Chen X.,Ehime University |
Fujiwara T.,Kochi University |
Nakamachi K.,Maezawa Industries Inc. |
Kawaguchi Y.,Japan Sewage Works Agency |
And 2 more authors.
Desalination | Year: 2012
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 wastewater during 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 results revealed 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. © 2011.
Fujita M.,Ibaraki University |
Tsuji K.,Japan Sewage Works Agency |
Akashi A.,Kobe Steel
Water Science and Technology | Year: 2010
The cell numbers of ammonia-oxidising bacteria (AOBs), Nitrospira and Nitrobacter in activated sludge used to treat wastewater from a thermal power plant in Japan were examined for nine months using a real-time PCR quantification technique. AOB cell numbers ranged 2.8 × 10 10-2.3 × 10 11 cell/L. The amoA clone analysis showed that the only Nitrosomonas halophila was responsible for ammonia oxidation over the period. Nitrospira were in the range of 2.6 × 10 9-2.4 × 10 10 cell/L and Nitrobacter were less than 1% as common as Nitrospira. Meanwhile, maximum nitrification rates, maximum ammonia- and nitrite-oxidation rates obtained from aerobic batch tests, ranged 0.5-1.3 mmol-N/L h and 1.0-2.5 mmol-N/L h, respectively. No clear correlations were observed between the cell numbers of AOBs or Nitrospira and their maximum rates, because the maximum cell-specific ammonia- and nitrite-oxidation rates varied remarkably over the ranges of 1.1-11.9 and 2.4-21.6 fmol-N/cell h, respectively. To explore the factors controlling maximum cell-specific nitrification rates, the relationship to influent nitrogen loads per AOB or Nitrospira cell numbers was investigated. Fairly good correlations were obtained. Considering the effluent ammonia and nitrite concentrations were zero and only Nitrosomonas halophila had a role in ammonia oxidation over the period, we conclude that the amount of nitrogen oxidised per AOB or Nitrospira cell numbers likely controls maximum cell-specific ammonia- or nitrite-oxidation rates, respectively. © IWA Publishing 2010.
Shinya F.,METAWATER Co. |
Tsuboi H.,METAWATER Co. |
Miyata A.,METAWATER Co. |
Shimada M.,Japan Sewage Works Agency |
Yamashita H.,Japan National Institute for Land and Infrastructure Management
Water Practice and Technology | Year: 2015
This study discusses efforts being made to realize energy self-sufficiency in a sewage treatment plant, and to achieve both energy conservation with low-load water treatment based on thorough, intensive solid-liquid separation and 'energy production' by using sludge treatment capable of converting recovered biomass into energy with maximum efficiency. Intensive solid-liquid separation resulted in higher suspended solids and Biological Oxygen Demand (BOD) removal rates than those achieved with conventional primary settling tanks. Using thermophilic digestion of raw sludge, recovered by intensive solid-liquid separation, and garbage as substrates, the Volatile Solids (VS) decomposition rate was 70% and generated digestion gas was 759 Nm3/t-loaded VS on average under conditions of Hydraulic Retention Time (HRT) 5 days and a VS load of 6.0 kg-VS/m3/day. The generated digestion gas was totally used to generate power with phosphoric acid fuel cells. © IWA Publishing 2015.
Isaka K.,Hitachi Ltd. |
Itokawa H.,Japan Sewage Works Agency |
Kimura Y.,Hitachi Ltd. |
Noto K.,Hitachi Ltd. |
Murakami T.,Japan Sewage Works Agency
Bioresource Technology | Year: 2011
A pilot plant involving a nitritation-anammox process was operated for treating digester supernatant. In the preceding nitritation process, ammonium-oxidizing bacteria were immobilized in gel carriers, and the growth of nitrite-oxidizing bacteria was suppressed by heat-shock treatment. For the following anammox process, in order to maintain the anammox biomass in the reactor, a novel process using anammox bacteria entrapped in gel carriers was also developed. The nitritation performance was stable, and the average nitrogen loading and nitritation rates were 3.0 and 1.7kgNm -3d -1, respectively. In the nitritation process, nitrate production was completely suppressed. For the anammox process, the startup time was about two months. Stable nitrogen removal was achieved, and an average nitrogen conversion rate of 5.0kgNm -3d -1 was obtained. Since the anammox bacteria were entrapped in gel carriers, stable nitrogen removal performance was attained even at an influent suspended solids concentration of 1500mgL -1. © 2011 Elsevier Ltd.
Hashimoto T.,Japan Sewage Works Agency |
Onda K.,Ebara Corporation |
Morita T.,Ebara Corporation |
Luxmy B.S.,Ebara Corporation |
And 3 more authors.
Journal of Environmental Engineering | Year: 2010
This study aimed to investigate the contribution to estrogen removal from the activated sludge of an estrogen-degrading bacterium, Novosphingobium sp. Strain JEM-1, isolated by the writers from the activated sludge. The cell numbers of the Strain JEM-1 were investigated in two full-scale wastewater-treatment plants using real-time PCR. Strain JEM-1 appears to be commonly distributed in the activated sludge. The cell numbers of Strain JEM-1 in the oxidation ditch process were higher than those in the conventional activated sludge (CAS) process, and the effluent concentrations of E1 in the CAS process tended to decrease with increased cell numbers of Strain JEM-1. In a bench-scale experiment to investigate bioaugmentation with Strain JEM-1, there was a significant difference in the effluent concentrations of estrogens between the experimental series and the control series. Linear relationships were observed between cell numbers of Strain JEM-1 and the efficiency of removal of estrogens. These results suggest that Strain JEM-1 contributes to the estrogen removal in the activated sludge. © 2010 ASCE.