A Case Study Of Enhancements On Flocculation Of Different Preoxidation Methods Base On Mopanshan Reservior

In northern China, lots of water treatment plants have difficult in treatinglow-temperature and low-turbidity raw water in winter. Flocs tend to loose inlow-temperature and low-turbidity raw water. Raw water of Mopanshan watertreatment plant comes from Mopanshan reservoir, and is typical low-temperatureand low-turbidity water in winter. There are large amounts of foam in theflocculation tanks and sludge on the top of inclined plates in the sedimentationtanks. To improve the effect of coagulation, large amount of coagulant is added intoraw water, which increases the cost and reduce the pH of effluent of the Mopanshanwater treatment plant. So to find ways suitable for Mopanshan water treatment plantto enhance coagulation becomes more and more urgentThe study adopted different pre-oxidation processes to enhance treatment ofraw water from Mopanshan reservoir. Trough comparing coagulation enhancementeffect of different pre-oxidation processes, oxidant suitable for treating Mopanshanwater treatment plant was selected. The application of pre-oxidation calls for lessinvestment and is more flexible, so it is a good way to be used in Mopanshan watertreatment plant.First, the oxidation performance of potassium permanganate, chlorine andozone was studied. The results showed that optimum dosage of potassium was0.3mg/L, and the coagulation effect was better dosing potassium before PAC thanafter PAC. Optimum oxidation time of potassium was5min. Under optimalconditions, the removal efficiency of UV254and CODMnboth exceeded50%. Theoptimum dosage of chlorine was2.0mg/L, and the optimum oxidation time ofpotassium was30min. The removal efficiency, especially of CODMn, was higherwhen dosing chlorine before dosing PAC.Oxidation effect of ozone was obviously affected by Contact time. When Contacttime surpassed15min, the improvement of coagulation effect was limited, so15min wasselected as the contact time that Follow-up experiments used. The enhancement effectimproved as dosage of ozone increased, but it was not obvious when the dosage of ozoneexceeded4mg/L. when contact time was15min and ozone dosage was4mg/L, theremoval efficiency of turbidity and CODMnincreased by11%and11.5%respectively. The enhancement of TOC removal was limited because ozone couldnot organic matter in water into H2O and CO2. Dosage of ozone could raise thenumber of flocs, and number of flocs whose diameter was in the range of2-5umand20-78um increased more obviously.Then, the oxidation performance of potassium, chlorine and ozone was compared. The pre-oxidation effect of ozone was the best, while the combination ofchlorine and potassium come second. The combination of chlorine and potassiumhad better removal efficiency of ammonia nitrogen. The application of ozone needsheavy investment because of installing ozone generator. So the water treatmentplant could adopt combination of chlorine and potassium as the pre-oxidationprocess, which can reduce the cost of production..