Ingeniería

Desalination 286 (2012) 24–33

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Desalination
journal homepage: www.elsevier.com/locate/desal

Evaluation of a novel oxidation ditch system with dual DO control technology for biological nutrient removal by mass balance analysis
Xiaoqiang Chen a,⁎, Taku Fujiwara b, Kazuo Nakamachi c, Yukio Kawaguchi d, Fumitake Nishimura e, Kunio Ohtoshi ba

The United Graduate School of Agricultural Sciences, Ehime University, 3-5-7 Tarumi, Matsuyama, Ehime 790-8566, Japan Agriculture Unit, Natural Sciences Cluster, Research and Education Faculty, Kochi University, 200 Monobe B, Nankoku, Kochi 783-8502, Japan Maezawa Industries, Inc., 5-11 Naka-cho, Kawaguchi, Saitama 332-8556, Japan d Toda R&D Branch Office, Technology & Strategy Department,Japan Sewage Works Agency, 5141 Shimosasame, Toda, Saitama 335-0037, Japan e Graduate School of Engineering, Kyoto University, Kyotodaigaku-katsura, Nishikyo-ku, Kyoto 615-8540, Japan
b c

a r t i c l e

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a b s t r a c t
A novel pilot-scale oxidation ditch (OD) system with an anaerobic tank and dual dissolved oxygen (DO) control technology was used to treat raw domestic wastewaterduring 310 days of operation. Three intensive sampling sessions indicated that the dual DO control technology could create stable aerobic and anoxic zones along the main ditch, even with large influent fluctuations. Dramatic total nitrogen (TN), total COD, and total phosphorus removal efficiencies were achieved within ranges of 78–90%, 83–91%, and 69–82%, respectively. June nitrogen balance resultsrevealed that 60% of influent TN was denitrified and that 92% denitrification occurred in the main OD, demonstrating the advantage of the dual DO controls. In addition, COD balance values showed that 67% of the mineralized COD was due to denitrification, and aerobic oxidation was minimized. With lower influent BOD/N ratios of 4.0–4.7, significant TN removal performances were obtained in this OD system.Maximizing COD for denitrification and minimizing aerobic degradation suggest that this novel OD system shows promise for highly effective sewage treatment with effective COD consumption. Crown Copyright © 2011 Published by Elsevier B.V. All rights reserved.

Article history: Received 27 May 2011 Received in revised form 24 October 2011 Accepted 25 October 2011 Available online 30 November 2011Keywords: Oxidation ditch Dual DO control technology Mass balance analysis

1. Introduction Activated sludge process is a complex system in which a range of bacterial conversion and transport processes occurs. Strict effluent demands requiring nitrogen and phosphorus removal from wastewater

treatment plants (WWTPs) also make it difficult to design and operate [1]. For biological nitrogen removal,the limited carbon sources for denitrification usually make total nitrogen removal unreliable [2]. For biological phosphorus removal, nitrate in the returned sludge recycled to an anaerobic stage will reduce phosphorus release [3,4]. In those

Abbreviations: Qinf., influent flow rate (L/d); Qeff., effluent flow rate (L/d); Qr, inner recirculation flow rate (L/d); QR, returned sludge flow rate (L/d);Qwas, waste sludge flow rate (L/d); fCV, COD/VSS ratio in sludge (gCOD/gVSS); fN, nitrogen fraction in sludge (gN/gVSS); fP, phosphorus fraction in sludge (gP/gVSS); Mwas,VSS, waste sludge mass (gVSS/d); COD, VSS, MLVSS concentration in OD (g/L); Cinf.,TP, total phosphorus concentration in influent (gP/L); Ceff.,TP, total phosphorus concentration in effluent (gP/L); COD,TP, total phosphorusconcentration in OD (gP/L); Cinf.,SP, soluble phosphorus concentration in influent (gP/L); Ceff.,SP, soluble phosphorus concentration in effluent (gP/L); CAT,SP, soluble phosphorus concentration in anaerobic tank (gP/L); COD,SP, soluble phosphorus concentration in OD (gP/L); CR,SP, soluble phosphorus concentration in returned sludge (gP/L); Minf.,TP, influent total phosphorus mass (gP/d); Meff.,TP, effluent...