Mixed waste streams

Design criteria for carbon adsorption include type and concentration of contaminant, hydrauhc loading, bed depth, and contact time. Typical ranges are 1.4—6.8 L/s/m for hydrauhc loading, 1.5—9.1 m for bed depth, and 10—50 minutes for contact time (1). The adsorption capacity for a particular compound or mixed waste stream can be deterrnined as an adsorption isotherm and pilot tested. The adsorption isotherm relates the observed effluent concentration to the amount of material adsorbed per mass of carbon. 

MSWIs can accept virtually any mixed waste stream as long as it falls within its calorific window of 9-13 MJ/kg (hence including material containing regular plastics and PVC content). Furthermore, the heavy metal content should not be excessive (since this can make the quality of the slag not suitable for re-use) and the material should be destructible at the rather low incineration temperature of MSWIs (850 °C). Some waste will not be efficiently destroyed. 

According to the vendor, this project could provide a compact, low-cost reactor to treat aqueous mixed waste streams containing nitrates or nitrites, eliminate the need for chemical reagents, and minimize or eliminate secondary wastes such as nitrous oxide and secondary products such as ammonia, H2, and O2 that are prevalent with other nitrate destruction processes. By removing nitrates and nitrites from waste streams before they are sent to high-temperature thermal destruction and vitrification, production of NO can be decreased with the attendant decrease in off-gas system requirements. Biocatalytic nitrate destruction is applicable to a wide range of aqueous wastes with a highly variable composition. All information is from the vendor and has not been independently verified. 

Thermal desorption treatment is generally considered to be an alternative to incineration. Thermal desorption operates at much lower temperatures than incineration and keeps the heating systems independent of the wastes, which minimizes off-gas production. The technology can be used as a waste minimization process, isolating and concentrating waste constituents, or as a product recovery process. Thermal desorption can also be used to separate contaminants in mixed waste streams by removing volatile constituents. 

Phosphate-induced metals stabilization can be used for the remediation of metals in mixed waste streams concurrently with other remediation technologies such as vapor stripping or bioremediation of organics. Using apatite to treat soils contaminated with lead, cadmium, and/or zinc can significantly reduce the amount of metals leached from the soil. The amount of apatite needed for treatment is less than 1% by weight. The reaction between metals and apatite is immediate, and the apatite can be heavily loaded with metals. 

One particularly vexing problem for waste management professionals is that of mixed wastes (radioactive plus RCRA and/or TSCA waste) disposal. Caught between conflicting regulatory jurisdictions and remediation options, which frequently prove to be mutually exclusive, mixed waste streams and matrices contaminated with two or more types of contaminant represent a... 

Separation of Metals from Simulated Mixed Waste Streams through Hydrothermal Crystallization in Supercritical Water... 

This incremental cost increase may be justified when stabilizing mixed waste streams or waste streams containing As, Cr, and Hg, because simple acid washing will not stabilize these waste streams. To stabilize Hg, in addition to the CBPC formation, a sulfide pretreatment is used [55]. The pretreatment converts the contaminants into their most insoluble sulfide forms, then the CBPC formation produces a waste form that is far superior to any other treatment. This dual treatment has the advantage of being performed at room temperature in a one-step mixing process. 

Radiochemical methods which allow sequential determination of radionuclides are often desirable for reasons of speed and cost-effectiveness, for example in mixed waste streams or in waste characterization for nuclear decommissioning. Although a variety of methods are in use for the analysis of in concretes, they tend to use large reagent volumes and involve... 

The methods of recycling depend very much on the type of the waste stream and the degree of cleanliness. The relatively clean PCW can be processed by similar methods as those used for industrial scrap. The readily identifiable constituents of such mixed waste streams, e.g., soft drink bottles (PET) and milk containers (HDPE) can be separated and recycled as single polymer recyclates. After removing these containers, the tailings of PCW are made of 50-75 wt% of PE s, 25 wt% of PS, ABS and their blends, and... 

A result of the complexing ability of organic molecules is that waste streams containing potential ligands are difficult to decontaminate. Usual methods such as selective extraction or precipitation may work poorly or not at all. The content and chemistry of mixed waste streams must be accurately determined before a clean-up technique is selected. 

Bennet also finds that addition of its BRC 200 compatibilizer to a mixed waste stream of equal parts of LDPE, LLDPE, HDPE, VLDPE. and PP homopolymer and copolymer boosted impact strength, to higher than the single components, in injection moulded parts. Compatibilizers containing branched ethylene. EVA. and elastomers, are added to scrap LDPE, HDPE, and PP to make drainage pipes. 

Despite increasing research efforts it is not yet economical to separate the wide variety of plastics that end up in the waste stream. The ideal is streams of single, clean and homogeneous recyclates, which present little technical effort for recycling. Of course, streams of this type, mainly industrial, can and are recycled. However, mixed waste streams present more of a technical and economic challenge to recover. 

Whether the material is reprocessed as a mixed waste stream or is sorted into separate fractions, it still needs to undergo some treatment. A typical recycling route for waste plastics can he split into two types of processes ... 

---