1. Any spills (or portion thereof) which can easily or economically be cleaned up by physical techniques should be remediated in this manner.  For example, any waste that can be recovered or removed by pumping, skimming, or scraping should be done in a conventional manner.  This usually removes a high concentration of waste very rapidly.  Bioaugmentation and resultant biodegradation of wastes is best used as a “polishing” technique: ridding the soil or environment of wastes that are either too dilute or are too widespread so as to make the removal by physical means impractical or too expensive.  Once the largest portion of waste is removed by physical techniques, then the microflora that are augmented into an area can finish degrading the wastes remaining.  Bioaugmentation to help eliminate the deleterious effects of spills and to clean up that area of the environment should not be used as the sole technique in most large, highly concentrated spills, or where exceedingly deep penetration of the soil with high concentrations of toxic substance exits.

2. Petroleum products in general (such as kerosene, gasoline, fuel oil) are considered carbonaceous waste (contain carbon).  These products usually do not include appreciable nitrogen, potassium, or phosphorous which microorganisms need to metabolize the hydrocarbon.  This means that in most cases, the spill area must be supplemented with nitrogen and phosphorous and sometimes potassium and other needed nutrients.  These substances often may be added in the form of regular fertilizer.  Slow release lawn fertilizers are superior to garden fertilizers because there is less chance of polluting runoff with them.  In addition, because they are coated, they are generally more soluble in the hydrocarbons themselves than are typical fertilizers.  Finally, the nitrogen: phosphorous ratio in these lawn fertilizers is better than in many garden fertilizers for microbial supplementation.

The application of the fertilizer should be made at a rate coinciding with that needed to maintain a 200:10:1 C:N:P: ration in the area.  There may be some exemptions from this general rule.  In spill areas, the application should be made monthly.  Analysis will, in turn, tell after applications whether the nitrogen or phosphorous is building up in the soil or wastewater faster than the microbes can make use of it and further applications should be adjusted accordingly.

3. The microbial mixture being used to treat waste should be added in a slurry made at the rate of 1 kg (liter) or less per 5 liters of chlorine-free water.  The slurry should be mixed in container free of pesticides, disinfectants, algicides, or other chemicals.  The slurry is sprayed over the area to be treated and usually some wetting agent or biodegradable, nonionic biodegradable surfactant is included with the slurry.  This helps to emulsify the petrochemicals so that surface area subject to attack by the microbes is greatly expanded.  Triton X-45 (manufactured by ICI) or equivalent biodegradable nonionic surfactant type competitive products are generally suitable when the spills include kerosene, fuel oil, jet fuel, crude oils, varsol, gasoline, etc. The slurry should be added to spill area as soon as it is prepared. Generally, shallow soil incorporation of the microbe/surfactant/fertilizer mixture is advisable (as with a power cultivator, tiller, plow or other soil turning device). 

Periodic turning of soil results in re-contact of bacteria and carbonaceous contaminants.  This physical treatment aerates the soil, adding much needed oxygen for optimal rate of waste breakdown.  Periodic tilling assists in redistributing moisture, temperature and added nutrients.  Effective removal of hydrocarbons will be at very slow rates where aeration is not present.

4. Determination of heavy metal content of the soil can be important for the success of the project.  High concentrations of heavy metals such as lead and mercury can effect the efficiency of the removal of hydrocarbonaceous compounds from the soil environment.  Some bacteria are more affected by metallic ions than others.  Chromium, cadmium, zinc, and manganese are more deleterious to some microbes than others.  Removal of metals can be accomplished in some cases by a certain category of microbes, a certain class of autotrophic bacteria.  However these bacteria are not easily cultivated nor preserved for practical application.  They can cause the metal to be more easily physically or chemically separated from a system, but do not cause the metal to mysteriously disappear from the environment.

5. Periodic testing during the bio-remediation project is essential.  Often closely monitored feasibility or demonstration trials are run early in the course of the project to determine the expected effects of the bioremediation agents used.  These small trials help to determine the proper concentration and type of bioremediant to be used along with timing for most economical action, as well as a host of other necessary information.

6. Where ground water is a problem, being close to the surface of the soil, or in close proximity to hydrocarbon spill, it is common practice to dig strategically placed wells surrounding the area of the spill and in the center of the spill.  Pumping is carried out so as to isolate the spill and to prevent the flow of the spill from moving into the general ground water.  This technique for the minimization of flow of the waste results in volumes of water which are contaminated and must be treated.  The biological treatment aid is usually added to the resultant waste water and the waste is removed from the water in aqueous/aerobic phase.  In some cases specific types of mobile treatment equipment are used.  These equipment types include upflow biotower, biological reactor vessels, settling and flotation equipment, etc.

7. Highly polymerized or exceedingly long chained or high molecular weight hydrocarbons are more resistant to breakdown due to their protected multiple bonding, insoluble nature, and lack of surface area for catalytic and/or microbial attachment. The biooxidation of the heavier portions of crude oils, tars, etc. is very slow for this reason.

8. Other parameters which affect biological activity must be monitored and adjusted where necessary for optimal rates of bioremediation to occur.  Examples of these parameters include pH; chlorine, bromine (or other halogen) concentrations; hydrogen sulfide, sulfite and other reducing agent concentration; and cyanide concentrations.

9. When a blend of organic carbonaceous compounds in encountered, some compounds will almost always be degraded first and more rapidly than other compounds.  Consortia (more than one strain or type of microbe) of microorganisms are almost always more effective bioremediants than single microbial strains.  The consortium of microbes works to rid the system of toxic intermediate compounds more rapidly and often results in the more efficient removal of a board spectrum of chemical compounds from an ecosystem due to the greater variety of crucial hydrolytic enzyme systems than one strain may possess.