Academic journal article Journal of Environmental Engineering and Science

The Variation of Nitrifying Bacterial Population Sizes in a Sequencing Batch Reactor (SBR) Treating Low, Mid, High Concentrated Synthetic Wastewater

Academic journal article Journal of Environmental Engineering and Science

The Variation of Nitrifying Bacterial Population Sizes in a Sequencing Batch Reactor (SBR) Treating Low, Mid, High Concentrated Synthetic Wastewater

Article excerpt

Abstract: The purpose of this study was to correlate the population size of ammonia-oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB) with nitrification performance under various operational conditions (chemical oxygen demand (COD) concentration, dissolved oxygen (DO), and hydraulic retention time (HRT)) and influent allylthiourea (ATU) shock. The AOB (genera Nitrosomonas and Nitrosospira) and NOB (genera Nitrobacter and Nitrospira) communities were analyzed using fluorescent in situ hybridization (FISH). Ammonia-oxidizing bacteria and NOB accounted for 6.2 [+ or -] 0.9% and 2.5 [+ or -] 0.3% in total biomass, respectively. The population sizes of AOB and NOB varied with different levels of COD, DO, and HRT. Nitrosomonas and Nitrospira were dominant under conditions favorable for nitrification, while Nitrosospira outcompeted Nitrosomonas under adverse conditions (low [N[H.sub.4.sup.+]], low DO, short HRT, and ATU shock), and Nitrobacter outcompeted Nitrospira at high substrate concentrations (COD and [N[H.sub.4.sup.+]]). Under ATU shock that inhibited the oxidation of N[H.sub.4.sup.+] to N[O.sub.2.sup.-], AOB population was substantially reduced with the stepwise increase of ATU dosage, and led to a corresponding decrease of NOB population. There was a discrepancy between nitrifying bacterial populations and their functions. Although AOB outnumbered NOB in all tests and became more dominant at low DO and short HRT, N[H.sub.4.sup.+] oxidation, instead of N[O.sub.2.sup.-] oxidation, was the rate-limiting reaction for nitrification and susceptible to the adverse conditions. The study demonstrated the importance of elucidating the shifts of nitrifying bacterial population to optimize process design and operation at different influent characteristics, aeration intensity, retention time, and potential influent toxic shock.

Key words: fluorescent in situ hybridization (FISH), nitrification, nitrifying bacteria, sequencing batch reactor (SBR), dissolved oxygen (DO), hydraulic retention time (HRT), allylthiourea (ATU) shock.

Resume : Cette etude etait concue pour correler la taille de la population des bacteries oxydant l'ammoniac (AOB) et des bacteries oxydant les nitrites (NOB) a la performance de nitrification sous diverses conditions de fonctionnement (concentration de la demande chimique en oxygene [DCO], l'oxygene dissous et le temps de retention hydraulique) et une surcharge d'allylthiouree de l'influent. Les communautes d'AOB (genres Nitrosomonas et Nitrosospira) et de NOB (genres Nitrobacter et Nitrospira) ont ete analysees au moyen de l'hybridation in situ en fluorescence (FISH). Les AOB et les NOB representaient respectivement 6,2 [+ ou -] 0,9 % et 2,5 [+ ou -] 0,3 % de la biomasse totale. Les tailles de populations d'AOB et de NOB variaient selon les differents niveaux de DCO et d'oxygene dissous, et le temps de retention hydraulique. Nitrosomonas et Nitrospira dominaient sous les conditions favorables a la nitrification alors que Nitrosospira emportait la competition sur Nitrosomonas dans des conditions defavorables (faible [N[H.sub.4.sup.+]], faible niveau d'oxygene dissous, court temps de retention hydraulique et surcharge d'allylthiouree) et Nitrobacter emportait la competition sur Nitrospira a de fortes concentrations de substrats (DCO et [N[H.sub.4.sup.+]]). Sous une surcharge d'allylthiouree qui a inhibe l'oxydation du N[H.sub.4.sup.+] a N[O.sub.2.sup.-], la population d'AOB a ete substantiellement reduite avec l'augmentation progressive du dosage de la surcharge d'allylthioure e et a mene a une diminution correspondante de la population des NOB. Il y a des divergences entre les populations des bacteries nitrifiantes et leurs fonctions. Bien que les AOB soient plus nombreuses que les NOB dans tous les essais et soient devenues plus dominantes a une faible concentration en oxygene dissous et a un court temps de retention hydraulique, l'oxydation N[H.sub.4.sup.+] au lieu de l'oxydation du N[O. …

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