充てん塔式ろ床の圧力損失と液ホールドアップに及ぼす生物膜の影響 : 充てん塔式ろ床法による有機性廃水の処理(第6報)

概要

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In a packed-tower biofilter for wastewater treatment, the effects of biofilm conditions around the packing on pressure drop were investigated under various conditions of ventilation and hydraulic loading. Unfavorable biofilm conditions caused channeling, ponding and plugging, affecting the pressure drop and liquid hold-up of the biofilter. With hydraulic loadings of 45 to 180 (m^3/m^2/day), liquid hold-up in the biofilter increased at ventilation rates below 180 (m^3/m^2/day), which was thus defined as the critical rate for ponding. To prevent ponding, the ventilation rate should be set at 270 to 360 (m^3/m^2/day), giving a safety coefficient of 50%. With an adequately developed biofilm, the liquid hold-up was approximately 1.7-fold that in the absence of a biofilm, and the retention time of wastewater also increased 70%. The pressure drop across the biofilter increased markedly with excess biofilm growth on the packing. When the excess biofilm was dislodged into the biofilter, it caused ponding, channeling and even plugging. In this situation, the pressure drop increases to 10-fold that in the normal situation. Pressure drop was considered a useful indicator for maintaining optimums conditions of the biofilm for wastewater treatment.
1982-09-25