オデイ ハッセイ ヨクセイ リン カイシュウガタ ゲスイ コウド ショリ ギジュツ ノ カイハツ

京都大学0048新制・課程博士博士(工学)甲第11873号工博第2566号新制||工||1359(附属図書館)23653UT51-2005-N707京都大学大学院工学研究科環境工学専攻(主査)教授 津野 洋, 教授 武田 信生, 教授 田中 宏明学位規則第4条第1項該当Doctor of EngineeringKyoto UniversityDA

Techno-economic evaluation of ozone-oxidation for sludge reduction at the full-scale. Comparison between the application to the return activated sludge (RAS) and the sludge digestion unit

Ozone oxidation was applied to a fraction (30 %) of the return activated sludge (RAS) of a full-scale Wastewater Treatment Plant for reducing the high sludge production (20 t/week). The amount of sludge sent to final disposal was decreased by 50 % and 75 % at 0.55 kgO3/h and 0.80 kgO3/h dosage, respectively. When the same ozonation system was applied to the aerobic digestion (0.06, 0.50, 0.67 kgO3/h), the reduction was 27–77 %. A thorough economic analysis was carried out considering the overall sludge quantity finally extracted from the plant in the presence and absence of ozonation, the corresponding costs of final disposal and the ozone oxidation operation costs. The net cost saving for sludge disposal was calculated to be 66.6 €/d and 109.9 €/d due to ozone in the return activated sludge at the two dosages, respectively. When ozonation was applied to the recycled sludge of the digestion unit, the net cost saving was in the range 235–655 €/d, depending on the reduction percentage achieved. The ozone oxidation showed to become economically convenient for a sludge disposal cost lower than that sustained by the Company. The results obtained prove feasibility of ozonation for sludge reduction in both locations of the WWTP: therefore, with respect to other disintegration techniques, ozonation possesses a high technical and economic advantage along with a high versatility. Furthermore, it is also shown the feasibility of lowering the applied dosages with respect to the past experiences, since effectiveness of the system is still guaranteed

Ozonation of return activated sludge for disintegration and solubilisation with synthesized titanium oxide as catalyst

Ozonation of activated sludge in the present of titanium dioxide (TiO2) as catalyst to enhance the production of hydroxyl radical was evaluated in comparison to the sole ozonation process. In this process, the catalytic ozontion showed improvement in increasing ozone consumption and improving activated sludge disintegration and solubilisation. The reduction of total suspended solid (TSS), volatile suspended solid (VSS) and soluble chemical oxygen demand (SCOD) solubilisation was better in the catalytic ozonation system. Initial pH 7 of activated sludge was found best to disintegrate and solubilise the sludge flocs. However upon additional of sodium hydroxide (NaOH) in pH adjustment enhanced the solubilisation of organic matter from the flocs and cells, making the initial pH 9 is the best condition for activated sludge solubilisation. Yet the initial pH 7 of activated sludge supernatant was the best condition to achieve SCOD solubilisation due to sludge floc disintegration, when it had stronger correlation between TSS reduction and SCOD solubilisation (R2=0.961). Lower amount of catalyst of 100 mgTiO2/gTSS was found to disintegrate and solubilise the activated sludge better with 30.4% TSS reduction and 25.2% SCOD solubilisation efficiency, compared to 200 mgTiO2/gTSS with 21.9% and 17.1% TSS reduction and SCOD solubilisation, respectively