7 Del. Admin. Code § 7103-71.0

Current through Register Vol. 28, No. 3, September 1, 2024

Section 7103-71.0 - Phosphorus and Other Constituent Loading Rates

71.1 Annual loading rates and site life limitations must be determined for phosphorus and other constituents present in the wastewater, since there is a potential that any one of these constituents may limit the site life of the facility.

71.2 Phosphorus present in the wastewater is removed primarily through adsorption and precipitation reactions in the soil profile and through plant uptake. The soil profile can be considered to have a finite phosphorus adsorption capacity associated with each layer. However, there is the potential that the adsorption capacity of the entire soil profile may eventually reach saturation and soluble phosphorus will appear in the percolate. As a result of this, phosphorus may become the land limiting constituent (LLC) over time. Conditions which may indicate that phosphorus has become the LLC include:

1) A rise in phosphorus concentrations as indicated by groundwater monitoring well test results over three consecutive sampling periods, or

2) Phosphorus adsorption test results indicate that the phosphorus adsorption capacity of the site has decreased to a level at which the adsorption capacity of the site is no longer sufficient to assimilate excess phosphorus not taken up by the vegetation. Once phosphorus has become the LLC the phosphorus application rate must be reduced to crop uptake levels. Under such conditions, high phosphorus utilization vegetation may be grown to increase the phosphorus assimilative capacity.

71.3 The site assimilative capacity for heavy metals must be determined on a constituent by constituent basis to determine the site life for a facility. The number of years wastewater may be applied to a site shall be based on the allowable cumulative metal loading rates (values) established in Table 2 of the Guidance. Spray irrigation activities shall be terminated when any one of the cumulative metal limits is reached.

7 Del. Admin. Code § 7103-71.0