Study On Enhanced Coagulation-ultrafiltration Treatment To Micropolluted Cellar Water And Its Characteristics Of Organic Matters

In order to solve the serious water shortage problem in the arid and semiarid regions in Northwest China, the national policy “121 rainwater collection project” has been basically popularized. Local people collect and store rainwater, and are widely used for irrigation, production, human and animal drinking etc. The collection cellar water as the main source of drinking water, the quality is directly related to the health of the local residents. However in recent years, by the industrial development, air pollution, natural rainfall confluence into the cellar of the process, rain in the air condenses into the atmospheric pollutants; In the rain collecting surface such as roofs and courtyards, the hillside, the threshing floor, gravel and subjected to secondary pollution, when the water stored in the cellar, cellar wall and sediment microorganism will produce a certain pollution; And due to the constraints of the local economy, the large number of use pesticides and chemical fertilizers, the domestic livestock breeding wastewater free emission and other external factors, the problem of cellar water quality cannot be solved for a long time. For this end, the research object of this topic is to study the rainwater collection cellar water in the arid and semiarid area of Northwest China, in order to ensure the safety of drinking water for local residents, using PAC as coagulant, and HPAM as coagulant aid, and a combination of powder activated carbon to enhance coagulation; And combined ultrafiltration process, search dosing PAC, PAC/HPAM, and PAC/HPAM/ powdered activated carbon with unlrafiltration process to treatment cellar water, and explore the pollution of the ultrafiltration membrane.The ellar water in arid and semiarid region of Northwest China, environmental impact of collection and storage processes, the water quality is poor and the sediment content is much, the average turbidity is 19.4NTU, CODMn is 5.16mg/L, UV254 is 0.088 mg/L, and NH3-N is 0.64 mg/L, are all more than the rural areas?living standards for drinking water health?, present a micro-polluted state. Molecular weight of organic matter in cellar water is mainly concentrated in the range of >100KDal and <5KDal, distribution of polarization is the features of northwestern micro-polluted cellar water organic molecular weight distribution.In the use of enhanced coagulation treatment of micro-polluted cellar water experiments. First of all, the only dosing PAC for cellar water processing, to explore the PAC optimal investment increased at the same time of pollutants removal effect of research. Experiments, it is found that the coagulant dosage in 15~17.5mg/L, the CODMn, UV254, NH3-N, turbidity of pollutant removal in cellar water rate is respectively 36%, 49%, 33%, 82%, after combining the ?-potential and fractal dimension analysis,adsorption bridging and net capture swept volume is the main mechanism of the removal of pollutants; Individually dosing PAC to cellar water of each sub region of organic compounds have certain removal efficiency and the >100KDal molecular weight of organic matter removal effect is more obvious.Secondly in the experiment of adding coagulant aid, the HPAM compound PAC was used to explore the best dosage of HPAM and its influence on water quality, as well as the dosing order of HPAM and PAC. The study found that HPAM mixed particle coagulation produces denser and faster precipitation, when the HPAM dosage is 0.15 mg/L, the adsorption of long chain polymer coagulant powerful sweep the cellar water CODMn, UV254, NH3-N, the removal rate of turbidity is better than adding PAC time don't improve 11%, 6%, 4%, 12%; And the coagulant of organic molecular weight distribution is balanced, the organic molecular weight of each interval are removed; Using HPAM as coagulant, the dosage HPAM after the first dosing PAC sequence, can make full use of the adsorption of long chain polymer can the agent and the swept volume effect; On the premise of cellar water pollutant treatment effect can reduce the use amount of PAC, the results show that the addition of 0.15mg/L HPAM after the optimum dosage of PAC from 15~17.5mg/L to 10~12.5mg/L, and can guarantee the pollutant removal effect.The enhanced coagulation to cast PAC/HPAM, use the buffer solution of cellar water pH to adjust, studies have found that weak acid water environment is conducive to organic matter removal, and the weak alkaline water environment of NH3-N and turbidity removal effect is better. With the pH drinking water standard in our country, and change the pH operating conditions, the final selection of pH as raw water, the initial value of 7.7.Thirdly, using the PAC/HPAM/ powder activated carbon compound to enhance coagulation experiment, the optimum dosage of powdered activated carbon, the removal effect of organics with different molecular weight range, and adding order for PAC/HPAM. The study found that with the powdered activated carbon adding, the enhanced coagulation of organic matter treatment effect more obvious, and the removal rate of NH3-N and turbidity will have little effect; Dosing powdered activated carbon in the 1min before PAC/HPAM, experiment determine the powdered activated carbon of the optimal dosage was 20mg/L, the removal rate of effluent pollutant CODMn, UV254, NH3-N, turbidity were increased to 54%, 66%, 40%, 97%, the powerful surface adsorption capacity of powder activated carbon is the removal of the main mechanism of organic pollutants; With the powdered activated carbon dosing, for each interval of organic compounds have certain removal rate. And the <5KDal molecular weight of small molecule organic matter, adding powder activated carbon to remove the effect of the best.To explore the micro-polluted cellar water with different enhanced coagulation treatment after by ultrafiltration, further influence on the quality of raw water, and fouling problem of ultrafiltration membrane, only dosing PAC, PAC/HPAM, and PAC/HPAM/ powdered activated carbon several strengthening coagulation treatment, use the dead end flow and cross flow two pressure filtration ways to next ultrafiltration, ultrafiltration membrane flux decreased amplitude and membrane cleaning after the recovery have obvious difference. The cellar water directly through the ultrafiltration membrane, the removal effect of raw water quality is not ideal, and the pollution of ultrafiltration membrane is serious, single cycle endometrial specific flux decreased dramatically, the flux recovery of each cycle after cleaning is poor, final cycles of ultrafiltration membrane flux ratio as low as 0.03; Adding PAC mixed after compared to the directly ultrafiltration, ten complete cycles of membrane specific flux ratio increased from 0.03 to about 0.2, single cycle flux decline has obvious improvement after cleaning, the recovery of membrane flux is improved compared with PAC/HPAM and directly ultrafiltration, final cycles of membrane specific flux from 0.2 to 0.6, mixed coagulation in a dense cake layer can also be ultrafiltration flux recovery after better; And adding powder activated carbon, wrapped the powdered activated carbon floccule loosely attached in the membrane surface are more likely to be backwash, and the small molecule organic matter removal effect is more obvious, after ten cycles of membrane ratio flux from 0.6 to 0.7, the loose mud cake layer also make cleaning membrane flux recovery degree of the best.