Pretreatment Surcharge Program
Wastewater surcharges are charged to businesses that discharge wastewater exceeding normal strength standards. Business wastewater can be more heavily concentrated with solids and organic matter than residential wastewater, making it more expensive to treat.
- Surcharge Fee Overview
All customers subject to a surcharge are notified by letter, and monthly surcharge fees are applied to the utility bill. Fees are based on quantity and quality.
Quantity is based on the lower of:
- The actual amount of discharged wastewater
- For customers without separately metered irrigation systems, the average winter discharge
Quality is based on the amount of solids and organic matter in your wastewater. Much of the cost of treating wastewater comes from solids removal and the oxygen required to stabilize and digest organic matter. A surcharge applies when average discharge quality exceeds one or more normal-strength quality standards established for typical residential wastewater. Quality is determined from site-specific sample results for Biochemical Oxygen Demand (BOD), Chemical Oxygen Demand (COD) and total Suspended Solids (SS). For customers whose site-specific samples have not been or cannot be collected, surcharges are assessed using quality standards for similar businesses based on Standard Industrial Classification (SIC) codes.
Normal strength values (milligrams per liter)
Parameter Normal Value Suspended Solids (SS) 200 mg/L Biochemical Oxygen Demand (BOD) 200 mg/L Chemical Oxygen Demand (COD) 450 mg/L - Surcharge Formula
Using an average of all applicable sample results, a surcharge is calculated for every permitted source of industrial waste.
If the COD is 2.25 times or less than the BOD, use:
S = V × 8.34 [A (BOD − 200) + B (SS − 200)]
If the COD is more than 2.25 times the BOD, use:
S = V × 8.34 [C (COD − 450) + B (SS − 200)]
Variable Definition S Surcharge in dollars appearing on the monthly utility bill V Wastewater billed in millions of gallons during the billing period 8.34 Pounds per gallon of water A Unit charge per pound of BOD in excess of 200 mg/L — currently $0.7411/lb. Does not apply if BOD is below 200 mg/L. B Unit charge per pound of SS in excess of 200 mg/L — currently $0.6047/lb. Does not apply if SS is below 200 mg/L. C Unit charge per pound of COD in excess of 450 mg/L — currently $0.3294/lb. Does not apply if COD is below 450 mg/L. BOD Biochemical Oxygen Demand in milligrams per liter (mg/L) SS Total Suspended Solids in milligrams per liter (mg/L) COD Chemical Oxygen Demand in milligrams per liter (mg/L) 200 Normal BOD and SS in mg/L 450 Normal COD in mg/L The surcharge billed (S) changes with wastewater volume billed (V), which may vary month to month. For this reason it is often more useful to discuss surcharges in terms of the Surcharge Factor (SF) — the quality component of the formula:
SF = 8.34 [A (BOD − 200) + B (SS − 200)]
Or, if COD is more than 2.25 times greater than BOD:
SF = 8.34 [C (COD − 450) + B (SS − 200)]
You can also use the Surcharge Calculator to determine your surcharge.
- Sample Surcharge Calculations
Example 1
BOD average 614 mg/L SS average 111 mg/L COD average 1,200 mg/L Wastewater average 0.0116 million gallons per month Step 1: Determine which formula applies.
1,200 ÷ 614 = 1.95 — this ratio is less than 2.25, so use:
S = V × 8.34 [A (BOD − 200) + B (SS − 200)]
Step 2: Calculate the surcharge.
- S = 0.0116 × 8.34 × {[0.7411 × (614 − 200)] + [0.6047 × (111 − 200)]}
- S = 0.0116 × 8.34 × {[0.7411 × 414] + [0*]}
- S = 0.0116 × 8.34 × 306.82
- S = $29.68/month
* No SS charges apply because SS is below the 200 mg/L surcharge threshold.
Example 2
BOD average 614 mg/L SS average 799 mg/L COD average 1,860 mg/L Wastewater average 0.0934 million gallons per month Step 1: Determine which formula applies.
1,860 ÷ 614 = 3.03 — this ratio is greater than 2.25, so use:
S = V × 8.34 [C (COD − 450) + B (SS − 200)]
Step 2: Calculate the surcharge.
- S = 0.0934 × 8.34 × {[0.3294 × (1,860 − 450)] + [0.6047 × (799 − 200)]}
- S = 0.0934 × 8.34 × {[0.3294 × 1,410] + [0.6047 × 599]}
- S = 0.0934 × 8.34 × [464.45 + 362.22]
- S = 0.0934 × 8.34 × 826.67
- S = $643.94/month
Verify your results with the Surcharge Calculator.
- Request Resampling
Businesses that currently pay a wastewater surcharge may request resampling and reassessment. Submit a Surcharge Resampling Request Form or send a written request to:
Austin Water Pretreatment Program 3907 S. Industrial Drive, Suite 100 Austin, TX 78744
If the request is granted, resampling will consist of two sample collections on two separate consecutive days. The newly calculated surcharge applies to future utility bills only — no credits or debits are applied retroactively.
If No Major Changes Have Occurred
- The customer is responsible for resampling and analysis costs per the current City of Austin Approved Fee Schedule.
- Payment must be received before resampling, which will be scheduled within 30 working days of payment receipt. Austin Water may deny or delay resampling if resources are limited.
- New results plus historical data from up to three previous calendar years will be averaged to calculate the new surcharge.
- Customers may request only one resampling per calendar year.
If a Major Change Has Occurred
If the customer documents a major change in pretreatment devices or the elimination of a waste-producing device:
- Resampling will be performed at no additional cost.
- The new surcharge will be calculated based on the new resampling results only.
- Tips to Reduce Your Surcharge
Taking steps to reduce the concentration of solids and organic matter in your wastewater can lower your surcharge, reduce pollution and prevent costly plumbing problems including sanitary sewer overflows.
- Keep waste cooking oil out of drains. Before washing, wipe oily pans with a paper towel and collect used oil for disposal at rendering facilities (PDF).
- Scrape food from plates into the trash before washing. Food waste — whether whole, chopped or pureed — does not belong in the drain. Garbage disposals and grinders have been prohibited in commercial kitchens in the Austin Water service area since 2008.
- Sweep floors before washing them down to remove all trash and debris.
- Install and maintain screens over all sink and floor drains.
- Conserve water — see water-saving tips for ideas.
- Follow an appropriate grease trap pump-out schedule. Many traps require cleaning more often than the 90-day minimum in Austin City Code § 15-10-197. See the Grease Trap Maintenance page for more information.
- Do not use prohibited enzymes, bacteria or other agents at your facility per Austin City Code § 15-10-22(23).
Improvements will not be reflected in your surcharge until your wastewater is next resampled and reassessed. If you have taken steps to improve your wastewater quality, you can request surcharge resampling.
- Resources