4-nine destruction efficiencies

Incinerators burning solid PCB wastes must have a 99.9999% destmction efficiency (six-nines). For each 1 milUon g of PCBs fed, only 1 g is allowed to leave the stack. TSCA standards are much more restrictive than RCRA, which allows 1 g to be released for each 10,000 g of waste fed (99.99%, or four-nines destruction efficiency). 

In 1974 Midwest Research Institute operated a pilot-scale multiple chamber incinerator to evaluate for EPA the operational variables for pesticide incineration (8). The system included a. pilot-scale incinerator, a three-stage scrubber system, and a scrubber water treatment system. Nine pesticides (aldrin, atrazine, captan, DDT, malathion, mirex, picloram, toxaphene, and zineb) in 15 liquid and solid formulations were studied. Destruction efficiencies generally exceeded 99.99% over a range of temperatures and retention times ( 950 to 1100°C, 1.2 to 6 s, and 80 to 160% excess air). This study also documented the generation of measurable quantities of cyanide in the incinerator off-gas during the incineration of organonitrogen pesticides. 

The committee was also asked to evaluate the trial burn practices at the incineration-based facilities and compare them with similar practices in industry. Each Chemical Materials Agency (CMA) incineration facility has several types of incinerators and each has been required, by permit, to carry out a surrogate burn on all of its furnaces after start-up and before feeding any agent. A surrogate trial burn is required to demonstrate the ability of the unit to achieve a 99.9999 percent ( six nines ) destruction and removal efficiency and unit operability. They have then been required to carry out a trial burn with each agent. After the trial burn, the feed rates are reduced to 50 percent until the trial burn data... 

The committee concluded in its previous report that biological treatment is a doubtful candidate for treatment of MMD neutralent. Reasons included the relatively low destruction efficiency (typically around 90 percent for most compounds, as opposed to the five or six nines usually sought in destroying hazardous materials), the presence of compounds that are known to be difficult to destroy by biotreatment (e.g., chloroform, hexachlorobenzene, and hexachlorobutadiene), the fact that the process yields large volumes of off-gas that must be treated, and that the equipment is bulky and not easily transported. A previous test of biotreatment for GB and VX hydrolysate was unsuccessful (NRC, 2000). 

By federal law (as described in Chapter 22), hazardous waste incinerators must meet a minimum destruction and removal requirement, i.e., that the principal organic hazardous constituents (POHCs) of the waste feed be incinerated with a minimum destruction and removal efficiency (DRE) of 99.99% ( four nines ). The destruction and removal efficiency is the fraction of the inlet mass flowrate of a particular chemical that is destroyed and removed in the incinerator or, equivalently. 

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