Friday, July 30, 2010

Typical Soil Washing Process

Ex situ soil separation processes (often referred to as "soil washing"), mostly based on mineral processing techniques, are widely used in Northern Europe and America for the treatment of contaminated soil. Soil washing is a water-based process for scrubbing soils ex situ to remove contaminants. The process removes contaminants from soils in one of the followingtwo ways:

* By dissolving or suspending them in the wash solution (which can be sustained by chemical manipulation of pH for a period of time); or
* By concentrating them into a smaller volume of soil through particle size separation, gravity separation, and attrition scrubbing (similar to those techniques used in sand and gravel operations).

Soil washing systems incorporating most of the removal techniques offer the greatest promise for application to soils contaminated with a wide variety of heavy metal, radionuclides, and organic contaminants. Commercialization of the process, however, is not yet extensive.

The concept of reducing soil contamination through the use of particle size separation is based on the finding that most organic and inorganic contaminants tend to bind, either chemically or physically, to clay, silt, and organic soil particles. The silt and clay, in turn, are attached to sand and gravel particles by physical processes, primarily compaction and adhesion. Washing processes that separate the fine (small) clay and silt particles from the coarser sand and gravel soil particles effectively separate and concentrate the contaminants into a smaller volume of soil that can be further treated or disposed of. Gravity separation is effective for removing high or low specific gravity particles such as heavy metal-containing compounds (lead, radium oxide, etc.). Attrition scrubbing removes adherent contaminant films from coarser particles. However, attrition washing can increase the fines in soils processed. The clean, larger fraction can be returned to the site for continued use.

Complex mixture of contaminants in the soil (such as a mixture of metals, nonvolatile organics, and SVOCs) and heterogeneous contaminant compositions throughout the soil mixture make it difficult to formulate a single suitable washing solution that will consistently and reliably remove all of the different types of contaminants. for these cases, sequential washing, using different wash formulations and/or different soil to wash fluid ratios, may be required.

Soil washing is generally considered a media transfer technology. The contaminated water generated from soil washing are treated with the technology(s) suitable for the contaminants.

The duration of soil washing is typically short- to medium-term.
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Thursday, July 29, 2010

Real-time Networked Coastal Erosion Monitoring System

A consortium comprising WFS Technologies, Swansea Metropolitan University and Valeport Ltd has delivered the world's first ad hoc distributed network of seabed sensors for measuring the effects of coastal erosion. Sensor data regarding the movement of seabed sediment is communicated in real time using WFS wireless through-water radio modems, initially to a surface buoy and then via a GSM link to a server for display over the internet.

Radio provides reliable wireless communications in complex subsea environments such as shallow water and in the surf zone, making it ideally suited to coastal erosion monitoring applications.

More than half of the world's population lives within 60km of a coastline zone. As changing global climate and rising sea levels speed up coastal erosion, researchers need to monitor what is happening beneath the surface of the sea. Understanding coastal erosion has typically been by observation and measurement of exposed coastal areas rather than using quantitative data. The estimation of these effects has left us with only partial picture of what is really happening.

Historically, placing seabed instrumentation in the coastal erosion zone has proved challenging.

Seabed located sensors can be deployed to gather data, but provide no real-time data visibility and so may be subject to failure or movement in the dynamic environment. Wired systems have been attempted, but the deployment of a buried cable from shallow-water, up the beach means a considerable investment for each monitoring node and is prone to failure. The use of radio based wireless technology to relay data provides a robust, reliable and low cost real-time data monitoring solution, permitting remedial action to protect the coastline to be taken at the earliest opportunity.

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Wednesday, July 28, 2010

Research explores fire, mercury link

Researchers recently received federal funding to continue a study aimed at exploring high levels of mercury found in fish at Vallecito Reservoir, which a researcher at the University of Colorado thinks might be the result of the 2002 Missionary Ridge Fire.

The San Juan Generating Station in Waterflow and the Four Corners Power Plant in Fruitland are believed to be the primary source of atmospherically deposited mercury in La Plata and Montezuma counties.

CU's lead researcher Joseph Ryan thinks that a large wildfire could volatilize latent mercury that stuck to the top layer of soil.

The Missionary Ridge Fire burned more than 70,000 acres north of Durango in June and July 2002. Ryan said a fire of that intensity could have oxidized sulphur molecules that bind mercury in organic matter in the soil.

Ryan said a large wildfire could also introduce mercury into water another way, by speeding erosion and allowing the mercury to wash into a water source.

"Nobody's really looked at this before," Ryan said. "That's probably why the National Science Foundation is funding us."

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Sunday, July 25, 2010

Brownfield land

Brownfield sites are abandoned or underused industrial and commercial facilities available for re-use. Expansion or redevelopment of such a facility may be complicated by real or perceived environmental contaminations.[1] Cf. Waste (law).
Example of brownfield land at a disused gasworks site after excavation, with soil contamination from removed underground storage tanks.

In the United States city planning jargon, a brownfield site (or simply a brownfield) is land previously used for industrial purposes or certain commercial uses. The land may be contaminated by low concentrations of hazardous waste or pollution, and has the potential to be reused once it is cleaned up. Land that is more severely contaminated and has high concentrations of hazardous waste or pollution, such as a Superfund site, does not fall under the brownfield classification. Mothballed brownfields are properties which the owners are not willing to transfer or put to productive reuse.[2]

In the United Kingdom and Australia, the term applies more generally to previously used land

… read New Report Shows Brownfield Redevelopment in Cities Leads to More Jobs, Increased Tax Revenue - 99 Cities Surveyed on the Merits of Recycling America`s Land