| مستخلص: |
In this study, four coagulants were used to investigate their performances for the treatment of raw landfill leachate. Two inorganic coagulants, namely, ferric sulfate, Fe2 (SO4 )3 and zinc sulfate, ZnSO4 were compared to two types of palm date seeds, that is, khlas and sukkari as natural coagulants. Type of coagulant, dosage, pH and rapid mixing speed were designated as input variables, that is, operating conditions. In order to determine and compare the leachate treatment performances of the four coagulants, four responses were selected for this research, namely, chemical oxygen demand (COD), color, ammoniacal nitrogen (NH3 –N) or simply ammonia and total suspended solids (TSS). A response surface model (RSM) was developed for each selected response to find the optimum operating conditions for the input variable and for each coagulant that result in maximum removals. 72 experiments under different operating conditions were performed of which 18 runs were conducted for each type of coagulant wherein 100 mL of raw landfill leachate was the sample volume used for each run. The optimum operating conditions were found in the models and experimentally validated. The optimum dosage of ferric sulfate, zinc sulfate and khlas was found to be 6 mL. However, a lower dosage of 4.32 mL was found to be the optimum for sukkari. The optimal pH for ferric sulfate and sukkari was 5, whilst a pH of 9 was obtained for khlas and zinc sulfate. Finally, the optimum rapid mixing speeds for khlas and sukkari were rounded off to 195 and 200 rpm, respectively. Meanwhile, higher optimal rapid mixing speeds of 240 and 250 rpm were rounded out for ferric sulfate and zinc sulfate, correspondingly. Hence, the optimal reductions of COD, color, ammonia and TSS by (ferric sulfate–zinc sulfate) were rounded off to 55%–53%, 89%–73%, 15%–17% and 91%–89%, respectively. On the other hand, the optimum removals obtained by the natural coagulants (khlas–sukkari) were as the following: 12%–15% COD, 53%–56% color, 12%–14% ammonia and 78%–67% TSS. As regards the maximum removals of COD, color, ammonia and TSS by (ferric sulfate–zinc sulfate), they were found and rounded off to 60%–60%, 89%–84%, 18%–21% and 95%–96%, respectively. Contrariwise, the maximum reductions obtained by the natural coagulants (khlas–sukkari) were as the following: 16%–24% COD, 70%–74% color, 17%–17% ammonia and 91%–82% TSS. Thereupon, the natural coagulants showed effective removals, notably in terms of color, ammonia and TSS that could adequately replace the inorganic coagulants. A big margin of improvement in the removal of COD and other pollutants by khlas and sukkari could possibly be achieved in the upcoming studies by extensively investigating the preparation techniques of the natural coagulants. [ABSTRACT FROM AUTHOR] |
