Performance And Engineering Demonstration Of GAC-UF Hybrid Process

With the deterioration of water pollution and the improvement of drinkingwater standards, the drinking water treatment technology is facing a higherrequirement. The general activated carbon process and ultrafiltration both presentlimitations, but it would have an excellent complementarity and fully guarantee thewater quality and safety when the two processes are combined together. The processof Shatoujiao water treatment plant of Shenzhen had combined the activated carbonprocess with ultrafiltration with a production scale of40000m3/d. This paper hadtaken an investigation on the process, both the treatment efficiency and operatingparameters were studied and optimized, simultaneously the application of theprocess and the engineering of the project were summarized and evaluated.The effluent turbidity of the GAC-UF hybrid process remained lower than0.1NTU and it was0.07NTU on average, the particles more than2μm remained lowerthan10CNT/mL and it was4CNT/mL on average, the total bacterial count wasalways lower than1CFU/mL, zooplankton was not detected, and the removal ratesof CODMn, DOC and UV254were33%,26%and45%. The GAC-UF hybrid processran quite well and almost all water quality indicators were significantly better thanthe drinking water standard GB5749-2006. The organic matter indicators such asCODMn, DOC and UV254were removed mainly by activated carbon filter, and themicrobiological indicators such as total bacterial count and zooplankton wereremoved mainly by ultrafiltration. The combination of activated carbon andultrafiltration showed a quite good complementarity and a high effluent quality.The optimization test of backwash time of activated carbon filter showed that6minutes or more of backwash time could achieve a quite well effect. Theoptimization test of backwash cycle of activated carbon filter showed that thebackwash cycle had little effect on the treatment efficiency of activated carbon filter,and the treatment efficiency of turbidity and particles were not affected when theCODMnremoval and effluent bacteria rose partly while the backwash cycle extended.The backwash cycle6d was suggested. The iodine value, methylene blue value,specific surface area and pore volume of the activated carbon descended fast at first,then became stable gradually. With a thin thickness of the activated carbon layer,high loading had an obvious effect on the treatment efficiency of activated carbonfilter.The orthogonal test of gas scrubbing time, gas intensity, backwashing time andbackwashing intensity showed that the membrane fouling was lightest with35s of gas scrubbing time,9m3/h of gas intensity,70s of backwashing time and160L/(m2·h) of backwashing intensity. The test of flux and backwash cycle ofultrafiltration showed that flux and backwash cycle had almost no effect on thetreatment efficiency of ultrafiltration and the treatment efficiency of ultrafiltrationwas very stable. Backwash cycle and flux had some effects on the membrane fouling.The rising rate of transmembrane pressure was directly related to the filtration fluxand a longer backwash cycle also contributed to a higher rising rate oftransmembrane pressure. The membrane integrity tests showed that theultrafiltration membrane had quite good stability and sustainability, and there werenot any membrane breakage or fracture under the long-term operation.The advanced treatment process engineering of Shatoujiao water treatmentplant was a quite good demonstration for process upgrading with insufficientbuilding areas. For the large quantity of analogous water treatment plant within thiscountry, it would provide very useful references on the selection of advancedtreatment process and the way of transformation.