Worksheet for Calculating Biosolids Application Rates in Agriculture

Dan Sullivan and Craig Cogger
Oregon State University and Washington State University-Puyallup

Cumulative Loading of Trace Elements

Under EPA regulations (40 CFR Part 503.13), managers must maintain records on cumulative loading of trace elements only when bulk biosolids do not meet EPA Exceptional Quality Standards for trace elements (Table 4).

When required, the steps in tracking trace metals are:

• Obtain biosolids trace element analyses from the wastewater treatment plant database.
• Compute pounds of element per dry ton of biosolids. Multiply mg/kg (dry weight basis) by 0.002.
• Keep records of the amount of biosolids applied to the site each year (in dry tons per acre).
• Compute pounds of element applied per acre. Multiply pounds of element per dry ton by dry tons applied.
• Compare cumulative pounds of element applied with the cumulative loading rate limit (Table 5).

Table 4. Biosolids concentration limits for land application. Source: EPA 40 CFR Part 503.

*EPA Table 3 and Table 1 refer to tables in EPA biosolids rule (40 CFR Part 503).

**Molybdenum Table 3 level is under review by the EPA.

Table 5. Cumulative loading rate limits for bulk biosolids that do not meet EPA-Table 3 criteria and are applied to agricultural land. Source: EPA 40 CFR Part 503.13.

*Molybdenum limit is under review by the EPA.

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Worksheet for Calculating Biosolids Application Rates in Agriculture, PNW 511-W
by Dan Sullivan and Craig Cogger
(Oregon State University and Washington State University-Puyallup)
March 1, 2000