| With the accelerating of China’s urbanization process, small towns are playing animportant role in environment protection and sustainable economic development in China.The salinity wastewater nutrient removal process of small towns is different from large cityWWTP process because of its intermittent and non-steady flow of sewage. In this study,characteristics of different denitrifying phosphorus removal process are investigated; thekey operating conditions and optimizations of AOA-SBR are found by orthogonal test.Biodegradable characteristics of domestic sewage are studied in A/O/A-SBR process. Aftersludge salinity acclimation with domestic sewage, degradation of pollutants is revealed onthe condition of the shock of intermittent and continuous test. Effects of salinity on thebiological nutrient removal process are investigated. Degradation of pollutants is simulatedusing matlab and ASM2d model in A/O/A-SBR. The first proposed salinity correction termabout the phosphorus uptake/release process and the nitrification process based on ASM2d,nutrient removal activated sludge mathematical model on saline wastewater is established.The experimental results showed that phosphate accumulating organisms utilizedelectron acceptor according to its occurrence sequence. This ability is stable and feasible.The ratio of anoxic phosphorus uptake rate and aerobic phosphorus uptake rate (PUR) isdistinguished between phosphorus-accumulating and denitrifying phosphorusaccumulating organisms (DNPAOs) in biological nutrient removal (BNR) process. Resultshows that A/O/A-SBR is more beneficial than the traditional process of BNR.In the anaerobic(1.5h)/aerobic(3h)/anoxic(2.5h)-SBR process, removal efficiency ofCOD, phosphorus, ammonia nitrogen and TN are84.1%~94.8%,82.9%~92.2%,89.7%~98.3%and75.6%~85.8%,respectively.Effluent concentration are lower than "urbansewage treatment plant emission standards"(GB18918-2002) primary B standard.With an adequate adaption period and gradually increased salt concentration, effect ofsalinity on the conventional activated sludge are showed that the higher the concentrationof salinity, the lower the phosphorus release rate and phosphorus uptake rate; effects ofsalinity on the decrease of anoxic phosphorus uptake rate is greater than the decrease ofaerobic phosphorus uptake rate and denitrification rate. Meanwhile, the decrease ofphosphorus uptake rate is greater than the decrease of aerobic phosphorus release rate.When salinity is higher than7g/L, nitrite accumulation is found during the course ofnitrification. This showed that Nitrobacter is more sensitive to high salinity thanNitrosomonas. And as salinity increased, the inhibitory effect further enhances. In the SBR, the addition of4g/L,7g/L and10g/L series of salinity, nitrite accumulation is0to2.94%,41.6~52.2%and58.7~69.6%,respectively. Short-cut denitrification could be realized bythe increase of salinity; in the system integrated nitrate and nitrite, and denitrification rateof each series has no significant change.The experiment investigates the effects of intermittent shock of salinity on thebiological treatment, impact of low salinity was similar to high salinity, significant effect ofsalinity on the phosphorus removal, ammonia-nitrogen removal with minimal impact.System from low salinity shock return to normal level takes about72hours, the impact ofhigh salinity is required to restore about130hours. It has the tolerant ability of low-salinitymore than high salinity in the system.The experiment investigated the effects of continuous shock of salinity on thebiological treatment, the experiment showed that when the salinity from the10g/L,respectively, increases to15g/L,20g/L and25g/L. The higher the salinity, the lower theanaerobic phosphorus release rate. The aerobic and anoxic phosphorus uptake rate, inwhich the rate of anaerobic phosphorus release and aerobic phosphorus uptake rate effectsaffects by salinity changes are basically the same, the anoxic phosphorus uptake rate hassignificant change.In salinity acclimation period and the intermittent shock period, effect of salinity onnitrification rate is relatively small; but salinity continuous shock on the nitrification rate ofsalinity has decreased substantially when the salinity of20g/L, the nitrification rate is21.6%of salt-free conditions; salinity of25g/L, the aerobic nitrification completelyinhibited. Nitrite accumulation in the salinity of15g/L is maximum, it is80.1%.Heterotrophic bacteria has a stronger tolerant of high salinity capability than nitrifiersand PAOs. During salinity acclimation period and intermittent shocks period, PAOscompares to the nitrifying bacteria are more sensitive to salinity; after a acclimation, in thecontinuous impact of salinity conditions, the PAOs on the salinity tolerance of slightlystronger on nitrifiers. In A/O/A-SBR, the result showed that the salinity tolerant limit ofPAOs is20g/L under salinity continuous shocks condition; nitrifiers is15g/L undersalinity continuous shocks condition.In ASM2d model, salinity inhibition term is introduced into the biochemical processof the model. After the simulation and optimization, the model is established on simulatesalinity wastewater treatment. The aerobic phosphorus uptake inhibitory factor KsalXPH,anoxic phosphorus uptake inhibition factor KsalXPQ, anaerobic phosphorus releaseinhibition factor KsalSP and nitrification inhibition factor KsalXH recommended values are:12.0g/m~3,10.8g/m~3,14.6g/m~3,15.3g/m~3,respectively. |
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