Study On Nitrogen Removal With Activated Sludge Enhanced By Halomonas Strains For High-salt Nitrogenous Wastewater

At present,ammonia nitrogen is one of the main pollutants in China's water bodies.Wastewater from industries such as leather processing,seafood farming,and landfills is generally high-salt nitrogen-containing wastewater.This type of wastewater has a relatively low nitrogen removal efficiency in the process of activated sludge,bioreactors,etc.that rely on microbial denitrification and purification.The main reasons are High salt will significantly inhibit the growth and metabolism of microorganisms[1].Therefore,the theoretical and technical research of high-salt nitrogen-containing wastewater microbial denitrification purification treatment is of great significance.Halomonas(Halomonas),in response to high osmotic pressure,will synthesize small organic molecules osmotic pressure compensation solute Ectoine(1,4,5,6-tetrahydro-2-methyl-4-pyrimidinecarboxylic acid;1,4,5,6-tetrahydro-2-methyl-4-pyrimidinecarboxylic acid,)has significant salt tolerance.Ectoine synthetic strains can be divided into Ectoine non-secreteU type and Ectoine secreted type[2-3].Ectoine secreted strains will be able to secrete extracellularly and accumulate Ectoine in the medium under the condition of basically constant osmotic pressure.Ectoine secreted by secretory strains can confer salt tolerance to other microorganisms in a specific system[2].In recent years,studies have reported that certain strains of Halomonas can perform nitrification,denitrification,or simultaneous nitrification and denitrification(SND)under high salt conditions[4].SND denitrification has the advaltages of completing the nitrification and denitrification process in the same reactor.Part of the acid and alkali generated during the nitrification and denitrification process can neutralize each other,which can reduce the amount of buffer used[4].This article is based on the Ectoine-secreting Halomonas strain with high-salt SND denitrification and the ability to confer salt tolerance to other microorganisms in a specific system.The Ectoine-secreting Halomonas strain was used to enhance the salt tolerance of activated sludge to construct the "Synthesis-secretion-absorption" system to improve the nitrogen removal efficiency of high-salt nitrogen-containing wastewater.In this paper,a strain B01 which can synthesize and secrete Ectoine under the induction of NaCl and has high SND denitrification ability is screened and identified.Strain B01 was identified as a strain of Halomonas by 16S rDNA and named Halomonas sp.B01.Activated sludge was carried out under the conditions of Halomonas sp.B01 30 g/L NaCl.The optimized conditions for SND denitrification of salt-tolerant enhanced activated sludge are:temperature 30?,sodium acetate as carbon source,and carbon to nitrogen ratio of 5:1.Under optimized conditions,the enhanced nitrogen removal rate of activated sludge reached 94.3%,which was 75.5%higher than that of unintensified sludge.The results of salt-tolerant enhanced sludge dehydrogenase enzyme and denitrification-related enzyme activity analysis showed that the enzyme activity of salt-tolerant enhanced sludge dehydrogenase(DHA)remained high at 4-6 d(45.2 U±1.0 U),The average enzyme activity is increased by 117.1%than that without salt resistance.After the system SND denitrification and stable operation for 7 days,the activity of Halononas sp.B01 salt-tolerant activated sludge Amo,Nar,and Nir were 12.6 U,14.1 U,and 11.3 U,respectively,which were lower than the three enzyme activities of the salt-tolerant enhanced sample Increased by 215.0%,281.0%and 465.0%respectively.The microbial diversity analysis of the activated sludge before and after intensification was carried out based on the Illumina platform.The results showed that the salt-tolerance-enhanced activated sludge system at the door classification level removed four dominant bacteria that were shared with the non-salt-tolerance-enhanced activated sludge.In addition to the gates(Proteobacteria,Firmicutes,Patescibacteria,Actinobacteria),three types of gates including Bacteroidetes,Chloroflexi,and Acidobacteria were added.At the genus classification level,the salt-tolerant activated sludge system has been increased in addition to the five dominant bacterial genus(Escherichia-Shigella,Lactococcus,Klebsiella,Enterobacter,Citrobacter,Acidovorax)shared with the non-salt-tolerant activated sludge.Halomonas,Mangrovibacter,Prolixibacter and Proteus are were added.Moreover,the Halomonas genus was only detected in the salt-tolerant activated sludge system,and the fortified strain Halomonas sp.B01 has become one of the dominant functional bacteria of the salt-tolerant activated sludge.Ectoine synthesized and secreted by Halomonas sp.B01 and activated sludge indigenous bacteria constitute the "Ectoine synthesis-secretion-absorption" mode.The nitrogen removal efficiency of the enhanced activated sludge under high salt has been significantly improved.It showed that the enhanced strain Halomonas sp.B01 assisted the salt-tolerance of activated sludge microbial flora.