UBC Theses and Dissertations
Passive membrane systems for small communities Oka, Patricia Ayuningtyas
Submerged hollow fibre ultrafiltration (SHFUF) is an established drinking water treatment technology viable for community-scale use. It can effectively treat surface water up to 4-log removal of colloids, pathogenic bacteria, and viruses. However, current use of SHFUF in small/ remote communities is hindered by the system’s complexity and high construction and operating costs. The present study focuses on the development of a novel and simple SHFUF system that can operate passively and with limited mechanical complexity for the production of drinking water in small/ remote communities. The experimental program was divided into four main stages; each stage was instrumental in eliminating component of a SHFUF system that contributes to its complexity (ie. backwash, permeate pump, aeration and recovery cleaning) and achieving an optimized state feasible for a small community use. Surface water containing 6-7 ppm dissolved organic carbon (DOC) was used for the pilot-scale experiments. In Stage 1, the contributions of periodic backwash in SHFUF were assessed through a comparative study of with and without backwash systems at sub-critical fluxes of 10, 20 and 30 L/m²h. While the benefits of backwash were clearly observed at 30 L/m²h, backwash was less necessary at lower permeate fluxes. At 10 L/m²h, flux was successfully maintained over the 2-month operation without backwash, indicating that backwash can be eliminated when operating at a low flux. Elimination of backwash reduces power requirements, increases throughput, and simplifies the system. In Stage 2, further simplification to the system was achieved through gravity permeation at a constant hydrostatic pressure. Gravity permeation at 10 L/m²h could be maintained with a head of 37 mbar. In stage 3, further reduction in energy consumption was achieved through operations under reduced air sparging conditions. Although reduced aeration decreased the permeate flux that could be maintained, this decrease can be compensated by proportionally increasing the number of membrane modules. In stage 4, recovery cleaning was confirmed to recover all of the permeability loss during the 2-month operation. Results from the present study confirm that technical complexity and energy requirements of SHFUF can be substantially reduced and made feasible for use in small/ remote communities.
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Attribution-NoDerivs 2.5 Canada