| Author | Islam, Md. Serajul |
| Call Number | AIT Thesis no.EV-82-25 |
| Subject(s) | Tanning--Waste disposal
|
| 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 | The purpose of this research work was to study the effect of trivalent and hexavalent chromium on the activated-sludge treatment of tannery waste. A complete characteristics analysis and treatability study of tannery waste was performed. Since Cr-III toxicity is a direct function of Cr-III in soluble form and solubility is a function of pH alkalinity and waste characteristics; particular emphasis was given on the study of the solubility of
trivalent chromium. In case of Cr-VI, an effort was made to investigate the uptake of hexavalent chromium by activated sludge for consequent removal.
Results of the research work showed that 81% of the COD can be removed from tannery waste by activated-sludge process in a detention time of 12 hrs.
The trivalent chromium toxicity is due to its soluble form. At any
influent Cr-III concentration, the available soluble Cr is less than 4 mg/t and the rest is retained with MLSS in the reactor in precipitated form (pH= 6.8 - 9.0). A daily addition of 100 mg/t of Cr-III for 10 days with
a gross accumulation of 576 mg/t (28.8% of MLSS on dry wt. basis) of precipitated Cr-III and 4 mg/t of soluble Cr-III, the laboratory activated-sludge
units showed no loss in efficiency.
The hexavalent chromium toxicity is a function of only MLSS concentrations at and above F/M ratio of 0.25. A metal to biomass ratio, i.e. Cm/Cx;
ratio of 0.005, is the safe limit for Cr-VI. Below F/M ratio of 0.25, the toxicity is a function of both substrate and MLSS concentrations and increases
with the decrease of substrate and MLSS concentrations. A maximum uptake of 45 mg of Cr-VI is possible with 2 gm of MLVSS. |
| Year | 1982 |
| Type | Thesis |
| School | School of Environment, Resources, and Development |
| Department | Department of Development and Sustainability (DDS) |
| Academic Program/FoS | Environmental Engineering and Management (EV) |
| Chairperson(s) | Samorn Muttamara ; Vigneswaran, S. |
| Examination Committee(s) | Chongrak Polprasert |
| Scholarship Donor(s) | Belgium Government |
| Degree | Thesis (M.Eng.) - Asian Institute of Technology, 1982 |