Wastewater lagoons are man-made basins that leverage natural decomposition to biologically treat organic waste. They are typically composed of 4 volumes:
As lagoons age, the sludge layer grows, and the liquid treatment volume shrinks. The rate and pattern of sludge buildup differs based on several factors, including the lagoon type:
At $350 per dry ton of sludge on average, normal operations with 2,500–5,000 dry tons can easily spend $1,000,000 on dredging.
As the sludge storage volume of any lagoon nears capacity, it is recommended to remove half of the accumulated sludge, most commonly through dredging. At $350 per dry ton of sludge on average, normal operations with 2,500–5,000 dry tons can easily spend $1,000,000 on dredging. Even if performed only at the target 15-to-20-year mark, the costs are daunting, and excess accumulation forces many wastewater lagoons to deal with sludge much sooner.
If sludge is allowed to accumulate beyond the sludge storage volume, the other 2 volumes (treatment and effluent storage) become too depleted to ensure adequate retention time, forcing water out of the lagoon before it has been fully treated. Combined with the fact that excess accumulation spurs widespread anaerobic degradation in facultative and aerated systems, this leads to:
… Lagoons treated with bacteria experience sludge reductions from 40% all the way up to a whopping 91%.
Fortunately, these problems and dredging can be eliminated or, at the very least, deferred in all but the most severe cases of sludge accumulation.
For aerated systems, the entire lagoon should receive adequate dissolved oxygen, and the entire water column should be thoroughly mixed to facilitate the greatest direct contact between bacteria and solids. Operators may need to consider switching, supplementing, or repositioning aeration technologies that are causing “dead zones” (such as lagoon bottoms with surface aerators) or are mixing too mildly (such as fine bubble aeration systems).
To reduce existing sludge and prevent future buildup specifically in anaerobic and facultative conditions, many operators are turning to bioaugmentation with blends of specialized bacterial strains, bio-stimulants, and micronutrients. In trials conducted by EnviroZyme®, lagoons treated with bacteria experience sludge reductions from 40% all the way up to a whopping 91%. Remediation by bacteria is a fraction of the cost of dredging and also contributes to significant improvement of important physicochemical parameters.
While the courses of action available to treat sludge are relatively limited, consisting really only of dredging, aeration/mixing, and bioaugmentation, the ever-improving science behind bioaugmentation products is continuously boosting treatment outcomes and reducing treatment cost. EnviroZyme’s Sludge and Lagoon Pucks are our latest technology to maximize sludge reduction, accelerate waste digestion, and improve settling in emergency and maintenance situations. Because it is a biological extruded solid puck, it sinks deep into lagoons’ sludge layer for maximum exposure and effectiveness.
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