Optimization of Immersed Membrane Integrated in Sedimentation Tank of WTP Ngagel Surabaya

The Surabaya River is the primary source of raw water for water supply, but its quality is not satisfactory, especially regarding organics, Escherichia coli (E. coli), microplastics, and TSS. The Ngagel Water Treatment Plant (WTP) treats the Surabaya River water using conventional systems like coagulation, flocculation, sedimentation, and filtration. However, the performance of these conventional systems is not as good as the processing with membranes. To test the effectiveness of immersed membrane microfiltration, research was conducted to integrate it into the Ngagel WTP sedimentation unit. The objective was to evaluate the performance of the microfiltration membrane module in terms of flux, filtrate quality, and the effects of baffles and air scouring on the membrane performance. The microfiltration membrane was placed in the downstream sedimentation tank, with variations in baffle slope, air scouring, and pressure. The study compared the levels of organics, E. coli, microplastics, and TSS in the Surabaya River with regulatory standards, showing that these parameters exceeded permissible limits, highlighting the urgency for improved treatment solutions. The findings demonstrate the applicability of this approach to other WTPs facing similar challenges, contributing to advancements in membrane-based treatment strategies. The study revealed that an operational suction pressure of 0.6 to 0.9 bar would produce a flux of 43 to 392 L/m²/h. The quality of the filtrate was in the range of 0.28 to 0.41 NTU for turbidity, 0 to 9.5 mg/L for TSS, 2 to 15 particles/L for microplastics, 11 to 16 mg/L for organic substances as permanganate value, and 0 MPN/100 mL for E. coli. The research also found that adding baffles resulted in a 12% increase in the volume of filtrate produced. However, the addition of baffles did not affect the quality of the filtrate. Furthermore, adding air scouring with pressures of 0.3 and 0.6 bar resulted in an 88% recovery volume of filtrate.