Passive treatment system

A further advantage of installing a pilot wetland was the provision of an experimental basis for passive treatment systems which could be used at other sites within the WISMUT project. 

Constrncted wetlands are a passive treatment system. Therefore, operation and maintenance costs are very low compared to that of active treatment processes (D10500Q, p. 1). Construction costs vary considerably from site to site. Constrncted wetlands may be not be financially viable at all sites (D20499J, p. 2). 

Constmcted wetlands use biological processes inherent in natnral wetlands and a system designed to optimize those processes to treat wastewater contaminants specific to a particnlar site. Constructed wetlands are passive treatment systems that mimic, rather than overcome, natnral processes. Consequently, the cost of operation and maintenance is significantly lower than for... 

Unit cost values for excavation, geomembranes, or clay cell liners and other construction costs are identical for both anaerobic and aerobic passive-treatment systems. 

Nuttall, C. A. 2003. Testing and performance of a newly constructed full-scale passive treatment system at Whittle Colliery, Northumberland. Land Contamination and Reclamation, 11,... 

This refers to both active chemical treatment and passive treatment systems such as wetlands. There are numerous technologies and strategies available for water treatment for metals removal. They tend to be expensive in terms of capital and operating costs and should be considered a last resort. These include ... 

Passive perimeter gas control systems are designed to alter the path of contaminant flow through the use of trenches or wells, and typically include synthetic flexible membrane liners (FMLs) and/or natural clays as containment materials. The membrane is held in place by a backfilled trench, the depth of which is determined by the distance to a limiting structure, such as groundwater or bedrock. A permeable trench installation functions to direct lateral migration to the surface, where the gases can be vented (if acceptable) or collected and conveyed to a treatment system (Figure 10a and 10b). 

An active perimeter gas control system can have any of the same configurations as a passive perimeter system with the addition of any combination of gas extraction wells, gas collection headers, vacuum blowers or compressors. Their ultimate purpose is to direct the gas to a treatment or utilization system. 

MANAGEMENT OF PASSIVE BIOLOGICAL WATER TREATMENT SYSTEMS FOR MINE EFFLUENTS... 

The unit cost of this technology, including disposal, was approximately 4/m. It is estimated that treatment will have to continue until at least 2020. This has prompted our search for alternative, less expensive techniques which take into account expected changes in mine water chemistry, as well as the decreasing load of contaminants over time. Soon after commissioning the conventional treatment plant, it became clear that a passive or semi-passive biological treatment system would be needed for the long-term. Therefore, WISMUT adopted a two-step approach, in which ... 

The question which often arises in the context of passive biological water treatment systems is that of waste and waste disposal. The following wastes have to be handled and disposed of in the Pohla wetland ... 

The vendor states that savings associated with the EnviroMetal Process are due to the low operation and maintenance costs for treatment walls. Because contaminants are destroyed rather than removed, process monitoring costs are negligible, and little or no waste products require disposal or regeneration on a regular basis. The vendor also states that since the technology is a passive treatment, there is no need for manual labor to operate, monitor, and maintain the system (D14522C, pp. 19, 20). 

Passive, in situ treatment system for contaminated groundwater. 

Younger, P. L., Jayaweera, A. et al. 2003. Passive treatment of acidic mine waters in subsurface-flow systems exploring RAPS and permeable reactive barriers. Land Contamination and Reclamation, 11, 127-135. 

In many studies the chemisorption and the surface reaction is just the first step in a series of solid state reactions that take place as atoms from the surface move into the bulk. Corrosion, oxide, carbide and other compound formations are generally initiated at the surface and then propagate into the bulk. There may be a concentration gradient of certain constituents at the surface in a multicomponent system that would influence the mechanical or chemical properties of the system. Hardening of materials and other forms of passivation treatment frequently involve introduction of certain substances only in the near surface region. For the investigation of these problems RHEED is a powerful technique. 

Staub, M. W. and R. R. H. Cohen. 1992. A passive mine drainage treatment system as a bioreactor Treatment efficiency, pH increase, and sulfate reduction in two parallel reactors. In Achieving Land Use Potential Through the Reclamation. Proceedings of the 9th National Meeting of the American Society of Surface Mining and Reclamation. June 14-18, 1992, Duluth, MN, pp. 550-562. 

Methods for cleaning and passivating stainless steels are presented in ASTM A 380, Practice for Cleaning, Descaling, and Passivation of Stainless Steel Parts, Equipment, cmd Systems and ASTM A 967, Specification for Chemical Passivation Treatments for Stainless Steel Parts. 

Semi-Active (Adaptive-Passive) Systems Refer to an adjustable passive vibration control scheme, that is, the passive treatment can adjust itself in response to changes in the structure. For example, the stiflfiiess, damping coefficient or other variables of the passive control scheme can change automatically so that optimal vibration mitigation is induced. These variable components, also known as tunable parameters of the control system, are re-tailored via a properly developed semi-active control algorithm. Being more versatile than passive control techniques and more affordable (in terms of cost and energy consumption) than active control schemes, has made semi-active control methods very popular. 

The alternative metal pre-treatment processes to grit blasting use a variety of different chemical routes. It is sufficient to say here that these can be very efficient, but do occupy rather large factory floor areas and can, if not controlled correctly give variable quality of prepared surface. The usual chemical pre-treatment systems consist of acid etching of the surface followed by several water dips and subsequent phosphate or in some circumstances cadmium plating and passivating (render inert). Many of these treatments will have been carried out by the metal processor and are not the rubber bonder s processes. 

Fig. 3. Schematic diagram showing the use of a combination of treatment techniques including low oxygen gas barrier, sulphate reduction barrier and a passive treatment wetland system at the point of discharge (after Blowes et al. 1994).

Aluminium is unlikely to form a sulphide but on sulphate reduction may be precipitated as a hydroxide or adsorbed by the organic substrate. Similarly MnS has a higher solubility than other sulphides and is unlikely to precipitate unless other metals are removed first or are present in low concentrations. In aerobic systems Mn is not rapidly oxidized, unlike iron, and may pass almost entirely through an aerobic wetland. A separate passive treatment would be required where Mn concentration is high enough to precipitate the metal by a mechanism such as ... 

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