Evaluation of the effectiveness of leachate biological treatment using bacteriological and parasitological monitoring

Abstract

Leachate of the uncontrolled landfill contains pollutants, which is discharged directly into the environment. The main objective of this study is to evaluate the reduction of bacteriological and parasitological risks by four biological treatments: sequencing batch reactor, anaerobic, intensive aeration and combination of the three processes. The results showed high bacteriological pollution in the raw leachate: 1.12 × 107 CFU/ml, 6.7 × 106 and 5.26 × 104 for total coliforms, faecal coliforms and Streptococci, respectively, parasites of intestinal helminths are also present: 11.86, 9.49, 9.83, 8.81 eggs/L for Enterobius vermicularis, Ascaris lumbricoides, Trichuris and Hymenolepis nana, and the values are higher than the standards for discharge into the natural environment. After sequencing batch reactor treatment, a decrease is noted in bacteria, Staphylococci, total coliforms and Streptococci with 99.63%, 97.11%, 99.93% and 94.62% abatement, respectively. This process also removes 75% of total unviable form and 80% of viable form of parasites. Intensive aeration and anaerobic treatments allowed the total elimination of total coliforms. Anaerobic processing allowed a reduction of 33.4% of unviable forms and 37% of viable forms of parasites, while a reduction of 63% of unviable and 77% of viable parasites was reported by intensive aeration. The combined treatment improves the results with abatement rates to 100% for total coliforms bacteria, and viable forms of the genus parasites: Capillaria sp., Toxocara (nematodes), Hymenolepis nana and Taenia (cestodes). A principal component analysis showed very significant correlations between all measured variables (bacteria and parasites). Combined treatment appears to be the best treatment to reduce biological risks of leachate.