Biosolutions Newsletter

Vol. 3, Issue 11,  May  2003

In this issue, find out how to use MICROCAT® products to enhance pulp and paper wastewater treatment system performance - foam control, odor control, better settling, improved BOD/COD removal, better cold weather performance, better removal of specific organics, like phenolics - to name a few enhancements.

For 20 years, Bioscience, Inc. has offered a complete line of biological products for pulp and paper industry wastewater treatment. The company continues to add formulations specifically designed to solve problems in treatment plants serving pulp and paper manufacturing, such as filamentous bacteria (which cause poor settling), foaming and odors. MICROCAT® microbial products are also widely used to alleviate such common problems as high effluent BOD or COD, high temperature process instability, and poor cold weather performance.

Filament Control Case History

Activated sludge treatment plants receiving pulp and paper wastes often encounter operating difficulties due to filamentous bulking. MICROCAT-XF is  formulated to reduce filamentous microbe population, thus improving sludge settling and reducing effluent suspended solids, which in turn enhances system performance and lowers operating costs. The formulation contains a combination of enzymes selected for their ability to destabilize many filamentous organisms, thus disfavoring filamentous growth and allowing for an increased population of more beneficial microbial forms. 

MICROCAT-XF has demonstrated improved sludge settling in an on-site pilot plant simulating a large UNOX pure oxygen activated sludge treatment plant receiving bleached kraft process wastewater. The pilot plant utilized two identical process trains, each with its own oxidation and clarification units.

MICROCAT-XF was added daily in powder form to one of the two trains for a five-week period, at first in large quantities, then in maintenance doses. Sludge volume indexes (SVI) were monitored in both trains for the entire five-week program. SVI values from the full scale treatment plant were also measured  to ensure that the pilot plant accurately simulated the existing system. Weekly mixed liquor samples from the experimental train were microscopically examined for filament concentrations, types and lengths.

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The treated pilot plant train exhibited consistently lower SVI values than the untreated train and the full-scale system. Only once, following a black liquor spill, did SVI values in the experimental train move above those in the control. During this spill event the mixed liquor revealed continuing low filament concentrations and the presence of a "young" sludge that resulted in the poor settling. Following another, smaller black liquor spill on day 28, SVI values again increased in both trains, but without any evident increase in filament concentrations in the train using MICROCAT-XF.

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Odor Control Case History

A recently-introduced product, MICROCAT-ANL, contains microorganisms that oxidize hydrogen sulfide to elemental sulfur, suppressing the "rotten egg" odor that often occurs when insufficient oxygen is available to the biomass in pond or lagoon systems. It is designed for use under the anoxic or anaerobic conditions that generate such odors. The elemental sulfur is occluded by the bacterial cells, making it unavailable for quick conversion back to sulfide.

The microorganisms in MICROCAT-ANL can also improve biodegradation under oxygen-poor conditions and reduce the formation of insoluble deposits characteristic of such conditions. The product is supplied in liquid form and is usually metered into the system or sprayed onto the offending material.

In one 7 MGD wastewater treatment plant serving a pulp and paper mill, use of MICROCAT-ANL has eliminated complaints from neighbors about hydrogen sulfide odors emanating from primary clarifiers and a sludge belt press filter room for over two years since the beginning of its application, while also reducing the recovery time from shock loads. 

For the complete case study click here (Adobe Acrobat reader required.)

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Hot Wastewater Processing and Enhanced BOD/COD Removal

Hot wastewater is often a problem in pulp and paper waste treatment plants. High temperatures (crossing the mesophilic / thermophilic transition zone at around 40 degrees C) can cause poor system performance such as high effluent suspended solids and poor settling due to microbial populations shifts.

MICROCAT-HT combines preselected, adapted microbial strains that have enhanced waste degradation capability in the thermophilic transition range of 35 to 43 degrees C. These aerobic and facultative anaerobic microorganisms metabolize organics and flocculate at the high end of the mesophilic range and into the low end of the thermophilic range thus enhancing performance of the system.

Finally, the staple product used by the pulp and paper industry for BOD/COD removal enhancement is MICROCAT-XP, with its selected aerobic and facultative anaerobic bacteria and enzyme package with an enhanced ability to degrade lignins, cellulosics, sizes, surfactants and fibrous solids.

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