7 Del. Admin. Code § 7103-20.0

Current through Register Vol. 28, No. 4, October 1, 2024

Section 7103-20.0 - Site Assimilative Capacity and Land Requirement

Each wastewater application site has a capacity to accept wastewater, bring about treatment, and channel decomposition products into environmentally sound pathways. One important step in land treatment design is to determine the site assimilative capacity so appropriate loading rates can be determined for each of the major waste constituents and from that the amount of land required. Municipal wastewater application is usually limited by hydraulic loading and/or nitrogen. The limiting constituent in industrial wastewater may be nitrogen, heavy metals or other constituents. The limiting constituent must be determined using the site assimilative capacity and waste generation rates.

20.1 The three basic types of site assimilative capacity are (Figure 2):

20.1.1 Above-ground removal of decomposition products from the site. This includes nutrient removal by crop uptake and subsequent harvest, CO2 and NH3+ volatilization, N2 or NOx loss from denitrification and loss of applied water by evapotranspiration.

20.1.2 Permanent storage in the soil. The most important examples are P fixation by reaction with Al and Fe and trace metal fixation by reaction with organic matter and various mineral fractions of the soil.

20.1.3 Removal from the site by drainage. Both anions (NO3- Cl- SO4=) and cations (Na+ K+ Ca++ Mg++) move with drainage water, but the anions move more rapidly since they are not attracted to the negatively charged soil particles. A portion of the applied water leaves the site by draining into the groundwater.

20.2 These three pathways must be considered in detail for each system design since the importance of each is a function of the site and the waste being applied.

7 Del. Admin. Code § 7103-20.0