Characterization of sludge properties for sewage treatment in a practical-scale down-flow hanging sponge reactor: oxygen consumption and removal of organic matter, ammonium, and sulfur Naoki Nomoto, Masashi Hatamoto, Muntjeer Ali, Komal Jayaswal, Akinori Iguchi, Tsutomu Okubo, Masanobu Takahashi, Kengo Kubota, Tadashi Tagawa, Shigeki Uemura, Takashi Yamaguchi and Hideki Harada ABSTRACT The characteristics of sludge retained in a down-flow hanging sponge reactor were investigated to provide a better understanding of the sewage treatment process in the reactor. The organic removal and sulfur oxidation conditions were found to differ between the first layer and the following three layers. It was found that 63% and 59% of the organic matter was removed in the first layer, even though the hydraulic retention time was only 0.2 h. It is thought that the organic removal resulted from aerobic and anaerobic biodegradation on the sponge medium. The sulfate concentration increased 1.5–1.9-fold in the first layer, with almost no subsequent change in the second to fourth layers. It was shown that oxidation of sulfide in the influent was completed in the first layer. The result of the oxygen uptake rate test with an ammonium nitrogen substrate suggested that the ammonium oxidation rate was affected by the condition of dissolved oxygen (DO) or oxidation–reduction potential (ORP). Naoki Nomoto Department of Energy and Environment Science, Nagaoka University of Technology, 1603-1, Kamitomioka Nagaoka, Niigata 940-2188, Japan and Present address: Department of Chemical and Biological Engineering, National Institute of Technology, Ube College, Tokiwadai, Ube, Yamaguchi 755-8555, Japan Masashi Hatamoto Department of Civil and Environmental Engineering, Nagaoka University of Technology, 1603-1, Kamitomioka Nagaoka, Niigata 940-2188, Japan Muntjeer Ali Masanobu Takahashi Hideki Harada New Industry Creation Hatchery Center, Tohoku University, 6-6-04 Aza-Aoba, Aramaki, Aoba-ku, Sendai, Miyagi 980-8579, Japan Komal Jayaswal Department of Civil Engineering, Indian Institute of Technology Roorkee, Roorkee-Haridwar Highway, Roorkee, Uttarakhand 247667, India Akinori Iguchi Faculty of Applied Life Sciences, Niigata University of Pharmacy and Applied Life Sciences, 265-1, Higashisima, Akiba-ku, Niigata, Niigata 956-8603, Japan Tsutomu Okubo Shigeki Uemura Department of Civil Engineering, National Institute of Technology, Kisarazu College, 2-11-1, Kiyomidaihigashi, Kisarazu, Chiba 292-0041, Japan Kengo Kubota Department of Civil and Environmental Engineering, Tohoku University, 6-6-06 Aza-Aoba, Aramaki, Aoba-ku, Sendai, Miyagi 980-8579, Japan Key words | developing country, down-flow hanging sponge, retained sludge, sewage treatment 608 © IWA Publishing 2018 Water Science & Technology | 77.3 | 2018 doi: 10.2166/wst.2017.557 Downloaded from http://iwaponline.com/wst/article-pdf/77/3/608/212681/wst077030608.pdf by guest on 08 October 2021