Partial lagoon cleanouts help balance performance and budgets

DATE POSTED: August 28, 2020

If you’re going to clean out a cell or two at your wastewater lagoon, there are circumstances when a partial cleanout might be the best, fastest way to quickly fix an urgent capacity or performance issue until the lagoon is ready for a full desludging.

Partial cleanouts, using the Bishop Solids Management Solution, can most often be completed while the lagoon remains in operation, so there’s no need to decommission the cell or disrupt the process flow. Bishop Water can quickly diagnose lagoon performance issues caused by excess sludge and determine the volume and locations of sludge that should be removed from the cell. 

Once a plan is ready, the team can mobilise a dredge, its mobile polymer conditioning system and prepare a laydown area for Geotube® containers, are used to collect, dewater and consolidate the solids. Or, if the volume of sludge is small, they can be filled and removed inside 30-yard roll off boxes, making transportation and disposal fast and simple.

Partial sludge cleanouts can also become part of an ongoing lagoon maintenance program to ensure optimum performance. Rather than waiting until sludge accumulation reaches a critical level, lagoon operators or Bishop Water technicians can monitor sludge accumulation in the lagoon and when needed, proactively perform a partial cleanout to maintain an optimized level of performance.

Partial lagoon cleanouts have been used by many lagoon operators to achieve operational and economic benefits including: 

  • Quickly restore lost storage and treatment capacity in the lagoon; 
  • Correct flow issues caused by sludge accumulation that create short-circuiting of lagoon flow and reduced retention time; 
  • Defer the cost of a full lagoon cleanout over an extended period of time; 
  • Maximize the capacity and dewatering of each Geotube® container. Partially filled containers can remain onsite for continued filling at the next cleanout interval. They will experience significant volume reduction between fill intervals, which will reduce the number of containers needed as well as hauling and disposal costs.

Learn more about Bishop Solids Management Solutions for partial lagoon cleanouts. 

Contact us to discuss your lagoon clean out needs. 

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Is your treatment plant suffering from washout?


Every wastewater plant can experience washout—a condition where high hydraulic loading causes microorganisms to be flushed out of a treatment cell at a faster rate than they can be replenished. It most often happens during periods of peak sanitary flow or during wet weather and its occurrence may be on the rise as we experience more frequent and severe storms due to climate change. Inflow and infiltration can compound the problem adding more water to the sanitary system and further diluting the treatment process.

Diagnosing washout at your plant

Reducing retention times in primary, secondary and tertiary processes is the most common approach to enable the plant to accommodate the higher hydraulic loading and avoid the need to bypass one or all of the treatment steps. But due to the faster flow, operators may see a decline in the treated effluent quality.

The telling sign of washout is that even after the influent flow returns to normal levels, the quality of treated effluent may continue to suffer for many hours or even days after the event. This lag in performance indicates that a significant portion of the microbiological population has been lost to washout and the remainder is unable to provide adequate nutrient removal. The condition will continue until the microbiological population is re-established to the optimum level. 

Fall washout = winter performance problems

In the warmer months, the microbiological population can rebound fairly quickly. But since temperature plays a major role in the rate of microbiological growth, a washout in the fall or winter can have serious long-term consequences to plant performance, particularly for wastewater lagoons or other plants where secondary treatment occurs outdoors. In these plants, the microbial population may not fully recover until the spring, which means the plant could have to operate at reduced capacity or face compliance issues through the cold-weather period. 

Build a better home for bacteria

Bishop BioCord™ Reactors are a fixed-film technology that can help alleviate the washout problem. BioCord is like a condominium for bacteria, enabling the formation of a robust biofilm with preferred microorganisms that are strongly attached to the growth media and resistant to washout. Even though suspended microorganisms may be lost to washout, microorganisms in the BioCord reactors remain in the system and continue to provide treatment while also helping re-establish suspended bacteria to optimum levels.  

BioCord Reactors can be installed directly into a treatment lagoon. They quickly establish a robust, stable biofilm that is resistant to washout and enhances plant performance in cold-weather conditions. 

The BioCord Reactor system is also designed to provide robust cold-weather performance. BioCord biofilm develops in layers enabling both BOD- and ammonia-reducing bacteria to coexist and thrive. Layering also helps insulate inner microorganisms from cold water to remain active during the winter and continuing to provide nutrient removal. 

Learn more about BioCord Reactors.

Contact us to discuss your concerns about washout and other wastewater treatment needs.

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