Chatree Kulchatchai creator Samorn Muttamara Chairperson Nguyen, Cong Thanh Examination Committee Vigneswaran, Saravanamuthu Examination Comittee Federal Republic of Germany (DAAD) Scholarship Donor text series technical report th Bangkok Asian Institute of Technology 1984 continuing eng 32 p. The study of a pilot scale slow sand filter using the influent which passed through a coconut hzsk fiber prefilter, with the effluent rate from the slow sand filter of 0.15 m3 /m2 /h can be summarized as follows: The first experimental run: As the effluent from the prefilter was filtered by slow sand filter, it was found that the colour removal was in between 15.9- 28 .1%, turbidity removal 31.5- 42.1%, coliform removal 74-80.5% . During this experimental run, anaerobic condition took place in the process . The second experimental run: The effluent from prefilter was aerated so that the D.O. content was up to 5-6 mg/l before entering the slow sand filter. After passing through the slow sand filter, it was found that colour removal was in between 46.9-49.2% turbidity removal 38 . 2-42.3% and coliform removal 75.7-89.4% while the aerobic condition took place in the process. In this experiment, the degree of pollution of raw water was considerable high with COD of 130 mg/ l. Therefor e , it may be said that the Horizontal coconut husk fiber prefilter tube is unsuitable for high polluted raw water since it may create anaerobic condition in the slow sand filter also. therefore , raw water quality plays a very important role in the application of horizontal coconut husk fiber prefilter tube as the prefilter of the system. A special study submitted in partial fulfillment of requirements for the Diploma of Asian Institute of Technology, School of Environment, Resources & Development Special Studies Project Report (M. Eng.) - Asian Institute of Technology, 1984 Filters and filtration Asian Institute of Technology. http://203.159.5.9/ait-thesis/detail.php?q=B20776 http://203.159.5.9/ait-thesis/detail.php?q=B20776 121095 20260817171222.0