12VAC5-590-865: Conventional filtration treatment

A. Conventional filtration treatment is generally used for surface water sources. It is defined as a series of four processes: coagulation, flocculation, sedimentation, and filtration. The specific design parameters shall consider the water supply characteristics and variability in quality due to seasonal and climatic events.

B. Conventional filtration treatment plants shall provide staged, multiple treatment process units to allow individual units to be taken out of service without disrupting operation.

C. The department may require presedimentation of waters containing high turbidity or organics (as measured by TOC).

1. Presedimentation basins utilizing a coagulant feed shall have hoppered bottoms or shall be provided with continuous sludge removal equipment. The minimum hydraulic detention time shall be three hours. The department may require greater detention times depending on the source water quality and the level of pretreatment required.

2. Presedimentation basins without coagulant feed shall provide a minimum hydraulic detention time of 24 hours. The design shall address future needs for solids removal and handling.

3. Incoming water shall be dispersed across the full width of the line of travel as quickly as possible. Short circuiting shall be minimized. The department may require baffling on large basins.

4. Provisions for bypassing presedimentation basins shall be provided.

5. Surface runoff shall be prevented from entering presedimentation basins or reservoirs.

6. Dikes shall be structurally sound and protected against wind action and erosion.