L. The results indicate that nonwoven membrane filtration can improve microbial contamination and decrease the demand of chlorine for disinfection of wastewater final effluent. The nonwoven membrane filtration can decrease the water scarcity gap in South Africa for direct water reclamation by improving effluent wastewater.
M. Tech. (Department of Chemical Engineering, Faculty of Engineering and Technology), Vaal University of Technology.
E. coli, Nonwoven membrane filtration, Water Quality Index, Water re-use, Water Use License, Single Factor Pollution Index