انت هنا الان : شبكة جامعة بابل > موقع الكلية > نظام التعليم الالكتروني > مشاهدة المحاضرة

Hazardous Waste

الكلية كلية الهندسة     القسم  الهندسة البيئية     المرحلة 4
أستاذ المادة سعاد مهدي غليوة الفتلاوي       4/20/2011 10:35:33 AM

Hazardous Waste

 

 

 

For centuries, chemical wastes have been the by-products of developing societies. Disposal sites were selected for convenience and placed with little or no attention to potential impacts on groundwater quality, runoff to streams and lakes, and skin contact as children played hide-and-seek in a forest of abandoned 55-gal drums.

 

 

Engineering decisions here historically were made by default; lack of planning for handling or processing or disposal at the corporate or plant level necessitated “quick and dirty“ decision by mid- and entry-level engineers at the end of production processes. These production engineers solved disposal problems by simply piling or dumping these waste products “out back.” Attitudes in the United States began to change in the 1960s, 1970s, and 1980s.

 

 

Air, water, and land are now no longer viewed as commodities to be polluted with the problems of cleanup freely passed to neighboring towns or future generations. Governments have responded to public concerns with revised local zoning ordinances, updated public health laws, and new major Federal Clean Air and Clean Water Acts. In 1976, the Federal Resource Conservation and Recovery Act (RCRA) was enacted to give the U.S. Environmental Protection Agency (EPA) specific authority to regulate the generation, transportation, and disposal of dangerous and hazardous materials.

 

 

The law was strengthened in 1984 with passage of the Hazardous and Solid Waste Amendments to RCRA. In the 1990s we found that engineering knowledge and expertise had not kept pace with this awakening to the necessity to manage hazardous wastes adequately.

 

 

 

 

 

 

 

 

WASTE PROCESSING AND HANDLING

 

Waste processing and handling are key concerns as a hazardous waste begins its journey from the generator site to a secure long-term storage facility.

 

 

Ideally, the waste can be stabilized, detoxified, or somehow rendered harmless in a treatment process similar to the following:

 

 

Chemical Stabilization

 

 

 In this process, chemicals are mixed with waste sludge, the mixture is pumped onto land, and solidification occurs in several days or weeks. The result is a chemical nest that entraps the waste, and pollutants such as heavy metals may be chemically bound in insoluble complexes. Asphalt-like compounds form “cages” around the waste molecules, while grout and cement form actual chemical bonds with the trapped substances.

 

 

 Chemical stabilization offers an alterative to digging up and moving large quantities of hazardous waste, and is particularly

 

suitable for treating large volumes of dilute waste. Proponents of these processes have argued for building roadways, dams, and bridges with a selected cement as the fixing agent. The adequacy of the containment offered by these processes has not been

 

documented, however, as long-term leaching and defixation potentials are not well understood.

 

 

Volume Reduction:

 

 

 Volume reduction is usually achieved by incineration, which

 

takes advantage of the large organic fraction of waste being generated by many industries,but may lead to secondary problems for hazardous waste engineers: air emissions in the stack of the incinerator and ash production in the base of the incinerator. Both

 

by-products of incineration must be addressed in terms of risk, as well as legal and economic constraints (as must all hazardous waste treatment, for that matter). Because incineration is often considered a very good method for the ultimate disposal of hazardous waste,.

 

 

Waste Segregation:

 

 

 Before shipment to a processing or long-term storage facility,

 

wastes are segregated by type and chemical characteristics. Similar wastes are grouped in a 55-gal drum or group of drums, segregating liquids such as acids from solids such as contaminated laboratory clothing and equipment. Waste segregation is generally practiced to prevent undesirable reactions at disposal sites and may lead to economics of scale in the design of detoxification or resource recovery facilities.

 

 

DetoxScation:

 

 

 Many thermal, chemical, and biological processes are available

 

to detoxify chemical wastes.

 

 

Options include:

 

 

neutralization

 

ion exchange

 

incineration

 

pyrolysis


المادة المعروضة اعلاه هي مدخل الى المحاضرة المرفوعة بواسطة استاذ(ة) المادة . وقد تبدو لك غير متكاملة . حيث يضع استاذ المادة في بعض الاحيان فقط الجزء الاول من المحاضرة من اجل الاطلاع على ما ستقوم بتحميله لاحقا . في نظام التعليم الالكتروني نوفر هذه الخدمة لكي نبقيك على اطلاع حول محتوى الملف الذي ستقوم بتحميله .