Page 51 - Alpha Tech Pet, Inc. - Distributor Support Binder (April 2013)

Unlike collection systems, waste treatment plants can actively promote the development of effective
microorganisms. A municipal waste treatment plant with return activated sludge can work as a chemostat to
actively select microorganisms capable of degrading the organics present. A chemostat is a continuous growth
chamber that adapts a population to a specific waste by continuously feeding that waste and allowing the most
successful organisms to be re-seeded back into the chemostat. (This process is similar to the selective adaptation
techniques used by Novozymes to develop specialized strains in the laboratory, however, Novozymes has infinitely
more control of the process with the ability to actively select initial isolates from selected environmental sources
and the ability to challenge these organisms in specific ways.)
By the selective nature of the activated sludge process and the relative consistency of the municipal waste
stream, the “soil” organisms introduced to a WTP in relatively small numbers through infiltration or in larger
numbers with the transfer of sludge from another treatment plant, have an opportunity to establish a place in
the population and impact the degradation process. A well-designed, well-operated municipal activated sludge
plant has little need for bioaugmentation once an effective population is established. However, operational
problems, under designed systems, shock loading of industrial influents, or plant start-up may present
opportunity for benefit from bioaugmentation. The term bioaugmentation is used to indicate that these added
organisms are not designed to replace the natural population but to establish a position in the microbial
population to augment the activity of natural organisms present to achieve a targeted effect.
THE MECHANISM OF MICROBIAL BREAKDOWN
Microorganisrns remove grease by degrading grease compounds at the oil/water interface. Once established in
the specific microcosm in which they will work, the microorganisms themselves produce bio-surfactants that
assist in making the grease more bio-available through emulsification. Microbes tend to collect at the surface of
grease and oil due to the oleophilic nature of the cell wall and due to ability termed “chemotaxis”. Chemotaxis is
the ability whereby bacteria recognize compounds such as oil and grease as food sources and, if motile, move in
the direction of that food source.
Bacteria increase contact with such food sources by producing extracellular polymers that allow the organisms to
attach to surfaces such as grease and scum deposits. Once attached, the organism produces biosurfactants and
extracellular enzymes those breakdown particles into molecules small enough to be transported into the microbial
cell. After these compounds are taken into the cell, intracellular enzymes break down these compounds into
progressively smaller compounds. When metabolized completely, the compound will be broken down into carbon
dioxide and water (mineralized). Each time the compound is broken into a smaller compound (catabolism) the
organism gains energy. This energy is partially used to grow additional biomass (anabolism), and, thus, the
process continues. Selectively adapted microorganisrns recognize grease as a plentiful food source. This “food”
increases the metabolism of each organism as well as producing more organisms with the same metabolic
capability.
Attached microorganisms continue to grow and while some cells are sloughed into the waste stream. Others
maintain colonization of the pipe and scum surfaces for continued activity in that section of line. Continuous
seeding is required to “inoculate” new deposits and rejuvenate those areas of biofilm that may be lost by friction
or by physical breaking away of deposits. Microorganisms tend to travel and colonize through minute crannies in
the line deposits allowing both freeing of deposits from line surfaces and additional degradation of these
deposits.
The breakdown of grease is a complicated pathway requiring numerous individual enzymes. Bacteria are
extremely efficient “enzyme factories”. They have the capability of recognizing organics present in an
environment and respond by producing the enzymes required breaking down those specific organics. A
consortium of organisms rather than a single strain is most effective in breaking down a complex waste, such as
grease in a waste stream, due to the myriad of different grease components present and complicated metabolic