A thesis submitted in partial fulfilment of the requirement for the degree of Master of Engineering

Thesis (M.Eng.) - Asian Institute of Technology, 1993

All natural water environment e. g. rivers, has a self-purification capacity which help improve their quality through reduction of BOD and recovery of DO, when some pollutants are discharged into them. Rock bed filtration is one of such methods to enhance the self-purification capacity of rivers and other water resources. Two pilot-scale rock bed reactors were constructed and experiments were carried out using two types of rock media with under two conditions of non-aeration and aeration systems. In the non-aeration system, two parallel filters were separately filled with broken bricks in the first reactor and whole bricks in the second reactor at a mean BOD loading of 22 g BOD/m2.d of first reactor and 18 g BOD/m2.d of second reactor. After two months operation, both rock bed reactors were supplied with the aeration inside and at the bottom of the reactor at a mean BOD loading of 16 g BOD/m2.d of first reactor and 17 g BOD/m2.d of second reactor. The experimental results revealed that the rock bed reactor with aeration system showed an over-all superiority in purification efficiency as compared with the non-aeration system. It can be concluded that, the rock bed filtration method is a low-cost and least-maintenance technique to treat the moderately-polluted water.