BOD Surcharges & Your Water Bill
Did your business receive an expensive water bill and you’re not sure why? It might be because of surcharges associated with Biological Oxygen Demand or Total Suspended Solids. Your local water utility uses both metrics to determine whether your business needs to pay a surcharge to cover the cost of additional cleanup for your business’s wastewater.
What is Biological Oxygen Demand?
Biochemical oxygen demand (BOD) is a measure of the oxygen utilized by bacteria to reduce the organic material contained in wastewater. It is an indicator of the organic strength of wastewater. Food waste and oils in your wastewater are among the most common causes of high BOD levels. As the concentration of waste in water increases, greater amounts of energy are required to clean the water to safe standards. It is more expensive and time-consuming to clean wastewater contaminated with higher BOD levels.
What are Total Suspended Solids?
Total suspended solids (TSS) are any waterborne particles that are greater than 2 microns in size. This includes sand, sediment, and very small pieces of food waste in your wastewater. These solids typically make your water appear murky or dirty and are an indication of how clean your wastewater is. The more solids contaminate your water, the more expensive and difficult it is to clean.
Why BOD and TSS matter to commercial kitchens
Most water and sewer providers require that any commercial kitchen be outfitted with a grease interceptor or trap. This system is designed to collect wastewater discharged from food preparation facilities, such as restaurants, schools, convenience stores, and more, to prevent oil and grease from being discharged into the sewer. High levels of grease and oil may result in the sewer becoming clogged. This can result in an increased cost of cleaning for the water and sewer provider and costly fines to the customer responsible for discharging the grease. To prevent this, Southwaste recommends regular grease trap service. Most regulatory agencies enforce a “90-Day or Less” Grease-trap service minimum standard, depending on the grease trap size and gallon throughput.
In addition to monitoring the discharge of fats, oils, and grease (FOG), many municipalities include a pretreatment program that actively monitors wastewater discharge for BOD and TSS. To offset the cost of treating more contaminated water, a surcharge program is often implemented that applies additional fees or surcharges to water and sewer bills for those customers who discharge waste streams greater than typical concentrations. Often the limits assigned to BOD and TSS concentrations are based upon system-wide averages that include residential and lower-use customers. As a result, the large-scale commercial customer will more often see BOD and TSS levels above the system average and face hefty surcharges unless they implement proper kitchen practices.
How are sewer surcharges calculated?
High BOD and suspended solid surcharges can be an unexpected additional cost for a business but are necessary due to the high cost of cleaning the highly contaminated water. Some local governments and municipalities publish their surcharge rate formulas for reference such as the Dallas City Code or City of Houston’s Code of Ordinances. Please refer to your specific water/sewer provider for your specific rates. Depending on your local rates, increased water contamination of food waste can quickly add up to an unexpected and expensive utility bill.
How to avoid sewer surcharges
How can your kitchen avoid the high cost of sewer surcharges? There are some simple kitchen practices and best standards that may minimize strong concentrations of waste in your wastewater. The strategies for minimizing BOD/TSS concentrations or preventing fat, oil, and grease overflow are often the same. Here are a few simple tips to keep your BOD levels under control and keep sewer surcharges in check.
Minimize the amount of food your team sends down the drain. Implement staff training to ensure your team knows how to keep as much food waste as possible out of sinks and drains. Instruct your team to place as much food waste as possible in solid waste barrels, train kitchen staff on the process of a three-compartment sink, and ensure dishwashers are being used appropriately.
Use effective kitchen equipment. There are strainers designed for sinks and dishwashers that capture as much of the solid material as possible. Consider purchasing or fabricating strainers with smaller holes to capture more food particles.
Maintain pretreatment devices. Grease traps and grease interceptors require regular service to work correctly. Many municipalities and local governments mandate a specific frequency of service for your grease trap, but depending on your volume of waste, you may require more frequent service. Work with a professional wastewater company like Southwaste Disposal to ensure that your trap stays functional and does not contaminate local sewer systems. An effective pretreatment device, when serviced at appropriate intervals can make a significant difference in the FOG, TSS, and BOD levels of your wastewater.
Ensure your grease trap is accurately sized. An appropriately sized trap can make a significant difference in the BOD and TSS levels that reach your sewer system. A larger trap provides greater settleability of the solids. The longer detention time of an appropriately sized trap allows the temperature of the discharged water to be lowered. Because fats and grease solidify when cool, allowing more time for water to cool prevents suspended particles from entering the sewer system. Replacing a trap can be costly, so we recommend working with a grease trap specialist like Southwaste to ensure that your pumping frequency and kitchen practices are appropriate to your needs and that your trap meets all local sizing requirements.
Consider biological supplements. Some studies have shown that, where used correctly, biological augmentation can lower oil/grease and BOD and TSS concentrations significantly. To be effective, the temperatures of the trap and detention time need to be carefully monitored. Temperatures should generally not exceed about 110 degrees Fahrenheit, and the detention time should be several hours. However, it is not recommended to attempt biological supplementation without a detailed plan created by a professional which can be prohibitively expensive for many small businesses. Additionally, many local municipalities and sewer providers actively prohibit biological supplementation.
Check your plumbing system. In older or poorly designed buildings, we have found instances where the floor drains or food sinks bypass the grease trap or interceptor. As a result, any food waste that goes into these drains is not caught by the grease trap. Make sure that all plumbing in the food preparation area goes to the interceptor or grease trap, especially if you consider using biological augmentation.
Use Floor Drains Correctly. When floor drains are close to equipment drains, it can be very tempting to discharge oil or grease improperly. Additionally, when performing regular cleaning of the kitchen, it can be very easy to skip sweeping kitchen floors to collect solids before mopping. Debris, food waste, cooking oil, and more that may get pushed into floor drains can contribute to high BOD and TSS levels, as well as cause expensive clogs. It’s important to remember that the time saved is not worth the potential for a contaminated sewer system and the associated surcharges.
Call Southwaste
Our team can ensure that your trap is appropriately sized and that your kitchen’s trap is serviced with the necessary frequency. Our team also offers professional hydro-jetting of kitchen lines which can remove accumulated build-up within your kitchen lines and, when used preventatively, can avoid an expensive plumbing bill.
Southwaste representatives are prepared to answer any questions you may have or schedule a site visit to review your organization’s wastewater process. Let us show you how we can support your efforts toward sustainable wastewater management. Contact us to schedule a site visit or ask questions about BOD and TSS related maintenance.
