Recycling Contaminants

The costs of the EPOC Water, Inc. (EPOC) microfiltration technology are affected by system flow rates, amount of recycle, contaminant type and concentration, reagent type and amount, and the type and size of dewatering equipment used (D11314U, p. 15). 

Tn municipal recycling contamination occurs whether or not vinyl is present. Other resins are just as much a contamination problem as vinyl. Except for commingled plastics applications, different plastic materials cannot be mixed successfully in most recycled products applications. This is why it is crucial to separate efficiently one plastic from another. 

As the temperature falls following wort boiling, any bacteria or wild yeast present on surfaces will multiply in the nutrient rich medium. Problems can also arise if wort is saved and allowed to stand (such as with weak wort recycling). Contaminated wort can result in a decreased fermentation rate, off-flavors/odors, and haze and therefore should be checked at each batch. Enterobacteria are the most common contaminants and the tolerance is less than lOcfu/ml, with zero tolerance of wild yeast... 

The applications to recycling include use as an allowable material which would not hinder recycling (because it would be easily dissolved) and as a recyclable product. A PET beverage bottle which is afFixed with such a soluble film plastic label, cup adhesive and ink, would allow for less contaminant in the PET recycle. Contamination of paper label residue and adhesives is a problem with PET bottle recycling. This also allows for recycle of the adhesive and film by precipitation from the alkaline wash. 

Fig. 2.39 Diagram of a URTF with oxygen lancing technology The URTF delivers unique process technology for recycling contaminated metals.

Salt, B. et al.. Recycling contaminated spent blasting abrasives in portland cement mortars using solidification/stabilization technology, Report CTR 0-1315-3F, U.S. Department of Commerce, National Technical Information Service (NTIS), Spring-field, 1995. 

PVC has been criticized by Greenpeace and also by the Association of Postconsumer Plastic Recyclers, which in 1998 labeled PVC a recycling contaminant, pointing to the failure of a year-long effort to find markets for recycled PVC and the fact that many of their members had to landfill recovered PVC bottles because they could find no markets for them. After that report, the Vinyl Institute funded a pilot project aimed to jump-start... 

Recycling byproducts or contaminants which damage the reactor. When recycling unconverted feed material, it is possible that... 

Heterogeneous catalysts are more common. However, they degrade and need replacement. If contaminants in the feed material or recycle shorten catalyst life, then extra separation to remove these contaminants before the feed enters the reactor might be justified. If the cataylst is sensitive to extreme conditions, such as high temperature, then some measures can help to avoid local hot spots and extend catalyst life ... 

Recycle waste streams directly. Sometimes waste can be reduced by recycling waste streams directly. If this can be done, it is clearly the simplest way to reduce waste and should be considered first. Most often, the waste streams that can be recycled directly are aqueous streams which, although contaminated, can substitute part of the freshwater feed to the process. 

In early designs, the reaction heat typically was removed by cooling water. Crude dichloroethane was withdrawn from the reactor as a liquid, acid-washed to remove ferric chloride, then neutralized with dilute caustic, and purified by distillation. The material used for separation of the ferric chloride can be recycled up to a point, but a purge must be done. This creates waste streams contaminated with chlorinated hydrocarbons which must be treated prior to disposal. 

In both batch and continuous processes, it may be necessary to clean equipment to prevent contamination of new product. Materials used for equipment cleaning often cannot be recycled, leading to waste. 

MP-suspension by automated ASTM-bulb Magnetization current by Hall-Sensor Magnetization time UV-Light intensity All Liquids (fluorescence, contamination) Process times and temperatures Function of spraying nozzles, Level of tanks Flow rates (e.g. washing, water recycling) UV-Light intensity... 

Steps ia polypropylene recycling iaclude size reduction of grinding, washing, rinsing, and dryiag to remove contaminants and produce PP flakes... 

The greatest concern with PVC is as a contaminant in other polymers being recycled, particularly PET. Approximately 12 million pounds of PVC was recycled in 1993, about half from packagiag (25). AppHcations for recycled PVC iaclude as an inner layer sandwiched between two virgin PVC layers in pipe and sheet for bHster packagiag and other packagiag appHcations. 

The mixture is cooled and noncondensable gases are scmbbed with water. Some of the resultant gas stream, mainly hydrogen, may be recycled to control catalyst fouhng. The Hquids are fractionally distilled, taking acetone overhead and a mixture of isopropyl alcohol and water as bottoms. A caustic treatment maybe used to remove minor aldehyde contaminants prior to this distillation (29). In another fractionating column, the aqueous isopropyl alcohol is concentrated to about 88% for recycle to the reactor. 

Anhydrous hydrazine, required for propellant appHcations and some chemical syntheses, is made by breaking the hydrazine—water azeotrope with aniline. The bottom stream from the hydrate column (Fig. 4) is fed along with aniline to the azeotrope column. The overhead aniline—water vapor condenses and phase separates. The lower aniline layer returns to the column as reflux. The water layer, contaminated with a small amount of aniline and hydrazine, flows to a biological treatment pond. The bottoms from the azeotrope column consist of aniline and hydrazine. These are separated in the final hydrazine column to give an anhydrous overhead the aniline from the bottom is recycled to the azeotrope column. 

The potassium combines with the sulfur to form potassium sulfate, which condenses as a soHd primarily in the electrostatic precipitator (ESP) or baghouse. The recovered potassium sulfate is then deUvered to a seed regeneration unit where the ash and sulfur are removed, and the potassium, in a sulfur-free form such as formate or carbonate, is recycled to the MHD combustor. It is necessary also to remove anions such as Cf and E which reduce the electrical conductivity of the generator gas flow. These are present in the coal ash in very small and therefore relatively harmless concentrations. As the seed is recycled, however, the concentrations, particularly of CF, tend to build up and to become a serious contaminant unless removed. 

Nuclear utiUties have sharply reduced the volume of low level radioactive waste over the years. In addition to treating wastes, utiUties avoid contamination of bulk material by limiting the contact with radioactive materials. Decontamination of used equipment and materials is also carried out. For example, lead used for shielding can be successfully decontaminated and recycled using an abrasive mixture of low pressure air, water, and alumina. 

Retention and drainage additives are vital to the use of recycled fibers. Papermakers consider recycled fibers to behave like virgin fines, while recycled fines behave like filler. Drainage on the paper machine can be impeded and first-pass retention reduced by the use of recycled fiber (9). Additionally, the negative impact of contaminants found in recycled fibers can be minimized by the appropriate use of dispersants and other pitch-control additives. 

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