Experimental Study Of High Salinity Wastewater Treatment By Cyclic Activated Sludge Technology Process(CAST)

In recent years,high-salt wastewater biological treatment has been the hotspot of research in academe and engineering world,and various new technologies are emerging in endlessly.CAST(Cyclic Activated Sludge Technology) process is a new techniques which is based on SBR(Sequencing Batch Reactor) and combined with biological selection principle. Since it can provide SND(Simultaneous Nitrification and Denitrification) with good technical conditions to realize high efficiency denitrogenation,so it does not only proved short flow, high efficiency,space saver,but also has good effect on removing organism and nitrogen and so on.In this paper,the organics degradation rate and NH₄⁺-N removal efficiency are studied in high salinity wastewater by CAST process.At first,compared the active sludge acclimations,under two conditions of increasing the seawater proportion to 70%gradually and remaining 50%seawater load at beginning.And then the effects of influent concentration of COD,NH₄⁺-N and stock salinity on the whole activate sludge system are also studied.Under normal temperature(25℃),experimental results showed that the removal rate of COD and NH₄⁺-N from high-salt wastewater is about 85%and 87%respectively under the condition of the influent COD concentration is 350mg/L,But the fomer need longer acclimated time than the latter one.After acclimation,the Sâ…¥(sludge volume index) decreased with the increasing of salinity,and sludge settling property has improved.Under the experimental condition of pH around 7.0;dissolved oxygen:2.0～3.0mg/L; sludge concentration about 3500mg/L;the influent concentration of COD and NH₄⁺-N are 350mg/L and 40mg/L respectively,the removal efficiency of organics and biological nitrogen decreased with the salinity increasing.When the salinity exceeded 17.25g/L(50% seawater propotion),the removal efficiency of organics decreased significantly,the result shows that the limit for microorganisms salt-tolerant of organics removal is 17.25g/L. Compared to organics removal efficiency,the influence of salinity was not remarkable in the scope of 70%seawater proportion,this kind of difference is due to the influence of different degree in removing organics and NH₄⁺-N with salinity.In the steady high salinity sludge system,with the influent concentration of COD and NH₄⁺-N increasing,the removal efficiency drops.In addition,the salinity shock effect of 30% proportion seawater on COD and NH₄⁺-N removal efficiency is light in the steady CAST system,and the salinity shock of 70%proportion seawater need three cycles to come back the initialization,and no seawater need five cycles.