Water-Pollution Control

Summary

Water pollution control is a multidisciplinary field that endeavors to reduce or eliminate the discharge of chemical and biological compounds into natural waterways. Legal standards set a level playing field so that the economic burdens and opportunities fall with approximate equality for all enterprises, industries, and municipalities.

Definition and Basic Principles

Water pollution control involves preventing excessive contaminants from reaching any usable watercourse. Understanding the various contaminants that may enter a body of water is essential to this subject. It is also necessary to understand the extent of the reactions of receiving waters to wastewater discharges.

Water pollution itself has such a commonly understood everyday meaning that the definition can appear almost unnecessary. However, scientific measurement and legal enforcement require precise definitions. The Clean Water Act defines “pollutant” as “dredged spoil, solid waste, incinerator residue, sewage, garbage, sewage sludge, munitions, chemical wastes, biological materials, radioactive materials, heat, wrecked or discarded equipment, rock, sand, cellar dirt and industrial, municipal, and agricultural waste discharged into water” (33 U.S.C. Sec. 1362). Toxic pollutant is separately defined to mean those that “after discharge and upon exposure, ingestion, inhalation or assimilation into any organism, either directly from the environment or indirectly by ingestion through food chains, will… cause death, disease, behavioral abnormalities, cancer, genetic mutations, physiological malfunctions” in organisms or their offspring. The act then references a table of toxic pollutants assembled by the Committee on Public Works of the House of  Representatives. It authorizes the administrator of the Environmental Protection Agency (EPA) to add additional pollutants to the list.

Organic wastes include fecal material from humans and animals, either from municipal sewage systems or concentrated livestock agriculture. Most water naturally has some minerals dissolved in it, which vary by locality. When higher concentrations of iron, copper, chromium, platinum, mercury, nickel, zinc, and tin are discharged into waterways because of mining or industrial operations, the concentration can be toxic to aquatic life and cause metabolic diseases or cancer in humans who drink or bathe in the water. Discharges of petroleum and a tremendous number of oil-derived hydrocarbon compounds are toxic or carcinogenic. Common fertilizers, based on phosphorous and nitrogen compounds, cause overgrowth of some aquatic plants, particularly algae.

Background and History

Cities have had sewers and drains since ancient times, but only to flush raw sewage into nearby rivers to be carried away by the current. This certainly contributed to many plagues and epidemics, including the spread of cholera in the nineteenth century. From the dawn of the Industrial Revolution, manufacturing and mining have routinely been located near water sources because water is used in industrial processes, and water sources are convenient places to dump waste products. In the United States, concern that refuse and pollutants were creating obstacles to safe navigation inspired the federal Rivers and Harbors Appropriation Act of 1899. Not until the Federal Water Pollution Control Act of 1948 did the first federal legislation tentatively address water pollution as a hazard to human life and safety.

The Federal Water Pollution Control Act Amendments of 1972 established the first comprehensive regulatory framework for water pollution control. Similar measures emerged in North America, Europe, Australia, and Japan during the 1960s and 1970s. Some nineteenth-century precedents include attempts in Britain to regulate primary manufacturing sources of pollution and secure clean water for household use, German legislation allowing local authorities to place conditions on manufacturing methods, and Dutch laws aimed at controlling hazards and nuisances from industrial sources. Still, the German Civil Code of 1873 was typical of the era. It set forth that individuals should tolerate pollution as it was essential to economic development.

In April 2024, the Environmental Protection Agency (EPA) announced the first legally enforceable standard concerning the standards, transparency, and testing of drinking water for around 100 million Americans. The new rule aims to limit perfluoroalkyl and polyfluoroalkyl substances (PFAS) in drinking water as part of the EPA’s PFAS Strategic Roadmap. PFAS are "forever chemicals" known to negatively impact the liver, heart, immune system, and developmental processes. Limiting these chemicals to 4.0 parts per trillion for PFAS and requiring around 66,000 water systems to report levels of such chemicals is likely to reduce human exposure to PFAS and better inform the public about the contents of their drinking water.

How It Works

Water pollution laws in the United States, since the adoption of the Clean Water Act of 1972, begin with the baseline standard that the discharge of any pollutant by any person into any navigable waterway or tributary flowing into a navigable waterway, is prohibited. Since immediate adherence to this standard could prove physically and economically infeasible, the law provides that any exception must be authorized by a permit issued under the National Pollutant Discharge Elimination System (NPDES), either by the EPA or an authorized state agency. The type of pollutants allowed, concentration, and total amount are specified in the license. The standard for issuing permits requires the use of the best available technology to reduce or eliminate water pollution. The ruling agencies have also weighed the economically practical cost.

Treatment Methods. Three common types of treatment are known as primary treatment, secondary treatment, and tertiary treatment. Primary treatment extracts pollutants that will settle out by grit removal, screening, grinding, and sedimentation. Secondary treatment utilizes the natural degradation of organic wastes by biological oxidation, using activated sludge, trickling filters, and oxidation ponds. Tertiary treatment involves a wide range of chemicals to remove substances that remain in water after primary and secondary treatments. Sludge removed in either of the first two stages must be disposed of, sometimes by incineration, sometimes by landfill. Tertiary treatment uses chemical and electrical processes to remove more elusive nonorganic pollutants.

Point and Nonpoint Source Pollution. Point source pollution comes from a discrete, easily identifiable source, such as a pipe. Responsibility can be established, chemical content and volume measured, and controls put in place. Nonpoint source pollution enters a watershed through runoff from large areas, such as agricultural land, paved urban surfaces draining into storm drains, even lawns and golf courses, or in precipitation, as in the case of acid rain. While most federal law addresses point source pollution, Section 319 of the Clean Water Act authorized the EPA's Nonpoint Source Management Program (NSMP), which provides grants to states, territories, and tribes, and calls for state-level plans to implement measures for nonpoint source pollution control.

Applications and Products

The two sources of water pollutants most effectively targeted by NPDES are manufacturing and domestic waste. Most of the latter enter municipal sewage systems, as does some manufacturing waste. Industries must sometimes pretreat their effluent before discharging it into municipal sewers. This is more difficult to enforce than a specific factory with its discharge system into a river or lake.

Physical Technology. One of the first steps in primary treatment is a screening system to remove large objects. Removing grit often requires a conveyor system, which allows sand and dirt to settle out of the water stream. The activated sludge process is one of the most visually familiar to anyone who has viewed a common wastewater treatment plant—large concrete tanks with walkways between them, continually agitated by rotary aerators to mix oxygen into the sludge, which hastens biological processes to break down organic compounds. Thermal conditioning units and a pressure cooker digest sludge and separate most water from the sludge. Sludge is further dried by vacuum-filtration equipment—a rotating roll spread with sludge with a vacuum applied through the roll to extract more water, leaving a semi-dried cake that falls off. This can be disposed of in a landfill but is often incinerated.

Chemical Processes. The tertiary treatment uses many methods to remove pollutants that do not settle out in primary or secondary treatment. These include coagulation, flocculation, nitrification, denitrification, adsorption, ion exchange, and electrodialysis. These have high capital investment and operation costs and require highly skilled personnel for operation and maintenance. Flocculation removes solids suspended in water—but it is ineffective in removing dissolved compounds. The name derives from “floc,” a clumping of different precipitated materials. Generally, one or more chemicals are added to the water being treated, which form a gel or other precipitate that attracts other suspended materials. One common combination is potassium aluminum sulfate and ammonia, which react to form aluminum hydroxide. Adsorption introduces powdered activated carbon to remove even small traces of pollutants. Since there is no chemical bonding, recovered pollutants can be collected and cycled back into industrial processes, offsetting costs or generating a net profit. Adsorption technology is appropriate for the removal of heavy metals and complex organic compounds, including pesticides, silicates, aluminum compounds, wood- and petroleum-based carbon compounds, and resins.

Careers and Course Work

A wide variety of careers are available in the public, private for-profit, and private not-for-profit sectors. These include the design, manufacture, and operation of wastewater treatment facilities by municipal government and industrial sources. Most government jobs relate to enforcing water pollution control laws, preparing long-term strategies, or reviewing and funding research projects. Water is one of four program divisions within the EPA, which also has a research and development program concerned partly with water pollution. EPA includes ten regional offices and laboratories and a network of laboratories and research centers. Many careers in this field involve measuring existing pollution, establishing what is and is not a hazardous substance and what concentrations are tolerable, advocating for new measures, and litigation.

Undergraduate degrees in environmental science typically require courses in biology, natural history, soil science, geology, chemistry, physics, calculus, instrumental methods of analysis, scientific presentations, and interdisciplinary courses such as principles of life sciences, understanding the earth, and ecology. Some colleges offer specific courses on pollution control technology, toxicology, water quality analysis and management, solid waste management, industrial hygiene, and water pollution biology. In addition to graduate programs in environmental science, many law schools offer degree programs in environmental law, including courses on water pollution control, natural resources law, regulation of toxic substance risk, and environmental issues in business transactions.

Environmental law is a considerable specialty requiring a law degree for attorneys and coursework with a specific emphasis on environmental law for paralegals, preferably with relevant science courses. Understanding the facts to be litigated requires a basic undergraduate familiarity with chemistry and biology. Legal practice options include working for government enforcement agencies at the state or federal level, defending alleged polluters against administrative or judicial actions, advising businesses on compliance, and representing advocacy organizations in civil actions.

Monitoring pollutants requires processing and analyzing vast quantities of data, which requires complex computer software. The EPA has used software called BASINS (Better Assessment Science Integrating Point and Nonpoint Sources) to perform assessments of water quality and of specific watersheds. Compliance with detailed regulations requires software for enforcement and to help businesses integrate compliance into their daily operation.

Social Context and Future Prospects

Many companies of various sizes and maturity supply instrumentation for water quality monitoring, sanitation systems, water storage systems, filtration systems, chemicals to neutralize pollutants (adding a basic compound to neutralize an acid or vice versa), piping and pumping equipment, and a variety of components and wastewater treatment products. The market is considered stable in the United States and other comparable nations.

It is also likely to expand exponentially in developing nations. Countries like China are expected to continue developing their research and production. Finding new methods to make reclaiming and recycling into profitable operations is an open area of study with much to discover. More efficient methods of recovery, which would bring the cost of reclaiming metals in particular below the cost of purchasing newly mined quantities, have yet to be thoroughly explored.

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