Heavy contamination

Parameter Typical values for uncontaminated soils Slight contamination Contaminated Heavy contamination Unusually heavy contamination... 

To avoid generating warmer air layers below the ceiling, air nozzles are utilized to mix the warmer air down into the occupied spaces. This system is well suited for applications where it is important to keep an even temperature throughout the room. It is not suited for rooms with heavy contaminant loads, where zoning is preferable. 

As indicated earlier, heavy contamination can be buried, sealed or removed. Burying of the material should be well below the root growth zone, and this is normally taken as 3.0 m below the final ground-surface level. Sealing for heavy contamination to prevent vertical or lateral leaching through groundwater flow can be with compacted clay or proprietary plastic membranes. Removal from site of the contaminants is normally only contemplated in a landscaped scheme where the material, even at depth, could be a hazard to public health directly or phytotoxic to plant life. 

For installations in areas of heavy contamination, such as quarries or cement works, additional filtration or automatic self-cleaning is required otherwise, the air filter will clog up rapidly. Filter condition indicators are available and are recommended. 

The commonest staining trouble is iron stain —the blue-black stain caused by the interaction of soluble iron corrosion products and the natural tannins in wood. Hardwoods are generally more susceptible than softwoods. Steel wool should not be used for smoothing wood surfaces. Iron stains, if not too severe, can be removed with oxalic acid. Heavy contamination with soluble iron corrosion products usually results in migration and conversion to rust deposits in the wood. 

Configurations used include tubes, plate-and-frame arrangements and spiral wound modules. Spiral wound modules should be treated to remove particles down to 20 to 50. im, while hollow fiber modules require particles down to 5 im to be removed. If necessary, pH should be adjusted to avoid extremes of pH. Also, oxidizing agents such as free chlorine must be removed. Because of these restrictions, reverse osmosis is only useful if the wastewater to be treated is free of heavy contamination. The concentrated waste material produced by membrane processes should be recycled if possible but might require further treatment or disposal. 

Practical Aspects There are a number of process-specific concerns that are accounted for in good design. In regenerate systems, sorbents age, losing capacity because of fouling by heavy contaminants, loss of surface area or crystallinity, oxidation, and the like. Mass-transfer resistances may increase over time. Because of particle shape, size distribution, or column packing method,... 

D [Discriminatory destructive distillation] A thermal deasphalting process which uses the same short contact time concept as the MSCC process and a circulating solid for heat transfer between reactor and generator. It is claimed to be most effective on heavy contaminated whole crude oils or residues. Developed by Bar-Co and now offered by UOP. 

All the alkali metals are extremely reactive chemically. Both for safety reasons and for protection from heavy contamination they should be handled with care, under an inert atmosphere or protective media. 

Although the procedure works well for most antibodies, it may produce a fairly heavy contamination with non-IgG proteins with some samples, if this is the case, reduce the concentration of PEG. Consequently, carrying out a pilot-scale experiment before fractionating all of the sample is best. 

The heavy contamination of areas on which livestock dipping vats are located is recognized, as is the contamination of streams and ponds from careless dumping and cleaning of spray tanks. Pesticides used in homes and gardens may be partially disposed of in the sewer, ultimately reaching streams, lakes, and oceans. Milk and other products not... 

In the case of heavy contamination, early warning is essential. Gamma radiation, which in nearly all cases will be associated with radioactive material emitted in an accident, can be easily measured. Many instrument systems can measure dose rates caused by gamma radiation from environmental levels (and therefore well below any critical dose rate) up to extremely high levels. The higher the level, the faster and easier it can be measured. Therefore, on the instrumentation side, the requirements for fast early warning can be met. 

Effect of crops. Heavy contamination of plants with mustard or arsenicals will destroy crops. Lighter contamination may cause partial defoliation. Arsenical agents will leave sufficient arsenic to render the plant toxic, and nerve agents may penetrate plants so as to make them toxic. 

---