Study On Nitrogen Removal Efficiency From Pretreated Low C/N Spandex Wastewater Using One-Stage Partial Nitritation And Anammox Process

Water eutrophication was becoming more and more serious,and the discharge standards of nitrogen and phosphorus were becoming more and more strict.The traditional nitrogen removal process cannot treatment low C/N wastewater,and it is extremely important to develop economical and efficient nitrogen removal technology.Spandex wastewater with anaerobic pretreatment is a typical low C/N wastewater.One-stage partial nitrification/anammox?PN/A?process doesn't require additional carbon sources,and the application and promotion of this process will be the key to treating this wastewater.In this project,nitrogen was removed from pretreated low C/N spandex wastewater using the one-stage PN/A process.The granular sludge stored in the continuous stirred tank?CSTR?was used to explore effective regulation pathways and important impact factors for rapid adaptation to higher concentrations of ammonia nitrogen.It would be used to treatment the pretreated spandex wastewater in the internal-loop airlift reactor?ALR?by asynchronous domestication.The impact of C/N enhancement on the nitrogen removal efficiency was explored and the regulation strategy was discussed in the one-stage PN/A process.The specific research contents and results were as follows:?1?The changes of ammonia nitrogen concentration in the influent would affect the synergy between functional bacteria,resulting in system instability.The inoculated granular sludge suitable for high ammonia nitrogen wastewater was limited and difficult to start quickly.The granular sludge stored at room temperature for 2 months was used as inoculated sludge.The two phases were adapted to 275 mg·L^-1 and 400 mg·L^-11 ammonia nitrogen concentration by increasing 125 mg·L^-1.Three regulation strategies of rapidly adapting to high ammonia nitrogen load were studied.The strategy of smoothly increasing load was conducive to the rapid recovery of sludge activity.After the functional microorganisms were enriched,Sludge resistance to load shocks was improved,and the sludge could directly adapt to the influent ammonia nitrogen concentration of400mg/L.High free ammonia?FA?concentration is an important factor in inhibiting sludge activity.FA should be less than 16.6 mg·L^-1.The f-value??NO₃^--N/?TN?was taken as an important basis for dissolved oxygen?DO?regulation and DO was positively correlated with the ammonia nitrogen removal load.?2?At present,the one-stage PN/A theoretical study is mainly based on artificial ammonia nitrogen wastewater,and there is less research on the impact of water quality changes caused by artificial water to actual wastewater about nitrogen removal efficiency.By gradually acclimating the proportion of influent pretreatment wastewater,investigated the effect of anaerobic pretreatment of spandex wastewater on the nitrogen removal efficiency and the performance of granular sludge in the one-stage PN/A reactor.After 89days,the asynchronous domestication strategy was successful,and effective nitrogen removal was achieved in the one-stage PN/A process.The total nitrogen removal load was 3.2 kg·?m³·d?^-1.The effect of pretreatment wastewater on the system led to DO concentration decreasing;sludge activity inhibition and activated sludge yield increasing.After adapting to the pretreated wastewater,the type and proportion of elements contained in the granular sludge hardly changed.?3?Since anaerobic wastewater generally contains a certain amount of organic carbon,the pretreatment process is adjusted to change the organic matter content in the wastewater,and the effect of C/N increase on the nitrogen removal efficiency is studied.The results show that when the pretreatment wastewater C/N is lower than 0.45,the nitrogen removal performance in the reactor is stable;when the C/N rises to 0.6,the total nitrogen removal rate is rapidly lower than 53%,and the nitrite is seriously accumulated,FNA will lead to deterioration of nitrogen removal,and anaerobic ammonium oxidation bacteria?Anammox,AMX?has a higher inhibitory effect on C/N increase than for aerobic ammonia oxidizing bacteria?AOB?.After recovering the synergy between AMX and AOB by reducing DO,the strategy of extending hydraulic retention time?HRT?can increase the total nitrogen removal rate to 72.7%.This is due to a reduction in nitrogen load and an increase in MLSS rather than recovery of AMX activity.Increasing the C/N to 0.6 reduces the BET specific surface area of the sludge particles by 60.95%and the BJH void ratio by 25.02%.Therefore,the high-efficiency granular sludge should have a large specific surface area and a small pore size distribution.After 176 days,the system became the simultaneous partial nitrification,AMX and denitrification?SNAD?process.83.1%of the nitrogen was removed by AMX,16.9%of the nitrogen was removed by denitrifying bacteria?DNB?,and AMX remained the major nitrogen removal pathway.Strategies such as increasing organic carbon(153 mg·L^-1),decreasing DO concentration(1.3 mg·L^-1),and prolonging HRT?2.3 h?are beneficial to the enrichment and activity enhancement of denitrifying bacteria.This study will provide a new idea for the nitrogen removal of high ammonia nitrogen and low C/N wastewater using the one-stage PN/A process,providing a good basis for applications and providing reliable parameters for regulation.