紙粉及び古紙添加による余剰汚泥単独脱水の効果

摘要

The waste paper addition facility has been used to reduce the water content of dewatered sludge when the sludge condition turned worse at the Kasai Water Reclamation Center, one of the wastewater treatment plants in Tokyo. The waste paper addition facility dissolves paper powder and waste paper in water and adds them to mixed sludge before entering dehydrator. We can more reduce water content of dewatered sludge by decreasing ratio of excess sludge in mixed sludge, but we have to dewater excess sludge alone for that To solve the problem, we tried to dewater excess sludge alone by adding paper powder and waste paper to excess sludge. Through some experiments, we confirmed it was possible. Therefore, we set an exclusive sludge treatment train for dehydration of excess sludge added paper powder and waste paper with an existing belt press type dehydrator. We invented the way of reducing water content of whole dewatered sludge by dewatering of excess sludge alone with the treatment train while decreasing the percentage of excess sludge in mixed sludge for dehydrators of other treatment trains. As a result of continuous practical use of the treatment train for dehydration of excess sludge alone from fiscal 2011 to fiscal 2012， we reduced the water content by 1.4 percentage points on average. We confirmed the system was very effective in whole sludge treatment process; a 33.5% reduction in unit requirement of auxiliary fuel consumption for incinerator, a 10.8% reduction in unit requirement of power consumption, a reduction of 3,571t-CO_2 in annual greenhouse gases emissions, etc.%東京都下水道局葛西水再生センターの汚泥処理管理業務を実施するにあたっては，汚泥性状が悪化した際に，紙粉や古紙を水で溶解し脱水機投入汚泥(混合汚泥)に添加する古紙添加設備を活用して，脱水汚泥含水率の改善を図ってきた.低含水率化を更に進めるためには，混合汚泥中の余剰汚泥比率を下げる手法があるが，その分，余剰汚泥を単独で脱水する必要がある.そこで，余剰汚泥に紙粉及び古紙を添加して単独で脱水することを検討し，実験したところ，単独脱水が可能であることを確認した.これを受け，紙粉及び古紙を添加した余剰汚泥を既存のベルトプレス脱水機で脱水する専用の系列を設けた.この系列で余剰汚泥単独脱水を行うとともに，他の系列の脱水機に投入する混合汚泥の余剰汚泥比率を下げ，脱水汚泥全体の含水率を低減する手法を考案した.2011(平成23)〜2012(平成24)年度に，余剰汚泥単独脱水系列を連続して実際に運用し，含水率を平均1.4pt低減した.これにより，補助燃料使用量原単位33.5％削減，電力使用量原単位10.8％削減，温室効果ガス年間排出量3,571t-CO_2削減など，汚泥処理プロセス全体で多大な効果を確認した.