Technical Study On Enhanced Treatment Of Nitrogen And Phosphorus In Wastewater By Modified Zeolite

The shortage of water resources is a major problem facing our country.Reclaimed water is recognized as the second source of water,the research and popularization of reclaimed water reuse is of great significance.According to the "13th Five-Year" eco-environmental protection plan,China will further promote the use of reclaimed water.The reuse of recycled water to landscape water is one of the main ways to reuse sewage.Domestic reclaimed water is being used in landscape water at an early stage.The water bloom is one of the most important problems in the process of reusing the reclaimed water,and the high concentration of nitrogen and phosphorus in the water is the main cause of the problem of water bloom.Biological nitrogen and phosphorus removal process has the advantages of simple operation and simple post-processing.However,it is difficult to meet the first grade discharge standard and reuse standard if the biological nitrogen and phosphorus removal process is applied alone.If the biological nitrogen and phosphorus removal process is added on the basis of the two level treatment,it is difficult to show its low cost advantage.The adsorption method and ion exchange method have the advantages of small area,simple process,stable effect,less sludge production and convenient operation,and have greater advantages in the treatment of nitrogen and phosphorus.The special crystal structure of zeolite has unique adsorption and ion exchange ability.Zeolite has strong selective adsorption capacity for ammonia nitrogen,but hardly adsorbed on nitrate nitrogen,nitrite nitrogen and phosphorus.In this paper,the Zhejiang clinoptilolite was modified to obtain lanthanum modified zeolite,sixteen alkylpyridine bromide(CPB)modified zeolite and composite modified zeolite.Lanthanum modified zeolite can effectively remove phosphorus.CPB modified zeolite can effectively remove nitrate nitrogen,and composite modified zeolite has the ability of simultaneous removal of nitrogen and phosphorus.Based on the analysis of various influencing factors of lanthanum modified zeolite,the optimum preparation conditions of lanthanum modified zeolite were obtained:the concentration of lanthanum chloride is 4g/L,the pH value of the solution is 9.6-9.7,the modification time is 10 h and the solid-liquid ratio is 1:40.The optimum preparation conditions of CPB modified zeolite are as follows: the concentration of CPB is 5g/L,the modified temperature is 35,the modification time is 24 h and the solid-liquid ratio is 1:30.Composite modified zeolite obtained from lanthanum modified zeolite modified by CPB surfactants that has the ability of simultaneous removal of nitrogen and phosphorus.However,compared with the modified zeolite alone,the removal rate of zeolite decreased,considering economical and technical considerations,composite modified zeolites are not used.The pH and temperature of the solution have little effect on the ability of the lanthanum-modified zeolite to remove phosphorus.The pH has a certain influence on the ability of the CPB-modified zeolite to remove nitrate nitrogen but has little effect.The adsorption characteristics showed that the Langmuir equation had a good fitting effect on the adsorption of phosphorus and nitrate nitrogen.The maximum adsorption capacity of lanthanum modified zeolite to phosphorus is 10.57mg/g.The maximum adsorption capacity of CPB modified zeolite to nitrate nitrogen is 1.33mg/g.The pseudo two stage reaction kinetic equation can better describe the adsorption process of nitrate nitrogen and phosphorus.The zeolite powder was added to the mixing tank and the zeolite particles were added to the filter column as filter media.And the standard of surface water IV water is the effluent water quality standard.Only consider the treatment of low concentrations of nitrogen and phosphorus with a filtration process,the filtration time is 3min for natural zeolite,6min for lanthanum modified zeolite,7min for CPB modified zeolite,in this case,the filtration process has a better removal effect of low-concentration target pollutants..Only add natural zeolite filter,The contact time of natural zeolite filter is 3min.,the removal effect is relatively poor.The experimental study found that a proper amount of zeolite powder was added to the mixing pool.The contact time of the filter column was as follows: natural zeolite 3min,lanthanum modified zeolite 10 min,CPB modified zeolite 10 min,at the same time,a proper amount of zeolite powder is added to the mixing pool..In this case,the mixed precipitation filtration process can continue to work for 44 hours under the water quality standard for Class IV surface water.