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Virginia Administrative Code
Title 9. Environment
Agency 25. State Water Control Board
Chapter 790. Sewage Collection and Treatment Regulations
12/30/2024

9VAC25-790-650. Sludge pumping.

Pump capacities shall be adequate but not excessive. Provisions for varying pump capacity are desirable.

1. Duplicate units shall be provided where failure of one unit would seriously hamper treatment works operation.

2. Positive displacement pumps or other types of pumps with demonstrated solids handling capability shall be provided for handling raw sludge.

3. The minimum positive head necessary for proper operation shall be provided at the suction side of centrifugal type pumps. A positive head of 24 inches or more may be desirable for all types of sludge pumps. Maximum suction lifts shall not exceed 10 feet for positive displacement pumps.

4. Adequate sludge sampling facilities shall be provided. Provision of quick closing sampling valves installed at the sludge pumps would be an adequate means of sampling. The size of valve and piping shall be at least 1-1/2 inches.

5. Sludge withdrawal piping for anaerobic digesters and gravity thickeners shall have a minimum diameter of six inches for gravity withdrawal and four inches for pump suction and discharge lines. Where withdrawal is by gravity, the available head on the discharge pipe shall be at least four feet and preferably more. Also, where gravity withdrawal is to be used as the primary withdrawal method, the piping for the primary sludge clarifier pump should be so arranged as to permit use of the pump for removal of digested sludge. Downstream gravity piping for transport of sludge shall be laid on uniform grade and alignment. Slope on gravity discharge piping should not be less than 3.0%. Provisions shall be made for draining and flushing discharge lines, and special consideration shall be given to the corrosion resistance and continuing stability of supporting systems for piping located inside the digestion tank.

Statutory Authority

§ 62.1-44.19 of the Code of Virginia.

Historical Notes

Former 12VAC5-581-710 derived from Virginia Register Volume 18, Issue 10, eff. February 27, 2002; amended and adopted as 9VAC25-790-650, Virginia Register Volume 20, Issue 9, eff. February 12, 2004.

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