Research On Electrolysis Technology For Nitrogen And Phosphorus Removal In Management Of Urban River

With the rapid development of industrialization and urbanization, a large amount ofindustrial and sewage wastewater were discharged into rivers, thus causing eutrophication ofurban rivers, which in severe cases, leads to black or stunk rivers. It has affected the qualityof residents’ life. The major pollutants discharged into urban rivers were nitrogen andphosphorus, ect. Scholars and experts of home and abroad have studied on the removal ofnitrogen and phosphorus from polluted urban rivers. General methods used to improve thewater quality are sediment dredging and aquatic vegetation reclaimation, etc. But there arestill some problems. Nitrogen and phosphorus removal by electrolysis is a new watertreatment technology, which has some advantages, such as high removal effects, short HRT,few occupied space, less investment, and convenient maintanence, etc. In this study, theresearch object is the water of Xu tang qiao River in Wuxi high-tech zone, Jiangsuprovince.Through research on electrolysis experimental for nitrogen and phosphorus removal,using single factor experiment and orthogonal experiment, operationa parameters wereoptimized. And on this basis, electrolytic integration process was established for nitrogen andphosphorus removal, to investigate efficiency of nitrogen and phosphorus removal from theactual water. Then technology of aeration and electrolysis integration process for nitrogen andphosphorus removal was established, to further removal of nitrogen and phosphorus from theactual water. Furthermore, through studied on affect on aquatic plants by technology ofaeration and electrolysis integration process for nitrogen and phosphorus removal, weunderstand feasibility of electrolysis technology for nitrogen and phosphorus removal onmanagement of urban river.The results are as follows:1. The electrolysis process for phosphorus removal lasted30min, removal efficiency ofTP was increased with electrolysis time extended. According to single factor and orthogonalexperiments, the primary and secondary sequence of the parameters was determined: the gapbetween electrodes> the initial pH> the applied voltage>initial phosphate concentration.The optimum was as follows: concentration of initial phosphate is2.5mg/L, the standingtime is3h, the initial pH is6, the gap between electrodes is1.5cm, the applied voltage is11V; In the optimal operation conditions, removal efficiency of TP in the actual river reached90%by electrolysis, under the simulated river. In the electrolysis process for phosphorusremoval, pH has a significant increase, and the value is between10to12; the cost ofelectrolysis technology for phosphorus removal is low, when TP removal efficiency couldreach90%, consumption of system energy is about200kW·h/kg.2. The electrolysis process for nitrogen removal lasted180min, removal efficiency of NH4+-N and TN was increased with electrolysis time extended. According to single factor andorthogonal experiments, the primary and secondary sequence of the parameters weredetermined: chloride concentration> the initial pH> initial NH4+-N concentration>theapplied voltage. The optimum was as follows: concentration of initial phosphate is15mg/L,concentration of chloride is40mg/L, the initial pH is9, the gap between electrodes is1.0cm,the applied voltage is10V. In the optimal operation conditions, NH4+-N and TN removalefficiency of the actual river reached81.24%and48.27%by electrolysis; In the electrolysisprocess of nitrogen removal, pH has a significant reduction, and when electrolysis time is180min, the lowest pH is close to3. The cost of electrolysis technology for nitrogen removal isabove electrolysis technology for phosphorus removal. System energy consumption is about400kW·h/kg, under the condition of electrolytic90min.3. The effluent quality of integrate electrolysis technology was stable. Removalefficiency of TP, NH4+-N and TN were96%,85%and60%, respectively.The pH was kept atabout7.5, which conforms to discharge standards of surface water. Aeration contributed a lotto ammonia removal, especially when applying aeration technology to the second phase ofthe integration process. It was effective to improve the removal efficiency of NH4+-N and TN,but had little effect on TP removal. When applying the technology of aeration and electrolysisto the natural water body, it was found that helped relieve the stress of heavy polluted waterto them.This study provides technology reference for controlling the eutrophication of waterbody and the urban river pollution, which has a certain practical guiding significance.