パイロットプラントを用いた高塩基度PACの濁度の除去性及びアルミニウムの残留性に関する評価

摘要

The objective of this study Is to evaluate the performance of high-basicity polyaluminum chloride (high-basicity PACI, baislclty=70%) In comparison In normal PACI (basicity=50%) on turbidity removal and residual aluminum concentration control. Experimental tests were carried out using a pilot scale plant of a sand filtration and a membrane filtration with a coagulation-sedimentation pretreatment. Turbidity removal ratio of the pretreatment by the high-basicity PACI was almost same as that by the conventional PACI. The turbidity of the sand-filtrated water after the high-basicity PACI coagulation and sedimentation decreased more rapidly in filter ripening period than that after normal PACI. The residual aluminum concentration In both sand- and UF-membrane- filtrated waters after hlgh-basiclty PACI coagulation and sedimentation were lower corresponding to the lower dissolved aluminum concentration in the coagulated water. The total head losses in sand filters were not significantly different between the two types of PACI, and the UF transmembrane pressure buildups were not significantly different. These results indicated that the application of high-basicity PACI in place of normal PACI was effective in the residual aluminum concentration control.%高塩基度PAC（塩基度72％）を用いた場合の濁度の除去性とアルミニウムの残留性について、凝集沈澱一砂炉過及び膜炉過プロセスを有するパイロットプラントを用いて、従来型PAC（塩基度51％）と比較・評価した。高塩基度PACは、凝集沈澱プロセスにおける濁度の除去性は従来型PACと同等であったが、砂炉過の初期漏出濁度の清澄化が早い傾向がみられた。また、高塩基度PACの使用によって、沈澱水中に残留する溶解性アルミニウム濃度が低減されたことで、最終処理水中のアルミニウム濃度が低減された。砂炉過の損失水頭や膜差庄の挙動への影響も限定的であったことから、高塩基度PACは残留アルミニウムの低減に有効であることがわかった。