top of page

Sludge Reduction

The Science

Image by Ivan Bandura

IPTs technology utilizes a highly specialized blend of various species of bacillus bacteria added to the collection system. The resultant augmented microbiological activity reduces the volume of sludge produced by degrading organic carbon in the sewer, solids inventory within the plant, and solids in aerobic and lagoon digestion processes. Facultative, spore forming bacteria (at up to 108 times greater than indigenous sessile bacteria in wastewater) dosed into the outer reaches of the sewer network establishes more sustainable microbiology in the sewer network to improve raw wastewater quality, and reduce influent load to the WWTP

IPT’s process is the continual addition (twenty-four hours-a-day, seven days-a-week) of high concentrations of naturally-occurring, non-pathogenic bacteria at multiple points within the collection system in order to (1) grow throughout the surface of the sewer pipes and thereby dominate the sewer biofilm with beneficial bacteria, (2) improve the ability of the sewer biofilm to degrade (improve the wastewater quality and/or reduce the organic load to the WWTP) the organic material, and (3) take advantage of the retention time of the wastewater within the sewer, allowing the added bacteria additional time to degrade the waste.

Sludge Reduction

There are several mechanisms of reducing sludge production in a biological wastewater treatment processes such as (i) increase the degradability of the hydrolysable or inert substrate, (ii) increase the cell decay or lysis, (iii) increase the cell maintenance energy, and (iv) decrease the biomass yield. The bacillus formulation includes common heterotrophic soil bacteria that are specifically selected and formulated to effectively degrade a wide variety of organic compounds found in wastewater.

These organisms provide increased conversions of existing sewer processes through hydrolysis due to enzyme production that breaks down slowly-biodegradable materials (cellulose, starch, etc.)

This process makes the materials more bio-available (rbCOD), which allows the organisms to transport the material into the cell structure as smaller molecules for use within the cell. Enzymes produced include: amylase, cellulase, chitinase, maltase, mannanase, xylanase, proteases, lipase, nucleases and phosphatase.  This process relies on competition between bacteria for survival. In their attempt to dominate the sewer system, the bacteria reduce fungicidal and pathogenic organisms by secreting antibiotics and toxins such as bacitracin, surfactin, polymyxin, difficidin, subtilin, and mycobacillin.

Therefore, the domination of the bacteria not only reduces nonbeneficial microbial activity, but also uses the cell lysate as a food source for metabolism. Since the organisms are facultative, they are compatible with all environmental condition in the sewer network (i.e., aerobic, anoxic and anaerobic) and do not require the presence or absence of dissolved oxygen (DO) in order to function. Carbon transformation under low oxygen and anaerobic conditions yields less biomass per pound of carbon transformed. Each pound of organic material transformed in the sewer during transit reduces the net sludge production at the treatment plant. For example, The City of Portage, IN started the bioaugmentation program in September 2010 and within four months biomass yield decreased ~14% from 1.3 to 1.1 lbs sludge/lbs influent BOD.

Under nutrient limited condition or extreme environmental stress, the bacteria form a spore to protect them from the unfavorable environment. However, sporulation is an energy intensive process that results from the absence of nutrients available for growth. When nutrient limitations become too severe for the maintenance of the bacterial cells, these sporeforming bacteria cannibalize other cells and feed off of the resulting solubilized nutrients to delay sporulation.

In addition to the positive effects of improved influent quality and reduced influent load, the In-Pipe process vastly increases the total quantity of active and beneficial bacteria entering the wastewater treatment plant. The active and beneficial new biomass entering the plant reduces the time required within the treatment process for organics and nutrient removal.

  • See More
    Andrews JH, Harris RF. 1977. r- and K-Selection and Microbial Ecology. Adv Microbial Ecol. 9:99-147. Atlas, RM and Bartha R. 1987. Microbial Ecology: Fundamentals and Applications. Benjamin/Cummings Publishing Co. Menlo Park CA USA. Castignetti, D. and Hollocher T. 1982. Nitrogen Redox Metabolism of a Heterotrophic, Nitrifying-Denitrifying Alcaligenes sp. from Soil. Appl Environ Microbiol. 44(4): 923- 928. Fenchel TM and Jorgensen BB. 1977. Detritus Food Chains of Aquatic Ecosystems: The Role of Bacteria. Adv Microbiol Ecol. 1:1-58. Gottschalk, G. 1986. Bacterial Metabolism, 2nd edition. Springer-Verlag, Inc. NY. Gray TR, Parkinson D (editors). 1968. The Ecology of Soil Bacteria. University of Toronto Press, Canada. 681 pages. Kuenen JG and Gottschal JC. 1982. Competition among Chemolithotrophs and Methylotrophs and their interactions with Heterotrophic Bacteria in Microbial Interactions and Communities Volume 1, pp 153-186. La Riviera JWM. 1977. Microbial Ecology of Liquid Waste Treatment. Adv Microbiol Ecol. 1:215-259. Priest, F. 1977. Extracellular Enzyme Synthesis in the Genus Bacillus. Bacteriol Rev. 41(3): 711-753. Richardson DJ, Watmough NJ. 1999. Inorganic Nitrogen Metabolism in Bacteria. Curr Opin Chem Biol. 3:207-219. Richardson DJ, Wehrfritz JM, Keech A, Crossman LC, Roldan MD, Sears HJ, Butler CS, Reilly A, Moir JW, Berks BC. 1998. The diversity of redox proteins involved in bacterial heterotrophic nitrification and aerobic denitrification. Biochem Soc Trans. 26:401-408. Robertson LA, Cornelisse R, Zeng R, Kuenen JG. 1989. The effect of thiosulfate and other inhibitors of autotrophic nitrification on heterotrophic nitrifiers. Antonie van Leeuwen. 56:301-309. Roth D. and Lemmer H. 1994. Biofilms in Sewer Systems- Characterization of the bacterial biocenosis and its metabolic activity. Wat. Sci. Tech. 29(7): 385-388. Seviour RJ, Mino T, Onuki M. 2003. The Microbiology of Biological Phosphorus Removal in Activated Sludge Systems. FEMS Microbiol Rev. 27: 99-127. Strous M and Jetten MSM. 2004. Anaerobic Oxidation of Methane and Ammonium. Annu. Rev. Microbiol. 58: 99-117. Tchobanoglous G, Burton FL, Stensel HD. 2003. Wastewater Engineering: Treatment and Reuse/Metcalf & Eddy 4th edition. Tata McGraw-Hill Publishing Company Limited. New York USA. Verstraete W and Alexander M. 1972. Heterotrophic Nitrification by Arthrobacter sp. J Bacteriol. 110(3): 955-961.
bottom of page