Surrogate waste

Before the contaminated soil was processed, the system was tested using surrogate wastes to ensure the emission requirements could be met. Three different series of tests were conducted using various combinations of fuels and wastes. An oxy/pro-pane burner in the PCC was used to incinerate PCB-contaminated soil for the series A and B tests. The only difference between A and B was that propane and oil with 1% PCB, respectively, were used as fuels in the SCC. In series C, the PCC was not operated, while the fuel for the SCC was oil with 42% PCB. 

The primary purpose of the test facility is to have equipment capable of creating surrogate waste streams similar to those commonly encountered in industry and destroy them under controlled conditions with adequate instrumentation to quantify parameters that affect the process. Destruction of waste streams is achieved by proper mixing, sufficient temperature, and adequate residence time in the TO. These parameters are often referred to as the three T s of combustion time, temperature, and turbulence. In addition to waste destruction, the effects of the three T s on other parameters such as CO and NO emissions can also be carefully studied in a test facility. A schematic of a horizontal thermal oxidizer is shown in Figure 33.1. 

Table 33.3 illustrates how an exothermic waste gas stream may be simulated with a simpler surrogate waste stream. 

Formaldehyde and formic acid are the two primary intermediates formed during the conversion of EG to CO2. Phenol, hydroquinone, benzoquinone, and benzoquinone epoxide arc a few of the intermediates formed during the initial stage of BZ oxidation. EG has been used as a surrogate waste in detailed investigations of the MEO process [13] since studies of its partial oxidation by Ag(n) had been previously published [22-24], BZ has been studied [ 13] since it will be aprimary constituent of mixed waste generated by the DWPF [17]. 

Figure 15.9. Heating value of the gases produced during pyrolysis of different surrogate wastes.

Mercury 8.1 pg/dscm Hazardous waste feed restriction of 1.9 ppmw and 120 pg/ dscm MTEC or 120 pg/dscm total emissions 120 hazardous waste MTEC feed restriction or 120 pg/dscm total emissions 11 pg/dscm 1.2 E-6 lb/MMBtu or 6.8 pg/ dscm depending on Btu content of hazardous waste TCI as surrogate... 

Aqueous samples are extracted with methylene chloride by liquid-liquid extraction. The extract is concentrated and then exchanged to hexane. Soils, sediments, and solid wastes are extracted by sonication or Soxhlett extraction. Samples should be spiked with one or more surrogate standard solution to determine the accuracy of analysis. Some of the internal standards mentioned above may also be used as surrogates. If only the PCBs are to be analyzed, hexane instead of methylene chloride may be used throughout. Oil samples may be... 

To the extent that risk is used as a basis for waste classification, it is not used consistently. Different values for acceptable risk are assumed for different hazardous waste disposal situations. In addition, a variety of surrogate measures (e.g., ingestion toxicity, total radioactivity) having varying relationships to risk have been used to classify wastes. 

There are two possible alternatives to using risk directly as the basis for waste classification non-risk-based systems and surrogate systems. Non-risk-based systems could use any conceivable attribute of hazardous waste as a basis for classification, including its source (see Sections 4.1 and 4.2 for examples) or the date it was produced. These bases are at best somewhat related to risk and at worst are totally unrelated. Because of this variable relationship, the use of non-risk-based approaches to waste classification could result in an unacceptable risk if the waste is managed in a way that does not provide adequate long-term protection, or an inappropriate allocation of resources if relatively innocuous wastes are managed in the same way as much more hazardous wastes. 

The risk index normally is determined by computing the risk or by using dose as a surrogate for risk. In the example in Section 7.1.3.1, the calculated dose associated with intrusion into the waste is divided by the assumed maximum allowable dose to estimate the risk index. In the example in Section 7.1.3.2, limits on acceptable concentrations are developed as surrogates for the allowable risk. The concentrations in the waste are then divided by these allowable concentrations to determine the risk index. The same approach is used in the example in Section 7.1.3.3, except the allowable concentrations are lower because a less protective disposal option is evaluated. The consequences of alternative assumptions about intrusion scenarios on classification of the Hanford waste are considered in Section 7.1.3.4. 

For the purposes of this example, it was assumed that the waste was placed 4 m deep and covered with a cap and soil that was at least 3 m thick. As a consequence, the assumed scenario was an onsite drilling event. The dose analysis assumes a two-fold volume increase (50 percent dilution) of the drill tailings by uncontaminated material. The mixture of waste and uncontaminated cover material is spread on the surface of the site, and individuals working in the area are exposed to the tailings for 1,000 h. The thickness of the layer of contaminated drill tailings is assumed to be about 5 cm and the area to be about 3.3 m2. Using dose as a surrogate for risk, analysis of this scenario yields a dose of0.002 mSv from all radionuclides. Since the assumed allowable dose is 20 mSv (see Table 7.1), the risk index would be 0.002/20 = 10 4, which is well below the value of unity, and the waste would be classified as low-hazard. 

Inclusion of a test representative of the fish level of organization in future PEEP bioassay batteries is nevertheless highly advisable owing to the specific adverse effects that liquid wastes can manifest on this trophic level. To offset the constraints mentioned above, appropriate surrogates can now be found with tests conducted with fish cells. Indeed, fish cell bioassays such as those reported in this book (see Chapters 14 and 15, volume 1 of this book) offer reliable and relevant alternatives to whole organism testing that alleviate sample volume and budgetary considerations. 

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