Limestone drains

In 1990, an anoxic limestone drain was installed upstream of a wetland treating acid drainage from another coal-contaminated area of the Fabius Coal Preparation Plant. The total installation cost was approximately 19,000 (D124607, p. 135). 

In 1995, the Somerset County Conservation District in Somerset County, Pennsylvania, constructed wetland treatment systems and limestone drains at four separate locations in the Oven Run/Pokeytown Run watershed. The estimated cost of the Oven Rnn/Pokeytown Rnn Project was 5.2 million (D204284, p. 34). 

An anoxic limestone drain is considered a snfticient method of adding alkalinity to acid rock drainage. 

Brodie, G. A., C. R. Britt, T. M. Tomaszewski, and H. N. Taylor. 1991. Use of the passive anoxic limestone drains to enhance performance of acid drainage treatment wetlands. In W. Oaks and J. Bowden, Eds. Proceedings Reclamation 2000 Technologies for Success. Durango, CO, pp. 211-222. 

Naim, R. W., R. S. Hedin, and G. R. Watzlaf. 1991. A preliminary review of the use of anoxic limestone drains in the passive treatment of acid mine drainage. In Proceedings of the 12th Annual West Virginia Surface Mine Drainage Task Force Symposium. Morgantown, WV, pp. 23-38. 

In order to ensure continued neutralization it is necessary to avoid precipitation of blinding minerals on the surface of the alkaline material. This can be avoided if the water is anoxic and ferric iron and aluminium are not present in the water. Anoxic limestone drains are designed to achieve this (Fig. 7). These work by reacting CaCOs with the drainage acidity in an anaerobic environment such that ferric hydroxide precipitation will not occur. If it does then this leads to mantling of the limestone and effectively reduces the efliciency of the drain. This effect occurred at the Cwmstywth drain in central Wales and led to a complete failure of a limestone drain (Fuge 1993). 

Fluidized combustion of coal entails the burning of coal particles in a hot fluidized bed of noncombustible particles, usually a mixture of ash and limestone. Once the coal is fed into the bed it is rapidly dispersed throughout the bed as it bums. The bed temperature is controUed by means of heat exchanger tubes. Elutriation is responsible for the removal of the smallest soHd particles and the larger soHd particles are removed through bed drain pipes. To increase combustion efficiency the particles elutriated from the bed are coUected in a cyclone and are either re-injected into the main bed or burned in a separate bed operated at lower fluidizing velocity and higher temperature. 

The formations inside limestone caves are made up of limestone, too. Water that drains through the cracks in rock and into a limestone cave often contains dissolved limestone. As the drop of water hangs from the ceiling, some of the carbon dioxide trapped... 

Iron making. Molten iron is produced for steel making in blast furnaces using coke, iron ore, and limestone. Blast furnace operations use water for noncontact cooling of the furnace, stoves, and ancillary facilities and to clean and cool the furnace top gases. Other water, such as floor drains and drip legs, contribute a lesser portion of the process wastewaters. 

The copper sulfide and iron oxide from this reaction are then mixed with limestone, CaC03, and sand, Si02, in a blast furnace, where CuS is converted to Cu2S. The limestone and sand form molten slag, CaSi03, in which the iron oxide dissolves. The copper sulfide melts and sinks to the bottom of the furnace. The less-dense iron-containing slag floats above the molten copper sulfide and is drained off. The isolated copper sulfide is then roasted to copper metal ... 

It is common practice to equip a drainage system or sump with a pump to return the collected inventory to storage or process facilities. Alternatively, for certain toxic materials, the spill is sometimes altered chemically to a nonhazardous substance by draining the spillage to a basin filled with a neutralizing slurry where the reaction forms an insoluble sludge. For acids, in particular, soda ash, limestone, or weak caustic solutions may be used. The reacted product becomes a solid that is neutral and can be disposed of accordingly. 

Stiller, A. H., J. J. Renton, T. E. Rymer, and B. G. McConaghy. 1984. The effect of limestone treatment on the production of acid from toxic mine waste in barrel scale weathering experiments. In Proceedings, Fifth West Virginia Surface Mine Drain Task Force Symposium. Morgantown, WV. p. 9,0. 

Caves are present through much of the limestone. The topographically highest caves have formed in the Murrindal Limestone in the centre of the synclinorium. These caves vary from simple shafts to complex joint-controlled mazes of narrow passages, but all display predominantly vertical development. The Murrindal Limestone caves are believed to have formed beneath an Eocene river system, and were probably drained by incision of the rivers in the Late Eocene - Early Oligocene (Webb et al., 1991). 

The success of these comparisons is due to the particular type of water of this specific syncline of the folded Jura where the highly-acid running water, drained from bogs, changes to hard water when it passes through the underlying limestone. The importance of the soil for the chemical composition of the groundwater is underlined. 

Dyfonate. This chemical was not on the 1984 list. It was found at 0.11 ppb in a spring draining a solution limestone aquifer in northeast Iowa (49). It is a marginal leacher i.e., its persistence and mobility are less than most of the other ground-water contaminants (20. 

Metolachlor. Both state reports of metolachlor are new. It was found in 4 out of 82 wells sampled in the USGS central Pennsylvania study (57). Metolachlor was also found in a well in an incipient karst area and two springs draining a solution limestone aquifer in northern Iowa (48, 49). Concentrations typically range between 0.1 and 0.5 ppb. 

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