A Thesis submitted in partial fulfillment of the requirements for t he degree of Master of Engineering, School of Environment, Resources and Development

Thesis (M.Eng.) - Asian Institute of Technology, 1990

Deep bed filtration- has been used successfully as tertiary wastewater treatment in some treatment plants. Several studies have been conducted mainly with the conventional filter which is equipped with the coagulation and sedimentation as pretreatment facilities. The effectiveness of this filter was studied mainly in reducing the suspended solids of the secondary treatment plant effluent. Not much data is avail able on the removal of biological parameters. Semi experiment. dual - media pilot-scale deep bed filter was used in the Different types of filters like coarse medium , and declining rate filters were tested for their applicability in treating secondary effluent. Experiments with different operating conditions were carried out in order to investigate its performance in terms of headless development , filter run length and removal of turbidity, suspended soli ds , COD, BOD, Phosphorus and TKN. The operating conditions included coarse single- medium filtration of 0.84- 1.19 mm and 2.00-2 . 38 mm, dual -media consisting of anthracite of 1 . 41-1.68 mm in size over sand of 0. 71 - 0.84 mm in size , constant and declining rate filtration, with or without flocculant addition. Comparative study with different operating conditions indicated that dual -media filter with declining rate filtration arrangement provided relatively long filter run and high filtrate quality. This filter provided a filter run length of 5 hours and produced filtrate volume of 214 1, while the average filtrate quality varied between 62 . 7% to 88.8% . In this study, filtration with contact flocculation arrangement. was used as single step treatment which will reduce the capital cost significantly although operating cost may be little higher due to short filter run. The mobile bed filter will solve this problem of frequent washing.