CHAPTER 15 ENVIRONMENTAL CONCERNS: WASTES AND POLLUTION 501 Because of this concern the legislation governing secured landfills continues to mount. There are now specific standards that stipulate which hazardous wastes can and cannot be placed in secured landfills without further processing(some wastes must undergo treatment before being placed in the landfill). Many authorities desire this means of disposal to be phased out Deep well Injection Another means of disposing of hazardous waste is deep well injection, a form of disposal developed by petroleum refineries. Deep well injection consists of pump- ing the hazardous waste, by way of lined wells, far below drinking water aquifers into layers of permeable rock that are surrounded by impermeable rock. About 25% of all hazardous waste in the United States is disposed of by deep well injec tion. The major objection to deep well injection is that, like the secured landfill, there may be seepage of hazardous waste out of the well and into the water supply Incineration of Hazardous Waste Appropriately controlled incineration is one of the most efficient means of manag. ing hazardous waste; however, it is also one of the most expensive. Nadakavukaren identified four major benefits of this means of disposal: (1) conversion of toxic com pounds to harmless ones, (2) reduction in the volume of waste, (3)destruction instead of isolation of waste, and(4) possible energy recovery during combustion This method of disposal consists of burning the wastes at very high tempera- tures. It requires the appropriate mixture of air and fuel to ensure complete com- bustion. Gaseous by-products are recombusted to minimize the release of hydrocarbons and other harmful gases. Airborne products of combustion are sub ject to special filtration(scrubbers and electrostatic precipitators) to eliminate air pollution. In 1993, the Epa began looking closely at hazardous waste incinerators to make sure they were operating safely. Hazardous Waste Recycling and Neutralization The best solution to hazardous waste disposal once it,'s created is recycling in a system in which a hazardous waste created by one process becomes the raw mate- rial for another. Unfortunately, finding someone who can use your hazardous waste is not easy. In Europe, waste exchanges have been created to help parties carry waste exchanges out mutually agreeable exchanges. These waste exchanges are managed by inter- mange exchonges mediaries who help to establish contacts between those who want to dispose of witten between those hazardous wastes and those who can use them as raw materials who wart to dispose ical,chemical,or biological processes. Examples include extracting toxic metals use them as row from waste, adding a base to an excessively acidic waste, and promoting thematerials growth of microbes that feed on hazardous waste-a method that has been used successfully with oil spills Source reduction Source reduction represents the best solution to the problem of hazardous waste. Increased public concern and the high cost of disposal have led hazardous waste pro- ducers to invest in technological research to reduce the amount of waste produced