I have just finished a quick summary course on bioaugmentation. Every day I see bioaugmentation, nutrients, and other additives offered as a panacea for all sorts of problems in waste treatment. The course below covers the basics of bioaugmenation including how products are designed and what to expect if you use bioaugmentation including its limitations.
Commonly encountered microbes are roughly classified into the three temperature groups (1) Psychrotroph (low temperatures), (2) Mesophile (medium temperatures usually 15 - 40 deg C), and (3) Thermophile (Temperatures from 45 - 80 deg C). Most of our wastewater treatment plants operate in the mesophile temperature range for much of the year.
The image above gives the general ranges of the organisms where you should also note the overlap in each group. I have come to see the transition zone from one group to the other as a "Problem Zone" where none of the individual groups is completely in its optimum growth range. Frequently we see this problem as increase in effluent suspended solids (TSS) for both the low and high temperatures. Also with low temperatures slowing metabolic activity in general, the low temperature problem zone also can cause problem with BOD/COD removal.
In my field of bioaugmentation or adding in select cultures to wastewater systems to enhance treatment, we add organisms that are very successful in the problem zone ranges to quickly establish the new microbial population that nature is taking its time to develop. By adding cultures, the system can be rapidly brought back under control for the entire period of high or low temperatures.
Almost all organic compounds can be transformed by microbes into carbon dioxide, water, and new cellular material. Problems arise when the degradation rate occurs only under specific conditions not present at the site or the decay rate is so slow that changes are required for bioremediation to be a viable cleanup option.
A site's bioremediation potential is first evaluated by determining the types and extent of pollutants present. Following site characterization, a remediation plan is developed based on the pollutants present, site characteristics, environmental variables, and cleanup time frame.
The compounds present may include some organics that are slow to degrade or have a degree of toxicity/quasi-toxicity to many microbes. In these cases, the time for cleanup can be reduced by first adding the mixing/aeration and fertilizers as used in biostimulation; then on-site time can be further reduced by avoiding the adaptation and lag phase growth of indigenous microbes via the use of bioaugmentation.
Using data from the site characterization, microbiologists can develop a microbial blend containing organisms having specific metabolic pathways for degrading target organics. Another consideration is the ability of organisms to produce biosurfactants, that improve activity by enhancing hydrophobic compound solubility. The extent of the benefit depends upon the "fit" of the microbial inoculum used and the general state of indigenous microbes already at the site. Overall, usually the decrease in on-site remediation activities including labor, lab testing, and risks associated with an active remediation project can pay for the use bioaugmentation.
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