The Research On MAP Method And Natural Zeolite Combined For Nitrogen And Phosphorus Removal

Nitrogen and phosphorus are important elements which causes eutrophication. With the economic growth and the improvement of people's living standard, there are more and more nitrogen and phosphorus existing in the domestic sewage and industrial waste water,and they bring great trouble to wastewater treatment,and it is difficult to achieve denitrification and dephosphorization at the same time using the existing wastewater treatment technology, and it can cause high level of nitrogen and phosphorus existing in some processing unit. This study adopts sludge dewatering liquid as the research object water sample, combines the high-efficiency dephosphorization of MAP method and the high adsorption ammonia nitrogen of zeolite to find a new combined technics that can make denitrification and dephosphorization at the same time possible.The main research contents and results include the following aspects:(1) The nitrogen and phosphorus removal performance of Henan Gongyi zeolite is studied. Orthogonal experiment method is used in this experiment. grain size,dosage,rotate speed,adsorption time and pH which are the factors in nitrogen and phosphorus removal process are considered. Research shows that, grain size,dosage and rotate speed are the main factor.when grain size is greater than 60 mesh, rotate speed is 200r/min, dosage is 100g/L,pH is 6 and adsorption time is 120 min, ammonia nitrogen removal efficiency is 49.2% and the phosphorus removal rate is 95.3%. The process of ammonium adsorption by Gongyi zeolite is in accordance with Langmuir adsorption isotherm. The maximum ofNH+4-N adsorption is 8.117mg/g.(2) In order to choose the appropriate zeolite to combination, technical and economic comparison have been done between Henan Gongyi and Zhejiang Jinyun zeolite.The method of zeolite sdsorption makes main use of the high sdsorption ammonia nitrogen of zeolite.Accoeding to the mensuration,the adsorption capacity of ammonia nitrogen of Henan Gongyi zeolite is 8.190mg/g and the adsorption capacity of ammonia nitrogen of Zhejiang Jinyun zeolite is 14.31mg/g.Though Henan Gongyi zeolite has high phosphorus revomal ability,price and transportation expenses are lower then Zhejiang Jinyun zeolite, the zeolite of Zhejiang Jinyun is economical in the same removal rate. Therefore, this study adopts zeolite from Zhejiang jinyun.(3) The study has been done on the compound modes of these two processing methods. The efficiency of the compound mode on denitrification and dephosphorization is much higher then the single zeolite adsorption or the MAP precipitation method. It is beneficial for MAP precipitation method after zeolite adsorb nitrogen and phosphorus which particle size is less than 1mm.But when particle size is greater than 1mm, the change of solution pH value is not obvious after zeolite adsorption and N/P ratios after zeolite adsorption make against MAP method. So the MAP-zeolite adsorption were choosed as the compound mode.(4) Optimal operating conditions of combination process was studied.The performance of denitrification and dephosphorization of this combination process has been studied by the combination of orthogonal experiment and single factor analysis method.Through orthogonal experiment, the best operation conditions of combination process have been confirmed:aeration rate is 0.5mg/L, hydraulic retention time is 30min, zeolite column high isl6cm. N/P ratios are 1.5:1. Then intermittent water experiment was done using sludge dewatering liquid, when aeration rate is 0.5mg/L, hydraulic retention time is 30min, zeolite column high is 16cm,The removal rate of nitrogen and phosphorus is above 80%. In the end, Continuous fill test has been done. Tthrough the treatment, the water quality was stable, the average removal rate of nitrogen and phosphorus respectively were 80.97% and 93.11%, the remained concentration of ammonia nitrogen was 28.7mg/L, the remained concentration of phosphorus was 1.65mg/L.The effluent can meet the second grade of national wastewater effluent standards. This validates the performance of nitrogen and phosphorus removal of combination process, and provides technical support to the project operation of this process.