Study On Gac-sand Short Process Advanced Technology For Water Treatment

At present, the pollution of drinking water source increases, and the major role of conventional drinking water treatment technology is to remove the bacterial and turbidity in the water, however, it basically has no removal effect for the ammonia-nitrogen and the nitrite-nitrogen in the water. Intensive filtration can achieve the technology target of removing ammonia-nitrogen to some extent, and it is enforceable for the technology transformation of drinking water plant.Against the raw water conditions in GuangZhou, this paper carries out a research into water treatment effect of GAC-sand filter. Because of the need for regular disinfection, drinking water plants in GuangZhou need to conduct pre-chlorination, in order to guarantee the CT value of chloramines disinfection, this paper mainly research water treatment effect of GAC-sand filter in the condition of higher pre-chlorination quantity. This research lies closely at the needs of actual production, and has some theoretical and practical application value.Study results of water treatment effect of GAC-sand filter are as follows:In the process of micro-polluted and high-polluted water treatment test, carbon layer thickness and sand layer thickness of GAC-sand filter are 0.5m and 0.7m respectively, filtration rate is 9m/h. Sand layer thickness of sand filter are 0.9m, filtration rate is 8~10m/h.(1) Turbidity removal rate of GAC-sand filter is basically the same with sand filter, so GAC-sand filter can reach basically the same turbidity removal ability of sand filter.(2) In the process of micro-polluted water treatment test, the average value of DO, pH and chlorine in the influent are 4.48mg/L, 7.60 and 2.13mg/L respectively; In the process of high-polluted water treatment test, the average value of DO, pH and chlorine in the influent are 4.09mg/L, 7.62 and 2.77mg/L respectively.(3) The whole process of micro-polluted water treatment test, the average value of CODMn, NH4+-N and NO2--N in the influent and effluent are 1.48mg/L, 0.70mg/L, 0.006mg/L and 1.08mg/L, 0.10mg/L, 0.071mg/L respectively; The whole process of high-polluted water treatment test, the average value of CODMn, NH4+-N and NO2--N in the influent and effluent are 2.58mg/L, 3.32mg/L, 0.022mg/L and 2.03mg/L, 2.24mg/L, 0.518mg/L respectively. It can be seen from this that GAC-sand filter does not apply to the treatment of high-polluted water, apply to the treatment of micro-polluted water.Micro-polluted water treatment conduct aeration test with the gas-water ratio (0.45~0.55):1, removal quantity of GAC-sand filter to CODMn and NH4+-N increase nearly by one fold, and NO2--N is less than 0.1mg/L in the influent. Therefore, for micro-polluted water treatment, when the pollutant concentration to be higher so that effluent quality can not achieve relevant drinking water quality standards, aeration can be added to GAC-sand filter to strengthen the water treatment effect.(4) GAC-sand filter is washed by means of gas-water joint backwashing, first 3min gas washing, then 7min water washing, the washing period is 24h. The intensity of gas washing is 15~20L/(m2.s), and the intensity of water washing is 9.3~10.5L/(m2.s). In the process of backwashing, the running of carbon is slight. After 2~4h from the end of backwashing, the pollutant treatment effect of granular active carbon can get back to the effect before backwashing and achieve the best. As time goes on, pollutants removal effect decreases gradually.(5) Granular active carbon have only been minor wear after being used. As the running time goes on, iodine sorption value and methyleneblue sorption value of granular active carbon lower gradually, and it need one year to reach the iodine sorption value 600mg/g and the methyleneblue sorption value 85mg/g. Therefore, granular active carbon should be regenerated after one year using.Based on the experimental results, in the perl river delta region, when the quantity of pre-chlorination is very high, the applicable water quality of GAC-sand filter is seasonal micro-polluted water in which NH4+-N is less than 1.0mg/L and CODMn is less than 3.4mg/L. And the water purification effect of GAC-sand filter can be heightened through appropriate to reduce pre-chlorination quantity.