Potential leachability of toxic heavy metals in Bangkok sewage sludge | |
| Author | Pichit Poonpolwatanaporn |
| Call Number | AIT Thesis no.EV-00-13 |
| Subject(s) | Sewage sludge--Thailand--Bangkok Leaching--Thailand--Bangkok |
| Note | A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering |
| Publisher | Asian Institute of Technology |
| Abstract | Utilization of sewage sludge on agricultural land as crop fertilizer is rece1vmg increased emphasis because sewage sludge contains heavy metals and pathogen. Heavy metals are potentially toxic to human life and the environment. The objectives of this research were to investigate the potential leachability of toxic heavy metal and pathogen reduction in sewage sludge. Chitosan and zeolite were used as adsorbing materials for heavy metal removal. Batch adsorption experiments of chitosan and zeolite mixed with dewatered sewage sludge from Si-Phraya CWTP were determined in the application ratio 0.1:10, 0.5: 10, 1.0:10, 2.0:10, 3.0:10 and 4.0:10 by weight, respectively. The experimental result showed that 1.0:10 chitosan-sewage sludge mixture and 3.0:10 zeolite-sewage sludge mixtures were the optimum ratios for the removal of heavy metals in sewage sludge. Moreover, remained nutrients after treated were still sufficient for plant growth. Four leachants, which are tap water in pH normal range (pH 7.07), tap water in 1.0 unit of pH less than normal range (pH 6.07), effluent from Si-Phraya CWTP (pH 7.20) and effluent adjust pH less than 2.0 (pH 1.5) were used in leaching test to compare the leachability and adsorption ability of heavy metals in optimum conditions. It was found that the treatment of heavy metals by using commercially available chitosan and zeolite improved both the absorption and removal efficiencies. Furthermore, the influence of the pH values of leachants on the removal capacities in leaching test was examined. It was found that from neutral to acid conditions, the heavy metals leaching was increased with the decrement of pH value in leachants. It can be concluded that at approximate neutral pH of the leachants, heavy metal removal from sewage sludge was minimum. However application of adsorbing materials mixed with sludge had caused a decreasing of heavy metals released. The magnitude of reduction however depends on rate of materials (zeolite and chitosan) used, the higher the ratios, the better results can be expected. Based upon column leaching test experiments, zeolite had higher heavy metal removal capacity over chitosan. The effect of fecal coliform reduction in different application rates of chitosan solution and incubation times was determined by using multiple-tube fermentation technique as indicator. The reduction efficiency increased with the increases of application rates and incubation time. The US EPA standards required that the fecal coliform in sewage sludge without restrictions must be lower than 1,000 MPN/g. (dry weight sludge solids). The experiment results showed that for the lower application rate it took more than 7-day to meet the standard. However, at more than 0.40% of chitosan solution, only 7 days were enough for reduction fecal coliform to meet standard. |
| Year | 2000 |
| Type | Thesis |
| School | School of Environment, Resources, and Development (SERD) |
| Department | Department of Energy and Climate Change (Former title: Department of Energy, Environment, and Climate Change (DEECC)) |
| Academic Program/FoS | Environmental Engineering and Management (EV) |
| Chairperson(s) | Preeda Parkpian;Fukushi, Kensuke |
| Examination Committee(s) | Nguyen Cong Thanh;Suwalee Chandrkrachang |
| Scholarship Donor(s) | Mahanakorn University of Technology |
| Degree | Thesis (M.Eng.) - Asian Institute of Technology, 2000 |