| In recent years, eutrophication is attracting more attention. The major factors causing water eutrophication include load of nitrogen (N) and phosphorus (P), particularly P, P is the limiting factor of algae growth. Effective Control of phosphorus can cut the main nutritional source of algae growth, which was the important means to control water eutrophication, and has become one of the research hotspot in the domain of water research technology.Coagulation experiment was carried out by using PAC1of different basicity. The contents, distributions and algal availability of phosphorus were studied before and after coagulation. Results show that:phosphorus removals were significantly different among the four coagulants with different basicities. In the coagulation experiment, Ala plays an important role for the removal of phosphorus, and the coagulant with lower basicity showed higher phosphorus removal efficiency, PACl0showed the best performance of phosphorus removal. Dissolved and particulate phosphorus decreased obviously with the increase of coagulant dosage. When the coagulant dosage reached a certain value, dissolved and particulate phosphorus would entirely turned into deposit phosphorus. It is proved that the demand of coagulant for turbidity control was unequal to that for phosphoms removal. In the experiment, the best turbidity removal would be get when the coagulant dosage was about0.02-0.1mmol·L-1, while the desired phosphorus removal need much higher dosage. The release of AAP in the sediments increased first and then decreased with the increase of coagulant dosage. It was indicated that AAP in sediments can be controlled effectively by adding superfluous coagulant compared to turbidity removal, which is very important to control phosphorus chronically. It was showed that the turbidity removal can not be as the sole criterion in the process of water treatment, the need for the release of AAP, total phosphorus removal should be considered, which need a larger coagulant dosage. In this study, alum chloride and ferric chloride were selected as the coagulants, and ozone, a strong oxidant, as the preoxidation agent to develop an effective coagulation process with the emphasis of phosphorus removal from eutrophication water. Effects of pre-ozonation on the removal efficiency of phosphorus contained in eutrophicated raw water during coagulation were investigated. Results show that:the removal efficiency of both total phosphorus and dissolved phosphorus increased gently at four different ozone dosage as the dosage increased from0to1.5mg·L-1. Dissolved phosphorus increased and particulate phosphorus reduced gradually with the increase of the ozone dosage. The removal efficiency of dissolved phosphorus is higher than particulate phosphorus and total phosphorus. AlCl3exhibit better removal efficiency than FeCl3in removing turbidity and phosphorus. When the ozone dosage was1.5mg·L-1, the coagulant dosages of about0.1mmol·L-1would get the best turbidity removal in the experiment, while much higher dosage was needed to achieve desired phosphorus removal. The amount of AAP (Algal available phosphorus) in the sediments was analyzed before and after preoxidation. Although ozone can enhance coagulation for turbidity and phosphorus removal, the release content of AAP increased distinctly compared with the raw water. These results suggest that preoxidaton is beneficial for phosphorus removal during coagulation, but it also increase the release of AAP.The comparison of aluminum iron compound coagulant and AlCl3was studied. The results show that aluminum iron compound coagulant can effectively remove the turbidity at the remove rate of88.5%when the sedimentation time was only15min, which exhibits better coagulation effect and reduce the explosive consumption to a certain extent. For the removal of phosphorus, the removal efficiency of total phosphorus can reach up to95%, the dissolved phosphorus can be removed completely, which was much large than AICI3, and the removal efficiency of dissolved phosphorus was more than total phosphorus, which was consistent with the anticipation. The orthophosphate in sediment after coagulation was detected, with the increase of coagulant dosage, the release amount of orthophosphate decreased, the release of orthophosphate in sediment treated by compound coagulant was far lower than AICl3.Pilot Plant Research on Treatment of organic wastewater with high COD and phosphorus of chemical fertilizer plant by using compound coagulant. The results indicated that the great removal efficiency can be obtained when use the compound coagulant for fertilizer plant wastewater, the turbidity removal rate can reach up to95%, while the removal rate of phosphorus, COD, DOC, UV254were72.5%,53.7%,31.5%,90.1%. The treated organic sewage met national discharge standards completely, on the whole, the removal rate of dynamic test was lower than static coagulation test. |
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