José Romero Morgaz
3.1. Estructura de trabajo de los proyectos EMPACT
This section briefly reviews basic considerations in the pretreatment of industrial waste-water before its discharge to the municipal wastewaste-water treatment system. Additional
details regarding industrial wastewater pretreatment can be found in Industrial Waste-water Management, Treatment, and Disposal (WEF, in press) and the other references cited in this section.
INDUSTRIAL WASTEWATER CHARACTERISTICS. Industrial wastewaters may contain organic and/or inorganic constituents that may be detrimental to the op-eration of a POTW. The composition of industrial wastewater may change as raw ma-terials and processes are changed. Fluctuations may occur in the flow and composition of wastewater. Wastewater characteristics vary widely from one type of industry to an-other and even among plants within the same industrial category. Because the list of regulated pollutants is broad, almost any industry may be a source of one or more of these pollutants. Refer to Table 4.1 for a partial list of industries with categorical dis-charges and potential contaminants of concern for these industries.
INDUSTRIAL WASTEWATER PRETREATMENT PROCESSES. The pre-treatment requirements for industrial wastewater depend on the wastewater charac-teristics, particular pollutants requiring removal, flowrates, and degree of pretreatment needed. The various wastewater treatment processes are generally classified as physi-cal, chemiphysi-cal, and biologiphysi-cal, and each is described briefly below. Detailed discussions of industrial wastewater characteristics, specific pretreatment applications, and design of industrial wastewater treatment systems can be found in the literature (Eckenfelder, 1999; Nemerow, 1978; WEF, in press). Such information is beyond the scope of this chapter.
Reductions in the volume or strength of raw wastewater may often be achieved through industrial recycling or reuse systems, improved housekeeping practices, and production process modifications to reduce constituents of concern. Application of these industrial plant controls should be considered and can make a significant differ-ence in the pretreatment requirements for an industry.
Physical processes are designed to remove targeted constituents from waste streams by removing the constituents without producing any change in the constituent. Com-monly used physical processes include filtration, adsorption, stripping, and solids sepa-ration using screening, sedimentation, or flotation. The result of physical pretreatment is a waste stream with lower concentrations of the targeted constituents, while the physi-cally removed constituents must be managed separately for disposal.
Chemical processes produce a change in the targeted constituents in the waste stream by chemically altering the constituents or chemically binding the constituents to other chemical compounds. Neutralization, oxidation, reduction, and coagulation are
examples of chemical processes. The result of physical pretreatment is a waste stream with lower concentrations of the targeted constituents, while the chemically removed constituents must be managed separately for disposal. Examples of commonly used coagulants include aluminum and iron salts. Oxidants typically used include chlorine, peroxide, ozone, or oxygen.
Biological processes are primarily designed to reduce dissolved organic materials.
Aerobic biological processes include trickling filters and other fixed-film systems and activated sludge systems, including sequencing batch reactors. Anaerobic processes, such as anaerobic filters and anaerobic reactors, have been used for high-strength in-dustrial wastewater. Many inin-dustrial wastewaters may require a pretreatment step to reduce toxic pollutants that would otherwise interfere with the operation of biologi-cal units.
Treatment technologies for heavy metals removal generally include a precipita-tion process. Sometimes, effective treatment may require a chemical oxidaprecipita-tion step before precipitation. The pH of the wastewater and the oxidative state of the metal in-fluence treatment effectiveness. Sulfide addition precipitates arsenic, and lime or caus-tic addition can precipitate many metals as hydroxides. Causcaus-tic converts hexavalent chromium to the trivalent state and then precipitates the trivalent chromium. Other incompatible pollutants, such as cyanide, are oxidized under alkaline conditions using chlorine.
One of the following four types of treatment processes can remove organic compounds:
• Stripping by air or steam;
• Advanced oxidation processes using various combinations of ozone, hydrogen peroxide, and UV light;
• Adsorption on activated carbon or a synthetic resin; and
• Biological degradation.
The performance of any of those processes for a specific application varies greatly and depends on the nature of the organic compound and the presence of other pollutants.
Therefore, a small-scale model study on the specific waste to be treated is recom-mended before developing any of these processes.
For reference, Figure 4.1 presents a general list of common contaminants and the general treatment systems that may be used to pretreat wastewaters containing these contaminants before discharge to the POTW.
FIGURE4.1 General treatment systems commonly used to remove major contaminants.*
REFERENCES
Eckenfelder, W. W. Jr. (1999) Industrial Water Pollution Control, 3rd ed.; McGraw-Hill:
New York.
Nemerow, N. L. (1978) Industrial Water Pollution; Addison-Wesley: Reading, Massachusetts.
U.S. Environmental Protection Agency (1992) Control Authority Pretreatment Audit Check-list and Instructions. U.S. Environmental Protection Agency: Washington, D.C.
U.S. Environmental Protection Agency (1983) Guidance Manual for POTW Pretreatment Program Development, EPA-833/B-83-100; U.S. Environmental Protection Agency:
Washington, D.C.
U.S. Environmental Protection Agency (1986) Pretreatment Compliance Monitoring and Enforcement Guidance. U.S. Environmental Protection Agency: Washington, D.C.
U.S. Environmental Protection Agency (1987) Guidance Manual for Preventing Inter-ference at POTWs, EPA-833/B-87-201; U.S. Environmental Protection Agency: Wash-ington, D.C.
*VOCs = volatile organic compounds, RBCs = rotating biological contactors, N = nitrogen, and P = phosphorus.
Contaminants
U.S. Environmental Protection Agency (1989a) Guidance for Developing Control Authority Enforcement Response Plans. U.S. Environmental Protection Agency: Washington, D.C.
U.S. Environmental Protection Agency (1989b) Industrial User Permitting Guidance Manual, EPA-833/B-89-001; U.S. Environmental Protection Agency: Washington, D.C.
U.S. Environmental Protection Agency (1994) Industrial User Inspection and Sampling Manual for POTWs, EPA-831/B-94-001; U.S. Environmental Protection Agency:
Washington, D.C.
U.S. Environmental Protection Agency (1999) Introduction to the National Pretreatment Pro-gram, EPA-833/B-98-002; U.S. Environmental Protection Agency: Washington, D.C.
U.S. Environmental Protection Agency (2004a) Local Limits Development Guidance, EPA-833/R-04-002A; U.S. Environmental Protection Agency: Washington, D.C.
U.S. Environmental Protection Agency (2004b) Local Limits Development Guidance Appen-dices, EPA-833/R-04-002B; U.S. Environmental Protection Agency: Washington, D.C.
U.S. Environmental Protection Agency (2007a) Current National Recommended Water Quality Criteria. U.S. Environmental Protection Agency: Washington, D.C., http://
www.epa.gov/waterscience/criteria/wqcriteria.html (accessed March 2007).
U.S. Environmental Protection Agency (2007b) EPA Model Pretreatment Ordinance, EPA-833/B-06-002; U.S. Environmental Protection Agency: Washington, D.C.
U.S. Environmental Protection Agency (2007c) General Pretreatment Regulations. Code of Federal Regulations, Part 403, Title 40.
U.S. Environmental Protection Agency (2007d) Guidelines Establishing Test Proce-dures for the Analysis of Pollutants. Code of Federal Regulations, Part 136, Title 40.
U.S. Environmental Protection Agency (2007e) Specific State Program Status. U.S.
Environmental Protection Agency: Washington, D.C., http://cfpub.epa.gov/npdes/
statestats.cfm?viewspecific (accessed March 2007).
Water Environment Federation (in press) Industrial Wastewater Management, Treatment, and Disposal, 3rd ed.; Manual of Practice No. FD-3; Water Environment Federation:
Alexandria, Virginia.
Safety
Standard for Fire Protection Practice for Wastewater Treatment Plants and Collection Facilities 5-12 Chlorine Storage and Chlorine
Room Design 5-13
Chemical Delivery and Distribution 5-14 National Fire Protection Association 5-15
Microbiological Hazards 5-15
Hepatitis A and E 5-19
Hepatitis B, C, D, and G 5-20
Personal Hygiene and Health
Protection 5-21
Confined Spaces 5-23
Limited Entry and Egress 5-24
Ventilation Hazards 5-24
Copyright © 2008 by the Water Environment Federation. Click here for terms of use.
INTRODUCTION
Safety, by definition, is (1) freedom from danger, risk, or injury; or (2) a device de-signed to prevent accidents (American Heritage Dictionary, 1997). This is a book defini-tion; however, in the field, safety can mean many different things. It can mean working in a manner that will not endanger the lives and limbs of workers and passersby. It can also mean working to avoid losing work days. Unfortunately, safety can also be spo-ken about, but not practiced.
How does this happen? Everyone knows that there should be work practices used where no one gets hurt or sick. However, often, there are pressures to produce more work on time and more cheaply, and this can result in careless mistakes by workers and even uncorrected bad work habits. Pressures to produce more work on time and
Limited Occupancy 5-24
Requirements of a Written
Program 5-29
Confined Space Regulations for
Collection System Workers 5-36 Trenching and Excavation Safety 5-37
Ladder Safety 5-39
Signage and Traffic Patterns 5-49 Safety Considerations in Plant Design 5-51 Accident Reporting and Investigation 5-52 Occupational Safety and Health
Administration 300 Logs 5-53 Safety Programs and Administration 5-53 Management Responsibilities 5-62 Employee Responsibilities 5-62
Training 5-63
References 5-64
Suggested Readings 5-66
more cheaply actually create an atmosphere or culture in which administrators may say the right things but really do not mean them. The term buy-in has become popular in management training, and it is used to signify an emotional investment in a topic.
Management tries to get workers to “buy-in” to a program. The programs can range from profit sharing, to disciplinary actions, to esprit de corps, to safety. It is the re-sponsibility of management to ensure that personnel understand the idea of working safely. Management can accomplish this in many ways, including through training, disciplinary action for unsafe work, on-site inspections, bonuses for employees, and fostering willing participation in safety programs by paying for them. It is easy for management to talk about safety without paying for it, especially in current times, when there seems to be no extra income to establish or maintain such programs. Some examples of this would be failing to provide the following: compensation for safety shoes for people who require steel-toed shoes, on-site training before workers use new equipment, or annual hearing tests for workers who regularly work where there is noise greater than 85 dB. Management must make sure that any initiative that is started is well-funded and continued. One of management’s many responsibilities is to estab-lish a work culture that embraces and supports safe work practices.
Workers bear much responsibility in this attitude also. After all, when the worker is out in the field, he or she is the one doing the work, and he or she bears the results of his or her own actions. If he or she does not, those working closely with him or her will.
The wastewater treatment profession is fraught with danger. Wastewater treatment professionals work around many different kinds of hazards, including electrical, bacte-riological, viral, confined space, engulfment, mechanical hazards, and simple hazards, such as oncoming traffic and traffic control. The job requires the worker to maintain awareness at all times.
It would be nice to believe that everyone in the world wished protection, advance-ment, fulfilladvance-ment, and the best for their fellow humans. It is sad that this is not always the case. Workers are sometimes careless because “it is not their problem”, or a worker may think “nobody will know if I do . . . “, or workers may be thinking about personal problems while working. Management sometimes will have financial constraints or be apathetic toward their laborers. Other times, poor judgment is involved that leads to injuries. A biosolids hauler once washed out his trailer with a power washer and en-tered the tank without thinking. He died within minutes from lack of oxygen. He may have been insufficiently trained or simply made a mistake; either way, he paid for this mistake with his life. It is essential that workers make sure that their place of work ac-tually has a safety culture and does not just discuss one.
To protect workers who sometimes can be taken advantage of by administrative poli-cies that may not have the worker’s health as the primary concern, the federal
govern-ment created the Occupational Safety and Health Administration (OSHA) by passing the Occupational Safety and Health Act of 1970 (CFR 1910; Occupational Safety and Health Hazards, 2005) (there is a construction section of law, CFR 1926, that is pertinent to the wastewater treatment industry because it deals with trenching, ladders, and other things that collection system maintenance and infrastructure repair crews deal with). It is OSHA’s responsibility to ensure the safety of the worker by setting up rules and regulations that protect the worker.
Oddly enough, there are many workers who are not be covered by the OSHA safety rules. Some federal and state workers do not fall under the jurisdiction of the regulation. Also, the employer (town, special district, or municipality) must have a minimum of nine employees to be held to these regulations. As an administrator or su-pervisor, it is important to realize that all subcontractors who enter your facility to perform work must meet your safety and training standards. They are your responsibility. Still, the OSHA regulations are the industry safety standards for much litigation. They will be considered as the baseline for safety guidelines in this text. Most often, employers must realize that they fall under the general duty clause of the OSHA regulations.
The drafters of the Occupational Safety and Health Act also realized that they could not cover every set of circumstances that might arise in a safety and health haz-ard situation. So, they included a General Duty Clause, which states, in Section 5(a)1,
“Duties”, the following:
(a) Each employer
(1) Shall furnish to each of his employees employment and a place of employ-ment which are free from recognized hazards that are causing, or likely to cause, death or serious physical harm to his employees.
(2) Shall comply with occupational safety and health standards promulgated under this Act.
(b) Each employee shall comply with occupational safety and health standards and all rules, regulations, and orders issued pursuant to this Act which are ap-plicable to his own actions and conduct.
The OSHA General Duty Clause is the catch-all for employer compliance. If OSHA cannot issue a citation based on a specific regulation, it will cite under the Gen-eral Duty Clause. Remember, as an employer, you must provide a safe workplace for your employees. Mere compliance with all OSHA regulations may not be enough.
You must endeavor to ensure that your employees are safety conscious in all activities at your facility.