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Virginia Administrative Code
Title 12. Health
Agency 5. Department of Health
Chapter 590. Waterworks Regulations
6/23/2024

12VAC5-590-985. GAC contactors.

A. Granular activated carbon (GAC) contactors may be used to adsorb natural organic compounds, taste and odor compounds, and SOCs. The most common applications of GAC contactors in drinking water treatment plants are (i) post-filtration adsorption and (ii) filtration-adsorption, in which some or all of the filter media in a granular media filter is replaced with GAC.

B. General requirements.

1. A demonstration study using bench-scale or pilot-scale tests shall be conducted to determine the GAC media effectiveness, adsorption efficiency, and regeneration frequency.

2. GAC contactors shall be sized for the optimum empty bed contact time.

3. A minimum of two contactor units shall be provided.

4. Bypassing the GAC facility may be permissible under certain circumstances to accommodate seasonal water quality fluctuations and allow for blending water.

C. Hydraulic configuration.

1. Pressure vessel installation may be configured in parallel or in series.

2. For pressure contactors, pre-filter and post-filter pressure gauges shall be installed at each individual contactor unit.

3. The rate of flow through the contactors shall be controlled either manually or automatically to ensure equal flow through each contactor.

D. Design details.

1. For pressure contactors, the maximum pressure loss through the vessels shall be as determined by the product manufacturer.

2. Sample taps, isolation valves, and bypass piping shall be provided before and after each individual contactor unit.

3. Pipes, tanks, and appurtenances shall be corrosion resistant.

4. The GAC facility shall provide the ability to filter-to-waste to prevent carbon fines in the effluent water.

5. Unless otherwise approved by the department, disinfection shall be accomplished following the GAC contactors.

6. If backwashing of GAC specific units is required, then unchlorinated filtered water shall be used.

7. Turbidity monitoring of contactor effluent shall be considered.

8. The facility design shall include provisions for spent carbon disposal, GAC delivery, and storage.

Statutory Authority

§§ 32.1-12 and 32.1-170 of the Code of Virginia.

Historical Notes

Derived from Virginia Register Volume 37, Issue 20, eff. June 23, 2021.

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