Process Design And Operation Control Technology Of High Ammonia-Nitrogen Wastewater Pretreatment

The discharge of large amount of ammonia nitrogen wastewater has resulted in large water pollution in our country,especially the wastewater pretreatment with high concentration of ammonia nitrogen has became a vital problem of environmental,which needs to be solved currently.Based on the analysis of the sources and features of wastewater in a chemical enterprise in Shijiazhuang City,the pretreatment of the ammonia nitrogen wastewater was identified through air stripping process.And laboratory scale test,process design and running were also completed,aiming at offering guidance to the pretreatment of similar wastewater with high ammonia nitrogen.1)A laboratory scale test was carried with the process of air strippinng,of which the influencing factors on the removal rate of ammonia nitrogen including the gas-liquid ratio,the temperature of the wastewater,the stripping time and pH were investigated.The results showed that the optimum reaction conditions removing ammonia nitrogen by stripping method were 10.5 of pH,4h of reaction time,1 000:1 of gas-liquid ratio,and 55? of temperature.Under this conditions,the concentration of ammonia nitrogen wastewater decrease from about 2 870~3 510 mg/L down to 190 ~227mg/L after treatment by the stripping process,and the effluent NH3-N removal rate reached more than 93%.2)According the relevant standards,design code,and the laboratory scale test,the pretreatment of the ammonia nitrogen wastewater was identified through air stripping process in order to achieve low operating cost and good quality.The tail gas was absorbed by hydrochloric acid absorption system for reused.Then the design of the pretreatment was made,in which the main technical parameters and corresponding matching equipment was presented.The construction scale for the operation was 250 m~3/d,with which an occupied area was 156 m2,and total investment of wastewater pretreatment project was 2072.5 thousand yuan.3)On the basis of the construction of the project,the process running and optimize control parameters was completed.Determination of optimal operation parameters for air strippinng was 11 of pH,60? of temperature,10 000 m~3/h of air flow,and 4 h of reaction time.Under this conditions,the ammonia nitrogen concentration decreased from about 2 850~3 510 mg/L to 233~275 mg/L.And the effluent NH3-N removal rate reached about 91%.The sewage processing station running costs was 424.8 thousand yuan/a(6.18 yuan/ton),and economic benefit of ammonia gas recycle was 131.4 thousand yuan/a,and The total amount of removed NH3-N reached 2 043.9 t/a,respetively.Therefore,the project has good economic benefit,environmental benefit and social benefit.