Study On Degradation Of High Ammonia Nitrogen Salty Wastewater By Continuous Flow Short-cut Nitrification And Denitrification

When there is high concentration of ammonia nitrogen and salt in the sewage,it will bring great harm to the environment.The traditional activated sludge denitrification process may cause the system to collapse due to salt,so more and more people begin to focus on the new type of nitrogen removal Craftsmanship.Among them,the short-range nitrification and denitrification process can rely on activated sludge microorganisms to control the nitrification process in the ammonia oxidation stage,and then perform denitrification.Compared with the traditional denitrification process,it has the advantages of energy saving,fast reaction rate,and low sludge production.Therefore,this study aimed at high ammonia nitrogen saline wastewater by quickly starting continuous flow short-range nitrification and continuous flow denitrification,and studying the effects of salinity on continuous flow short-range nitrification and continuous flow denitrification.The results are as follows:(1)Under the condition of temperature 28±2?and dissolved oxygen 0.1-0.5 mg/L,continuous flow half-quantity short-range nitrification and domestication culture under semi-alkalinity conditions can achieve half-quantity short-range nitrification within 9 days.The removal rate was 53%,and the nitrite nitrogen accumulation rate was as high as 92.3%.The optimal operation of continuous flow semi-quantity short-range nitrification unit has a dissolved oxygen concentration of 0.2-0.3 mg/L.When continuous flow anaerobic ammonia oxidation is started directly with CSTR half-quantity nitrification effluent,the whole process of nitrification and denitrification can occur in the system,and anaerobic ammonia oxidation cannot be achieved.(2)It takes about 20 days to switch from continuous flow half-volume short-range nitrification to continuous flow short-range nitrification.During the conversion process,NOB bacteria were washed off by reducing the SRT to 18th to maintain good nitrosation.The ammonia removal rate was up to 98.36%,and the NAR was stable at 90%;by gradually increasing the concentration of NO2~--N in the influent It takes about 20 days to start continuous flow denitrification by way.When the NO2~--N concentration is about 300mg/L,the removal rate of NO2~--N is stable at about 87%;during the whole start-up process,the continuous flow denitrification sludge SDR shows an upward trend,Increased from 53.4 mg(NO2~--N)/(g(MLSS)·d)to about 62.5mg(NO2~--N)/(g(MLSS)·d).During the start of continuous flow denitrification,the sludge SV30gradually decreased from 75.0%to 40.5%.(3)At four salinity levels of 0,5,10,and 15g/L,the average value of NO2~--N concentration in continuous flow nitrification effluent is higher than 270mg/L,the average NAR is higher than 91%,and the effluent NH4~+-N The average value of N concentration is below 9 mg/L,and the average value of NO3~--N concentration is 25.26 mg/L,which is continuously decreasing to 11.22 mg/L.The continuous flow short-range nitrification sludge SAOR is relatively stable.Under the stress of salinity,the content of each component of EPS in continuous flow short-range nitrification sludge changed to some extent with the change of salinity.As the salinity increased from 0 g/L to 15 g/L,each component had an increasing trend with different amplitudes.When the concentration of NO2~--N in the inlet water of the continuous flow denitrification device is maintained at around300mg/L,the concentration of NO2~--N in the effluent fluctuates greatly,but the removal rate is maintained above 70%.Because the addition of salts inhibits the activity of dehydrogenase and reduces the microbial metabolic rate,it also leads to a reduction in the denitrification sludge SDR.When the salinity increased from 0 g/L to 5 g/L,the content of each component of the denitrifying sludge EPS reached the highest,and then gradually decreased as the salinity increased.The sodium acetate used in the test is easy to absorb and degrade,which causes the microorganisms to secrete more extracellular enzymes,which results in that the protein content of LB-EPS and TB-EPS in sludge is higher than that of polysaccharide at all salinities.