Study On Nitrogen Removal Characteristics Of Pseudomonas Sp.ZSY

Nitrogen is widely found in the natural world.The nitrogen in water is mainly in the form of inorganic nitrogen and organic nitrogen.In recent years,nitrogen pollution in water bodies has become increasingly serious with the large-scale use of pesticides and the discharge of industrial waste water containing nitrogen.Therefore,how to quickly remove organic nitrogen and inorganic nitrogen from water is an urgent environmental problem.Currently,some studies have been conducted on the removal of nitrogen from these two forms,mainly through ammoniating bacteria,nitrifying bacteria,and denitrifying bacteria,organic nitrogen and inorganic nitrogen are converted into nitrogen emissions.Many microorganisms are used in the process of nitrogen conversion,which makes the conversion process complicated and requires large investment.In the organic nitrogen conversion process,screening microorganisms that can ultimately convert organic nitrogen into nitrogen is easier than traditional denitrification processes.At present,there is less research on this type of microorganism.This project has attempted to screen out microorganisms that can convert organic nitrogen into nitrogen,and study the ammoxidation,heterotrophic nitrification and aerobic denitrification functions of the strain under aerobic conditions,and the ammoxidation and heterotrophic denitrification functions under anaerobic conditions.The main findings are as follows:In this paper,a strain Pseudomonas sp.ZSY which has both heterotrophic nitrification,aerobic denitrification,and ammoniating function was screened out from sludge in Guangxi estuary.We investigated the nitrogen removal performance of strain ZSY and found that:The strain ZSY can aminate ammonia nitrogen,aspartate,urea and ammonium oxalate to ammonium nitrogen under aerobic conditions,and under aerobic conditions,the above ammoniated product can be further converted to nitrogen by heterotrophic nitrification aerobic denitrification process.Under anaerobic conditions,the strain ZSY was inoculated in a medium containing both asparagine and ¹⁵N-labeled nitrate nitrogen,and the ammonium nitrogen,nitrate nitrogen and nitrite nitrogen of the product were determined,the strains were found to be able to remove these two nitrogen sources simultaneously.An isotope analysis of the product ammonium nitrogen did not reveal ¹⁵N-labeled ammonium nitrogen,indicating that the bacteria did not have DNRA function.Although nitrite nitrogen is toxic to bacterial growth,the experimental strain ZSY can still handle high concentrations of nitrate nitrogen and nitrite nitrogen under aerobic conditions,and also has good activity when treating 300mg/L of nitrite nitrogen.Under aerobic conditions,strain ZSY can utilize a variety of organic carbon sources for denitrification.When using sodium citrate and sodium lactate as carbon sources,denitrification has the best effect,and nitrate nitrogen removal efficiency is the highest.When examining the effect of initial nitrate concentration on the aerobic denitrification process,it was found that when the initial nitrate nitrogen concentration was less than 350 mg/L,it still had high denitrification capacity,and no nitrate and nitrite nitrogen accumulated during the period.Only with the increase of initial nitrate concentration,the denitrification time was prolonged.When the nitrate concentration was 50 and 10 mg/L,the complete degradation time of nitrate nitrogen was 12 h;when the nitrate concentration was 150 mg/L and 220 mg/L,the complete degradation time was extended to 24 h;when the nitrate nitrogen concentration was increased to 350 mg/L,the complete degradation time was extended to 48h;The optimal C/N ratio for the aerobic denitrification of strain ZSY was 15;When examining the effect of initial ammonia nitrogen concentration on the heterotrophic nitrification ability of the strain under aerobic conditions,it was found that the strain also showed better heterotrophic nitrification capacity when the ammonium nitrogen concentration was as high as 240 mg/L.However,when the concentration of ammonia nitrogen was increased to 450 mg/L,the removal efficiency of ammonium nitrogen was only 59.35%at 48h.With continued increase of ammonium nitrogen concentration,the heterotrophic nitrification ability of the strain was inhibited.In the process of simultaneous degradation of organic nitrogen asparagine and nitrate under anaerobic conditions,different initial nitrate concentrations have a certain influence on the ability of the strain to degrade asparagine.When the initial nitrate nitrogen concentration is within a certain range,the amount of asparagine degraded gradually with the increase of the initial concentration of nitrate nitrogen,and the amount of ammonium nitrogen produced is largest when the concentration of nitrate nitrogen is 280 mg/L.However,increasing the initial nitrate concentration will prolong the complete removal time of nitrate.Different C/N also affected the ammoniation ability of the strain.When the C/N was 15,the amount of ammonium nitrogen was highest,but when C/N was increased to 20,the ammoniation ability of the strain was inhibited.When C/N was 5,the complete removal time of nitrate nitrogen was prolonged to 24 h.When the C/N was increased to 20,the complete degradation of nitrate nitrogen was shortened to 10 h.At the concentration of 200 mg/L ammonium nitrogen,it still has the ability to degrade asparagine,but too high ammonium nitrogen concentration will inhibit the ammoniation ability of strain ZSY.However,the denitrification capacity of the strain was not affected when the initial ammonia nitrogen concentration was increased.