Rafael Lopez Perez TOXIC WASTE Pollution Prevention GENERAL CONSIDERATIONS DEFINITIONS Pollution prevention consists of all those activities that reduce the generation of hazardous waste. Many terms are used to describe these activities: waste minimization, waste reduction, source reduction, waste diversion, pollution prevention, recycling, and reuse. In a recent policy statements EPA suggested the following hierarchy for management of wastes: * Source reduction * Recycling * Treatment * Disposal In plant practices that reduce, avoid or eliminate the generation of hazardous waste as to reduce risks to health and the environment. Actions taken away from the waste generating activity, including waste recycling or treatment of wastes after they are generated, are not considered waste reduction. Also, an action that merely concentrates t hazardous content of a waste to reduce waste volume or dilutes it to reduce degree hazard, is not considered waste reductions The somewhat broader term pollution prevention has an evolving definition that includes: * Managing chemicals to reduce risk * Identifying and estimating all releases * Waste minimization VOLUME REDUCTION An appropriate place to initiate waste minimization investigations is to examine way: to reduce the volume of hazardous waste. This can be accomplished by a number methods including modifying production processes, segregation, and re-use.
It should be noted that under some regulatory schemes, simply reducing the volume of the waste without an accompanying reduction in toxicity would not be considered was minimization. Process Modifications Process modifications include changes in: Raw materials Equipment & Operating procedures Materials storage End products Hunt suggests the following additional measures to reduce dragout: Increase drain time Air knife (low pressure air to blow solution off parts) Spray rinsing over process tank Minimize concentration of metal in plating bath Rack parts to maximize drainage Use drip bars to hold racked parts over plating tanks TOXICITY REDUCTION A number of waste minimization techniques reduce the concentration of contaminant in a liquid or solid waste stream, without necessarily diminishing the volume of wastes produced. It is often possible to lessen the toxic characteristics sufficiently so that the remaining waste is no longer considered a hazardous waste. Process Modification: Some specific examples of modifications that result in a less toxic waste stream include dry powder painting and solvent recovery methods. Treatment and Disposal Methods Stabilization and Solidification INTRODUCTION In general terms, stabilization is a process where additives are mixed with waste to minimize the rate of contaminant migration from the waste and to reduce the toxicity of the waste. Thus, stabilization may be described as a process by which contaminant are fully or partially bound by the addition of supporting media, binders, or other modifiers. Likewise, solidification is a process employing additives by which the physical nature of the waste (as measured by the engineering properties of strength, compressibility, and/or permeability) is altered during the process.
Thus, objectives of stabilization and solidification would encompass both the reduction in waste toxicity and mobility as well as an improvement in the engineering properties of the stabilized mates al. Thermal Methods INTRODUCTION Incineration systems are designed to destroy only organic components of waste; however most hazardous waste is non-exclusive in its content and therefore will contain both combustible organics and non-combustible inorganics. By destroying the organ Erection and converting it to carbon dioxide and water vapor, incineration reduces the waste volume, and to the extent that the organic components include toxic component [email protected] threat to the environment. Hazardous wastes come in all physical forms: liquid, solid, and somewhere between. Commercial hazardous waste incineration systems have to handle the gamut of waste streams. Nevertheless, many hazardous waste incinerators a concerned only with liquid wastes.
While gaseous waste streams are not regulated as hazardous waste, the combustion of such wastes is certainly a part of the overall incineration process. The theory and equipment design for each type of waste is similar but different, and their combination into a single system is often required. REMEDY SELECTION The parties having a stake in the selection of a remedy come from diverse interests representing the local community, industry, environmentalists, the scientific and engineering professions, and government. Their concerns differ as do their values. They inevitably will disagree about what is the best remedy and even as to what level of protection is needed.
REMEDIAL ALTERNATIVES ANALYSIS 1. Site conditions can be very complicated. 2. Remediation is not straightforward but takes place usually over a long period of time and involves a number of interdependent steps. 3.
A great number of remedial alternatives can exist, each having its own technical tradeoffs. 4. Experience does not exist yet to show clearly how best to proceed. Because of these complicating factors, the selection of a remedy involves a great deal of judgment. The process of how this is done is important to ensure that relevant information and opinions are collected and considered. Selecting a remedy is equivalent to problem solving, and the literature is replete with models usually embodying a classic process as follows: o Problem definition o Establish objectives: o Develop alternatives o Analysis of alternatives BIBLIOGRAPHY Pollution: Causes, Effects and Control.
Roy M. Harrison Waste Not, want Not. WWF Hazardous Waste Management. Michael D. LaGrega, Phillip L.
Buckingham Jeffrey C. Evans Bibliography BIBLIOGRAPHY Pollution: Causes, Effects and Control. Roy M. Harrison Waste Not, want Not. WWF Hazardous Waste Management.
Michael D. LaGrega, Phillip L. Buckingham Jeffrey C. Evans.