Effect Of Nutrient Concentration On Biological Nitrogen And Phosphorus Removal In Aerobic/Extended-idle Process

The early researches by the group have shown that the nitrogen and phosphorusbiological removal can be realized in Aerobic/extended-idle(AEI) wastewater treatmentprocess, and there are detailed discussions for the mechanism and influence of biologicalphosphorus removal, based on previous studies, by controlling the initial concentration ofcarbon and nitrogen source respectively, the effect of biological nitrogen(N) andphosphorus(P) removal in AEI was studied in this research.To study the effect of carbon source concentration on nitrogen and phosphorus removalin Aerobic/extended-idle process, influent COD concentrations were controlled with200,400,600and800mg/L respectively. The experimental results showed that with influent P and Nconcentrations of12and30mg/L respectively, the highest N, P removal per unit VSS(4.31±0.08and6.15±0.22mg/g) were both detected under influent COD of400mg/L,indicating that activated sludge has the highest biological nitrogen and phosphorus removalactivity. P accumulating activity was enhanced when COD rose from200to400mg/L, butfurther increase of influent COD would result in deterioration of biological nitrogen andphosphorus removal activity although more amount of nitrogen and phosphorus wereremoved. On the basis of the above experimental results we run a second test, with influentCOD and P concentrations of600and12mg/L respectively, by increasing initial ammonianitrogen concentration from30mg/L up to50mg/L gradient of10mg/L, the results showedthat the phosphorus removal rate were84.3%,83.2%,78.5%or so respectively, there werealmost no ammonia nitrogen detected in effluent, the average total nitrogen effluent contentwere3.5,10.6,21.3mg/L respectively, Although the initial ammonia nitrogen concentrationchanged, the nitrogen removal amount stable at about28.2mg/L.The study found that nitrogen mainly removed in the way of simultaneous nitrificationand denitrification(SND), and the removal efficient was up to88.3%when initial COD/N was20,ammonia nitrogen oxidize to nitrate or nitrite when COD/N become lower, AEI processrun stably as there was no serious deterioration of phosphorus removal caused by nitrogenoxide. Typical cycle analysis showed that there may be other nitrogen removal ways except for SND, Both phosphorus and nitrogen removal were driven bypoly-β-hydoxyalkanoate(PHA), and the largest amount of PHA consumption per unit VSSwas observed under influent COD of400mg/L. The nutrient concentration influencedmicrobial metabolism, inducing different generation of microorganisms, which resulted indifference of the accumulation/conversion of intracellular polymers, and thus influenced Nand P removal performance.