Removal Of Ammonia Nitrogen Pollutants From Wastewater By Natural And Modified Zeolite

With the increasing sewage discharge standards promulgated by the state and local governments,the treatment efficiency of total nitrogenconcentration by the wastewater treatment plants(WWTPs)directly determines the production efficiency and economic benefits of the enterprises.Zeolite treatmenttechnologies are directed to ammonia nitrogen wastewater treatment and drink water treatment processes,but little research has been done on the removal performance of urban WWTPs.This paper selected zeolites from Shijiazhuang,Xinyang and Faku areas and took the actual influent of WWTPs as the research object to investigate the removal performance of chemical oxygen demand(COD)and ammonia nitrogen in the influent water.Besides,the zeolite was modified by high temperature,NaCl,alkaline,microwave and other means to improve its removal performance.Finally,based on its characteristics,the zeolite aeration filter process was developed.The contribution of total nitrogen removal from the influent was investigated.The main topics of this paper were:(1)The influence of seven factors on the removal of ammonia nitrogen by zeolite were investigated.The factors affecting removal were in the sequence as follows: reaction time>particle size>speed>pH> producing area >temperature>dosing amount.(2)Zeolite was modified by high temperature,salt,alkali,acid and microwave.It was found that the best modification method was hightemperature combined with NaCl addition.After modification,the removal rate of ammonia nitrogen reached 79.75%.(3)For the five modified zeolite methods,the high-temperature modification showed the largest difference between the highest and lowest removal rates,with a difference of 31.97%,and the difference between the highest and lowest removal rates of the other four modification methods did not exceed 15%.(4)When the residence time was 1h,the removal rate of COD and ammonia nitrogen was 26.8% and 86.4% respectively.The ratio of COD / ammonia nitrogen increased from 3.54 to 19.13 before and after treatment.Considering that too long stay time of empty bed is unfavorable to the project,1h is selected as the best stay time of empty bed in this test.(5)The "zeolite filter + biochemical treatment" process is developed.When the influent COD and ammonia nitrogen are 120 mg /L and 45 mg /L,the COD/ammonia nitrogen of the biochemical phase increased from 2.67 to 5.67,the theoretical value of the effluent total nitrogen concentration can be as low as 4.5 mg/L.