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The Research On Kinetics And Process Conditions Optimization Of Treating Wastewater With High Concentration Ammonia-Nitrogen By Chemical Precipitation Method

Posted on:2005-02-19Degree:MasterType:Thesis
Country:ChinaCandidate:D P LiuFull Text:PDF
GTID:2121360125958580Subject:Environmental Engineering
Abstract/Summary:PDF Full Text Request
Nitrogen in water environment exists mainly in the form of ammonia-nitrogen, which is the principal contaminant causing eutrophication of water body. With continual worsening of water quality and enhancing of public environmental protection consciousness many countries have constituted strict ammonia-nitrogen discharge standards, therefore, it has already become the focus and difficulty in the present wastewater treatment field to explore the economy and effective treatment technology for ammonia-nitrogen wastewater.Having the advantages of simple technology, high reaction speed, high removal efficiency, especially being suitable for the high concentration ammonia-nitrogen wastewater, chemical precipitation method for ammonia-nitrogen removal is blossoming while people are endeavoring in the further research on removing ammonia-nitrogen by biochemical process. In this paper, the process for ammonia-nitrogen removal was studied by adding some chemicals into the wastewater of a certain hard alloy plant to produce the struvite(MgNH4PO4 6H2O) precipitate.Ammonia-nitrogen in wastewater was removed by using magnesium hydrogen phosphate(MgHPO4 3H2O) as precipitant. Based on a large amount of experiments, the kinetic parameters about ammonia-nitrogen removal as struvite were studied, especially the effect of temperature and pH value etc. According to the kinetic characteristics, the ammonia-nitrogen concentration of the wastewater is reduced from 850 mg/L to 20 mg/L(removal efficiency is over 96 % ) while residual phosphorus content is under 20 mg/L controlling the pH in the range of 8.5 ~ 10. In addition, the struvite precipitate formed have not only compact crystal structure which shows good sedimentation capability, but also high purity without adsorption of toxic and harmful substances in wastewater, which ensures the possibility of struvite reutilization.In this paper, a new method based on neural network was used for optimizing orthogonal trial results to obtain the best reaction conditions. This method overcomes the shortcoming that the optimal results are always not in accordant to the truth, being sometimes not so good as that of a certain experiment by means of orthogonal analysis and regressive analysis. Furthermore, the purpose of double object optimization on the residual ammonia-nitrogen and phosphorus content isachieved. In a word, this new method provides a new way for the further research.In addition, a set of process flow was developed by author for ammonia-nitrogen removal from wastewater with struvite precipitation method, which can be used in practice.
Keywords/Search Tags:ammonia-nitrogen wastewater, chemical precipitation, ammonia-nitrogen removal, kinetic, optimization
PDF Full Text Request
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