چكيده به لاتين
To provide drinkable water out of runoffs, enormous volumes of sludge are produced every day in water treatment plants. Studies regarding sustainable management methods to apply to this Water Treatment Sludge (WTS), which can be cost-effective and environment-friendly have become of great importance. On the other hand, mineral tailings slurries contain a huge amount of water which can be reused after a successful turbidity removal. Therefore, this study aims at assessing the feasibility of turbidity removal of mineral tailings slurry produced during iron ore beneficiation (“Choghart-e-Bafgh” Iron ore beneficiation plant’s tailing), via utilization of two types of WTS (Ferric Chloride-based and Poly Aluminum-based) as efficient and frugal coagulants. In this regard, the effects of four factors namely coagulant dosage, initial pH, initial turbidity, and mixing conditions on three responses namely turbidity removal percentage, produced sediments volume per each unit of turbidity removal, and final pH were examined by the conventional method of varying One Factor at a Time (OFAT). Subsequently, Response Surface Methodology (RSM) with Central Composite Design (CCD), was employed to design main tests, process simulation, and optimization of coagulant dosage, initial pH and initial turbidity as the three parameters governing the Coagulation/Flocculation (C/F) process. Both turbidity removal percentage and sediments volume were separately simulated, for exploiting each of the coagulating sludges. A statistical verification which was based upon analyzing the variance of the models and evaluation of statistical plots revealed the agreement between laboratory and models-predicted results. According to the results of simulations and optimizations, sludge dosage of 0.41 g dried CS/L, initial pH of 10, and initial turbidity of 600 NTU was the optimum condition during the utilization of both coagulant sludges. Moreover, the predicted responses of optimal turbidity removal percentage and sediments volume were 100% and 3.76 mm respectively for FCS, and 75.62% and 3.58 mm respectively for PACS. The turbidity removal percentage and sediments volume obtained from the tests carried out to assess and verify the optimal conditions were 82.86% and 4.2 mm for FCS, and 78.13% and 3.68 mm for PACS which were in a compelling agreement with the predicted results. Turbidity removal of 89.72% was observed in utilization of a polymeric flocculant which is commonly consumed in “Choghart-e-Bafgh” Iron ore beneficiation plant. Therefore, according to the results obtained, coagulating performance of water treatment sludge as a by-product is unassailable. Also, in terms of coagulating efficiency and therefore turbidity removal performance, FCS showed to be slightly better than PACS.
