Re ECF Project: 9/2005
Project Title: Development of a novel and low-cost membrane bioreactor (MBR) for treating Hong Kong village sewage

Applicant: Hong Kong University of Science & Technology

Project Proponent: Prof. Guang-hao Chen

Total Approved Grant: $810,231.97 (ECF & WWGF: 50/50)

Duration: 15/1/2007 to 14/7/2008

Project Status/Remarks: Completed

This research project proposes to conduct a 12-month study to evaluate the feasibility of a low-cost MBR using recycled non-woven material as membrane to treat village sewage.

Summary of Findings/Outcomes:
The main objectives of this pilot trial of our low-cost MBR are 1) to demonstrate the quality of the effluent from the integrated bio-treatment process consisting of an anaerobic zone and an aerobic zone, 2) to evaluate the membrane module performance, and 3) to explore its feasibility in treating village sewage.

Objective 1: the pilot plant produced stable effluent quality that met the Hong Kong secondary sewage treatment discharge standards under varying flow rates, water temperatures and sludge concentrations, even when the maximum treatment capacity increased from 2 (design) to 4 m3/day (actual).

Objective 2: the low-cost module performed better than expected: i) the permeate flux rate was doubled as compared to the proposed flux rate (2 m/day); ii) membrane backwash was only once per 48 hrs; iii) the air-to-water ratio could be as low as 18 (m3/m3); and iv) neither in-tank nor off-tank chemical cleaning was conducted up to the date of this report.

Objective 3: In view of the stable and good effluent quality, the low operational cost similar to conventional activated sludge processes, based on the low air-to-water ratio (18), the low membrane backwash frequency (once per 48 hrs using 1.3 % effluent), the low trans-membrane pressure (<0.3 bars), a short HRT (6 hr), minimal excess sludge production, and automated membrane backwash. Therefore, the proposed MBR technology is feasible for village sewage treatment.