Malaysia's largest river bank filtration and ultrafiltration systems for municipal drinking water production

For the past 50 years, conventional gravity sand media filtration systems have been the primary and dominant water treatment systems in municipal drinking water treatment in Malaysia. Conventional media filtration can only deal reliably with particles larger than 0.01 mm (10 μm) in diameter (Percial et al. 2014). The microorganisms that transmit disease to humans vary significantly in size between about 0.03 and 1.0 μm for bacteria and viruses. Ultrafiltration (UF) is a good barrier for bacteria and viruses, with typical 0.02 μm pore size. Excellent filtrate quality in terms of turbidity (<0.3 NTU) has been reported from UF systems, which means that this technology can be used to produce potable water (Pearce 2011).

The case study of the plant was carried out to determine the actual performance of the combination of river bank filtration (RBF) and UF systems when producing drinking water at municipal scale. These data and findings from the study provide insight for local water authorities in Malaysia into the feasibility of using such combined systems in future. Emphasis is laid on consistent filtrate quality and production costs per cubic meter. Figure 1 shows the treatment process at the plant, which was designed to avoid the use of pre-filtration chemicals for coagulation and flocculation. Using the RBF intake system to pre-treat the raw water for the treatment plant reduces the load on the UF system significantly. Figures 2 and 3 show the completed RBF raw water intake system.

Wakaf Bunut water treatment plant started operating in March 2013, supplying high-quality drinking water to Tok Bali, Kelantan, Malaysia. The plant utilizes 120 units of Dizzer XL 0.9 MB 60 W UF modules to produce up to 14 million liters per day of water. These UF modules are manufactured by Inge GmbH (Greifenberg, Germany). The membranes are made from high-quality modified Polyethersulfone with patented Multibore membrane technology. Figure 4 shows the patented Multibore seven capillary UF membrane. Further discussion of the plant's performance is given below.

Since the plant went into operation, water quality and production cost data have been analyzed periodically to ensure their consistency. On site water quality analytical equipment has been used to analyze both raw and UF filtrate waters. Subsequently the plant's chemical and electrical consumption data are tabulated for cost analysis.

The plant is equipped with a programmable logic controller and automatic data acquisition equipment for full automation with minimal operator intervention. Figure 5 shows the plant's operating interface.

UF feed and filtrate water quality for the combined RBF and UF system are collected daily to determine the turbidity, pH and iron content. The analyses are determined on site to measure the effectiveness of the combined filtration systems. Figure 6 shows typical analytical equipment used at the plant. The arrangement of the 120 units containing the UF membrane modules is shown in Figure 7.

Chemical consumption for UF membrane cleaning and disinfection for the treated water are recorded during plant operation, and the actual power (kWh) required by the plant during operation is obtained from a central recorder and tabulated.

The Malaysian bench mark turbidity requirement for UF filtrate drinking water is less than 0.3 NTU. The results obtained from the UF filtrate produced at the plant are consistently below 0.3 NTU. Table 1 shows the data for 12 consecutive days at the plant for both the feed and final (UF) treated water. The iron content of the raw water is reduced significantly in passage through the UF membranes.

RBF is new to Malaysia for municipal drinking water treatment. Surface water is pre-filtered through river sand before delivery to the treatment system. The efficiency of the RBF system is analyzed by collecting surface (feed) and filtrate quality data. Table 2 shows the feed and filtrate quality from the RBF, which can reduce the feed water turbidity significantly by sand filtration. The reduced suspended solids concentration indicated by the low turbidity of the filtrate water from RBF passes lower loading to the UF membrane, enabling a higher UF feed water flux.

Chemical consumption for UF membrane cleaning, treated water disinfection, and the electricity requirements are tabulated in Table 3. The costs shown are based on the Malaysian electricity tariff and chemical prices and might differ in other countries. Malaysia's local water authorities can carry out feasibility analyses using these data to determine the sustainability of using the combined RBF and UF technology for potable water production.

The combination of RBF and UF at Wakaf Bunut water treatment plant has shown that they comprise a viable process train for the production of drinking water at municipal scale. Treated water from the plant meets local drinking water quality requirements consistently. The total cost of production per cubic meter of treated water is RM 0.13 (USD 0.04), which is reasonable. This indicative price is for reference only as the costs of maintaining distribution pipelines, pumps, reservoirs, etc. have not been taken into account.

The authors would like to thank Air Kelantan Sdn. Bhd. for providing actual treatment plant data for this paper.