Fat, Oil, and Grease (FOG) Removal in Wastewater Treatment

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Consequences of Untreated FOG Discharge

Untreated FOG discharge can impact wastewater plants in several ways.

Sanitary Sewer Overflows (SSOs)

FOG is one of the major causes of SSOs. A research paper from North Carolina State University found that FOG deposits contribute to 25% of SSOs. As hot, greasy water enters the collection network, it cools down, solidifying on the pipe walls. When FOG combines with other contaminants, it undergoes saponification. Saponification turns the FOG into a hard, insoluble fatberg that is extremely difficult to break down.

Operational Downtime

If FOG reaches treatment plants, it can cause significant infrastructure damage. FOG can coat equipment within wastewater systems, leading to inaccurate readings and operational inefficiencies. There is also the risk of downtime associated with repairs and constant maintenance.

Aerobic Basins

Another consequence of untreated FOG discharges happens within aerobic basins. FOG can create floating layers in aerobic basins that inhibit oxygen transfer. This can turn basins into anaerobic zones, which can harm the aerobic bacteria essential for biological wastewater treatment.

Financial and Compliance Risks

Beyond affecting system functionality, FOG accumulation in wastewater systems has financial implications as facilities are faced with costly equipment and infrastructure repairs.

Common Methods for FOG Removal in Wastewater Treatment

There are several methods to remove FOG, including:

• Mechanical separation. One of the primary methods to remove FOG in wastewater is dissolved air flotation (DAF). During the DAF process, water gets saturated with air through pressurization. As this water enters the DAF tank, it forms multiple micro-bubbles that attach to the FOG particles and float them to the surface for easy skimming.
• Chemical separation. In this FOG removal method, an oxidizing agent, such as hydrogen peroxide (H₂O₂), enters the wastewater. The agent breaks down the emulsified oils, helping with flotation and separation.
• Coagulation. Coagulants are another chemical tool often used in high FOG-loading environments. Adding aluminum or iron salts to FOG wastewater neutralizes electrical charges on emulsified oil droplets. This process allows the oil to clump together, making it easier to separate by settling or flotation.

Developing a FOG Management Strategy

Robust FOG management doesn’t rely on a single strategy. It’s often a combination of methods designed specifically to fit a facility’s FOG loading capacity.

If your facility needs a customized FOG management strategy, USP Technologies can help. We have extensive experience leveraging advanced wastewater treatment techniques to help you optimize your operations. Contact us today to learn more about how we can support your facility and improve your systems.