A thesis submitted in partial fulfilment of the requirements for the degree of Master of Engineering, School of Environment, Resources and Development

Thesis (M.Eng.) - Asian Institute of Technology, 1987

Laboratory scale batch and continuous-flow experiments were conducted on synthetic feed in order to find the effects of powdered activated carbon(PAC) addition to activated sludge system in the presence of mercury. The batch test results revealed that mercury (Hg++) concentrations of more than 2.5 mg/l were inhibitory to the microbial population and addition of PAC at 300 mg/l concentration could reduce the toxic effect and enhance organic removal from 50 % to 75 % when the Hg++ concentration was 5.0 mg/l. However, in the continuous-flow experiment at 5 mg/l Hg+concentration inhibitory effect was not pronounced and addition of PAC upto 1000 mg/l did not improve process performance in terms of organic removal. PAC addition also was not effective in improving the sludge settleability and was not able to prevent bulking of sludge in continuous-flow activated sludge process . However it can be useful to overcome shock loading effects due to heavy metal. The sludge growth parameters and kinetic constant of biological oxidation were determined for the reactors with 100, 500 and 1000 mg/l PAC and without PAC in the presence of 5. 0 mg/l Hg++ and are discussed here.