Study On The Backwash Technique Of Biological Activated Carbon Filter For Drinking Water In The Southern Typical Humid Areas

Ozone-biological activated carbon technology (O3-BAC) could improve the quality ofmunicipal water, which acquires the recognition of much water-supply organizations. Howev-er, in the Pearl River downstream region, which has a typical subtropical climate, the leakageof proliferated subminiature organism in the post-biological activated carbon filter wouldcause serious problem when traditional O3-BAC is applied. To solve this problem, we in-vented the new type O3-BAC process: Ozonation-BAC-disinfection-sand filter technology.This technology could prevent the penetration of subminiature organism, and the removalrates of ammonia nitrogen and organic matter are also improved. During the O3-BAC opera-tion, proper backwash is needed for the biological activated carbon filter. In this paper, dif-ferent types of backwash process were studied for the optimizing of these two types ofO3-BAC.For the traditional O3-BAC technology, the optimum backwash process is water back-wash with the combination of low-high-low intensity. The results showed that in the PearlRiver downstream region, when the backwash period reduced to3-5d, the macroscopic sub-miniature organism in effluent of BAC decreased obviously. This type of backwash could en-hance the “adsorption-biodegradation” process of BAC. Back wash with chlorine could con-trol the proliferation of subminiature organism, and the removal of organic matter was not af-fected seriously.For the new type O3-BAC technology, the optimum backwash process is the air-waterbackwashing process: firstly, draining the water off and backwashing with air for5min, theintense of air backwashing was12L/m2s·; secondly, backwashing with air mixed with water,the intense of water backwashing was8L/m2s· and the intense of air backwashing was6L/m2·s. The backwash time was reduced to15min, and the backwash period was extended to7d. This process could control the head loss effectively, but the effluent turbidity was a littlehigh. Despite of the fluctuation of effluent quality, the subsequent sand filter process couldeliminate this adverse factor. Optimization of the backwash process could ensure the opera-tion efficient of O3-BAC technology, and provide important guidance for the design and oper-ation of this effective water treatment technology.