White Paper: Lagoons—Under the Surface

An In-Depth Investigation of Bioremediation and Biological Factors Involved in Reducing Sludge at a Municipal Wastewater Treatment Facility Lagoon System

Heather Jennings, PE, Sr. Project Engineer, Probiotic Solutions®


In this study, the operators of a municipal wastewater treatment facility with 4 lagoons had determined that their 2 primary lagoons—10-foot-deep, with 25-million-gallon holding capacity each—had reached sludge depths of 5–7 feet, putting the lagoons at risk of upset and seriously impacting the facility’s wastewater processing capacity.

A bioremediation plan was implemented that included the use of a biostimulant to support microbial reduction of the organic solids in the system. Sludge judging was performed for the 2 primary lagoons at baseline and at quarterly intervals over a one-year  period to measure the impact of the bioremediation plan on sludge reduction. This was supplemented with ATP analysis to identify live biomass energy levels and DNA analysis to identify presence of and changes in relative representation of bacteria species at various stages of plan implementation. It also documented bacteria response to changes in influent due to episodic loading from industry, including a near-septic event. A modified sludge judge was used to collect samples from each of 3 layers of the lagoon:  bottom (sludge), middle (interstitial), and top (supernatant).

The results of the ATP and DNA analyses pointed out the often-misunderstood fact that wastewater treatment facility lagoon sludge is not inert: it is the most biologically active layer of the water column and can be efficiently controlled and reduced through proper bioremediation interventions. The ATP analyses also documented the lasting effects (3 months) of an episodic toxic loading on the 2 lagoons. The study reports the 47 most abundant bacteria species present at various quarterly samples and at each of the 3 water/sludge layers. Discussion is provided of the roles several of these bacteria species play in the bioremediation process.

 At the end of the one-year bioremediation plan, sludge depth for the 2 lagoons had been reduced by an average of 45%, with sludge depth at some sample points completely reduced to zero. This represented 17,800 dry tons of sludge that did not need to be  mechanically removed and hauled to a disposal location, a potential savings to the treatment facility of over $6 million.

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(32 pages, 34 figures, 37 tables)

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