| Extrusion wastewater is quickly separated from fresh municipal garbage by high pressure extrusion,which contained NH4+-N concentration over 1 000 mg/L with a C/N ratio of below 2.0 after anaerobic treatment.Partial nitrification and denitrification process is a biological nitrogen removal process by controlling the ammonia oxidation at nitritation stage,which has been deemed as one of promising technologies for nitrogen removal from low C/N wastewater as that it can also save oxgen demand and additional carbon source dosage.Based on these two aspects,in the present work,the partial nitrification and denitrification technology was employed to remove ammonia from extrusion wastewater in a sequencing batch reactor(SBR),during which the effects of operational conditions parameters and influential factors were evaluated to optimize the system operation,and to provide technical guideline to its practical application with high cost-effectiveness and low energy comsuption.Partial nitrification in SBR treating extrusion wastewater was sucessfully achieved due to the continuous inhibition of high free ammonia(FA)to nitriteoxidizing bacteria(NOB).By online controlling the bulk p H ranged from 7.5 to 8.0 and the dissolved oxygen(DO)no more than 1.0 mg/L,a FA concentration within SBR was more than 4.85 mg/L that could significantly constrained the biomass activities of NOB.With an influent ammonia concentration of 1 000 mg/L,continuous accumulation and enrichment of ammonia-oxidizing bacteria(AOB)were obtained in SBR to favor the nitritation where the ammonia removal rate and nitrite accumulation rate(NAR)was above 96.0% and 86.0%,respectively.After the nitrite accumulation occurrence,it was observed that there was synergistic function of the high FA and free nitrite(FNA)to maintain the stable partial nitrification.In contrary to the start-up phase,the increasing of influent ammonia concentration positively impacted both ammonia oxidation rate and nitrifier enzymatic activity.After the stable partial nitrification achieved,denitrification through nitrite was investigated in a SBR.It was observed that after a short start-up time of around four weeks,completely denitrifcation with dosed additional carbon source or extrusion wastewater organic substances could be obtained,implying that the partial denitrification was insignificantly affected by the carbon sources.Afterwards,by combination of partial nitrification and denitrification,a stably high total nitrogen removal efficiency from high strength extrusion wastewater was observed.When the influent TN was avergated at 1 000 mg/L,the SBR effluent TN was stably of below 40 mg/L.In contrast to conventional biological nitrogen removal through nitrification and denitrification,more than 21.6% aeration and 32.7% carbon source could be saved,respectively.More attentions were paid to the bacterial community structure in partial nitrification and denitrification process treating extrusion wastewater by using DGGE,high-throughput sequencing and q PCR.The analyzed results demonstrated that the abundance of functional microbes in SBR significantly related with the operational condition parameters and ammonia removal rate in nitrification and denitrification stages.In partial nitrification system,the copy number of AOB was more than four magnitutes higher than that of NOB,indicating there was significant NOB inhibition.The relative abundance of AOB and NOB was 12.8% and 0.03% respectively during the steady-state.As for partial denitrification process,the copy number of denitrifying bacter ia nir S was more than 3.5×103 copies/ng DNA,and their relative abundance was as high as 68.6% at steady-state,all which helped to the stably high TN removal efficiency from extrusion wastewater. |
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