Industrial wastewater users can meet municipality demands with planning and action.
by Sara Peters
September 25, 2019

When a new manufacturer opens its doors, the pomp and circumstance surround the product lines manufactured and sold. The excitement is for the profits to be made. However, the byproducts of the manufacturing process may pose a threat to those profits.

According to Brian Helminger, head of operations at Heart of the Valley Metro Sewage in Kaukauna, Wisconsin, the wastewater discharged to municipalities is not thought of as the “shiny” side of the business. Not planning for wastewater discharge and the user fees imposed by the municipality could be a tricky, and expensive, misstep for manufacturers. Here, Helminger provides information about wastewater user fees and how companies can reduce these costs.

wastewater discharge feesImage 1. Wastewater discharge fees can be a tricky and expensive misstep for those not prepared. (Images courtesy of Crane Engineering)

What Are User Fees?

A wastewater treatment facility’s role is to treat wastewater from homes and businesses for discharge to the environment. A wastewater treatment facility houses a delicate balance of organisms and bacteria that, when given the proper environment to live, will consume and breakdown sewage and other organic matter to purify the water. A wastewater treatment plant must ensure that the influent is within the parameters that sustain the valuable organisms and bacteria that make the process work.

Businesses often discharge different wastewater than the typical home at a higher volume. Therefore a user fee is imposed by the municipality to help cover the added cost of handling and treating wastes not covered by existing taxes or sewer charges.

User fees are appropriately applied to ensure each company pays its share to treat the waste. User fees are assessed by volume as well as the strength of the wastewater.

Fats, oils and greases contribute to elevated BOD and TSS levelsImage 2. Fats, oils and greases contribute to elevated BOD and TSS levels.

Determining Wastewater Strength

When determining the strength of a manufacturer’s wastewater (domestic or high strength), a municipality will look at the following factors:

Organic Loading
Organic loading is represented as BOD—biochemical oxygen demand—or the amount of oxygen needed to fully oxidize organics. It is typically tested as milligrams per liter (mg/l) and calculated as pounds per day (lbs/day). Wastewater with high organic loading is costly for municipalities to treat.

Solids Loading
Typically represented as TSS—total suspended solids—solids loading is a measurement of the suspended solids in wastewater. Like organic loading, solids loading is tested as mg/l and calculated as lbs/day. A high degree of solids is also costly for municipalities to remove and dispose of.

pH Levels
This is the most commonly treated factor for industries and is easily controlled by a chemical addition to the monitored discharge to the municipality. A pH level of 6.0 to 8.0 is acceptable. A pH lower or higher than this range can shock the municipal wastewater ecosystem, destroying microorganisms and effectively stopping the processes they perform to purify waste. Domestic-strength wastewater is ideal for the wastewater treatment plant. Determining threshold levels for what is considered “typical” domestic sewage varies by municipality and is defined in its sewer use ordinance.

Domestic strength wastewater definitions typically meet the following characteristics (or are close):

  • up to 250 mg/l BOD
  • up to 250 mg/l suspended solids
  • up to 6 mg/l phosphorus
  • up to 20 mg/l nitrogen

Wastewater that exceeds these limits is billed at high strength rates.

Surcharges

When companies discharge waste that is out of spec, or outside the parameters for which they have a permit, a municipality incurs additional expenses to treat the waste. These expenses are passed on to companies as surcharges.

Fats, Oils & Greases

Fats, oils and greases (FOG) are some of the biggest contributors to elevated BOD and TSS levels, resulting in additional surcharges and possibly more serious problems for sewer systems. FOG can cause blockages in pipes and is one of the most common sources of sewer overflows. If not treated properly, it can also cause harm to the environment and monetary harm to ratepayers.

FOG is particularly challenging for municipalities because it takes a long time to remove. Discharging waste with FOGs in excess of 100 mg/l is prohibited. This may cause collection system blockages and interfere with the operation of the wastewater system.

Surcharges for discharging wastewater with high levels of FOG add up quickly for food and dairy operations in particular. Companies can send thousands of dollars per year, quite literally, down the drain. Food production companies must be especially careful to keep FOG under control.

How to Stop Incurring Fees

To reduce costs on wastewater disposal, companies should look to consultants that specialize in industrial wastewater user compliance. Below are some solutions commonly recommended by consultants:

Flow Equalization Tanks
This is one way high-strength waste is diluted to meet specifications. The high-strength waste flows into one tank and comingles/homogenizes with low-strength waste. A pH adjustment can be made, where one could add acid to high pH waste to bring it down below 8.0 or add caustic soda to bring low pH up above 6.0. A flow equalization tank is probably the most basic and common way to address high-strength waste.

Grease Interceptor or Dissolved Air Flotation (DAF)
To remove grease from the waste stream, air is dissolved in the wastewater under pressure. The air is released at atmospheric pressure in the tank. The tiny bubbles attach to suspended grease particles in the fluid, causing grease to float to the surface where it is skimmed from the top. The grease and comingled solids are then transferred to a solids tank.

This heavy-strength solid FOG waste is then trucked away by a licensed industrial waste hauler. This method not only reduces the amount of FOG discharged to the municipality, but greatly reduces BOD levels as well. This method removes the phosphorus and nitrogen bound to the solids.

Sand Interceptor
Reducing organic solids in wastewater is important, but it is also important to reduce the inorganic solids as well. Inorganic solids like sand and grit contribute to TSS in wastewater. Sand interceptors or grit removal systems help with this.

Removing the grit can be done passively by slowing the flow of fluid to get the sand or grit to precipitate out of the wastewater, or mechanically by using filters.

Conclusion

Surcharges do not have to eat away at profits. Considering an investment in pretreatment can lead to major savings on the wastewater bill.

When companies are ready to take a look at reducing costs on the not-so-shiny side of the business, a wastewater consultant can help them get started.