Hydraulic short circuiting is the greatest deterrent to wastewater lagoon performance aside from toxic materials entering the lagoon Middlebrooks (2000). Engineers design lagoons with a certain treatment capacity in mind and accumulated sludge robs the system of that capacity. Retention time is critical to a pond system’s ability to kill pathogens, lower BOD, allow algae and bacteria floc to settle, and remove ammonia, nitrates and phosphates. The accumulated sludge in a pond can cause significant short-circuiting. The problem with accumulated sludge is not limited to the loss of critical treatment capacity, but accumulated sludge also causes something called benthal release.

Accumulated sludge is composed of dead and decaying algae and bacteria. This biomass stores nutrients such as ammonia, nitrates, phosphates, and organic acids. Benthal release is a process where the cellular material once stabilized and stored in the cell walls and cytoplasm of bacteria and algae, ooze back into the water column to feed new generations of bacteria and algae. When benthal release is occurring, the pond itself is generating its own BOD5 and feeding TSS problems.

As algae populations explode under nutrient enriched conditions, they generate oxygen during the sunlight hours but then consume it at night under dark conditions in a biological process called respiration. These populations of excess algae consume vast amounts of dissolved oxygen at night causing crashes in dissolved oxygen concentrations during the late evening to early morning hours. The presence of so many algae cells also results in massive algae bloom die-off causing increases in BOD5.

Low dissolved oxygen concentrations support denitrification (leading true nitrogen removal) but also causes rising (floating) sludge and sludge derived TSS problems. In addition, excess algae captured in the BOD bottle may also lead to increased BOD5 results, as algae consume oxygen (respire) in the test bottle or die – feeding bacteria causing greater rates of oxygen consumption and elevated BOD5 results. 

When lagoons fail they typically fail fast and they fail hard. When operating a lagoon under failed conditions there are no quick solutions to reverse things. By this point, State and Federal agencies are calling on the city for immediate actions to correct problems, fining them, or issuing NOV’s or orders of compliance. Turning a lagoon around quickly typically requires drastic measures like dredging, constructing another lagoon, or decommissioning the lagoon altogether. When forced to act quickly, solutions to lagoon problems usually wind up being very expensive.

With capacity losses and large volumes of sludge feeding nutrients back into the water column, the sludge mass is like a ticking bomb or a bomb with a short fuse. A lagoon loaded with sludge may function fine for awhile, but nobody knows just how short the fuse is or exactly when it will blow up.

A city somewhere in the Western United States had their lagoons desludged in December of 2008. Even though city employees did some of the prep-work themselves and paid to have electricity brought in to drive the pumps, centrifuges, and conveyors, they still spent $1,200,000 to remove 3,650 dry tons of sludge. In some places the sludge in the primary cell was up to 12 feet deep. The Wastewater Supervisor said if the city hadn’t done some of the prep work itself, or paid to have electricity brought in, the sludge removal project could have cost well over $1,600,000 because of generator rental and operational costs.

There is another option for sludge removal in lagoons. It does not require the mechanical removal of sludge but sludge is removed through biological/ biochemical pathways at a fraction of the cost of removing sludge with dredges, pumps, centrifuges, loaders, and trucks, and lagoons stay on line.

CBX ProOxidizer product is a unique biochemical that affects cell wall permiability and cellular metabolism for faster rates of biooxidation and endogenous respiration. Accelerated rates of endogenous respiration leads to sludge mass and volume reduction of about two (2) inches of sludge per month in most lagoon systems. For example with an average sludge blanket thickness of 5.289 feet, biologically removing 75% of the sludge would take about 2 years.

Sludge removal using CBX is about 1/10th of the cost of mechanically removing the sludge and lagoons can remain on line. With CBX ProOxidizer there are no disposal costs, no odors, no permits, no land application, land filling, and no trucking offsite. Sludge is oxidized on site while the lagoon remains online. Take that $1,296,000 lagoon sludge removal project and cut that cost by 90%... by doing a little more than you're doing right now.