Industrial Monitoring Programs (Surcharge Program)

(A)  Industrial Waste Surcharge Program
One element of industrial monitoring is the Surcharge Program.  Surcharges apply to Biochemical Oxygen Demand (BOD) and Total Suspended Solids (TSS) for some facilities.   Long term history, with analysis has established the levels of BOD and TSS in Amarillo domestic sewage.  These levels are established at 300mg/L for BOD, and 400 mg/L for TSS.  BOD and TSS are sampled, at the industry, and analyzed monthly by the City.  This is then applied to the entire monthly flow for the industry, and calculations are made for charges applied to treating extra strength sewage.  Note, in the following formula, domestic levels are subtracted.  The industry, therefore, pays a surcharge only for the amounts above domestic levels.   
The Surcharge Formula

S = Va(BOD-300) + Vb(TSS-400)

Where,

S is the surcharge amount in dollars
V is the monthly wastewater flow in Million gallons
a is the unit cost for removing 1 mg/l of BOD from 1 million gallons ($1.4663)
b is the unit cost for removing 1 mg/l of TSS from 1 million gallons ($0.6377)
BOD is the actual BOD obtained from monthly sampling and analysis
TSS is the actual TSS obtained from monthly sampling and analysis

Surcharges are not fines or penalties.  Surcharges are intended to recoup the cost of treatment of extra strength wastes by the Publicly Owned Treatment Works (POTW).  Surcharges must not be used to allow discharges of toxic pollutants that cause interference or pass through.
Example of Calculating Only A BOD Surcharge

BOD Portion

The monthly BOD sample result is 1000 mg/l
The industry used 5 million Gallons during the month
(5 MG) x ($1.4663) x (1000 mg/l – 300 mg/l) = $5,132.05
Surcharges, depending on permit requirements, can therefore be calculated for BOD, TSS, or both, as needed.