Administrative Code

Virginia Administrative Code

Article 9. Special Facilities

12VAC5-610-1080. Anaerobic lagooning of septage.

Article 9
Special Facilities

A. General. An anaerobic lagoon for the purpose of this chapter is a nondischarging facility consisting of an open impervious structure, constructed of earth or other material specifically designed for receiving and stabilizing septage and other sewage sludges. Industrial waste sludges and sludges containing toxic material shall not be placed in these lagoons.

B. General site requirements.

1. Engineering, geologic, soil and hydrologic evaluation. Geologic information required by the district or local health department and the division shall include, but not be limited to, soil characteristics, percolation information, maximum ground water table, direction of ground water movement and permeability.

2. Location.

a. Minimum setback distances for topographic features are the same as those for subsurface soil absorption systems and are contained in Table 4.2.

b. Buffer zone. Buffer zone criteria are contained in Appendix I.

c. Flood protection. The anaerobic lagoon and operational components shall be located at an elevation which is not subject to the 100-year flood/wave action or shall otherwise be adequately protected against the 100-year flood/wave action damage. The anaerobic lagoon shall remain fully operational during the 25-year flood/wave action.

d. Surface runoff. Adequate provisions shall be made to divert storm water around the anaerobic lagoon and otherwise protect the lagoon's embankments.

3. Access. An all weather access road shall be provided.

4. Fencing. The facility site to include treatment units and appurtenances shall be fenced with a five foot fence (woven wire plus barbed wire); gates and locks to provide controlled entry into the facility. The fence shall be posted with signs identifying the facility, safety and health dangers and trespass penalties. The fence shall not be constructed closer than 10 feet to the outside edge of any treatment unit or appurtenance.

C. Design requirements (see Figure V-1 for typical sections).

1. Receiving facilities.

a. An impervious pad or sufficient strength to support a loaded tank truck and with drainage to the lagoon shall be provided at the point or points where the contents of the tank truck is offloaded into the lagoon or receiving facilities.

b. The receiving and inlet facilities shall be designed to transport the septage into the lagoon, to distribute the septage as evenly as possible throughout the lagoon and to minimize generation of odors and suspension of solids.

2. Treatment units.

a. Anaerobic lagoons.

(1) Number and capacity. A minimum of two lagoons shall be provided. The combined total capacity of the lagoons shall provide eight months storage based on the average daily discharge into the lagoon.

(2) Operating depth. The normal operating depth shall be from three to five feet.

(3) Lagoon bottom. The lagoon bottom shall be level, constructed of impervious material (10%686 sm/sec) and be a minimum of two feet above the seasonal water table or at the original ground surface.

(4) Lagoon embankments. Embankments and/or dike walls shall be impervious and structurally stable. They shall be designed to permit access of equipment by appropriate lining or internal barriers necessary for sludge removal in a nuisance free and safe manner, and to minimize risk, supervision, operation and maintenance. Earthen embankments shall be sloped (minimum 1:3) and seeded with proper cover, subject to soil characteristics, to minimize erosion.

(5) Freeboard. A minimum freeboard of two feet above the normal depth shall be provided.

(6) Shape. A uniform shape shall be provided, i.e., round, square, or rectangular with no narrow or elongated portions. The lagoon shall not contain islands, peninsulas or coves unless they are part of the inlet/outlet design.

b. Sludge dewatering. When sludge dewatering units are provided they shall be designed in accordance with 12VAC5-580-700, Sludge Dewatering, Virginia Sewerage Regulations.

3. Supernatant disposal. Normally the lagoon supernatant should be included in the sludge mixed liquor which is disposed of on the land. When a system is designed to provide for separate supplemental supernatant disposal it shall be by subsurface soil absorption system. The minimum subsurface soil absorption system field size shall be based on the anticipated average daily supernatant generation rate and shall meet all applicable criteria contained in Article 1 (12VAC5-610-450 et seq.) of Part III and Article 5 (12VAC5-610-900) of this part. The lagoon outlet shall be designed to minimize the solids content of the supernatant withdrawn for disposal in the subsurface soil absorption system and shall be provided with a means to control the rate and quantity of supernatant withdrawal.


For Anaerobic lagooning of septage, see Virginia Administrative Code print product.

Statutory Authority

§§ 32.1-12 and 32.1-164 of the Code of Virginia.

Historical Notes

Derived from VR355-34-02 § 4.43, eff. February 5, 1986; amended, eff. May 11, 1988; Virginia Register Volume 16, Issue 16, eff. July 1, 2000.

12VAC5-610-1090. Lime stabilization of septage.

A. General. Lime stabilization of septage is a process consisting of the addition of hydrated lime in sufficient quantity usually 50 pounds per 1000 gallons, to raise the pH and hold it at 12 or higher for at least 30 minutes before dewatering or land spreading. The process normally requires mixing during the lime addition process as well as a mixing tank to facilitate the holding and mixing requirement.

B. Mixing equipment.

1. Mixing may be accomplished by recirculation through the pump truck. Mixing through the pump truck is limited to operations where no more than one load at a time is processed. In this case a mixing tank is not required.

2. When a mixing tank is required a minimum capacity of 2000 gallons shall be provided. Mixing tank volume in excess of 2000 gallons may be required on a case-by-case basis. When separate mixing capability is necessary it may be accomplished by either mechanical mixing or air diffusion.

a. Mechanical mixers shall be capable of maintaining the bulk fluid velocity above 26 ft/minute and an impeller Reynolds number greater than 1000.

b. Diffused air requirements range from 150 to 250 CFM/1000 Ft of tank volume for course bubble diffusers. The diffusers shall be mounted such that a spiral roll is established in the mixing tank away from the point of lime addition.

C. pH. Suitable methods of measuring pH values in excess of 12 shall be provided and maintained to measure the pH of the septage-lime mixture.

D. Dewatering. Dewatering is required prior to landfilling lime stabilized septage and may be desirable before land spreading. Criteria for dewatering facilities may be found in 12VAC5-580-700 of the Sewerage Regulations. In addition all filtrate from the dewatering facilities must be:

1. Disposed of in a subsurface soil absorption system; or

2. Collected in an impervious container or earthen basin for ultimate disposal in an approved sewerage system or treatment works or by land spreading.

E. Storage facilities. Regardless of the equipment used to land spread the lime stabilized septage, there will be extended time periods, particularly during winter, when the septage cannot be land applied. Therefore, storage facilities shall be provided. The design and construction of the storage facilities shall adhere to the following criteria:

1. General site requirements. If the storage facilities are to be constructed of manufactured materials, i.e., steel or concrete, the site requirements shall conform to 12VAC5-610-1080 B 2. Where an earthen storage facility is to be provided site requirements shall conform with 12VAC5-610-1080 B 1 and 2.

2. Design requirements.

a. Transfer facilities. When the storage facilities are located adjacent to the mixing facilities described in subsection B of this section the piping shall be arranged in such a manner to eliminate spillage, reduce splashing and facilitate distribution of the septage through the storage unit.

b. Receiving facilities. When the storage facilities are remote from the mixing facilities and require vehicular transport of the lime stabilized septage the receiving facilities shall conform to 12VAC5-610-1080 C 1.

c. Capacity. The storage volume shall be based upon a mass balance which considers as a minimum monthly pumping rates (number of loads pumped per month), number, location and nature of land spreading sites including soil type, crop cover and topography and seasonal application to cropped or pastured land. In no case shall the storage capacity be less than 60 days.

d. Storage facilities. When the storage facility is of a manufactured material (steel, concrete, etc.) it shall be watertight and fitted with appropriate piping and appurtenances to facilitate removal of the stored material. When the storage facility is of earthen construction it shall adhere to the design requirements contained in 12VAC5-610-1080 C 2 a (2), (3), (4), (5), and (6) above. See Appendix P.

Statutory Authority

§§ 32.1-12 and 32.1-164 of the Code of Virginia.

Historical Notes

Derived from VR355-34-02 § 4.44, eff. February 5, 1986; amended, eff. May 11, 1988.

12VAC5-610-1100. Storage facilities for unstabilized septage.

Unstabilized septage storage facilities shall conform to 12VAC5-610-1090 E above as applicable.

Statutory Authority

§§ 32.1-12 and 32.1-164 of the Code of Virginia.

Historical Notes

Derived from VR355-34-02 § 4.45, eff. February 5, 1986; amended, eff. May 11, 1988.

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