Controlled release bactericides affect reclamation success and provide assurance against post-reclamation water quality problems. They inhibit Thiobacillus ferrooxidans and aid in the establishment of beneficial heterotrophic bacteria necessary to support revegetation of the site. These conditions persist after the bactericide is depleted from the controlled release systems. Two coal refuse disposal areas, one in Ohio and one in West Virginia, were reclaimed using two different generations of controlled release bactericides. Case Study #1, located in Ohio, was reclaimed using first generation products with a release life of two years. Yet, six years after application, the treated area continues to have a dense vegetative cover while the untreated control area has only sparse vegetation. Water quality data from the treated area continue to show a significant improvement versus that from the control-area. Case Study #2, located in West Virginia, was reclaimed using third generation products with a controlled release life in excess of seven years. In its third year, the vegetation is lush and healthy except for the control area where vegetation is becoming sparse due to acid toxicity. The "Water quality data from the treated area corroborates these improvements and justifies the use of bactericides in reclamation.

Abstract. Post-reclamation acid discharge has haunted abandoned mine lands reclamation programs and the mining industry reclamation efforts. Many mine sites have been reclaimed, as mandated by regulations, but continue to generate acid. Such sites represent perpetual treatment problems for operators and, in the case of bond forfeitures or abandoned mine reclamation projects, they represent sources of perpetual surface and groundwater degradation. Post-reclamation discharge occurs when the Thiobacillus ferrooxidans bacteria, not destroyed prior to soil cover in the reclamation process, continue to thrive, even in a supposedly anaerobic environment. A post-reclamation remediation system utilizing subsurface injection of sodium hydroxide and an anionic surfactant offers a two phase integrated technologies approach. In Phase 1, the site is characterized by geophysical mapping with (1) electromagnetic terrain conductivity meters to determine locations of subsurface aquifers and (2) proton processing magnetometers to delineate zones of pyritic oxidation in the subsurface environment. Infiltrometers are also used to determine permeability which influences pressure requirements and distance between wells. Site conditions and water analyses help quantify requirements for injection of sodium hydroxide and bactericide. Phase 2 involves drilling two sets of injection wells; the first into the acidified water table for injection of20% sodium hydroxide solution to neutralize existing acid water, and the second into the acid producing material for injection of a 20% sodium hydroxide solution to neutralize existing acid salts, followed by a 2% solution of bactericide. The sodium hydroxide is injected to neutralize existing acid which prevents future acid generation. Results from a site in Pennsylvania, USA, which was treated in this manner are reported.

Anionic surfactants such as sodium dodecylbenzene sulfonate, sodium laurel sulfate, and others are effective in controlling acid production from sulfidic mate1ials such as overburden, coal, coal refuse, ores, waste rock, and tailings. Their use in practical mining and reclamation applications, however, is only being recently documented since longer term field data are only now becoming available. This paper describes three applications of bacterial inhibitors. The first is at a surface coal mine where special handling and bacterial inhibition have prevented acid drainage from highly pyritic (more than 0.5% pyrite, neutralization potential less than 30 st per 1,000 st of CaC0 3 equivalent, and net deficiency of neutralizers of 15 st per 1,000 st of CaC0 3 equivalent) dark shale overburden for over 2 yr. The second application is at an active refuse disposal area where alkaline addition at more than three times that indicated by acid-base accounting failed to control acid production in refuse with 13% pyritic sulfur and neutralization deficiency of 444 st per 1,000 st of CaCO, equivalent. Bacterial inhibitors were successful in reducing acidity and metals in site underdrain effluent by 88% to 90%. The third application was at a silver mine where waste rock containing up to 0.37% pyrite was treated with surfactant bactericides to reduce leachate acidity by 93% and sulfates by 70%.

No abstract

Three bactericides were used to treat uranium, nickel and copper tailings to determine the potential of using bactericides to control acid production in tailing piles. Ten gram samples were treated in beakers and placed in an incubation chamber set at 31 °c and 98~ humidity to optimize conditions for the activity of-acidophilic Thiobacillus. Induced leachates taken at 14 day intervals were analyzed for total hot acidity for a period of 56 days. The initial and final leachates were analyzed for concentrations of copper, zinc, cobalt, nickel and uranium. Initial leachates from untreated samples used for controls were tested •qualitatively far acidophilic Thiobacillus and developed strong positive responses. Bactericide treatments of copper tailings produced reductions in cumulative acidity by as •much as 33~. Correlative decreases were witnessed i'n all trace metals. This study indicates similarities between biogeochemical reactions of ore tailing materials and coal waste materials; therefore, bactericidal contrOl of acid production iri ore tailing piles should be effective.