A research study submitted in partial fulfillment of the requirements for the degree of Master of Engineering, School of Environment, Resources and Development

Thesis (M.Eng.) - Asian Institute of Technology, 1986

This research attempted to investigate the use of filter press in dewatering Bangkok septage. Results from pilot-scale study showed that due to the high moisture content of the septage, a long filtration time was needed to produce a cake of 26.9 % solids. However, this corresponded to a volume reduction of 0.98 as compared to a 0.80 volume reduction from literature. The filtrate contained an average COD of 117 mg/L, BOD of 27 mg/L and suspended solids of 34 mg/L. The efficiency of the filter press was affected by the characteristics of the septage sample being dewatered~ The specific resistance of the conditioned septage was determined using Jones' equation. It was found out that the addition of optimum dosage of chemicals improved the filterability of the septage to a high degree, in which the specific resistance of the septage was decreased from an average of 2870 x 107 s2jg to 681.1 X 107 s2jg. A comparison between the cost of using sand drying beds which are presently employed in Bangkok and filter press for dewatering indicate that it was more expensive to use filter press than sand drying beds. However, considering other factors like population growth which would result to an increase in sludge production in the future, filter press would be preferable since continued use of sand drying beds would mean an increase in land area requirements.