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9VAC25-32-450. Sampling, analysis, and preservation.

A. Representative samples of biosolids that is applied to the land or placed on a surface disposal site shall be collected and analyzed.

1. Raw sewage or sludge samples are to be collected prior to the treatment process unit operations.

2. Final treated samples are to be taken at a point following appropriate unit operations in the treatment process. An evaluation of biosolids treatment may require monitoring of fecal coliform levels in treated biosolids.

3. Composite samples shall be collected in accordance with the treatment works operation and maintenance manual.

B. Liquid biosolids. In the case of digesters and liquid storage holding tanks, a representative sample shall be composed of at least four grab samples obtained during daily operations at the facility or land application site. Samples of liquid biosolids obtained under pressure or vacuum should be obtained shortly after the beginning, during and at the end of the time period that the biosolids are produced at the sampling point.

C. Biosolids storage facilities. Equal volumes of biosolids shall be withdrawn from random locations across the width and throughout the length of the storage facility at the surface, mid-depth and near the bottom of the lagoon at each grab sample location. These grab samples shall be added to form a composite mix. A range of the minimum number of grab samples that should be obtained from various sizes of biosolids storage facilities in order to obtain a representative composite sample is presented in Table 1 of this section:


Surface Area (Acres)

Minimum Number of Grab Samples

Depth less than 4 feet

Depth greater than 4 feet

1 to 9.99

4 to 5

6 to 8

10 or more

6 to 8

9 to 11

D. Dewatered biosolids. Small, equally sized grab samples of the dewatered sludge stream may be taken at equally spaced intervals over the period of operation of the dewatering unit. Centrifuged biosolids samples may be taken from a belt conveyor or receiving hopper. Filter cake biosolids samples may be taken from a belt conveyor or a portion of the cake may be removed as it leaves the unit. The smaller grab samples should be combined to form a representative composite sample. A composite sample can be obtained over the daily operational period at the land application site.

E. Compost sampling. Collect composite samples composed of at least three grab samples of one kilogram or more so that a representative average level of compost characteristics can be obtained from analytical testing. This mixture should be used for analytical testing or for combination with other composites to obtain a total composite sample representing a fixed period of operation. Compost samples may be taken with a scoop or shovel and placed in flexible bags that can be thoroughly shaken to mix grab samples.

F. Biosolids samples shall be preserved and analyzed in accordance with methods listed in 40 CFR Part 136 and methods identified in 9VAC25-31-490. Calculation procedures in the methods shall be used to calculate the percent volatile solids reduction for biosolids. Any other acceptable test procedure not listed in 40 CFR Part 136 shall be specified in the VPA permit.

Statutory Authority

62.1-44.15 of the Code of Virginia; 402 of the Clean Water Act; 40 CFR Parts 122, 123, 124, 403, and 503.

Historical Notes

Derived from Virginia Register Volume 24, Issue 6, eff. January 1, 2008; amended, Virginia Register Volume 29, Issue 24, September 1, 2013; Volume 34, Issue 19, eff. June 13, 2018.

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