Removal Of Ammonium Nitrogen From Piggery Wastewater Through Adsorption By Natural Polymer

By 2014,there are 140984 large scale breeding farms and 9128 breeding aquatics village in China,which produced 0.287 million tons of ammonia nitrogen and 1.392 million tons of total nitrogen.Large scale poultry and livestock farms have exceeded more than industry in the discharge of ammonia nitrogen,and account for 38%in agricultural sources.With the ever-increasing market demands of the poultry and domestic animal products,the large scale and intensive breeding farms have been developed rapidly.The piggery wastewater contains abundant organic materials,ammonia nitrogen,phosphorus,suspended solids and pathogenic bacteria,thus it brings a lot of pressure to environment and threats to people.In 2015,there are 52 large-scale livestock farms become severe environmental monitoring objects.The piggery wastewater causes pollution to the environment,limits animal's development and does harm to people' s health.These problems should be urgently solved.The anaerobic-aerobic method was mainly used in the treatment of swine wastewater at home and abroad.Although most of the organic pollutants in wastewater were degraded in the anaerobic tank,the concentrations of nitrogen were still high in the digested swine wastewater,some of them were even higher than before.Biological systems?biological nitrification-denitrification?have provided an effective solution,where ammonium was firstly transformed to nitrite,then to nitrate,and finally to nitrogen gas.However,biological systems couldn't deal with the high shock loads of ammonium completely,so the phenomenon that ammonium concentrations in the effluent exceeds the discharging levels may frequently appear.Besides,the treatment of ammonium nitrogen wastewater of low organic content by a biological process usually needs to be supplemented with extra carbon source,which may increase the treatment costs.In this case,the efficient removal of ammonia nitrogen which uses adsorbent has been considered as a potential solution to the environmental pollution in recent years,and the ammonium adsorption using zeolites as adsorbent are gaining on interests.The adsorption?ion-exchange?is convenient to be implemented and easy to be controlled,and the physicochemical stability makes it available.Using zeolites,cationic exchange resin,activated carbon and clay as the adsorbent to ammonia nitrogen have been widely reported in the domestic and overseas.However,the above materials have not been widely applied because of the limitation of high processing and regeneration cost.In view of the above,this paper used a material which is a natural polymer that is yielded rich and large in quantity and can be recycled to treat piggery wastewater deeply.The main observations and conclusions are as follows:1.Natural polymer Y has the largest adsorption capacity of ammonia nitrogen when reaction time is 3 hours.The heightener of ammonia-nitrogen removal increased with pH and initial ammonia concentration.But as the increment of the temperature,the adsorption capacity descends.Four kinds of metal cations in various concentrations will impact the adsorption capacity of natural polymer Y,the degree as:Ca²⁺?Mg²⁺>K⁺>Na⁺.The adsorption of ammonia nitrogen by natural polymer Y belongs to the exothermic reaction,so natural polymer Y has a strong performance under the condition of normal or low temperature.As the increment of dosages,the ammonia removal efficiency of natural polymer Y increased.2.There was no significant difference in NH₄⁺-N adsorption capacity between natural polymer Y and cation exchange resin.Even though artificial zeolite can save reaction time,its capacity is 58% lower than natural polymer Y and cation exchange resin.With the wastewater filtrate pH increased,the ammonia nitrogen adsorption capacity of Y increased as well.The adsorption of ammonia nitrogen by natural polymer Y belongs to the exothermic reaction,so natural polymer Y has a strong performance under the condition of normal or low temperature.As the increment of dosages,the ammonia removal efficiency of natural polymer Y increased.3.Natural polymer Y is partially soluble and the soluble portion takes 17.2%of the integrated part.Under the condition of 500 mg L^-1 of NH₄⁺-N,pH= 10,25? the maximum binding capacity?MBC?of soluble fraction was 26.95 mg NH₄⁺-N g^-1 of DOC,the other part's adsorption capacity was 17.0 mg g^-1 of whole natural polymer Y.Co-existing metal cations played an important role in ammonia nitrogen binding to soluble fraction.MBC decreased with the increase of metal cations.Whereas,high concentration of ammonia nitrogen could blunt the effect of co-existing cations.Even though total co-existing metal cations was at high concentration,275 mg L^-1,the binding capacity coule still reach 3.38 mg NH₄⁺-N g^-1 of DOC,when initial concentration of NH₄⁺-N was increased to 2000 mg L^-1.4.It was found that several kinds of flocculant were able to polymerize the dissoluble part and made it become deposits.With the proper concentration of polymeric Aluminum and Ferric was added in,the total organic carbon?TOC?decreased from 1013 mg L^-1 to 50 mg L^-1 in under 4 minutes.What's more,TOC could decreased below 1 mg L^-1 if precipitation time could be extended to 1 hour.When there was no co-existing cations in the wastewater,flocculant made the bound NH₄⁺-N leach out slightly.The leaching out rate was different between different pH,they were 29.5%,14.5%and 18.3%in pH=6,8 and 10,respectively.However,when there was no metal cations in wastewater,bound NH₄⁺-N would no longer leach out after adding in flocculant.The results indicate that natural polymer Y with remarkable ammonium adsorption efficiency shows good prospect in practical application.