Experimental Study On GAC-sand Filter For Advanced Treatment In Waterworks

In recent years,the amount of water test results showed that the ammonia nitrogen,organic pollutants of raw water exceeding frequently occur. In the water supply system,biological outbreak from time to time, not only brought great difficulty in the conventionalwater treament, but also restricted to improve water quality directly.A granular activated carbon sand dual media filter （GSF） was investigated as anadvanced water treatment process of waterworks through the pilot test in Shenzhen. Thesedimentation tank water access GSFs, and made the GSFs operation parameters andproduction with ordinary sand filter similar to investigate the process on organic matterremoval characteristics.The main results of research:（1） By using the same flow velocity of6m/hr with the ordinary sand filter, GSFs’filtration cycle can reach48h, meet the needs of the production.（2） Under the condition of smaller water turbidity, GSFs have the same ability to removeturbidity with ordinary sand filter, the turbidity removal rate was64.32%and70.24%.（3） The quality of GSFs’ effluent was poor within15minutes after backwash, filteredstablely about20minutes later.（4） Under the high premise of chlorine,the GSFs had a good removal effect ofturbidity,CODMnand NH₄⁺-N. Effluent’s colority was under5degrees.（5） There was a certain amount of nitrite nitrogen accumulation phenomenon in theGSFs, This because of short time of filtering and it had the process of chlorine before filter.（6） Under the condition of pilot, gas and water was suitable for sand filter’s backwash,first, gas-washed for2minutes,then, waited for1minute,water-washed for7minutes at last.Itcan achieve an perfect backwash effect.