Ratio analysis of T. ferrooxidans data from soil samples (Table 3) indicates that over 400 times as many T. ferrooxidans remained in the refuse in the control area compared to the treated area. This prolonged low population density of T. ferrooxidans in the treated area is evidence of the effectiveness of the controlled release bactericide treatment. Refuse Paste pH of refuse in the treated area averaged 6.0 compared to 4.4 in the control area. Seep Water Quality The perforated pipe drains installed on the Route 43 site started seeping in May 1987. Water collected from these drains was analyzed and the data is shown in Figure 5. The vast improvement in acidity (98%), sulfates (95%), aluminum (99%), iron (99%), and manganese (95%), three years after reclamation is an indication of bactericide effectivedness and controlledrelease system longevity. Vegetation The treated areas on all sites have a denser vegetative cover and generate much less acidity than the untreated areas, although all have approximately the same amount of cover soil. The treated areas have much volunteer legume growth as a result of nitrogen fixation by the higher heterotroph population. ECONOMICS OF USING BACTERICIDES The cost of bactericide application is site-specific. The dosage is dependent on numerous factors, including site topography, hydrology, microbial activity, site material acid production and neutralization potential, adsorption capacity, sulfur forms and pyritic content, site size and site location. Treatment costs can vary from $1,500 per acre for a 30acre spoil area to $4,000 per acre for a 5-acre highly pyritic refuse pile. Bactericides offer several cost offsets. Liming can be drastically reduced since bactericides limit future acid production. Soil cover depth can be reduced to eight inches, which in turn reduces clearing, grubbing, transpor 10 tation and reclamation costs associated with borrow areas. Bactericides enhance revegetation and protect against hot spots and acid burnout, thereby minimizing site maintenance costs. Based on costs gathered from various sources (Rastogi and Sobek, 1986), Table 4 shows the potential for cost savings with bactericide treatment. Bactericides may save 30% or more in reclamation costs depending on the site characteristics, size and soil cover availability. While standard techniques may achieve successful revegetation, bactericides provide protection from post-reclamation water pollution problems as well. SUMMARY The following conclusions were developed from these studies: A. Refuse under the soil cover shows significant decreases in acidity, sulfates, manganese, iron and aluminum following bactericide treatment. These decreases were the direct result of the inhibition of T. ferrooxidans activity which reduces the generation of acid and the subsequent solubilization of metals. B. Bacteriological studies following bactericide treatments show that heterotrophic microorganism populations have proliferated. Heterotrophs promote stable luxuriant vegetation and establish the following biological cycle which assures self-generating healthy vegetation and minimize post-reclamation acid drainage problems. C. Seeps induced by the installation of french drains show that naturally occurring seeps, after bactericide treatment, can have greatly improved water quality. D. Controlled-release bactericide treatments are in fact long lasting and provide better results than standard lime-and-soil reclamation practices. B. Reclamation with bactericides is economical and can even reduce ACKNOWLEDGEMENTS The authors wish to acknowledge with thanks the pioneering efforts of Bob Baker and Dave Stroh of the Ohio Department of Natural Resources, and Pat Park and Dave Broschart of the West Virginia Department of Energy for cooperating with us in conducting these studies. REFERENCES Rastogi, Vijay and Andrew A. Sobek (1986). The economics of using bactericides in active mining and in reclamation to control acid mine drainage. 1986 National Symposium on Mining, Hydrology, Sedimentology and Reclamation, Lexington, Kentucky. Sobek, A. A., M. A. Shellhorn, V. Rastogi (1985). Use of controlled release bactericides for reclamation and abatement of acid mine drainage. International Mine Water Congress, Granada, Spain. Tuttle, J. H., P. R. Dugan, and W. A. Apel (1977). Leakage of cellular materials from Thiobacillus ferrooxidans in the presence of organic acids. Applied and Environmental Microbiology, 33, 459-469. Helping nature help itself Harmful, acid-producing bacteria are now being held in check with bactericides, permitting beneficial bacteria to develop healthy soil for successful revegetation by Steven A. Zaburunov, Technical Editor Bacteria can produce harmful acid. That's one reason why teeth will decay if bacteria are allowed to run rampant. It's also why water can turn so acidic when it passes by pyrite. Pyrite-loving bacteria (different from the ones that attack teeth) move in and multiply, producing much more acid than if the pyrite were left alone with the elements. the job, stopping AMD by killing the acid causing bacteria. But it had to be applied more than once. So a bactericide system called ProMac was developed by BFGoodrich that would release its medicine over prolonged periods of time, just like the famous cold capsules (see photo below). The only difference is that these controlled-release pellets keep working for over seven years instead of just twelve hours. No longer experimental, these commercially-available bactericide control systems were registered last December by the US EPA under the Federal Insecticide, Fungicide and Rodenticide Act (FIFRA), for use in controlling acid formation in mine soils. An amazing 95% to 98% of the acid in AMD (acid mine drainage) is caused by the catalyzing action of bacteria on pyrite. And this acid would be bad enough by itself, but once established, it dissolves metals which compound the vegetation damage and water pollution. When research first revealed that How it works certain bacteria accelerated the production of AMD, the next logical question was "Isn't there a simple bactericide that will selectively control this AMD bacteria? Wouldn't it be wise to attack the source of AMD rather than just treating the symptoms?" The answer was yes, but it required years of work and testing. At first, a bactericide was found that did The villain in AMD is bacteria called Thiobacillus ferrooxidans. These bugs live by oxidizing pyrite and ferrous iron. The ferric iron produced reacts with more pyrite to form more acid and even more ferrous iron for the bacteria to feed on. A tough skin protects the bacteria in this harsh, acidic environment which can fall below 1.9 pH. The bactericide is nothing more than a surfactant (also called detergent) that greatly weakens the slimy skin, allowing the bug to stew in its own juices. The bug-killing anionic surfactants used are also found in a wide range of household soaps, including toothpaste. This means they are commonly available, safe, and cost-competitive. By stemming the production of AMD producing bacteria, vegetation is allowed to gain a foothold. Once normal vegetation is restored, it takes over for the bactericides, producing conditions that should promote a healthy, defensive, living top soil. The bactericide systems permit the growth of heterotrophs (providing complex nitrogen and carbon organic compounds) which are needed for healthy vegetation. These heterotrophs promote humus and organic acids which are actually detrimental to the acid-producing bacteria and further inhibit them. After several years, or several times around the dynamic system (see diagram below), the heterotrophs out-number the AMD bacteria in overwhelmingly high ratios, about 500 to 1. In seven years, the |