Enhanced Carbon And Nitrogen Removal Performance Of Simultaneous Anammox And Denitrification (SAD) With Compatible Solutes Addition Treating Saline Wastewater

The discharge of saline wastewater is increasing day by day.To the question of unsatisfied performance of nitrogen removal in treating saline wasterwater,we used the acclimation of a freshwater-origin anammox and denitrification sludge having been domesticated by seawater.In this study,we investigated the effect of compatible solutes（mannitol,trehalose）on the performance of simultaneous anammox and denitrification（SAD）treating saline wastewater and the kinetics analysis.We also studied the recovery performance of SAD after mannitol inhibition.The enhanced performance of SAD with mannitol addition treating saline wastewater and kinetics analysis were studied.The optimum ARE（96.95 %）,NRE（93.70 %）and ORE（90.05 %）were achieved at 0.2 m M mannitol,during which ARR and NRR were improved by 27.08 % and 55.41 %,respectively,compared with no addition of mannitol.The maximum SAA and Vmax were improved by 24.00 % and 57.05 %,respectively.Mannitol（≤0.2 m M）could promot the particle size of granular sludge and sludge granulation.With the increasing addition of mannitol until 0.6 m M,ARE was only 36.78 % and the effluent NH₄⁺-N concentration was down to 49.82 mg/L.Tseng-Wayman model was the most suitable to describe nitrogen removal process with the addition of mannitol treating saline wastewater compared with Haldane model,Aiba model,Ewards model,Luong model and Han-Levenspiel model.The modified Logistic model,modified Boltzman model and modified Gompertz model were all suitable to describe the process of nitrogen removal in a typical cycle.The recovery nitrogen removal performance of SAD after mannitol inhibition were studied.The inhibitory effect of high concentration of mannitol（0.6 m M）on SAD is reversible.Gradually reduce the addition mannitol,the nitrogen removal performance of SAD could recover in 53 cycles.The modified Boltzman model can more effectively simulate the recovery process of SAD after inhibitionEnhanced performance of SAD with trehalose addition treating saline wastewater was investigated in SBR.The optimum nitrogen removal were achieved at 0.25 m M trehalose,NH₄⁺-N,NO₂^--N,NO3--N and COD could be completely removed.Compared with no addition of trehalose,ARE,NRE were improved by 50 % and 43 %,ARR and NRR were improved by 81.25 % and 75.00 %,the maximum Vmax and SAA were improved by 55.11 %and 52.36 %,respectively.With the increasing addition of trehalose till 0.5 m M,ARE was only 58.82 % and the effluent concentration of NH₄⁺-N was 33.25 mg/L.When the concentration of trehalose was 0.4 m M and 0.5 m M,the single-cycle p H value increases first and then decreases.The activity of anammox was inhibited by chemical balances between NH₄⁺-N and free ammonia in the reactor after the reaction time of 3.5 h.Therefore,it is of great significance to add appropriate amount of trehalose to relieve salt toxicity of SAD.Theaddition of trehalose can promote the granulation of sludge and increase the particle size of granular sludge.Compared with Haldane model and Aiba model,Luong model was the most suitable to simulate the nitrogen removal performance of SAD with trehalose addition treating saline wastewater.The NRRmax,Ks,Sm and n fitted from Luong model were 0.954kg/（m3·d）,0 mg/L,184.785 mg/L and 0.718,respectively.The effluent substrates concentration was controlled below 184.79 mg/L to optimize the operation condition of SAD with trehalose addition treating saline wastewater.The prediction formula of total nitrogen concentration was established by using these three models.Compared with the modified Logistic model and the modified Boltzman model,the modified Gompertz model was the most suitable to describe degradation of the substrate in a single-cyle.