| Author | Ahmmed, Sohel |
| Call Number | AIT Thesis no. EV-98-20 |
| Subject(s) | Heavy metals--Bioavailability
|
| Note | A thesis submitted in partial fulfillment of the requirements for the degree of Master of
Engineering, School of Environment, Resources and Development |
| Publisher | Asian Institute of Technology |
| Abstract | Sewage sludge usually contains significant heavy metals that may limit its land application.
Heavy metals in sewage sludge have been shown to be less plant available and low
concentration prior to the incubation process. In the present research DTP A test was
conducted for metal bioavailability whereas sequential step extraction was employed to
investigate metal speciation (into exchangeable, bound to carbonate, to Mn and Fe oxides, to
organic matter and in residue phase) and the effect of high moisture (flooded sludge) as well
as low moisture (wet and dry) content on metal speciation in incubation of Huay Kwang
sewage sludge for heavy metal.
The flooded sludge under specified period of time (10, 30 and 60 days) generally reduces
bioavailability of metal except Mn, which was quite constant (20% of total heavy metal). The
exchangeable and carbonated fractions (plant available) are also reduced and therefore the
potential hazard of releasing metals from sludge through adsorption and complexation of the
metals onto inorganic components to different extents for the different metals. Zn and Pb had
distinct affinity to oxides whereas for Mn and Cd, dominant fractions were exchangeable or
carbonated. Cu, Ni and Cr were associated mainly with organic or residual form (both of the
forms are sparingly available). The present of fecal coliform (2 - 5 x 104 MPN/g dry wt.)
indiGates the safe use in agricultural land but it should be monitored regularly.
During the period of wet and dry condition (9 - 12% moisture content) the dry sludge releases
more plant available metal due to stimulation of microor~anism and longer residual period.
The bioavailability of Pb was found highest 54% in 30 C. In contrast the plant available
fractions (exchangeable and carbonated) were found less in comparison with original one
(except Zn and Cu), indicating safe use in agricultural purpose. Mn was decreased
significantly in this condition. The residual fraction (mainly sulfides) was observed quite high
amount for almost all metals from original or flooded sludge, indicating stable metal mineral
complex and less threatening to plant. |
| Year | 1998 |
| 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; |
| Examination Committee(s) | Eckhardt, Ing. Heinz ;Apisit Eiumnoh; |
| Scholarship Donor(s) | The Royal Danish Government ; |
| Degree | Thesis (M.Eng.) - Asian Institute of Technology, 1998 |