evaluating the performance of three different coagulants for treatment of leachate of the isfahan compost plant, iran

background: untreated leachate is being discharged into the environment in many countries worldwide. leachate treatment methods have not been unified so far due to the variable composition of leachate. moreover, the lack of appropriate treatment and disposal of leachate causes environmental pollution. this study aimed to compare removal efficiency of chemical oxygen demand (cod) and total suspended solids (tss) of leachate of the isfahan compost plant using ferrous sulfate, ferric chloride and poly ferric sulfate, and identify the most convenient coagulant and co-coagulant. methods: this experimental study was conducted to investigate the cod and tss removal from leachate of the isfahan compost plant using different coagulants and co-coagulants. different concentrations and ph levels for each of the coagulants were tested and the most convenient coagulant was identified. this experiment was conducted using the jar test method. tss and cod levels were measured by standard methods of b-5210 and d-2540 respectively. findings: according to the results, ph level of 10, ferrous sulfate with the dose of 2 g/l and 2.5 g/l resulted in maximum removal efficiency of 43% for cod and 38% for tss. in ph = 10, ferric chloride with dose of 1.5 g/l and 2 g/l resulted in maximum removal efficiency of 31% for cod and 47% for tss respectively. in ph = 11, poly ferric sulfate with the dose of 2 g/l and 2.5 g/l resulted in maximum removal efficiency of 49% for cod and 51% for tss respectively. the most convenient co-coagulant for ferric chloride and poly ferric sulfate was snf-an913 that resulted in 41% and 58% cod removal, respectively. concerning ferrous sulfate, the preastol co-coagulant with 51% cod removal had the highest removal efficiency. conclusion: the best coagulant for cod and tss removal was poly ferric sulfate which contributed to better results with an alkaline ph. according to obtained data flocculation and coagulation can be used as convenient, inexpensive pretreatment methods to treat leachate of the isfahan compost plant, and process the leachate for a better and more convenient treatment using other methods.