One of the biggest benefits of using quality, flexible geomembrane liners in sewage lagoons is the improvements to the sludge removal process. Putting in a durable liner creates a clear boundary between the soil or gravel below the surface and the water and sewage above. When sludge accumulates on top of the liner, it’s possible to pump or rake it away until you know you’ve hit the bottom. Find out why sludge removal plays such an important role in lagoon maintenance and how to determine the right timing for your pumping processes.
Every sewage lagoon is designed around a specific retention period. This is the length of time expected for treatment and processing. By the end of the retention period, the water should be safe for its intended discharge, or reuse, if everything worked properly. Small anaerobic ponds are often designed for practically indefinite retention and only lose water to evaporation and during periodic pumping. On the other end, some large-scale ponds can safely discharge sewage after only a few days thanks to rapid cycling. If sludge is allowed to build up, the retention period changes because more water is forced out through the discharge or overflow system. Removing sludge at a regular interval to maintain retention times is the only way to ensure a system is working as designed.
Reduction in Volume
The main reason that sludge changes retention time is because it reduces the total volume of the pond. Every inch of sludge in the bottom of the pond displaces water that it could store. As the pond grows shallower over time, evaporation also speeds up. This can interfere with the desired treatment processes by causing the pond to lose too much water at the wrong stage. Sludge removal maintains appropriate depth for anaerobic digestion as well.
Potential Reuse of Wastewater and Sludge
Don’t think of sludge as just a problem to deal with. For many sewage treatment plant owners and lagoon managers, the removed sludge is a product of its own that generates an important source of funding for the system. When dried and sanitized with heat, sewage sludge is transformed into the fertilizer known as biosolids. This material is easy to apply, and safe, as long as it's handled properly. Biosolids are a valuable source of nitrogen, phosphorous, and potassium that doesn’t require any mining or destructive chemical processes. They can be treated and screened to remove or reduce unwanted compounds like pharmaceutical residues as well.
Checking Sludge Depth
Proper timing of sludge removal depends on the actual depth, not just a chart tracking the usual accumulation of waste. Trying to go by a previous year’s sludge accumulation could lead to a flood or release of sewage that is unsafe for discharge. Treatment lagoons should be checked anywhere from weekly to quarterly with a long pole designed for the job. A hollow tube works best because it allows you to take a sampling of the sludge for accurate measurement. For more informal measuring of residential lagoons, a long stick marked with length increments will likely work well enough. When the sludge is high enough to only leave 18 inches of water or less at the surface, the pond will definitely need cleaning. Some lagoons require sludge removal far more often than that to maintain a deeper depth.
Sludge removal is a routine part of sewage lagoon maintenance and ownership. Make it as easy as possible by lining the ground with a geomembrane from BTL Liners first.