Solids Reduction in a Municipal Lagoon System

Reducing Sludge in Wastewater Lagoons

One of the most persistent challenges in lagoon wastewater treatment is managing accumulated solids, or sludge.

Lagoon systems are designed to biologically reduce organic material during wastewater treatment. However, over time, solids can accumulate on the lagoon bottom and reduce available treatment capacity.

Traditionally, built-up sludge is removed through mechanical dredging. This process often requires heavy equipment, sludge dewatering, transportation, and off-site disposal.

Depending on site conditions and disposal requirements, mechanical sludge removal can cost approximately $300 to $500 per dry ton of solids.

Using Bioaugmentation for Lagoon Sludge Reduction

Bioaugmentation offers a biological approach to reducing accumulated sludge in wastewater lagoons.

By introducing concentrated cultures of beneficial bacteria into the treatment process, operators can increase microbial activity and support the biological breakdown of organic solids.

These microorganisms, commonly associated with natural soils and sediments, can help improve solids degradation and lagoon treatment efficiency when applied under appropriate conditions.

ProBiotic Dredging® for Biological Solids Management

BioLynceus® refers to this biological sludge-reduction approach as ProBiotic Dredging®.

Unlike conventional mechanical dredging, ProBiotic Dredging® focuses on supporting microbial activity to reduce organic solids within the lagoon itself.

Potential benefits include:

  • Reduced accumulated sludge

  • Increased lagoon treatment capacity

  • Less dependence on mechanical dredging

  • Reduced sludge hauling and disposal requirements

  • Improved long-term lagoon solids management

Using ProBiotic Scrubber® II for Lagoon Treatment

The following case study describes the use of BioLynceus® ProBiotic Scrubber® II (PBII) to reduce accumulated solids in a municipal wastewater lagoon system.

The treatment program was designed to support biological sludge degradation, recover lagoon capacity, and reduce the need for conventional dredging.

Figure 1. Case study lagoon system. PBII was injected into the collection system to reduce accumulated solids in the treatment cells.

Sludge Accumulation in a 0.3 MGD Lagoon System

A Publicly Owned Treatment Works (POTW) serving a community of approximately 2,700 residents was experiencing significant sludge accumulation in its wastewater lagoon system.

The facility consisted of three treatment cells with an average wastewater flow of approximately 0.3 MGD, although flow rates varied seasonally.

As organic solids accumulated on the lagoon bottom, the municipality faced the possibility of costly mechanical dredging if the sludge could not be reduced through another treatment method.

Exploring ProBiotic Dredging® as an Alternative

The head wastewater operator learned about BioLynceus® ProBiotic Dredging® during a wastewater training program.

ProBiotic Dredging® uses biological treatment to support the breakdown of accumulated organic solids within wastewater lagoons.

After evaluating the approach, the operator presented the biological sludge-reduction program to the city council as a potential alternative to conventional mechanical dredging.

Using Bioaugmentation to Reduce Dredging Costs

The city council approved a bioaugmentation program using BioLynceus® microbial products to help reduce accumulated sludge and potentially lower future dredging expenses.

BioLynceus® ProBiotic Scrubber® II (PBII) was introduced at several upstream locations within the wastewater collection system before the influent reached the first lagoon cell.

Applying PBII upstream allowed the microorganisms to enter the wastewater before it reached the lagoon treatment process.

Increasing Microbial Activity for Solids Degradation

ProBiotic Scrubber® II introduced a diverse population of microorganisms into the wastewater system to support the biological degradation of organic solids.

The treatment program was designed to:

  • Increase populations of solids-degrading microorganisms

  • Support organic sludge decomposition

  • Reduce accumulated lagoon solids

  • Recover treatment and holding capacity

  • Reduce dependence on mechanical dredging

  • Lower long-term sludge management costs

By increasing microbial activity throughout the collection and lagoon system, the municipality used bioaugmentation as part of a long-term lagoon sludge management and ProBiotic Dredging® strategy.

Figure 2. Average annual depth of clear water above the solid sludge profile in the first treatment cell. Depth measurements were collected at 12 locations around the lagoon. Increasing trends in average annual depth of clear water indicated an organic solids reduction via ProBiotic Dredging®.

Measuring Sludge Reduction in the Lagoon

Changes in lagoon sludge depth were monitored by measuring the depth of clear water from the surface to the top of the accumulated sludge layer.

Measurements were collected in the first treatment cell:

  • During the fall before treatment began

  • After the first year of PBII treatment

  • After the second year of PBII treatment

This provided a consistent method for tracking changes in accumulated solids over time.

Seven Inches of Sludge Reduction in the First Year

Before treatment, the average depth of clear water above the sludge layer was approximately 12 inches.

After one year of treatment with BioLynceus® ProBiotic Scrubber® II (PBII), the average clear-water depth increased to approximately 19 inches (Figure 2).

This represented an estimated 7-inch reduction in accumulated sludge depth during the first year.

Additional Sludge Reduction During the Second Year

During the second year of treatment, the average depth of clear water increased again to approximately 22 inches.

This represented an additional 3 inches of sludge reduction.

Over the two-year treatment period, measurements indicated a total reduction of approximately 10 inches of accumulated sludge in the monitored lagoon cell.

Maintaining Lagoon Capacity Without Mechanical Dredging

The reduction in accumulated solids helped the POTW maintain adequate lagoon treatment and holding capacity without mechanically dredging the treatment cells during the study period.

Wastewater treatment performance remained stable while the accumulated organic solids were biologically reduced.

Avoiding mechanical dredging also helped the municipality reduce the operational disruption, hauling, dewatering, and disposal requirements associated with conventional sludge removal.

Continuing Biological Lagoon Treatment

Based on the measured sludge reduction and continued treatment performance, the lagoon facility continued using BioLynceus® ProBiotic Scrubber® II as part of its long-term solids management program.

The treatment results demonstrated the potential benefits of bioaugmentation for:

  • Reducing accumulated lagoon sludge

  • Supporting biological solids degradation

  • Recovering treatment capacity

  • Delaying mechanical dredging

  • Supporting long-term lagoon maintenance

Reduce Lagoon Solids with ProBiotic Scrubber® II

BioLynceus® ProBiotic Scrubber® II is designed to support biological sludge reduction, lagoon solids management, treatment capacity, and reduced dependence on mechanical dredging.

Reference

  1. Gerardi, M. (2016). Wastewater Bioaugmentation and Biostimulation. Lancaster, Pennsylvania: DEStech Publications, Inc., p. 117.
    Wastewater Bioaugmentation and Biostimulation