BOD Surcharges & Your Water Bill

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 (BOD Surcharges) 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.  This is used in 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 from restaurants and other commercial kitchens, many municipalities include a pretreatment program. This program actively monitors wastewater discharge for biochemical oxygen demand (BOD). As well as monitoring total suspended solids (TSS). A surcharge program is often implemented to offset the cost of treating more contaminated water. It applies additional fees to water and sewer bills for those that discharge larger waste streams. The limits assigned to BOD and TSS concentrations are often based upon system-wide averages. This includes 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. Therefore, they face hefty surcharges. Unless they implement proper kitchen practices such as using their own grease traps. Rather than dumping used oil down storm drains.

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 food waste in the solid waste barrels. Train kitchen staff on how to use 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.