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下水汚泥焼却灰からの灰酸抽出に基づくリン回収の基礎検討査読

髙島正信

土木学会環境工学論文集 80 ( 25 ) 24-25008 2024年11月

越前町における集約バイオマスメタン発酵の経済性検討

髙島正信

福井工業大学研究紀要 ( 54 ) 29 - 33 2024年11月

前加熱下水汚泥の高濃度高温嫌気性消化における活性炭添加の影響査読

髙島正信

土木学会論文集 80 ( 5 ) 23-00227 2024年5月

髙島正信：福井県内二河川における魚類相とマイクロプラスチック汚染

髙島正信

福井工業大学研究紀要 52 168 - 172 2022年11月

Performance improvement and decolorization in the high-solid thermophilic anaerobic digestion of thermally pretreated sewage sludge 査読国際誌

M. Takashima and J. Yaguchi

Water and Environment Journal 2022年7月

This laboratory-scale study attempted performance improvement and decolorization in the high-solid thermophilic anaerobic digestion of thermally pretreated sewage sludge, as it tends to be disturbed by ammonia inhibition and color generation. Sewage sludge was adjusted to 7−8% total solids (TS), and pretreated at 150oC for 1 hour. The digesters were operated at 55oC and 20 days hydraulic retention time. An addition of powdered activated carbon (approximately 2% of the feed TS) significantly contributed to the removal of propionate, and reduced the color in digested sludge by about 27%. Microbial analysis detected less abundance of bacterial Synergistia and archaeal Methanosarcina, and implied more hydrogenotrophic methanogenesis with the activated carbon addition. Conditioning with ferric chloride for dewatering digested sludge mitigated the color of dewatered liquor by about 67%. Therefore, these methods were demonstrated to be effective and partly overcome the above-mentioned problems.

資源回収型下水処理法の基礎研究

髙島正信

福井工業大学研究紀要 ( 51 ) 7 - 12 2021年9月

High-solids thermophilic anaerobic digestion of sewage sludge: effect of ammonia concentration 査読

M. Takashima and J. Yaguchi

Journal of Material Cycles and Waste Management 23 205 - 213 2021年

High-solids thermophilic anaerobic digestion fed with sewage sludge of 7?8% and 9?10% total solids was investigated at the hydraulic retention time of 20 days in this lab-scale study. The anaerobic digester fed with 7?8% sewage sludge was successfully operated, resulting in volatile solids (VS) destruction of 57.8% and methane production of 0.327 L/gVS (at standard temperature and pressure). When fed with 9?10% sewage sludge, the control digester was upset after about 80 days of operation. Total ammonia nitrogen (TAN) of 2,500 mgN/L or more caused inhibition to anaerobic microorganisms. Another digester combined with weekly-batch ammonia stripping of digested sludge in a side-stream configuration (80oC, 2 hours, initial pH of 9 with NaOH and return ratio of 70%), was maintained at the average TAN of 1,720 mgN/L, and was able to continue without ammonia inhibition. TAN was a better indicator on inhibition of ammonia than free ammonia nitrogen (FAN). Microbial analysis revealed poor microbial diversity of digested sludge, that is, Class Clostridia for Bacteria and Geneus Methanothermobacter and Methanosarcina for Archaea were predominated. In conclusion, high-solids thermophilic anaerobic digestion can accommodate the influent sewage sludge up to 10%, as far as TAN is properly controlled in digester.

日野川の水環境と魚類相に関する調査研究

髙島正信

福井工業大学紀要 ( 50 ) 287 - 291 2020年12月

本研究では，おおむね広野ダムで赤潮が発生した以降の期間における日野川，広野ダムの流況と水質について調べ，それらの要素とアユ量との関係性について考察した．しかし，アユの生活史からもわかるように海まで下ることから沿岸環境の影響，進行していると思われる地球温暖化の影響，さらには一時的な渇水，雪解け水，建設工事の影響など，考慮すべき要素はきわめて多岐にわたる．これらとは別に，アユ漁獲量の減少はアユ釣り離れともいえる人々の嗜好性の変化が影響していることも伺えた．一方，環境DNA解析より，日野川はほぼ特定の魚種から構成され，比較対象とした永平寺川と異なることが示唆された．

余剰汚泥の前加熱処理を施した下水汚泥嫌気性消化における活性化と脱色査読

髙島正信、矢口淳一、奥畑博史

土木学会論文集（環境） 76 ( 7 ) Ⅲ_77 - Ⅲ_84 2020年12月

余剰汚泥に前加熱処理（150℃，1時間）を施した下水汚泥の高温嫌気性消化において，粉末活性炭の添加と塩化鉄による汚泥調質を適用した消化汚泥の活性化と脱色について検討した．流入全固形物質（TS）約7.5％，温度55℃，水理学的滞留時間20日の条件下，流入TSに対し約2％の活性炭を添加すると，有機物分解率とガス発生率はわずかしか改善されなかったものの，平均して消化汚泥中のプロピオン酸が96%，ろ液色度が29%減少した．よって，活性炭は中間代謝物質の微生物代謝促進に極めて有効であった．また，塩化鉄に両性ポリマーを組み合わせた消化汚泥の調質は，Fe添加率6～10％TSで脱水性を保ちながら，色度を最大約1/4まで低下させた．以上より，両法は前加熱処理に伴う着色という課題を小さくできることがわかった．

アンモニアストリッピングを組み合わせた下水汚泥の高濃度嫌気性消化査読

髙島正信、矢口淳一、中尾総一

下水道協会誌論文集 57 ( 687 ) 100 - 107 2020年1月

下水汚泥12～15%の高濃度嫌気性消化（中温35℃，水理学的滞留時間30日）において，アンモニア阻害の軽減を目的に消化汚泥のアンモニアストリッピングとその返送を組み合わせる方法を実験的に検討した．定常時の平均値として，VS負荷率3.98 kgVS/L-日でVS分解率56.5%，ガス発生率0.506 NL/gVSと良好な処理結果が得られた．消化槽内の全アンモニア濃度は平均2,570 mgN/Lであり，このような高負荷では3,000 mgN/L付近より低く維持すべきであると考えられた．アンモニアストリッピングは，温度80℃，初期pH約9，2時間の条件で回分式で実施し，平均アンモニア除去率63.0%が得られた．微生物叢解析によると，消化汚泥は比較的限られた微生物種から構成され，一般的な中温消化汚泥と異なっていた．以上より，消化槽内アンモニア濃度を適正に制御すれば，流入濃度15％程度においても安定な高濃度嫌気性消化が可能なことが示された．

下水汚泥の高濃度・高温嫌気性消化

髙島正信

環境浄化技術 19 ( 3 ) 48 - 52 2020年

下水汚泥の嫌気性消化における余剰汚泥濃縮・加熱と微生物解析

髙島正信，矢口淳一，中尾総一

福井工業大学研究紀要 ( 49 ) 41 - 47 2019年12月

本研究では下水汚泥の嫌気性消化において，流入余剰汚泥に対する汚泥濃縮ならびに加熱処理の効果を検討した．混合汚泥の嫌気性消化において流入余剰汚泥に加熱処理を組み込むと，コントロールと比較してVS分解率が約7%，メタン発生率が約13%改善され，その効果が確認された．一方，色度や溶解性CODCrは悪化し，これは従来，加熱処理の欠点として指摘されていたものである．一般に，加熱処理は脱水性を改善するといわれるが，今回はCST値で見る限りわずかに悪化し，加熱処理温度や余剰汚泥濃度が影響すると考えられた．消化汚泥の微生物解析によって，比較的限られた種が分解経路を担っていると推察された．

窒素・リン回収を伴う下水汚泥の高濃度・高温嫌気性消化システム査読

髙島正信、矢口淳一、中尾総一

土木学会論文集G（環境） 75 Ⅲ_435 - Ⅲ_442 2019年12月

下水汚泥9～10%を高濃度・高温嫌気性消化し，窒素・リンも回収するシステムについて検討した．消化汚泥のアンモニアストリッピングとその返送により消化槽全アンモニアを平均して1,760 mgN/Lに抑えたところ，VS分解率57.8%，メタン発生率0.321 NL/gVSが得られ，高分子凝集剤のみ用いる一液法の脱水が可能であった．アンモニアストリッピングは脱炭酸後，薬品添加なしで温度70℃，初期pH約9，2時間で実施し，流入汚泥からの窒素回収率20.7%が得られた．消化汚泥に対して水酸化鉄吸着剤を室温，pH4～5，24時間で適用すると，固形性リンの一部も溶解され，流入汚泥からのリン回収率54.6%が得られた．以上より，下水汚泥の高濃度・高温嫌気性消化およびアンモニア・リン酸回収の可能性が示された．

High-Solid Anaerobic Digestion of Sewage Sludge Incorporating Pre-digestion Ammonia Stripping of Waste Activated Sludge

M. Takashima, J. Yaguchi, N. Nakao

8th IWA-ASPIRE Conference and Exhibition, Hong Kong 2019年10月

This study investigated high-solid anaerobic digestion fed with sewage sludge of appro. 15% total solids (TS). Thermal pre-treatment and ammonia stripping of the waste activated sludge (WAS) portion was incorporated for ammonia removal and recovery. The laboratory anaerobic digester with an efficient volume of 2.0 L was operated at the hydraulic retention time of 30 days and loading rate of 4.0 g VS/L-d, achieving VS destruction of 60% and gas production of 0.50 NL/g VS. After thermal pre-treatment of 130 oC and 1 hour, the stripping device was operated batchwise at 80 oC and initial pH of 9 for 3 hours, recovering 18% of the WAS nitrogen as ammonia. The results indicated that the high-solid digestion is feasible, as the pre-digestion ammonia stripping can maintain total ammonia at appro. 3,000 mgN/L in digester. Improved ammonia production and removal during pre-treatment is needed for less inhibition and more recovery of ammonia.

Enhanced phosphate release from anaerobically digested sludge through sulfate reduction 査読

M. Takashima

Waste and Biomass Valorization 10 ( 11 ) 3419 - 3425 2019年10月

This study was conducted to demonstrate enhanced phosphate release in mesophilic anaerobic digestion of sewage sludge in relation to sulfate reduction. Sulfate was added as sulfuric acid to influent sewage sludge at the three levels, 0, 461 and 922 mg-S/L (0, 14.4 and 28.8 mmol/L, respectively). The sewage sludge used was one without artificial modification for 70 days, and then chemically pre-precipitated one artificially prepared by adding 4 g/L (17.9 mmol/L) of FePO4・4H2O for 77 days (Influent total phosphorus of 302 and 855 mg/L, respectively). The anaerobic digesters were operated at 35 oC and 20 days hydraulic retention time. The phosphate concentration in digested sludge at the final stage reached 7.3, 89 and 112 mg/L for the sewage sludge without artificial modification, and 114, 258 and 461 mg/L for the chemically pre-precipitated sewage sludge, at the three levels of sulfate addition respectively. The phosphate concentration was almost proportional to the sulfate concentration added, indicating that the introduction of sulfate to anaerobic digestion can enhance phosphate release. The enhanced phosphate release was attributable to sulfate reduction to sulfide and subsequent release of phosphate from ferric or ferrous phosphate. In addition to the above mechanism involving sulfate reduction, phosphate release was estimated to occur from ferric phosphate along with iron reduction. A possible disadvantage of involving sulfate reduction is that part of the methane is lost due to the consumption of methane precursors.

High-solid Thermophilic Anaerobic Digestion with Ammonia and Phosphate Recovery

M. Takashima, J. Yaguchi

3rd IWA Resource Recovery Conference, Venice, Italy 2019年9月

This study investigated high-solid thermophilic anaerobic digestion fed with sewage sludge of 9?10% total solids. Ammonia stripping in a side-stream configuration and selective adsorption by porous iron hydroxide were introduced to digested sludge, respectively, for ammonia and phosphate recovery. The laboratory anaerobic digester performed well at the hydraulic retention time of 20 days and loading rate of 3.96 gVS/L-d, showing VS destruction of 57.8% and gas production of 0.522 NL/gVS. The stripping device was operated batchwise at 70oC and initial pH of appro. 9.0 for 2 hours, recovering 20.7% of influent nitrogen as ammonia and keeping total ammonia at 1,760 mgN/L in digester. Also, 54.6% of influent phosphorus was recovered as phosphate by the selective adsorption, when conducted at the pH of 4?5 for 24 hours. The lower pH was advantageous for saving the amount of cationic polymer added and improving the dewatering characteristics of digested sludge.

下水汚泥の高濃度嫌気性消化における余剰汚泥前処理の効果査読

髙島　正信、中尾　総一

土木学会論文集G（環境） 74 ( 7 ) Ⅲ_187 - Ⅲ_194 2018年12月

下水汚泥の全固形物質（TS）約10%および約15%の高濃度嫌気性消化において，余剰汚泥部分に前処理を組み合わせ，消化性の改善とアンモニア阻害の低減について実験的に検討した．前処理は，流入TS約10%は加熱処理（130℃，1時間），約15%は加熱処理に続けてアンモニアストリッピング（約80℃，初期pH約9，3時間）とした．前処理が組み合わされると，両流入濃度ともVS分解率は約4%上昇したが，メタン発生率の向上はわずかだった．流入TS約15%では，アンモニアストリッピングによって消化汚泥中アンモニア性窒素が平均約3,100mgN/Lに抑制されたことが良好な運転につながった．よって，余剰汚泥の前処理を用いれば，流入TS約15%まで高濃度嫌気性消化の可能なことが示された．

Super-high Solids Anaerobic Digestion of Sewage Sludge? Effects of Solids Content and Ammonia Stripping

M. Takashima, N. Nakao

IWA World Water Congress and Exhibition, 16-21 Sept, 2018, Tokyo 2018年9月

This study evaluated super-high solids anaerobic digestion fed with sewage sludge of 10?20% total solids (TS). At 15% TS or higher, ammonia stripping in a side-stream or pre-digestion configuration was combined for ammonia removal and recovery. Laboratory anaerobic digesters performed well at the hydraulic retention time (HRT) of 20?30 days and loading rate of 4.0?5.2 gVS/L-d, and showed approximate VS destruction of >50% and gas production of 0.5 NL/gVS. The stripping device was operated batchwise at the temperature of 80oC and initial pH of 9 for 2?3 hours, showing average ammonia recovery of 6.6?16.8 mgN from g influent TS. The results indicated that methane production is possible up to the influent TS of about 20%, and the side-stream configuration is superior for ammonia recovery. High viscosity and deteriorated dewaterability of digested sludge pose a problem for operation, transport and further processing.

下水汚泥の嫌気性消化における余剰汚泥の濃縮・加熱効果

髙島正信，中尾総一

福井工業大学研究紀要 ( 48 ) 45 - 59 2018年6月

The objective of this study was to investigate the effects of concentration (12-15%) and thermal pretreatment (130oC) of the waste activated sludge portion in influent on anaerobic digestion of sewage sludge. The experimental results showed that the thermal pretreatment improves volatile solids destruction by several percent and gas production by more than 10 percent. The thermal pretreatment, however, produced more colored substances, which is disadvantageous. On the other hand, the concentration of waste activated sludge was not effective for those major operating parameters, and even made the dewaterability of digested sludge worse. Overall, it is concluded that thermal pretreatment of waste activated sludge can improve the performance of anaerobic digestion of sewage sludge.

Effects of thermal pretreatment and trace metal supplementation on high-rate thermophilic anaerobic digestion of municipal sludge 査読

M. Takashima

J. Env. Eng., ASCE 2018年2月

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