Study On The Optimization Of O₃-BAC Process For Headling The Risk Of Micro-Organisms Leak

Ozone-biological activated carbon （O₃-BAC） is an advanced drinking water treatmentprocess that is suitable for China’s national conditions. In recent years, O₃-BAC developsrapidly in Chinese water production industry. However, while it was applied in the hot andhumid areas of southern China, it can increase the risk of biological leak due to the climateproblem. The study is based on China’s National “Eleventh Five-Year” special water issue. Apilot system was set up in a water treatment plant in Guangzhou for handling the microbialleakage by optimizing the O₃-BAC Process, and to study the effect of percolation on themicrofauna by exchanging the positions of sand filter and carbon filter.Investigation was taken out in an O₃-BAC depth treatment waterworks. Results showthat the average microbial density was18.88ind./m³in the conventional treatment processsection, while it came to353.31ind./m³in the effluent of the carbon filter. It shown that thethe carbon filter in the traditional depth treatment of O₃-BAC process would suit for themicrofauna’s secondary breeding when applied in the the Pearl River Delta region, and thatinncrease the risk of water micro-biological leakage.Results showed that, CDS process can set the problem of microbial leaks in the effluenteffectively. It can control the microbial density in the effluent at a very low level by usingsmaller sand as filter media, and with ozone combined with chlorine for disinfection.However, smaller sand will cause higher head lost. Contact flocculation-direct filtration canenhance the filtering capacity of the sand filter, particularly for the one filled withhomogeneous sand media, with its filter thickness of1.2m, and the particle size of from0.9to1.1mm，and will not result in excessive head loss. Meanwhile, when combined with ozonedisinfection, it can greatly improve the ability of withholding microorganism in sand filter.Carbon filter in the CDS process filled with two-stage filtration, so that it can filter the inletwater preliminarily by0.7m-thick caramisite （Φ3-5mm） at the bottom, and make sure theturbidity of the water at0.5NTU before flowing into the carbon layer. This greatly improvedthe adsorption efficiency of the carbon filter, so that it can make the organic removal abilitythe same level with the SOC process. Meanwhile, when running at different ways, thedisinfection by-products in effluent of the CDS process are below the level set by the drinkingwater health standards, and the UMU genetic toxicity is negative.When the carbon filter of the CDS process was running under the air/water ratio of0.2:1,the head loss was between15cm²5cm, lower than the simulation carbon filter of SODprocess. However, ozone oxidation used in front of the carbon filter of the CDS process will cause more ozone depletion than when it is placed before the carbon filter of the SOD process.In view of the raw water of ClassⅡ, aeration can achieve a great purification effect and helpto extend the carbon filter backwash cycle, and reduce the head loss, so it can cancel theozone oxidation section in front of the carbon filter.