Academic journal article Journal of Environmental Engineering and Science

The Implementation of Single-Sludge Step-Feed Anoxic-Aerobic Process in a Domestic Wastewater Treatment Plant

Academic journal article Journal of Environmental Engineering and Science

The Implementation of Single-Sludge Step-Feed Anoxic-Aerobic Process in a Domestic Wastewater Treatment Plant

Article excerpt

Abstract: The single-sludge step-feed anoxic-aerobic process (SSFAOP) was implemented in the Xuzhou wastewater treatment plant (WWTP) in China to enhance ammonia and nitrogen removal performance. Influent flow splitting and step feeding in the aerobic zone were used to provide high concentrations of mixed liquor suspended solids (MLSS), long solids retention time (SRT), and short nitrification time. After implementation, removal efficiencies of ammonia nitrogen >90% and total Kjeldahl nitrogen (TKN) >80% were achieved. The amount of waste activated sludge (WAS) was significantly reduced, and sludge bulkings were eliminated. The application of SSFAOP also reduced capital and operational costs.

Key words: nitrogen removal, step feeding, anoxic-aerobic process, activated sludge, solid retention time.

Resume : Un processus anoxique-aerobie a alimentation etagee a un seul type de boue (SSFAOP), a ete implante a l'usine de traitement des eaux usees de Xuzhou, en Chine, afin d'ameliorer l'elimination de l'ammoniac et de l'azote. La division du flux et l'alimentation etagee de l'influent dans la zone aerobie ont ete utilisees pour obtenir des concentrations elevees en matieres solides en suspension dans la liqueur mixte (MLSS), un long temps de retention des solides (SRT) et un court temps de nitrification. Apres l'implantation, des efficacites d'elimination de l'azote ammoniacal (>90 %) et l'azote total Kjeldahl (>80 %) ont ete realisees. La quantite de boues activees dans les dechets (WAS) a ete substantiellement reduite et le gonflement des boues a ete elimine. L'utilisation du SSFAOP a reduit les couts en capitaux et operationnels.

Mots-cles : denitrification, alimentation etagee, processus anoxique-aerobie, boues activees, temps de retention des solides.

[Traduit par la Redaction]

Introduction

The single-sludge step-feed anoxic-aerobic process (SSFAOP) was designed and built to improve the effectiveness of ammonia and nitrogen reduction in wastewater treatment. The process is a single-sludge system characterized by a high concentration of mixed liquor suspended solids (MLSS), a long solids retention time (SRT) and a short hydraulic retention time (HRT) (Zhang and Xu 2002a). It was found that SSFAOP was feasible for full-scale implementation in wastewater treatment plants (WWTPs) after laboratory and pilot-scale testing.

Influent flow splitting and step feeding of raw wastewater were used in the SSFAOP. A split of influent raw wastewater was conveyed to the denitrification tanks, and the remainder of the influent was introduced in the aeration tank at several points. This resulted in high mean MLSS concentration and low food to microorganism (F/M) ratio in the aerobic process (Henze et al. 2001) and also led to relative dominance of nitrifying bacteria and the possibility of synchronization of carbonaceous biochemical oxygen demand (cBOD) removal and nitrification in the system (Zhang and Xu 2002b).

Laboratory and pilot-scale testing of the SSFAOP showed that it increased the nitrification rate and increased ammonia and nitrogen reduction efficiencies with a relatively short HRT in comparison with conventional activated sludge treatment systems (Xu et al. 2008). The SSFAOP had 20% higher cBOD reduction and 30% higher ammonia reduction than conventional activated sludge processes. Effluent ammonia concentrations of less than 3 mg/L were achieved from each pilot-testing run.

Based on the theoretical studies and the results of laboratory and pilot-scale testing, SSFAOP was considered feasible for full-scale applications. It was implemented on full scale at the Xuzhou WWTP to enhance ammonia and nitrogen reduction and to improve the operational reliability of the plant.

Process design

[FIGURE 1 OMITTED]

Former process

Xuzhou WWTP is a domestic wastewater treatment facility located in Xuzhou City, China. …

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