Aids Wastewater Systems
As environmental restrictions
tighten, many industrial waste treatment plant operators face compliance
levels that will seriously challenge the capabilities off their plants.
Bioaugmentation may be a viable "fix".
By Michael H. Foster, BS and
Rob Whiteman, PhD
The practice of utilizing specific microorganisms to carry out chemical
transformations has been applied in brewing, pharmaceutical and dairy
industries. Microorganisms also are critical components in the treatment
of municipal and industrial wastewaters.¹
In the treatment of wastewater, microorganisms (mainly bacteria) use the
soluble organic matter in the waste stream as a food source. The
bacteria consume the organic compounds and convert them into carbon
dioxide, water and energy to produce new cells. Ultimately, the soluble
pollutants are converted into insoluble biomass, which can be removed
mechanically from the waste stream and sent to disposal.
Wastewater treatment plants come in many types and configurations, but
this discussion will concentrate on aerobic treatment for industrial
Two of the most common general categories of aerobic water treatment
systems found in industrial plants are the once-through aerated lagoon
system and the activated sludge system.
In aerobic treatment systems, aerobic bacteria utilize oxygen in the
degradation of the organic compounds. Among these parameters must be
controlled. Among these parameters, dissolved oxygen levels, pH and
nutrient levels (ammonia and phosphorus) are the most critical.
Classical control strategies have focused on monitoring and controlling
the system parameters with little actual attention to the microorganisms
Bacteria are typically 1-2 um wide and 2-20 um long. Due to the small
size, shape or morphology can be examined only by using a high power
microscope (x1000) and staining techniques. The Gram Stain is the basic
criteria used to categorize groups of bacteria as either gram positive
of gram negative, indicating a fundamental variation in cell-wall
structure. Bacteria also are categorized using other criteria such as:
* Use of oxygen in degrading organic matter (uses oxygen only - aerobic;
can metabolize with or without oxygen - facultative; does not use oxygen
* Use of carbon sources (organic - heterotrophic; carbon dioxide -
* Optimum growth at different temperatures² (thermophiles - 55-75º C;
mesophiles - 30-45º C; psychrophiles: obligate - 15-18º C, facultative
- 25-30º C).
Most aerobic wastewater treatment systems operate in the temperature
range of 10-40º C and therefore contain mainly mesophilic bacteria.
These include both the gram positive types, such as Bacillus, and the
gram negative types, such as Pseudomonas.
In addition, other microorganisms interact to transform organic matter
into new biomass, carbon dioxide and water. Collectively, these
microorganisms are called the biomass.
The biomass is the "workforce" of a waste treatment system. In
a dynamic state of flux, different microbes are dying while others grow
and become more dominant. Under adverse conditions such as toxic shock,
certain bacterial populations may be reduced or eliminated, causing poor
effluent quality. Examples of toxic shock would be black liquor spills
in paper mills or a process upset in a chemical plant sending high
levels of terpenes to the wastewater plant.
Historically, under such conditions, waste treatment plants have been
slow to recover. National Pollution Discharge Elimination System (NPDES)
permits often have been violated or the manufacturing process stopped to
avoid the legal repercussions of NPDES permit violations.
The biological additives industry was started in the early 1960's to
address the problems of slow biomass recovery and to supplement lost
bacterial populations. The application of this technology is termed
Defining the Terms
Frequently, the terms bioremediation and bioaugmentation are used
interchangeably. Bioremediation will be defined here as the use of
selected microorganisms to accomplish a biological cleanup of a
specified contaminated area, such as soil or water; bioaugmentation will
be defined as the application will be defined as the application of
selected microorganisms to enhance the microbial populations of an
operating waste treatment facility to improve water quality or lower
operating costs. In other words, bioremediation deals with a definite
project or area, while bioaugmentation involves working to improve a
Bioaugmentation has been practiced since the early 1960's. Because of
frequent misapplication of additives or poor documentation of results,
the technology has been regarded as less than scientific.
A prevailing belief has been that, over time, the proper microbes will
populate the system and become acclimated to the influent. The approach
assumes that the indigenous population introduced via routes such as
windblown solids, rain water and the plant influent stream always will
contain the best suited organisms. In reality, even though the natural
population may develop into an acceptable one, there may be performance
limitations that only can be overcome through the induction of superior
strains of microorganisms.
In the aeration basin of a typical industrial waste treatment plant, one
should expect to find numerous species or strains of bacteria. This
bacterial diversity, as it is called, is necessary because some types of
bacteria degrade different compounds more effectively and efficiently.
These bacteria generally are well suited to handle the contaminants in
the waste influent and will become acclimated, over time, to provide the
desired results, assuming a steady state of operation is approximated.
Unfortunately, few industrial waste treatment plants ever achieve steady
state. The influent characteristics may change drastically from week to
week, or even day to day.
These variations may be due to production schedules of batch processes,
chemical spills in the production plant, or incapable plant equipment.
Many treatment plant biological populations never attain optimum numbers
or diversity of species.
Without bioaugmentation, the indigenous population should consist of
numerous types of organisms. Some of these organisms are more efficient
and effective than others at degrading the various compounds and
producing a settle able biomass. Figure 4 simplistically categorizes the
biomass into Population A (desired indigenous organisms), and Population
C (selected bioaugmentation organisms). The goal of the bioaugmentation program is to enhance the growth of Population A, establish the selected
organisms of Population C, and minimize Population B.
There is the question of why bioaugmentation products must be fed continuously
after the initial dosing of product. Due to system upsets
and influent composition changes, a maintenance dosage is required to
maintain the desired population diversity.
Proper monitoring of the system using statistical process control,
combined with microbiological analysis techniques, will provide the
information that the bioaugmentation consultant needs to maintain the
desired population. By using microscopic analysis and advanced plating
techniques, the consultant can correlate bacterial population
characteristics with plant performance for a particular waste treatment
system. Because every system is unique, the optimum population will vary
from plant to plant.
Typical bioaugmentation products consist of blends of several strains of
microorganisms, usually bacteria or fungi. The organisms are isolated
from nature and are not genetically altered in any way. They are
selected on the basis of accelerated reproduction rates and their
ability to perform specific functions, such as good floc-forming
capabilities to enhance settling or the ability to degrade specific compounds. The products are sold in a variety of forms, with dried
organisms on a bran carrier and liquid products being the two most
Product selection for a particular application is based on a combination
of laboratory treatability studies and field experience in similar
applications. Plant samples of wastewater influent and aeration basin
biomass are sent to the laboratory for product screening and
Typically, one week is required to complete the laboratory work. In some
cases, where the plant is in danger of permit violation, program
implementation must begin prior to lab work completion. In these cases,
the experience from similar application is critical in determining the
initial course of action. The program implementation and utilized to
make adjustments in the program, if necessary.
More Than Just Products
Successful bioaugmentation requires total system management. If the
microbiological population can be viewed as a workforce, then the
consultant or system manager is responsible for keeping the workforce
The system manager must provide an acceptable work environment by
controlling the key system parameters such as pH, temperature and oxygen
levels. He must compensate them with nutrients to ensure good growth and
a healthy population. He has to know to lay-off workers through wasting
to keep the population young and vital. Finally, the successful system
manager knows when to hire new workers to provide special skills not
found in his workforce. Bioaugmentation is the mechanism to provide
these skilled workers.
A critical part of the success of a bioaugmentation program is proper
application. Because every system is unique, it is essential that
products are properly applied. Bioaugmentation programs should be
implemented with the help of surveying the total system, assessing the
best solution to the problem and documenting the impact of the program.
Simply dumping a product into the influent is not bioaugmentation.
The purpose of bioaugmentation is to facilitate a gradual shift in the
microbial population, not to totally replace the existing biomass. The
population shift must be accomplished in a planned and controlled manner
to maintain the integrity of the microbial ecosystem. Over feeding the
selected microorganisms could result in a biomass no better equipped to
handle the broad range of compounds in the influent that the original
Proving The Results
The greatest difficulty in gaining acceptance of bioaugmentation as a
valid technology is proving cause and effect of the addition of the
specific organisms. Classical science would instruct the customer to run
a controlled experiment in his plant, concurrent with the
bioaugmentation program. In reality, this is rarely possible because a
few waste plants have identical, separate, side by side systems to allow
a rigorous head-to-head trial. Secondly, bioaugmentation is frequently a
last ditch effect to save a system from "shutting down" and
sending the plant into permit violation. Many times, in addition to
bioaugmentation, other system parameters are changed, introducing new
variables into the equation.
To effectively document the impact of the bioaugmentation program, plant
data for several months prior to the program should be plotted and
compared to the data after program implementation. For a bioaugmentation
trial to be meaningful, the trial must be run three to five times the
holding time for a once-through lagoon system, or four to six sludge
ages (mean cell retention time) for an activated sludge system.
Figures 5 and 6 illustrate two examples of impact of bioaugmentation at
two paper mill waste treatment plants. The paper mill in the first case
was facing permit violations for BOD in the effluent. Figure 5 shows the
improvement in BOD removal after the application of a bioaugmentation program. Within statistical significance, all operating variables, such
as incoming BOD and flow, were constant before and after the application
of the bioaugmentation program.
In the second example, the paper mill was experiencing both BOD and
total suspended solids (TSS) excursions. To maintain TSS compliance,
large amounts of polymer were being fed to the final clarifiers. Figure 6 shows the impact of the
bioaugmentation program in reducing polymer
usage. The graph shows the monthly cost of the bioaugmentation program
to be one-half to one-sixth of total monthly cost of polymer for the
nine months preceding program implementation.
These two cases provide excellent examples of the type of cause and
effect documentation that can be demonstrated with proper data
collection and analysis. In some cases, the program can be ceased to
confirm the efficiency of the treatment. However, once the problem is
solved, many users are reluctant to remove the program and risk system
deterioration and possible permit violation.
Several areas where bioaugmentation has proven to be beneficial are
ENHANCED BOD REMOVAL - Many systems, particularly once-through aerated
lagoons, are being asked to provide results for the 1990s with
technology from the 1960s and 1970s. It would cost millions in capital
to upgrade these systems. By increasing the microbiology numbers and
diversity via bioaugmentation, the desired results can be achieved. In
the pulp and paper industry in the southeastern United States,
improvement in BOD effluent levels of 30 percent have been documented.
IMPROVED SOLIDS SETTLING - An important step in biological waste
treatment is solids removal, usually through settling in a lagoon or
clarifier. Bacteria form a natural biopolymer that aid in settling.
Toxic shocks and system changes can result in a bacterial population
with little biopolymer and poor settling characteristics. The
traditional approach of adding organic polymers or inorganic coagulants
as settling aids can be effective but expensive. By inoculating the
system with organisms known to be both resistant to the toxicity and
excellent floc formers, polymer demand can be greatly reduced or
Typically the cost of bioaugmentation is significantly less than polymer
treatment. In addition, it provides an overall healthier biomass.
PREFERENTIAL DEGRADATION OF SPECIFIC COMPOUNDS - by adding selected
organisms, low levels of particular compounds can be achieved that are
not possible with the indigenous populations. Compounds such as phenols,
chlorinated aromatics and aromatic hydrocarbons are but a few compounds
that can be reduced with bioaugmentation.
IMPROVED NITRIFICATION - Many industrial waste plants have difficulty in
achieving nitrification because of design limitations or toxic shocks.
By regularly adding nitrifying bacteria, the proper population for
ammonia removal can be maintained.
OTHER AREAS - Other areas where bioaugmentation offers benefits include
odor reduction, oil and grease removal, rapid system start-up and
improved tolerance to toxic shock. Additionally, research continues to
explore new application areas for this evolving technology.
As environmental restrictions tighten, many industrial operators will be
faced will compliance levels that will seriously challenge the
capabilities of their existing wastewater treatment plants. In some
cases, bioaugmentation will be a cost-effective, short-term or
medium-term fix to keep them in compliance until system changes can be
implemented. In other instances, bioaugmentation will be the long-term
solution because of the lack of capital funds or expense of the
The concept of effectively managing the microbiological population of an
aeration basin in a new one. It involves much more than introducing new
organisms into the system. Total system management requires in-depth
understanding of waste plant operation and design, in addition to
environmental microbiology. By combining these two disciplines
effectively, the wastewater manager can be provided with the optimum
results for existing system.
¹ Grady, CPL and Lim, HC,
Treatment, Theory and application, pg 3.
²Stainer, RY; Doudoroff, M. and Adelberg, EA. The Microbial World, 3rd
ed., Page 316.
Palermo, DR and Holzer, KA, TAPPI Environmental Conference, 1992
Proceedings, Vol.3, Page 881.
Whiteman, GR, TAPPI Environmental Conference, 1992.
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