Application to Dedicated Lands

Dedicated land disposal means the application of biosolids to land for disposal purposes. The rates of application are much higher than agronomic rates, and no crop is grown. Disturbed land reclamation and high-rate land disposal are two types of dedicated land applications.

Disturbed Land Reclamation The surface mining of coal, exploration for minerals, generation of spoils from underground mines, and tailings from mining operations have created over 1.5 million hectares (3.7 million acres) of disturbed lands in the United States (U.S. EPA, 1983). These lands are usually a harsh environment for vegetation because of a lack of nutrients and organic matter, low pH, low water-holding capacity, low rates of water infiltration and permeability, and the presence of toxic levels of trace metals. The major reason for land reclamation is to revegetate a site so that water and wind erosion will be reduced. A revegetated site has the potential for agricultural production, animal grazing, and reforestation for lumber and pulp production. These benefits relate to the fact that biosolids can increase agricultural and forest utilization of disturbed lands and reduce environmental contamination from these lands.

Disturbed land reclamation consists of a one-time application of 110 to 220 dry metric tons/ha (50 to 100 dry tons/ac). If adequate topsoil is present on the site, annual application is feasible, especially if the site is used for reforestation for lumber and pulp production.

Dedicated Land Disposal Dedicated land disposal is application of biosol-ids on a continuing basis on a site where high-rate application of biosolids is acceptable environmentally. Avoidance of nitrate contamination of ground-water is the major criterion in selecting a suitable site. Groundwater contamination can be avoided by locating the sites remote from useful aquifers, intercepting and collecting leachate, and by installing impervious liners. Criteria for dedicated land disposal sites are presented in Table 10.4.

Application rates range from 30 to 250 dry metric tons/ha (13 to 110 dry tons/ac). The higher rates have been associated with sites that receive dewa-tered biosolids, have relatively low precipitation, and have no leachate problems because of site conditions or project design. Assuming a 50-year site operating life, total loading would be 1500 to 12,500 dry metric tons/ha (670 to 5575 dry tons/ac). Biosolids can be applied in slurry or dewatered form much like other land application methods.

TABLE 10.4 Criteria for Dedicated Land Disposal Sites

Parameter

Ideal Condition

Unacceptable Condition

Slope

< 3%

Deep gullies, slope >12%

Soil permeability

<10-7 cm/sa

>1 x 105 cm/sb

Soil depth

>3 m (10 ft)

<0.6 m (2 ft)

Distance to surface

>300 m (1000 ft) from

<90 m (300 ft) to any pond or

water

any surface water

lake used for recreational

or livestock purposes, or

any surface water body

officially so classified

under state law

Depth to groundwater

>15 m (50 ft)

<3 m (10 ft) to groundwater

table (wells tapping shallow

aquifers)c

Supply wells

No wells within 600 m

Within a radius of 300 m

(2000 ft)

(1000 ft)

a When low-permeability soils at or too close to the surface, liquid disposal operations can be hindered due to water ponding.

b Permeable soil can be used if appropriate engineering design preventing dedicated land disposal leachate from reaching the groundwater is feasible.

c If an exempted aquifer underlies the site, poor-quality leachate may be permitted to enter groundwater.

a When low-permeability soils at or too close to the surface, liquid disposal operations can be hindered due to water ponding.

b Permeable soil can be used if appropriate engineering design preventing dedicated land disposal leachate from reaching the groundwater is feasible.

c If an exempted aquifer underlies the site, poor-quality leachate may be permitted to enter groundwater.

Was this article helpful?

0 0
Organic Gardeners Composting

Organic Gardeners Composting

Have you always wanted to grow your own vegetables but didn't know what to do? Here are the best tips on how to become a true and envied organic gardner.

Get My Free Ebook


Post a comment