Research On Removal Efficiency And Simultaneous Nitrification And Denitrification Efficiency In Sequencing Batch Biofilm Reactor Of Low Saline Wastewater Treatment

In manufacturing process such as printing, dyeing, paper making, chemical making,pesticide making will produce a high salt content of organic waste; direct use ofseawater will also produce salinity wastewater. Inorganic ions in wastewater treatmentwill produce inhibition of biological nitrogen removal, leading to difficulties forbiological treatment of saline wastewater. Currently there are differences at home andabroad for salinity effects on biological wastewater treatment. In this paper, twosequencing batch biofilm reactors with different fillers were used for treatment ofsaline domestic wastewater by simultaneous nitrification and denitrification. Makestudies on the membrane of the SBBR, the effect of salinity on total nitrogen andCOD removal, the effect of salinity of simultaneous nitrification and denitrificationand the contribution of suspended sludge and biofilm in SBBR for nitrogen removal.The conclusions of this study can be summaried as follows:（1）The sequencing batch biofilm reactor forms biofilm under the condition ofinoculation sludge, in the stage of biofilm formation, COD removal efficiency in tworeactors was good, it reached above90%on the third day; ammonia removalefficiency was low and volatile, it reached80%after35days and keeps steadyremoval efficiency, the nitrifying bacteria culture matures. During the stage ofbiofilm formation, COD and ammonia removal efficiency were nearly in the tworeactors.（2）With the increasing of the salinity, the COD removal efficiency in the tworeactors had little change, the average removal efficiency was above88%, the CODremoval efficiency in the two reactors was nearly. At the salinity of0.15%, the initialtotal nitrogen removal efficiency was low due to the changes in operating mode. After43days the total nitrogen removal efficiency was above70%and was stable. After,the concentration of total nitrogen in the effluent increased as the salinity increasing.The total nitrogen removal efficiency was the best under the salinity of0.45%. Whenthe salinity was below0.45%, the salinity did no substantially affect on the totalnitrogen removal efficiency; when the salinity was above0.45%, the total nitrogenremoval efficiency decreased with the salinity increasing. SBBR with combinedpacking had slightly better total nitrogen removal efficiency than SBBR withsuspended filler.（3）When the salinity was below0.45%, the ammonia concentration in effluentof the SBBR with combined packing decreased with the salinity increasing, which isbecause the low salinity didn’t produce inhibition on the nitrification.; when the salinity was above0.45%, the ammonia concentration in the effluent increased withthe salinity increasing, nitrification process was inhibited. When the salinity increasedfrom0.15%to0.30%, the nitrite concentration in the effluent of the SBBR withcombined packing increased. Then as the salinity increasing, the nitrite concentrationin the effluent decreased, indicating that the adaptability of the nitrifying process wasstong to salinity. Part of nitrifying bacteria could adapt to high salinity, when thesalinity was lower than this concentration, the nitrite accumulation could be theinadaptation of the nitrate to the increasing of the salinity. After a period ofacclimation, the microbes can adjust their osmotic pressure to adapt certain salinity.The accumulation of nitrate nitrogen was not obvious under different salinity, thenitrate concentration in the effluent was below3mg/L. It states that the denitrificationprocess was good, low salinity had little inhibition of the denitrifying. The ammoniaand nitrite concentration in the effluent of the SBBR with suspended fillers was lowerthan the SBBR with combined packing, so the nitrification of SBBR with suspendedfillers was stronger. But the nitrite concentration was high, explain that thedenitrification capacity was lower than the SBBR with combined fillers.（4）As the salinity increasing, the simultaneous nitrification and denitrificationrate of the SBBR with combined fillers increased, when the salinity was0.60%, thesimultaneous nitrification and denitrification rate was100%. In the suspended fillerSBBR when the salinity was below0.45%, the simultaneous nitrification anddenitrification rate increased as the salinity increasing; when the salinity was above0.45%, the simultaneous nitrification and denitrification rate decreased as the salinityincreasing.（5）In order to study the contribution of the biofilm and suspended sludge in theSBBR, remove the suspended sludge of the combined packing SBBR into an emptyreactor, this is the suspended system; there was only attached state of microorganismsin the original SBBR, this is the biofilm system. The original SBBR is hybrid system.The total nitrogen removal efficiency in the hybrid system reached75%was thehighest; the removal efficiency in the biofilm and suspended sludge system were68%and67%, respectively. The simultaneous nitrification and denitrification rate in thehybrid system, suspended sludge system and biofilm were100%,20.3%and93.1%,respectively. Nitrification rate in biofilm system and suspended sludge system were0.317.and0.969. The biomass in the biofilm system is1.12times than in thesuspended sludge system, so the nitrification rate in the suspended sludge system was3.43times than the biofilm system. Therefore, in hybrid system the suspended sludgepalys a major role on the nitrification.