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Principles and Methods of Waste Management in the Process Industry

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Adebayo Bamidele Olanrewaju BSc, ASM, AMNIM, MNSE, MNSChE, CSSBB
Adebayo Bamidele Olanrewaju BSc, ASM, AMNIM, MNSE, MNSChE, CSSBB

This document discusses various types and methods of waste management. It begins by defining hazardous waste and identifying the main types as gaseous, liquid, and solid. It then outlines steps for waste inventory, characterization, segregation, and minimization. Various treatment and disposal methods are described such as landfilling, chemical treatment, biological treatment, thermal treatments, physical treatments, solidification/encapsulation, and energy recovery from waste incineration. The overall document provides an overview of classifying, handling, and processing different categories of waste.

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Adebayo Bamidele Olanrewaju
 Anything which is no longer of value and when improperly handled, can cause substantial harm to human health and safety or to the environment.
 GaseousWastes e.g. gas flaring, particulate dust, waste gases from stack, lime dust, acid fumes etc.  LiquidWastes e.g. waste acids, waste oil, effluents, waste lubricants etc.  Solid wastes e.g. sludge and slag, cans, plastics, broken glasses, battery casings, paper etc.
Inventory This involves taking stock of all waste types, quantities and sources.This helps to give a quick insight on the magnitude of waste at hand.
Characterization 1) Hazardous wastes are classified on the basis of their biological, chemical, and physical properties. 2) These properties generate materials that are either toxic, reactive, ignitable, corrosive, or radioactive.
 Toxic wastes are poisons, even in very small or trace amounts. They may have acute effects, causing death or violent illness, or they may have chronic effects, slowly causing irreparable harm.  Reactive wastes are chemically unstable and react violently with air or water.They cause explosions or form toxic vapours.  Ignitable wastes burn at relatively low temperatures and may cause an immediate fire hazard.  Corrosive wastes include strong acidic or alkaline substances. They destroy solid material and living tissue upon contact, by chemical reaction.  Radioactive wastes emit ionizing energy that can harm living organisms.
Segregation Segregation of waste entails separating wastes, putting into consideration their properties.
Minimization This requires lowering waste as low as possible.This can be achieved by means of the 3Rs:
1) Reduction: Understanding and developing processes that reduces wastes from the source. 2) Reuse: Seek to identify the usefulness of waste in other application with little or no modification in the waste. These include paper, metal, glass, plastic, and rubber. 3) Recycling: Converting waste into useful products for other application, recovery and reuse of heat energy, composting process which reclaims the organic parts of solid waste for reuse as mulch or soil conditioner.
 Properly disposing waste is very essential for optimal process operation.  It protects the environment from harmful industrial release. The following slides describe some ways of treating and disposing wastes. These methods include landfilling, chemical treatment, biological treatment, thermal treatments, physical treatments, solidification/encapsulation, ocean dump etc.
 It involves digging the ground, dumping the waste into it and covering.The types includes Inert Landfill Non decomposable waste (e.g. nuclear wastes) are buried at a distance of 500m below the earth surface. Sanitary Landfill Non- hazardous wastes, biodegradable materials, municipal wastes etc. Chemical Landfill For hazardous wastes from industries requiring pre- treatment before disposal.
 These include ion exchange, precipitation, oxidation and reduction, and neutralization.  Ion Exchange: In this, one or more undesirable ionic contaminants are removed by exchange with another non-objectionable or less objectionable ionic substance. e.g. in water purification processes.  Reduction/Oxidation (Redox): This chemically convert hazardous contaminants to less toxic compounds that are less mobile and/or inert. It involve transfer of electrons from one compound to another, where one compound is oxidized and other, reduced. Examples include, ozone, chlorine, hypochlorite (oxidizing agents), and ferrous sulfate, sodium bisulfite, sodium hydrosulfite (reducing agents).  Neutralization: It is the process of adjusting the pH of waste (e.g. effluents) through the addition of an acid or base, depending on the target pH and process requirements before disposal, making it more environmentally friendly.
High-temperature Incineration: which can not only detoxify certain organic wastes but also destroy them. Others include, fluidized-bed incinerator, multiple- hearth furnace, rotary kiln, and liquid-injection incinerator, used for burning waste in either a solid, liquid, or sludge form. One problem posed by hazardous-waste incineration is the potential for air pollution.
 Land-farming: In this technique, the waste is carefully mixed with surface soil on a suitable tract of land.  Bioremediation: Using microbes for stabilizing hazardous wastes on previously contaminated sites.  Others include adding microbes that can metabolize the waste, along with nutrients. In some cases, a genetically engineered species of bacteria is used. Food or forage crops are not grown on the same site.
This concentrates, solidifies, or reduces the volume of the waste. Physical processes include evaporation, sedimentation, flotation, and filtration.
Achieved by encapsulating the waste in concrete, asphalt, or plastic. Encapsulation produces a solid mass of material that is resistant to leaching. Waste can also be mixed with lime, fly ash, and water to form a solid, cementlike product.
The energy value of waste (refuse) can be as much as one-third that of coal, depending on the paper content, and the heat given off during incineration can be recovered by the use of a refractory-lined furnace coupled to a boiler. Boilers convert the heat of combustion into steam or hot water, thus allowing the energy content of the refuse to be recycled.
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Principles and Methods of Waste Management in the Process Industry

  • 2.  Anything which is no longer of value and when improperly handled, can cause substantial harm to human health and safety or to the environment.
  • 3.  GaseousWastes e.g. gas flaring, particulate dust, waste gases from stack, lime dust, acid fumes etc.  LiquidWastes e.g. waste acids, waste oil, effluents, waste lubricants etc.  Solid wastes e.g. sludge and slag, cans, plastics, broken glasses, battery casings, paper etc.
  • 4. Inventory This involves taking stock of all waste types, quantities and sources.This helps to give a quick insight on the magnitude of waste at hand.
  • 5. Characterization 1) Hazardous wastes are classified on the basis of their biological, chemical, and physical properties. 2) These properties generate materials that are either toxic, reactive, ignitable, corrosive, or radioactive.
  • 6.  Toxic wastes are poisons, even in very small or trace amounts. They may have acute effects, causing death or violent illness, or they may have chronic effects, slowly causing irreparable harm.  Reactive wastes are chemically unstable and react violently with air or water.They cause explosions or form toxic vapours.  Ignitable wastes burn at relatively low temperatures and may cause an immediate fire hazard.  Corrosive wastes include strong acidic or alkaline substances. They destroy solid material and living tissue upon contact, by chemical reaction.  Radioactive wastes emit ionizing energy that can harm living organisms.
  • 7. Segregation Segregation of waste entails separating wastes, putting into consideration their properties.
  • 8. Minimization This requires lowering waste as low as possible.This can be achieved by means of the 3Rs:
  • 9. 1) Reduction: Understanding and developing processes that reduces wastes from the source. 2) Reuse: Seek to identify the usefulness of waste in other application with little or no modification in the waste. These include paper, metal, glass, plastic, and rubber. 3) Recycling: Converting waste into useful products for other application, recovery and reuse of heat energy, composting process which reclaims the organic parts of solid waste for reuse as mulch or soil conditioner.
  • 10.  Properly disposing waste is very essential for optimal process operation.  It protects the environment from harmful industrial release. The following slides describe some ways of treating and disposing wastes. These methods include landfilling, chemical treatment, biological treatment, thermal treatments, physical treatments, solidification/encapsulation, ocean dump etc.
  • 11.  It involves digging the ground, dumping the waste into it and covering.The types includes Inert Landfill Non decomposable waste (e.g. nuclear wastes) are buried at a distance of 500m below the earth surface. Sanitary Landfill Non- hazardous wastes, biodegradable materials, municipal wastes etc. Chemical Landfill For hazardous wastes from industries requiring pre- treatment before disposal.
  • 12.  These include ion exchange, precipitation, oxidation and reduction, and neutralization.  Ion Exchange: In this, one or more undesirable ionic contaminants are removed by exchange with another non-objectionable or less objectionable ionic substance. e.g. in water purification processes.  Reduction/Oxidation (Redox): This chemically convert hazardous contaminants to less toxic compounds that are less mobile and/or inert. It involve transfer of electrons from one compound to another, where one compound is oxidized and other, reduced. Examples include, ozone, chlorine, hypochlorite (oxidizing agents), and ferrous sulfate, sodium bisulfite, sodium hydrosulfite (reducing agents).  Neutralization: It is the process of adjusting the pH of waste (e.g. effluents) through the addition of an acid or base, depending on the target pH and process requirements before disposal, making it more environmentally friendly.
  • 13. High-temperature Incineration: which can not only detoxify certain organic wastes but also destroy them. Others include, fluidized-bed incinerator, multiple- hearth furnace, rotary kiln, and liquid-injection incinerator, used for burning waste in either a solid, liquid, or sludge form. One problem posed by hazardous-waste incineration is the potential for air pollution.
  • 14.  Land-farming: In this technique, the waste is carefully mixed with surface soil on a suitable tract of land.  Bioremediation: Using microbes for stabilizing hazardous wastes on previously contaminated sites.  Others include adding microbes that can metabolize the waste, along with nutrients. In some cases, a genetically engineered species of bacteria is used. Food or forage crops are not grown on the same site.
  • 15. This concentrates, solidifies, or reduces the volume of the waste. Physical processes include evaporation, sedimentation, flotation, and filtration.
  • 16. Achieved by encapsulating the waste in concrete, asphalt, or plastic. Encapsulation produces a solid mass of material that is resistant to leaching. Waste can also be mixed with lime, fly ash, and water to form a solid, cementlike product.
  • 17. The energy value of waste (refuse) can be as much as one-third that of coal, depending on the paper content, and the heat given off during incineration can be recovered by the use of a refractory-lined furnace coupled to a boiler. Boilers convert the heat of combustion into steam or hot water, thus allowing the energy content of the refuse to be recycled.