Research On Adsorption-decreasing Technology For Sudden Pollution Of Intake Of Drinking Water Resources

In recent years, sudden source water pollution incidents frequently happened, posing a serious threat to security of urban water supply and critically restricting the balance of ecological environment. Through jar test combined with pilot test, emergency treatment efficiency of phenol, toluene, cadmium, diesel oil and atrazine by PAC adsorption was investigated in the background of sudden pollution occurred in Huangpu source water.Effect of carbon species, PAC dosage, adsorption time and pollutants'initial concentration on treatment efficiency was investigated in jar test. The experimental results show that bamboo charcoal has better removal ratio than coal-based, ligneous-based and coconut shell-based PACs. Increasing in PAC dosage can notably enhance removal ratio of phenol, diesel and atrazine on various concentration levels. Enhancing PAC dosage can significantly improve removal ratio of toluene and cadmium on low concentration level, but have little contribution for high concentration pollution. Contaminants were decreased mainly in 10 min and arrived adsorption equilibrium in 60 min, which fitted the seasoning principle in emergency treatment. The pseudo-second order adsorption kinetics can well fit the adsorption process. With the increasing of initial concentration, treatment ratio descended. The isothermal adsorption law for various pollutants can be well described by Freundlich model. Langmuir adsorption isotherm model can well fit the adsorption law for phenol, toluene and cadmium.Optimal PAC dosage for each concentration level contaminants and corresponding removal efficiency were determined by pilot test. Adding 10mg/L PAC can decrease 25μg/L phenol below standard value. When the PAC dosage was 35mg/L, phenol with initial concentration of 50μg/L could be decreased to around two times of standard value. When 250μg / L and 500μg / L phenol pollution occurred, even if adding the maximum levels of carbon dosage (50 mg/L), effluent concentration still exceeded 15 times of standard value. In this condition, the process of PAC adsorption combined with KMnO₄ oxidation was required for further decreasing. Toluene with concentration exceeding 5 times and 10 times of standard value can be removed almost completely by aeration device in surge tank. After aerating, toluene with concentration exceeding 50 times and 100 times of standard value can be decreased to exceeding 4.50 times and 38 times respectively. When toluene contamination with initial concentration of 70 mg/L occurred, adding 50 mg/L PAC, the average effluent concentration in the surge tank was exceeding 6.60 times of standard value. For 25μg/L cadmium pollution, adding 40 mg/L PAC, the average effluent concentration exceeded 2 times of standard value. For the 50μg/L, 250μg/L and 500μg/L cadmium pollution, adding PAC with content of 50 mg/L, the average effluent concentrations exceeded 4 times, 31 times and 60 times respectively. When diesel oil pollution occurred, mostly suspended diesel oil could be eliminated by arranging oil fence in water source intake. After separation, diesel oil exceeding 5 times and 10 times concentration of standard value could be completely removed. Diesel oil pollution exceeding 50 times and 100 times could be decreased to 0.30 mg/L and 0.60 mg/L respectively by oil separation. Then adding 15 mg/L and 30 mg/L PAC, the average effluent concentration exceeded only 1 times of standard value. For the atrazine pollution with initial concentration of 10μg/L and 20μg/L, adding 5 mg/L and 20 mg/L PAC respectively, effluent concentration was below standard value. For 100μg/L and 200μg/L atrazine contamination, adding PAC 50 mg/L, the average effluent concentrations exceeded 7 times and 14 times of standard value.PAC adsorption coupled with potassium permanganate oxidation was an effect emergency measure to cope with high concentration level phenol and diesel oil pollution. The experimental results showed that treatment efficiency of adsorption firstly in fore bay combined with oxidation in surge tank is higher than single way of PAC adsorption. For the initial concentration of 250μg/L and 500μg/L phenol pollution, adding 40 mg/L and 50 mg/L PAC in fore bay respectively and 2 mg/L KMnO₄ in surge tank, effluent concentration can be cut down to 5 times and 10 times of standard value. For diesel oil pollution with initial concentration of 2.50 mg/L and 5 mg/L , after greasing, adding 5 mg/L and 10 mg/L PAC in the fore bay respectively, adding 1 mg/L KMnO₄ in the surge tank, effluent concentration can be controlled to exceeding 3 times of standard value.