| Nitrogen and phosphorus are key factors leading to the eutrophication of water bodies, andphosphorus is also a precious non-renewable resources. With the increasingly stringentpollutant discharge standards and the growing scarcity of phosphorus resources, the researchand development of the technology for the removal of nitrogen and phosphorus fromwastewater and the resource recycling technology of phosphorus is undoubtedly important. Thestruvite precipitation method can simultaneously remove and recover ammonia nitrogen andphosphorus from wastewater, and the products recovered can be used as a kind of high efficientslow-release fertilizer, therefore it has a wide prospect for development and application.In this thesis, the removal of ammonia nitrogen and phosphorus from two kinds of highconcentration practical industrial wastewater by struvite precipitation method was firstlystudied. The influences of factors on the ammonia nitrogen and phosphorus removal andrecovery efficiency were investigated respectively, and the optimal process conditions wereobtained. In order to reduce the chemical consumption and the treatment cost, the new idea thatusing waste to treat waste was used. The two kinds of wastewater were mixed, and then weretreated by using the same method. The influences of factors on mixed wastewater treatmentwere also investigated, and the best process conditions for mixed wastewater were obtained.The structure, constituent and heavy metals content of the precipitates were analyzed byscanning electron microscope, X-ray diffraction, chemical analysis and other methods. Thereaction mechanism of the struvite precipitation method was also discussed. Finally, analyseswere conducted on the environmental and economic benefits of removal and recovery ammonianitrogen and phosphorus from wastewater by struvite precipitation method. The mainconclusions of the thesis were as follows:（1） Phosphorus was removed and recovered from high concentration phosphorus-containing wastewater that the concentration of PO43--P is5399.835475.62mg·L-1by struviteprecipitation method, while pH=9.5, n（Mg）:n（N）:n（P）=1.25:1.05:1,stirring speed was about200r·min-1, reaction time was20min, precipitation time was20min, the removal rate of PO43--P was99.96%, the concentration of PO43--P in the treated water was2.20mg·L-1,and the concentrationof NH4+-N in the treated water was213.14mg·L-1. （2） Ammonia nitrogen was removed and recovered from high ammonia nitrogen contentwastewater that the concentration of NH4+-N is562.97677.28mg·L-1by struvite precipitationmethod, while pH=9.5, n（Mg）:n（P）:n（N）=1.15:0.95:1, stirring speed was about150r·min-1,reaction time was20min, precipitation time was20min, the removal rate of NH4+-N was94.14%, the concentration of NH4+-N in the treated water was38.21mg·L-1, the concentrationof PO43--P in the treated water was49.43mg·L-1.（3） When treating the mixed wastewater containing high concentration phosphorus-containing wastewater that the concentration of PO43--P is7374.53mg·L-1and high ammonianitrogen content wastewater that the concentration of NH4+-N is717.47mg·L-1, while highconcentration phosphorus-containing wastewater and high ammonia nitrogen content waste-water were mixed1:4.5by volume, pH=9.5, n（Mg）:n（P）=1.2:1, stirring speed was about200r·min-1, reaction time was20min, precipitation time was20min, the removal rate of PO43--Pwas99.64%, the removal rate of NH4+-N was88.62%, the concentration of PO43--P in thetreated water was4.86mg·L-1, and the concentration of NH4+-N in the treated water was70.76mg·L-1.（4） The result of scanning electron microscope of the precipitates obtained under theoptimal process conditions indicated that the precipitates had rhombic structure. X-raydiffraction analysis results showed that the precipitates were mainly composed ofMgNH4PO4·6H2O.And the content of N, P and Mg were close to the theoretical content ofstruvite. The content of heavy metals elements in the precipitates was consistent with therequirements of the ecological index of arsenic, cadmium, lead, chromium and mercury forfertilizers（GB/T23349-2009）. And it can be recycled as slow-release fertilizer.（5） The result of experiment research and theoretical analysis indicated that the reactantmolar ratio and pH had a great influence on the effects of removal and recovery ammonianitrogen and phosphorus from wastewater by struvite precipitation method.（6） The struvite precipitation method can effectively remove and recover ammonianitrogen and phosphorus from wastewater.It has better economic and environmental benefits. Itcan greatly reduce the chemical agent costs by use the new idea that using waste to treat waste,it is a technically feasible and economically reasonable method, and has great development andapplication prospect. |
PDF Full Text Request