Biological pretreatment for membrane water treatment systems.

摘要

Biological processes are often used in the drinking water industry to reduce the amount of organic carbon present in the source water. This reduction of organic carbon will limit the production of disinfection by-products and reduce regrowth events within the distribution system. The goal of this work was to determine if biological pretreatment will reduce fouling in membrane water treatment systems. Biological pretreatment for membrane water treatment processes were shown to reduce biofouling of membrane surfaces using membrane cell counts, glass bead cell counts, total organic carbon measurements, fouling layer thickness measured by light microscopy and scanning electron microscopy, and membrane flux reduction. The organic carbon source was humic and fulvic acids extracted from Elliot Silt Loam Soil obtained from the International Humic Substances Society. The biological processes used biological activated carbon and iron-oxide coated sand as support media for the biofilm. The experimental design also included prechlorination and post-filtration as additional factors to be considered. Results indicated that biological pretreatment was capable of reducing downstream fouling of membrane water treatment processes. The biological pretreatment process coupled with filtration resulted in the best reduction of downstream fouling as measured by the assays employed, while prechlorination did not appear to impact the biofouling reduction. Destructive column sampling yielded cell count data that was used in a biofilm model to show that first-order kinetics adequately accounted for the cell reduction in the columns and that the organic carbon pool was comprised of two pools of substrate where one pool is more usable by the microorganisms than the other pool.