Passive treatment systems include Open/Oxic Limestone Drains, Anoxic Limestone Drains, Limestone Diversion Wells, Pyrolusite® Limestone Beds, aerobic and anaerobic Wetlands, a range of Reducing and Alkalinity Producing Systems, Permeable Reactive Barriers, Slag Leach Beds, sulphide passivation/micro-encapsulation, electrochemical covers, alkalinity producing covers and Gas Redox and Displacement Systems (GaRDS).
What are the different types of passive water treatment systems?
Constructed wetlands are an innovative and inexpensive treatment approach that have the potential to treat organic and inorganic compounds in wastewater from a range of sources. EPA™s Technology Innovation Office (TIO) provided a grant through the National Network for
What is a passive treatment wall?
Open Limestone Channels Open limestone channels are generally the simplest passive treatment method. Open limestone channels are constructed in two ways. In the first method, a drainage ditch is constructed of limestone and AMD-impacted water is directed to the ditch.
What is a passive treatment system for a settling pond?
Passive systems remove or neutralize contaminants in mine drainage by exposing them to air, limestone, vegetation in ponds, neutralization ditches, buried channels, and wetlands.
What are the target contaminant groups for passive treatment walls?
Passive treatment systems include Open/Oxic Limestone Drains, Anoxic Limestone Drains, Limestone Diversion Wells, Pyrolusite® Limestone Beds, aerobic and anaerobic Wetlands, a range of Reducing and Alkalinity Producing Systems, Permeable Reactive Barriers, Slag …
What is passive water treatment?
Passive water treatment systems are systems that do not require the ongoing addition of chemical reagents to conduct treatment. As a result these systems: Have low running and maintenance costs. Are long term treatment options.
What are passive treatment systems for acid mine drainage?
THERE ARE MANY TYPES of water treatment systems available for removing metals from acid mine drainage. Passive treatment systems are a relatively new technology that involves using sulfate-reducing bacteria or limestone or both to neutralize acidity and precipitate metals.
How is acid mine drainage treated?
Some common methods include: Reclamation of contaminated land by (1) adding lime or other alkaline materials to neutralize the acidity, and (2) adding uncontaminated top soil, planting vegetation, and modifying slopes to stabilize the soil and reduce infiltration of surface water into underlying contaminated material.
What is acid mine drainage?
Acid mine drainage is the formation and movement of highly acidic water rich in heavy metals. This acidic water forms through the chemical reaction of surface water (rainwater, snowmelt, pond water) and shallow subsurface water with rocks that contain sulfur-bearing minerals, resulting in sulfuric acid.Jul 8, 2021
What is passive physiotherapy?
Passive physiotherapy is therapy that is performed on the client rather than by the client. It can include techniques like massage, acupressure, heat packs, and mobilisation and machines like ultrasounds, interferential, TENS, laser, and traction.Nov 19, 2018
What does active treatment mean?
Treatment given to cure the cancer, such as chemotherapy or radiation therapy. This does not include long-term treatment such as hormone medication, which may be taken for several years to maintain remission. Search for "active treatment"
Which of the following would be the most effective strategy for neutralizing the acidity of the contaminated surface water?
Which of the following would be the most effective strategy for neutralizing the acidity of contaminated surface water? The addition of limestone to the surface water.
Where does mountaintop removal happen?
Mountaintop removal takes place primarily in eastern Kentucky, southern West Virginia, southwestern Virginia, and eastern Tennessee.
How can we reduce mining tailings?
Discover five ways the mining industry can reduce environmental impact and make its practices more sustainable.Lower-Impact Mining Techniques.Reusing Mining Waste.Eco-Friendly Equipment.Rehabilitating Mining Sites.Shutting Down Illegal Mining.Improving Mining Sustainability.Feb 18, 2020
How can you neutralize acid mine water?
The most prevalent method for treating AMD contamination is the addition of alkaline reagents such as lime, limestone, sodium carbonate or sodium hydroxide. This treatment aims at neutralizing acidic water and the precipitation of heavy metals.
What is land reclamation in mining?
Reclamation is the combined process by which adverse environmental effects of surface mining are minimized and mined lands are returned to a beneficial end use.
What are 2 negatives about mining?
Miners breathe dangerous gases and rock dust in the mine that can make them very sick. Harming the Environment: Mining can put dangerous pollution into the environment. Mines can destroy habitats that animals rely on to survive. Some mining companies try to repair the habitat.
What is multi-celled wetland remediation?
multi-celled wetland remediation system is used to treat groundwater contaminated by spilled fuel. Several years of operation have shown that the system is successfully removing BTEX and PAHs before discharge into a local stream.
What are the considerations for wetlands?
The design considerations for constructed wetlands systems are varied and site dependent1. Municipal wastewater treatment systems are most concerned with the reduction of suspended solids, organic matter, pathogens, phosphates, and ammonium and organic nitrogen. Other kinds of wastewater treatment wetlands may be concerned with these same contaminants in addition to other organic compounds, residual explosives, or metals. Some system designs anticipate exactly what kinds of contaminants the wetlands will receive, and at what levels, while others face variable and unpredictable wastewater flows. Some wetland systems treat specific substances, such as airplane deicer fluid. Other systems, such as a stormwater runoff system, may receive a mixture of contaminants, with levels of incoming water varying widely with season and year.
What is the purpose of the wetlands project?
The purpose of the project is to demonstrate how constructed wetlands might be implemented at other DoD sites to treat deicing fluid runoff. Extensive initial sampling is still taking place to establish accurate baseline levels of contaminants in surface water in the area. Goals for the wetland include reduction in biochemical oxygen demand levels, which increase with additions of propylene glycol. Monitoring for BOD5 will allow for evaluation of wetland efficiency at removing propylene glycol. The goal will be to achieve average levels of BOD5 < 30 mg/L. Other goals of this wetland project include implementing a low cost, low maintenance method of deicing fluid runoff treatment that will improve deicing logistics and flight scheduling, without creating odors or increasing bird air strikes.
How much water can a wetland treat?
The wetland system can treat 200 gallons of water per minute . Water has a residence time of about five days in the system. It has proved to be a successful project. Nitrate levels are consistently reduced to less than 10 ppm. The low long-term operations costs, low energy demands, and wildlife habitat creation contribute to the success of this project. The cost savings in implementing the wetland system over other technologies is estimated to be $15 million.
How are contaminants removed from wastewater?
Contaminants are removed from wastewater through several mechanisms. Processes of sedimentation, microbial degradation, precipitation and plant uptake remove most contaminants2. Heavy metals in a wetland system may be sorbed to wetland soil or sediment, or may be chelated or complexed with organic matter. Metals can precipitate out as sulfides and carbonates, or get taken up by plants. Compounds in sediment, such as iron oxides, show preference for certain metals. This behavior can affect how efficiently a metal is adsorbed in a wetland. A system that has reached the limits of its adsorption capacity can exhibit a reduction in contaminant removal rates. After a system has reached its capacity for metal sorption, metal sulfide formation becomes the main method of metal removal. Sulfate-reducing bacteria oxidize organic matter and reduce sulfate to form hydrogen sulfide. Hydrogen sulfide reacts with metals to form metal sulfides, which precipitate. Compared to sediments, plants do not take up much metal,
What is constructed wetlands?
Constructed wetlands are an innovative and inexpensive treatment approach that have the potential to treat organic and inorganic compounds in wastewater from a range of sources. EPAs Technology Innovation Office (TIO) provided a grant through the National Network for Environmental Management Studies (NNEMS) to prepare a technology assessment report on the use of constructed wetlands for applications other than municipal wastewater. This report was prepared by a first year graduate student from Washington State University during the summer of 2001. It has been reproduced to help provide federal agencies, states, consulting engineering firms, private industries, and technology developers with information on the current status of this technology.
Why are wetlands important?
As they are depleted and affected by development, the importance of natural wetlands in watershed systems becomes increasingly apparent. Efforts to restore and maintain wetlands have been crucial to water quality in many areas. A better understanding of the benefits that wetlands provide has led to the use of constructed wetlands to mimic the filtration processes that take place in the fragile ecosystem of a natural wetland. Constructed wetlands have great potential as a clean-up technology for a variety of wastewaters.
What is passive treatment?
Passive treatment systems are commonly but not exclusively aggregate-carbonate based, with or without the inclusion of organic matter. The design of passive systems must accommodate slow reaction rates and focus on minimising armouring (the coating of neutralising material with metal precipitates and/or gypsum). The scale of the systems is crucial their success, with water retention times essential in accounting for slow reaction kinetics (eg. slow limestone dissolution). Organic matter can be used to control the redox state of the system in order to minimise armouring. The life expectancy of a passive treatment system depends on the mass of limestone and/or organic matter in the system. The available porosity within the limestone and organic matter can also affect the life expectancy, as porosity determines the capacity to store treatment precipitates. Operation of a passive treatment system may become ineffective if the system gets blocked with treatment precipitates due to insufficient porosity within the limestone/organic matter layers. Passive treatment systems provide low cost solutions with low to medium capital costs (AU$5,000-200,000) and generally very low operating costs (<AU$1,000 / year).
What is the treatment of acid and metalliferous drainage?
broad range of technologies is available for the treatment of Acid and Metalliferous Drainage (AMD). These technologies utilise one or a combination of chemical, physical and biological processes, including pH control, adsorption/absorption, complexation, chelation, biological mediation, oxidation/reduction, electrochemistry, sedimentation, flocculation/ filtration/settling, ion exchange and crystallisation. By far the most common process for treating AMD is via pH control.
What is a pyrolisite bed?
Pyrolusite® Limestone Beds consist of limestone beds or channels inoculated with aerobic micro-organisms (generally algae) and are primarily constructed to treat AMD containing high concentrations of manganese. The aerobic micro-organisms produce oxygen (O2) which catalyses the hydrolysis of Mn2+ to the insoluble MnO2 (pyrolusite). The reaction generates
What is an LDW well?
LDW’s consist of a well (eg. an in-ground metal or concrete tank) that contains crushed limestone aggregate. Part of a fast flowing AMD stream is diverted, often via a pipeline, into the well (Milavec, 1999; Ziemkiewicz and Brant, 1996). The hydraulic force causes attritional grinding and abrasion of the limestone gravel, ensuring that armouring of the aggregate is prevented and a fine-grained limestone slurry overflows from the top of the well back into the main body of the AMD stream. In this way, partially treated water and excess particulate alkalinity is introduced back into the waterway.
What is anoxic limestone drain?
Anoxic Limestone Drains (ALD) are layers of coarse limestone aggregate buried in carefully constructed drainage lines along gently graded slopes (Kilborn, 1999). The limestone drain is encased within a low permeability liner and capped with clay. Care is taken to avoid the possibility of covering the limestone with clays or organic matter during operation, and to ensure that negligible air can be entrained into the drain. Synthetic liners are often used to encase the aggregate filled channels to facilitate oxygen exclusion. Acidic AMD is delivered directly into the covered drains as close to the source as possible, to avoid significant oxidation. Low oxygen conditions are maintained within the drain in order to keep dissolved iron in its reduced state (ie. ferrous iron; Fe2+). An elevated dissolved oxygen concentration within the influent AMD has the potential to promote the oxidation of ferrous iron to ferric iron (Fe3+), which can precipitate as iron-oxide/hydroxide (eg. Fe(OH)3). Formation of these precipitates can result in premature system failure due to limestone armouring, which can also significantly reduce the rate of limestone dissolution. Almost all operating ALD’s experience some armouring by iron precipitates. Long residence times (eg. at least 10-15 hours) are encouraged to prolong the interaction between the AMD and limestone.
How does AMD affect mining?
This is due to the corrosive effects of acid water on infrastructure and equipment, the limitations it places on water reuse and discharge, and the expense incurred implementing effective closure options.
Is pyrolusite good for AMD?
Pyrolusite® Limestone Beds are best suite d where the majority of the Acidity is related to soluble manganese concentrations (Milavec, 1999). AMD with the characteristics shown in Table 9 is generally suitable for treatment with Pyrolusite® Limestone Beds.
What does the EPA do to help restore wetland?
The EPA supports voluntary wetland restoration through opportunities for funding, partnerships with various federal and state agencies, and partnerships with independent groups.
What is voluntary wetlands protection?
Wetlands protection is defined as removing a threat or preventing the decline of wetland conditions (US EPA, 2007a). In addition to restoring compromised wetlands, voluntary protection of naturally occurring wetlands is a valuable part of voluntary wetland restoration and protection.
What is voluntary restoration?
Voluntary restoration and protection is the subject of this core element, with particular focus on restoring or protecting natural wetlands to maintain or attain a high level of overall wetland function/condition. Many states and tribes rely on voluntary restoration and protection activities as a basis for their wetlands programs.
Why are wetlands important to the US?
States and tribes enjoy numerous benefits of restoration and protection due to the many functions that natural wetland systems perform. The unique natural characteristics of wetlands make them an integral part of our natural infrastructure. Wetlands provide critical habitat, breeding grounds and sources of food for shellfish, fish, birds, ...
How do wetland ecosystems help wildlife?
How Do Wetlands Protect Wildlife Habitat and Support Economic Well-Being? 1 Wetlands provide critical habitat, breeding grounds and sources of food for shellfish, fish, birds, amphibians and other organisms. 2 Wetlands play a crucial role in many state and tribal fishing economies. 3 Wetlands are also preserved to provide feeding and resting grounds for migratory birds and to create habitat corridors for wildlife populations. 4 These services generate state and tribal commercial, recreational and aesthetic benefits as well. 5 Wetlands also control erosion, limit flooding, moderate groundwater levels and base flow, assimilate nutrients, protect drinking water sources and buffer coastal areas from storm surges. 6 States may pursue wetland restoration to improve water quality and comply with Total Maximum Daily Load (TMDL) pollutant allocations in impaired waters and watersheds.
How do wetlands help with floods?
Wetlands can play a role in reducing the frequency and intensity of floods by acting as natural buffers, soaking up and storing a significant amount of floodwater. A wetland can typically store about three-acre feet - three acres covered in water three feet deep - or one million gallons of water. Coastal wetlands serve as storm surge protectors ...
Why is it important to restore wetlands?
Wetland restoration and protection is important to maintain critical wildlife habitat, help meet state and tribal watershed goals and contribute to economic well-being. To achieve these goals, many states have invested in programs that help implement, support or coordinate local restoration efforts. States and tribes enjoy numerous benefits of ...
What is LS sand treatment?
LS sand treatment is the addition of sand-sized limestone to streams in a watershed (Zurbuch 1996 ). The sand is suspended by the streamflow and redistributed downstream, neutralizing acid as the energy of the stream transports the limestone (Fig. 10 ). Coating of limestone particles with Fe hydroxides can occur, but the energy of the water in the stream causes agitation and scouring of limestone to keep fresh limestone surfaces available for reaction. This technology can be more cost effective on a watershed scale than more conventional passive treatment of AMD discharges if resources for continued additions of limestone sand are available.
What is passive AMD?
When appropriately designed and maintained, passive systems can provide long-term, efficient, and effective treatment for many acid mine drainage (AMD) sources. Passive AMD treatment relies on natural processes to neutralize acidity and to oxidize or reduce and precipitate metal contaminants.
What is an AeW?
AeWs are used to collect water and provide residence time for Fe oxidation, hydrolysis, and settling of the metal hydroxide flocs (Fig. 2 ). If the water is not net-alkaline, limestone has to be added to create net-alkaline conditions; otherwise, the long-term efficiency and effectiveness of the AeW will be poor. AeWs are sometimes simply a shallow basin, although vegetation such as Typha (cattails) is typically planted in a loose substrate to improve wildlife habitat and aesthetics, and to promote slow flow and attachment sites for floc. Wetland vegetation also encourages more uniform flow for more effective treatment. Mn oxidation occurs more slowly than Fe oxidation, and is sensitive to the presence of Fe 2+, which will inhibit or reverse Mn oxidation (Luan et al. 2012; Wildeman et al. 1993 ). Consequently in aerobic, net-alkaline water, Fe and Mn hydroxides are removed sequentially with the practical result that Mn precipitation occurs (if at all) mainly in the later stages of the system after all of the Fe has been removed. AeWs are also commonly used as a final treatment stage like settling ponds and sometimes receive treated drainage from other treatment systems to capture the remaining fine suspended precipitates (Fig. 2 ).
Introduction
The Chemistry of Acidic Streams
- The following are five basic chemical measurements that can help determine which acid water treatment to use: 1. pH—Measures the amount of free hydrogen ions (H+) in water. The pH ranges from 0 to 14, with a pH of 7 being neutral and indicating water that is neither acidic nor basic. Water with a pH below 7 is acidic; water with a pH greater than 7 is basic. (See Figure 1.) The m…
Treatment Objectives and Guidelines
- Acid water treatment methods can be divided into two categories: Category I passive treatment methods and Category II passive treatment methods. The division is based on differences in treatment objectives. Category I methods aim to increase pH and alkalinity; Category II methods attempt to increase pH and alkalinity and remove metals.
Category I
- The following Category I methods are most often used to treat streams affected by acid rain. They can be used alone or in combination with each other. In fact, it has been recommended that treatment be done on a watershed basis using a combination of methods, including watershed liming, in-stream limestone sand, and wetland liming. A watershed is the area of land that contri…
Category II
- The following methods have mainly been used for treating acid mine drainage. Some of these systems could be appropriate for streams affected by acid rain, depending on the cost-benefit ratio as compared to the previous methods. The main difference among the following systems is that they are each designed to be most efficient given a different set of water quality parameter…
Conclusion
- The methods included in this publication may mitigate the effects of acid deposition and acid mine drainage, but prevention of these types of water quality problems remains the highest priority. Combinations of multiple applications of these systems may be required before any watershed-level benefits are achieved. Little information is available on the success of these sys…
Appendix A
- Glossary
Acid Runoff Episode: Chemically expressed as ANC less than or equal to 0 μeq/L. Occurs when the acid neutralizing capacity is equal to or less than zero following an increase in stream flow. For natural streams, an acid runoff episode means the stream is net acidic and cannot neutraliz…
Appendix B
- Treatment System Determination Guide
This downloadable workshop and flow chartwill help you select the appropriate treatment system depending on stream water chemistry and physical parameters.
Appendix C
- Cost Comparison
Costs are difficult to determine, given the high variability in site characteristics, lack of data, and other factors. The following tables provide a range of expected costs and are meant for comparison only. - Table 1. Comparison of costs for Category I treatment methods.
*Costs are dependent on amount of limestone required and transport method. Average costs of limestone delivered to sites in Pennsylvania vary from $25 to $75 per ton.
Literature Cited
- Appelberg, M. and T. Svenson. 2001. Long-term ecological effects of liming—the Iselaw Programme. Water, Air, and Soil Pollution. 130:1745–1750. Arnold, D. E., and M. J. Gray. 1998. An operational and biological evaluation of the treatment of acid mine drainage in streams by limestone-bed diversion wells. Trout Unlimited. Arlington, VA. Brown, D. A. 1988. The Loch Fleet …