Towards zero emission concepts: High content colloidal silica removal by using paper sludge ash as inorganic coagulant

Abstract

Zero emission could be defined as using resources effectively and prevent resources depletion, or activities that are being carried out to curb waste generation, reduce emissions, in order to achieve the maximum usage of wastes through loop recycling. This research goes online with this concept in which paper sludge ash (PSA) was utilized as inorganic coagulant for the treatment of wastes from semiconductors industries. Coagulation and flocculation experiments were carried out to assess the ability of the inorganic coagulant to remove high concentration colloidal silica wastes from microelectronics industry. Three different parameters were investigated, pH, coagulant dosage, and temperature. Surprisingly high removal efficiency was obtained when pH was higher than 8. The optimum coagulant dosage was 0.25 g of inorganic coagulant per 1gram of silica at concentration of 1.8% colloidal silica. Temperature was carried out under mild conditions from (10-40 oC). Increasing the coagulant dose at 20 oC or lower could help to achieve clear effluent. Long-term operating data were gathered by using continuous flow with Hi Biah System (HBS) for treatment actual wastes. Average results obtained for the fluent for TN, TP, T. Si, COD, BOD and S.S were 11, < 1, < 50, 10, 12 < 50PPM, 16 PPM, and <100 PPM respectively.