Shrinking Sludge in the Hoosier State

Aug. 16, 2018
Indiana WWTP treats ponds to reduce CBOD & TSS

At a wastewater treatment plant in Indiana, operators were struggling to keep their pond system in compliance and were facing enforcement action from the Indiana Department of Environmental Management for carbonaceous biochemical oxygen demand (CBOD) and total suspended solids (TSS) violations.

A routine measurement of the sludge blanket showed an average of 2 ft of accumulated sludge. An operating depth of just less than 5 ft meant the sludge blanket occupied about half of the pond volume. The city contacted Mike Napier of BioChem for assistance in removing the sludge. Napier recommended Bio Energizer to remove the sludge while the lagoons stayed online.


Accumulated sludge can lead to high TSS and biochemical oxygen demand (BOD) by releasing ammonia from the sludge blanket. This ammonia feeds algae and bacteria. Algae are a source of BOD as they consume oxygen under dark conditions and as they release their cellular material to the water column when they die.

In shallow ponds, accumulated sludge itself can slough off into the effluent, which adds to the TSS and BOD problem.


After seven months of treatment with Bio Energizer, about 1.5 ft of sludge was removed from the pond. As the lagoon was sludge judged at the end of the seven months, operators noticed how easily the sludge judge cut through the water and remaining sludge blanket being forced. The sludge judge bounced on the bottom of the pond. Core samples also indicated little to no odor present.

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