Concern for the environment is not a new issue, as evidenced by the notice printed in the January, 1944 issue of The Betz Indicator. (Figure 2-1)
In the 1960's it became evident that there could be a dark side to the economic development that resulted from the decades of rapid industrial growth following World War II. During this period the general public became aware of the consequences of improper waste material handling and industrial accidents. Frightening incidents at Love Canal, Seveso, and Bhopal in the 1970's and 1980's had tragic effects on members of the general public beyond the fence line of the facilities. In the past few decades, public awareness has grown concerning many other important environmental issues:
- acid rain
- global warming ("greenhouse effect")
- stratospheric ozone depletion
- tropical deforestation
- the urban trash crisis
- pesticides in groundwater
- hazardous waste disposal
- natural and synthetic carcinogens
Focus on environmental considerations has shifted from a single-medium approach (air, water, land) to a holistic approach. Early regulations permitted the removal of a solvent, such as trichloroethane (methyl chloroform), from contaminated groundwater by counter current air stripping. It was soon realized that while the water was no longer contaminated, an air pollutant had been created in the process. Today's regulations address the fact that moving a pollutant from one medium to another does not eliminate the problem. In the example given above, the solvent removed from the water must he condensed or adsorbed by activated carbon and recovered or incinerated.
Another change is a recognition that city sewers are an appropriate means of disposal only for those industrial wastes that are removed or degraded to environmentally compatible products in the municipal treatment plant. Industrial wastes that cause a degradation of effluent water quality or render the sewage sludge hazardous must be managed in ways that are environmentally acceptable. The accomplishment of this goal will require the continuing, long-term efforts of all concerned.
The cost of manufacturing a product now includes factors for waste disposal and pollution prevention. Often, it is more economical to alter processes to produce less waste or more benign wastes, and to recover usable materials from waste streams, than to make a contaminated waste stream suitable for disposal.
THE INDUSTRIAL USE OF WATER
It is becoming increasingly apparent that fresh water is a valuable resource that must be protected through proper management, conservation, and use.
Although two-thirds of the Earth's surface is covered by water, most of it is seawater, which is not readily usable for most needs. All fresh water comes from rainfall, which percolates into the soil or runs off into rivers and streams. The hydrologic cycle is dynamic, as shown in Chapter 1.
In order to ensure an adequate supply of high quality water for industrial use, the following practices must he implemented :
- purification and conditioning prior to consumer (potable) or industrial use
- conservation (and reuse where possible)
- wastewater treatment
Cooling systems are being modified in industrial applications to reduce the use of fresh water makeup. The operation of cooling towers at high cycles of concentration and the reuse of waste streams (including municipal plant effluent for cooling tower makeup) can contribute significantly to reduced water consumption.
Both groundwater and surface waters can become polluted as a result of the improper management of wastes (Figure 2-3). Because of the increasing demands for fresh water, there is a continuing need to share resources. Regulations will require the increasing treatment of all domestic and industrial wastewaters in order to remove industrial and priority pollutants and restore the effluent water to the quality required by the next user. Facilities that treat domestic waste must also control the more conventional pollutants, such as BOD (biological oxygen demand), ammonia, and nitrates, and restore the pH if it is out of the neutral zone.
Concerns about the safety of drinking water supplies are widespread. Although there are many pollutants that degrade water quality (including natural pollutants), those that attract the greatest public attention result from industrial activity and the use of agricultural pesticides and fertilizers.
Environmental regulations establish quality criteria for both industrial and domestic waste treatment discharges. Although some countries have more comprehensive laws and permit regulations than others, stringent pollution control standards will probably be adopted globally in the coming years.
Geographic boundaries are not recognized by the winds. Air quality issues are complicated by the fact that they are usually of multinational concern. Significant issues such as acid rain, stratospheric ozone depletion, and the greenhouse effect require a degree of international cooperation that is difficult to achieve (see Figure 2-4). Technologies available today can have a positive and measurable impact on these issues. Several chapters in this handbook describe technologies that increase boiler and industrial cooling efficiency. In paper mills, generating plants, steel mills, refineries, and other major energy consumers, each incremental increase in energy efficiency represents a reduction in required fuel. As a result of reduced fuel consumption, less carbon dioxide is produced, and where coal or other sulfur containing fuels are used there is also a decrease in sulfur oxide emissions. Fluidized bed boilers are being used increasingly to reduce the presence of acidic gasses (SOx and NOx ) in the boiler flue gas.
One of the problems faced by governments is the amount of energy required to accomplish wet scrubbing (to remove acid gases) and electrostatic precipitation of particulates. These processes, combined, consume up to 30% of the energy released by the burning of coal . While these processes reduce the contaminants thought to cause acid rain, they increase the amount of coal burned and thereby increase the production of carbon dioxide, one of the gases thought to cause the "greenhouse effect."
Many of the air pollutants of concern could be greatly reduced through the use of alternative energy sources, such as nuclear fission (and at some point, probably nuclear fusion), geothermal, wind, hydroelectric, photovoltaic, biomass, and solar. At this time, many of the alternatives are significantly more expensive than the use of fossil fuels, and each has its own problems. There are no clear and simple solutions; no source of energy has been developed that is both economically attractive and without environmental drawbacks.
Over the past several years, most industrialized countries have passed laws addressing air pollution concerns and industrial and power plant emissions. Nations have begun to come together in a cooperative fashion to formulate agreements and protocols to deal with global atmospheric concerns. There has been a multinational agreement to phase out the use of certain chloro- fluorocarbon compounds (used as refrigerant gases and for other purposes) because they have been linked with a reduction of ozone in the stratosphere. There is reason to believe that a reduction in stratospheric ozone will allow a higher level of UV radiation to reach the earth's surface, and this is expected to cause an increase in the incidence of skin cancer along with other undesirable effects.
There are movements to establish multinational agreements that provide incentives to allow economic progress to occur in developing countries without the destruction of their rain forests. The rain forests should be preserved not only for the sake of conservation but also because they remove vast quantities of atmospheric carbon dioxide through photosynthesis and thus have a favorable effect on global warming and the greenhouse effect.
Human understanding of atmospheric chemistry is far from complete. As our understanding grows there will undoubtedly be many changes in direction and emphasis regarding atmospheric pollutants. Because a sizeable amount of atmospheric pollution results from industrial activity and power generation, the scope and stringency of industrial air pollution regulations will continue to increase.
INDUSTRIAL WASTE REDUCTION AND ENERGY CONSERVATION
In the 20th century, industrialized nations evolved from exploiters of bountiful natural resources to conservators of scarce resources. In the early 1900's, the consumption of industrial products was modest and natural resources appeared to he limitless. As the demand for electric power and industrial products grew, the limitations of the Earth's natural resources became an increasing concern. Today, even developing countries are very interested in the controlled development and utilization of their resources.
In addition to producing a desired output at a certain cost, industrial producers must now consider the following objectives:
- to consume a minimum of raw materials and energy
- to minimize waste through efficient use of resources
- to recover useful materials from production waste
- to treat any residual waste so that it can be converted to an environmentally acceptable form before disposal
In addition to concerns about the depletion of natural resources, there are widespread concerns about waste disposal practices. The burying of untreated industrial wastes, whether classified as hazardous or nonhazardous, is no longer an acceptable practice. Landfill of stabilized residues from the incineration, thermal treatment, or biological oxidation/degradation of industrial wastes is the approach accepted by most countries today.
Certain materials that are the waste products of one process can be recovered for reuse in another application. For example, boiler blowdown may be used as cooling tower makeup in certain instances. Other waste products may contain valuable components that can be extracted. As the cost of waste disposal has escalated, it has become economically feasible to use alternative raw materials and to alter processes so that less waste or less hazardous waste is produced. The treatment of waste and wastewater so that it can be successfully reused is an increasing need .
The most efficient driving force for the selection of alternative, waste reducing raw materials and processes is the marketplace. Because of the high cost of waste treatment and disposal, certain processes can offset higher initial costs with reduced operating expenses. For example, membrane systems (reverse osmosis, electro dialysis reversal, etc.) have been used successfully to treat boiler makeup water and reduce the total level of contamination in the waste discharge in comparison with ion exchange systems. Membrane treatment of cooling tower blowdown has also been used to reduce the total quantity of wastewater. The stripping of carbon dioxide and ammonia from process condensate streams has made it feasible to reuse them as boiler feedwater. The reduction of cooling tower blowdown by the use of side stream softeners and/or filters, along with effective deposit control and corrosion inhibition programs, is also increasing.
Although global efforts are being made to ensure that the wastes from industrial processes are properly managed, the cost of remedying the damage from past practices must also be addressed. Injudicious burial of industrial wastes in the past has resulted in significant groundwater contamination (leaching) problems. Because the underground movement of chemicals leaching from dumping areas is extremely difficult to monitor and track, this form of pollution is of major concern to the general public. A large percentage of the world's population relies on groundwater from wells or springs for its potable water supply.
Because the turnover of an aquifer can take years, or even decades, any contamination can be serious. Fortunately, certain natural processes, including microbiological digestion, may break down leaching pollutants to nonharmful materials. One remedy that is gaining acceptance is the addition of certain nutrients and inoculum cultures to contaminated soils to accelerate the biological degradation of pollutants. This process is referred to as bioremediation and has many useful variants.
Industrial and commercial producers have an obligation to minimize consumption of the Earth's natural resources and to generate a minimum of pollutants and waste.
The term "zero risk" is often used to represent the ultimate goal of generating products without any possibility of producing environmental effects. As zero risk is approached (although in most cases it can never be fully attained), the cost to the producer and to society in general becomes increasingly larger for each increment of risk avoided (see Figure 2-7).
It has become clear to all nations that the protection of the environment is an immediate and ongoing concern. It will take a great deal of time and effort to redesign industrial processes to minimize wastes produced. Deposit and corrosion control treatments that are effective under demanding conditions and also environmentally acceptable are necessary. Efficient treatment. handling, feeding, and control systems are essential to ensure optimum system performance with minimum impact on the environment.
Figure 2-1. Concern for the environment and potential for recovery of valuable materials has been a concern for decades.
The above notice appeared in January 1994, issue of "The Betz Indicator".
Figure 2-3 Groundwater (and surface water) can become contaminated in variety of ways.
Figure 2-4. Interactions between the climate and human activities.
Figure 2-7. The cost of each increment of risk abatement becomes increasingly greater as 'zero risk' is approached.