MODELING OF PARTICLE REMOVAL IN THE FIRST COARSE MEDIA OF DIRECT HORIZONTAL-FLOW ROUGHING FILTRATION

摘要

Horizontal-Flow Roughing Filtration (HRF) is an alternative pretreatment method e.g. prior to Slow Sand Filtration (SSF). However, some of its limitations are that the effluent quality drops drastically at higher turbidity ( > 200NTU) and at higher filtration rate ( > 1m h~1). To overcome these drawbacks, we suggested Direct Horizontal-Flow Roughing Filtration (DHRF), which is a modified system of Horizontal-Flow Roughing Filtration (HRF) by addition of a low dose of coagulant prior to filtration. To optimize the DHRF configuration, a conceptual and mathematical model for the coarse compartment has been developed in analogy with multi-plate settler. Data from simple column settling test can be used in the model to predict the filter performance. Furthermore, the model developed herein has been validated by successive experiments. The conventional column settling test has been found to be handy and useful to predict the performance of DHRF for different raw water characteristics (e.g. coagulated or uncoagulated water, different amounts of organic matter, etc.) and different initial process conditions (e.g. coagulant dose, mixing time and intensity, etc.). An optimum filter design for the coarse compartment (grain size 20mm) has been found to be of 3m h~(-1) filtration rate with filter length of 4～4.5m.