Environmental Engineering Reference
In-Depth Information
10.8.2.4 Metals Loading
When biosolids are land applied, metals concentrations are closely
monitored and their loading on land application sites is calculated.
Loading(lb/ac)
=
MetalConcentration(mg/kg)
×
0.002 lb/dry ton
(10.30)
×
ApplicationRate(drytons/ac)
Example 10.33
Problem:
The biosolids contain 14 mg/kg of lead. Biosolids are currently
being applied to the site at a rate of 11 dry tons per acre. What is the met-
als loading rate for lead in pounds per acre?
Solution:
Loading Rate = 14 mg/kg × 0.002 lb/dry ton × 11 dry tons = 0.31 lb/ac
10.8.2.5 Maximum Allowable Applications Based on Metals Loading
If metals are present, they may limit the total number of applica-
tions a site can receive. Metals loading is normally expressed in terms
of the maximum total amount of metal that can be applied to a site dur-
ing its use:
MaximumAllowable Cumulative L
oad(lb/ac)
MetalLoading (lb/ac/application)
Applications
=
(10.31)
Example 10.34
Problem:
The maximum allowable cumulative lead loading is 48.0 lb/ac.
Based on the current loading of 0.35 lb/ac, how many applications of bio-
solids can be made to this site?
Solution:
48.0lb/ac
0.35 lb/ac
Applications
=
=
137
10.8.2.6 Site Life Based on Metals Loading
The maximum number of applications based on metals loading and
the number of applications per year can be used to determine the maxi-
mum site life:
ns
Number of Applications Plannedper Year
MaximumAllowableApplicatio
Site Life (yr)
=
(10.32)
