Water Pollution Standards: Defining Safe Water Quality

Water quality standards are an essential tool for maintaining and improving the health of our water bodies, including lakes, rivers, and oceans, which are vital for human health, the environment, and economic prosperity. These standards are set by states, territories, and authorized tribes, and they outline the desired conditions of water bodies and the measures needed to achieve and maintain those conditions. The Clean Water Act (CWA) is a key piece of legislation that regulates water pollution by prohibiting the discharge of pollutants into water bodies without a permit and setting technology-based effluent guidelines for treatment technologies. States play a significant role in managing nonpoint source pollution, such as agricultural runoff, and are responsible for setting water quality standards, monitoring, and identifying impaired water bodies. Water quality criteria, designated uses, and antidegradation requirements are the core components of water quality standards, ensuring that our water resources are protected for current and future generations.

Water Pollution Standards

Water Quality Standards (WQS)

WQS consist of three core components: designated uses of a water body, criteria to protect these designated uses, and antidegradation requirements to protect existing uses and high-quality/high-value waters. Designated uses include the protection and propagation of fish, shellfish, and wildlife, as well as agricultural, industrial, navigational, and recreational purposes. States, territories, and authorized tribes are required to specify goals and expectations for how each water body is used and to adopt water quality criteria to protect these designated uses. These criteria can be numeric (e.g., maximum pollutant concentration levels) or narrative (e.g., a criterion describing the desired condition of a water body).

States play a key role in managing water pollution from nonpoint sources, such as runoff from farms, parking lots, or streets, which is the leading cause of pollution of the nation's waters. They set water quality standards, monitor water quality, and identify water bodies that do not meet their standards. For waters that do not meet the standards, states must develop Total Maximum Daily Loads, or pollutant budgets, which are then approved by the EPA. The EPA and the states then work together to restrict pollution to these levels, such as by providing incentives to landowners to reduce nonpoint source pollution.

The Clean Water Act (CWA) is a principal piece of legislation in this area, aiming to "maintain the chemical, physical and biological integrity of the Nation's waters." Under the CWA, it is unlawful for any person to discharge any pollutant from a point source into waters of the United States without a permit from the EPA or an authorized state. The EPA issues technology-based effluent guidelines and discharge standards based on available and economically achievable treatment technologies. The EPA also regulates waste streams generated from offshore oil and gas activities and provides significant financial and technical resources to assist utilities in repairing and replacing their infrastructure in the face of extreme weather events caused by climate change.

Clean Water Act (CWA)

The Clean Water Act (CWA) is the primary federal statute regulating the protection of the nation's water. The CWA aims to prevent, reduce, and eliminate pollution in the nation's waters to "restore and maintain the chemical, physical, and biological integrity of the Nation's waters". The CWA is the principal law governing pollution control and water quality in the nation's waterways. It establishes conditions and permitting for discharges of pollutants into the waters of the United States under the National Pollution Discharge Elimination System (NPDES).

The CWA was enacted in 1948 as the Federal Water Pollution Control Act and was significantly reorganized and expanded in 1972, with subsequent major amendments in 1977 and 1987. The 1972 amendments led to the law becoming commonly known as the Clean Water Act. The CWA establishes the basic structure for regulating discharges of pollutants into the waters of the United States and regulating quality standards for surface waters. Under the CWA, the Environmental Protection Agency (EPA) has implemented pollution control programs such as setting wastewater standards for industry and water quality standards for all contaminants in surface waters.

The CWA prohibits the discharge of pollutants from point sources into waters of the United States without a permit from the EPA or an authorized state. The EPA issues technology-based effluent guidelines that establish discharge standards based on available and economically achievable treatment technologies. The CWA also addresses nonpoint source pollution, which is the leading cause of pollution in the nation's waters, and has funded the construction of sewage treatment plants.

Water quality standards (WQS) are provisions of state, territorial, authorized tribal, or federal law approved by the EPA that describe the desired condition of a water body and how that condition will be achieved or protected. States, territories, and authorized tribes establish WQS to protect human health and aquatic life in these waters. WQS consist of three core components: designated uses of a water body, criteria to protect designated uses, and antidegradation requirements to protect existing uses and high-quality/high-value waters. States, territories, and authorized tribes typically adopt both numeric (e.g. maximum pollutant concentration levels) and narrative (e.g. describing desired conditions) criteria.

Criteria and conditions

Water quality standards (WQS) are provisions of state, territorial, or federal law approved by the EPA that describe the desired condition of a water body and the means by which that condition will be protected or achieved. These standards are an important tool for restoring and maintaining healthy water quality for lakes, rivers, streams, estuaries, and other waters. WQS form the legal basis for controlling pollutants entering the waters of the United States.

WQS criteria are elements of state water quality standards, expressed as constituent concentrations, levels, or narrative statements, representing a quality of water that supports a particular use. When criteria are met, water quality will generally protect the designated use. States, territories, and authorized tribes adopt water quality criteria to protect the designated uses of a water body. These criteria can be numeric (e.g., the maximum pollutant concentration levels permitted in a body of water) or narrative (e.g., a criterion that describes the desired condition of a water body being "free from" certain negative conditions).

States, territories, and authorized tribes are required to specify goals and expectations for how each water body is used. Typical designated uses include the protection and propagation of fish, shellfish, and wildlife, as well as agricultural, industrial, navigational, and recreational purposes. For example, in Minnesota, water quality standards protect water bodies used for drinking water, swimming, fishing, irrigation, and more.

To implement and maintain these standards, states must review water quality data and information on discharges to identify specific water bodies where toxic pollutants may be adversely affecting water quality or designated water use. States must then adopt criteria for such toxic pollutants to protect the designated use. The EPA also plays a crucial role in providing guidance and approving state plans, such as in the case of mercury's effects on wildlife, where the EPA or the state, with EPA approval, must implement a monitoring program to assess the attainment of water quality standards.

Additionally, states play a key role in managing water pollution from nonpoint sources, such as runoff from farms, parking lots, or streets, which is the leading cause of pollution of the nation's waters. States set water quality standards, monitor water quality, and identify water bodies that do not meet their standards. For waters that do not meet the standards, states must develop Total Maximum Daily Loads, or pollutant budgets, which the EPA approves. The EPA and the states then work together to restrict pollution to these levels, such as by providing incentives to landowners to reduce nonpoint source pollution.

Nonpoint source pollution

NPS pollution generally results from land runoff, precipitation, atmospheric deposition, drainage, seepage, or hydrologic modification. As an example of NPS pollution, consider what happens after a heavy rainstorm. Water will flow across a parking lot and pick up oil left by cars driving and parking on the asphalt. This runoff then runs over the edge of the parking lot and eventually empties into a stream, taking pollutants with it. NPS pollution can also result from lawn fertilization, applying pesticides, road construction, or building construction.

Controlling NPS pollution requires improving the management of urban and suburban areas, agricultural operations, forestry operations, and marinas. Urban and suburban areas are a major source of NPS pollution due to the large amount of runoff produced by paved surfaces such as asphalt and concrete. These surfaces are impervious to water, so any water that comes into contact with them will run off and be absorbed by the surrounding environment. Construction sites typically implement simple measures to reduce NPS pollution, such as erecting sediment or silt fences and laying grass or straw along their borders.

Agricultural operations account for a large percentage of NPS pollution in the United States. When large tracts of land are plowed to grow crops, the soil is exposed and loosened, making it more vulnerable to erosion during rainstorms. Farms with large livestock and poultry operations, such as factory farms, are often point source dischargers. Other agrochemicals such as pesticides and fungicides can enter environments from agricultural lands through runoff and deposition as well.

Effluent limitations

The US Environmental Protection Agency (EPA) is responsible for issuing Effluent Guidelines, which are national regulatory standards for wastewater discharged into surface waters and municipal sewage treatment plants. These guidelines are industry-specific and based on the performance of treatment and control technologies. Pollutant discharges regulated by Effluent Guidelines must be measured using approved analytical methods to ensure accurate monitoring and compliance.

The EPA establishes different types of effluent limitations, including Best Practicable Control Technology (BPT), New Source Performance Standards (NSPS), and Best Conventional Pollutant Control Technology (BCT). BPT limitations are based on the average performance of facilities within an industry, considering factors such as age, size, and processes. NSPS, on the other hand, reflect achievable effluent reductions based on the "best available demonstrated control technology." This allows new sources to implement the most efficient wastewater treatment technologies, ensuring more stringent controls for all types of pollutants. BCT, as defined in CWA section 304(b)(4), addresses conventional pollutants from existing industrial point sources, with the EPA considering the cost-reasonableness of implementing these limitations.

Additionally, the EPA has identified specific pollutants as conventional, including biochemical oxygen demand (BOD5), total suspended solids (TSS), fecal coliform, pH, and oil and grease. Beyond these conventional pollutants, the agency has also designated 65 pollutants and classes of pollutants as "toxic," with 126 specific substances considered "priority" toxic pollutants. These classifications help states, territories, and authorized tribes develop water quality standards and effluent limitations to protect their water resources effectively.

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