What are BOD and TSS? How Do They Apply to My Business?
Biochemical oxygen demand, or BOD, and total suspended solids, or TSS, are the common measures of wastewater strength and a basis of sewer rates. BOD and TSS measures are used to determine what is required to breakdown or filter out the organic matter in wastewater in order to treat it to regulated standards.
Standard base sewer rates include costs associated with BOD and TSS per levels measured in residential wastewater. A food service establishment often has daily BOD and TSS concentrations much higher than the average home because of the more intensive food preparation and cleanup activities. Wastewater with higher amounts of food waste along with fats, oil, and grease cause higher levels of BOD and TSS. Extra strength charges cover the added cost of treating this additional BOD and TSS.
A business’s extra strength charges are based on its business class (sit-down restaurant, fast-food restaurant, brew pub, etc.) and whether or not certain best management practices are in place.
How to Estimate Your Charges
Extra strength charges may be reduced if certain best management practices are in place such as a grease interceptor, composting practices, and the absence of sink garbage disposals. Use the calculation worksheet and instructions below to estimate your charges. Having your City of Portland water/sewer/stormwater bill available can be helpful to find the information you need to complete the worksheet.
Estimate the extra strength charges for your establishment according to your business class (sit-down restaurant, fast-food restaurant, brew pub, etc.) and by qualifying best management practices in place at your business or establishment (grease traps/interceptors, absence of sink garbage disposals, and food composting/donation programs).
Step 1: Enter Your Account Number
Enter your water/sewer/stormwater account number on Line 5, Row A. Your account number is optional, but it is handy to include in case you need to contact the City about your account or if you are managing rate charges from multiple accounts.
Step 2: Determine Your Net Total Flow
From your water/sewer/stormwater bill, find your "Sewer Volume/Usage in CCF." From this number, subtract amounts (if any) that are credited for water that is not discharged to the sanitary sewer. Enter the resulting total in the green box on Line 5, row "E" next to the red numeral "1." This is your net total flow subject to extra strength charges.
Step 3: Enter Percentage of Flow by Business Class Rate Option
Food service establishments are listed on the calculation worksheet by business class and according to which best management practices are in place. Find the class and rate option which best matches your business and best management practices in place.
Enter the total percentage of flow in the green box in Row "E" next to the correct rate option. For accounts that serve a single business, this entry should be "100" representing 100 percent of the flow. If the account serves multiple businesses, flow may be apportioned on separate lines by entering the appropriate percentage of total flow for each business.
Step 4: Find Your Extra Strength Charges
After the above information is added to the worksheet, resulting charges for biochemical oxygen demand (BOD) and total suspended solids (TSS) will be automatically displayed at the bottom of the worksheet on Line 116 and on Line 117.
For More Information or Questions
For additional help in calculating or questions about your charges, contact our Cut Through the FOG program. Contact information is on this page.