Drinking Water Quality Standards – The Complete Guide

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The supply of safe drinking water is vital to the sustenance of life, and most developed countries recognize this access as a fundamental human right. The risks associated with drinking contaminated water have been a significant concern since the 20th century, especially as they pertain to preventable diseases.

Different countries have municipal and federal drinking water guidelines in addition to the international regulations spelled out by organizations like WHO.

What are Water Quality Standards?

Water quality standards are law provisions that describe the favorable condition of a water body and the methodology by which the stated condition will be preserved. These standards are meant to protect human and aquatic life by controlling pollution.

Water quality standards have various components, including the designated uses of the water body. Regions and territories are required to determine the goals and expectations of various water bodies. These purposes include drinking water, recreation, protection and propagation of aquatic life, and industrial and agricultural uses.

The water use is determined by analyzing the existing uses and the potential to dictate other purposes based on the analysis of the hydrological, chemical, biological, and physical attributes of the water as well as the financial implications of implementing the uses.

The territories also have to identify water quality criteria to safeguard the designated purposes of a water body. Such criteria can use numeric descriptions like the maximum pollutant levels allowed in a water body or narrative requirements.

Water quality standards also include an antidegradation policy that offers a framework for maintaining the water quality that has been achieved. These requirements protect the existing uses of a water body and those waters that have a higher quality than necessary. Different territories can also implement general policies, including low-flow regulations and mixing.

Who sets Water Quality Standards?

Most developed nations specify standards to be enforced in their territories. Developing countries without a framework for water quality standards use the guidelines provided for by the World Health Organization (WHO).

In the US, water quality standards are provided for by laws and regulatory bodies. The Safe Drinking Water Act (SDWA) addresses water designated for human consumption and spells out the standards for public water treatment facilities.

It acts as the chief federal law that ensures the safety of drinking water. This law is overseen by the United States Environmental Protection Agency (EPA) and it ensures that the states, localities, and localities observe these standards.

It is not required of states to establish secondary water quality regulations. The Clean Water Act (CWA) protects water bodies with standards guided by the intended uses for the specific water body. The American Water Works Association publishes guidelines that address the construction of water treatment plants and treatments.

The European Union has its drinking water policy that includes the European Drinking Water Directive (EDWD), which is published in 24 different languages. Member nations are obligated to enact local legislation to guide the mandate.

Regular inspection is mandated, and penalties can be imposed on non-compliant states. The water policy of the EU has been codified by the Water Framework Directive (2000), the Drinking Water Directive (1998), and the Directive on Urban Waste Water Treatment.

The UK observes various water quality standards and regulations. The Environment Agency maintains water standards in England, and the Scottish Environment Protection Agency (SEPA) is the regulatory authority in Scotland.

The regulatory bodies in Northern Ireland and Wales are the Environment and Heritage Services (EHS) and Natural Resources Wales (NRW), respectively. Businesses in the UK must access an environmental permit if they intend to direct any waste to water bodies.

What is TOC Level of Water?

Total Organic Carbon (TOC) measures the amounts of organic molecules or contaminants in purified water and aqueous systems. Water will naturally contain organic contaminants in various degrees from industrial and domestic wastewater.

Pollutants like herbicides and pesticides drain into water systems via rainwater runoff. The TOC test seeks to find out just how much organic content there is in water since water treatment does not entirely remove these elements.

TOC measures a variety of elements, including:

  • TC- Total Carbon
  • POC- Purgeable Organic Carbon
  • NPOC- Non-Purgeable Organic Carbon
  • TIC- Total Inorganic Carbon
  • DOC- Dissolved Organic Carbon
  • NDOC- Non-Dissolved Organic Carbon

TOC analysis involves sampling, oxidation, and detection. The sampling can either be done off-line or on-line. In off-line measurements, water samples are gathered in containers and taken to the laboratory.

This method is ideal when the TOC requirement for pure water is below 50 ng/g (ppb) since the chances of contamination are higher. In on-line measurements, the instrument is directly linked to the purified water body.

The oxidation step involves the use of instruments to oxidize organic molecules. Different oxidization methods are used to turn TC into carbon, including chemical oxidation, photocatalytic oxidation, and high-temperature combustion.

Why do We Need Water Quality Standards?

Water quality standards protect the current and potential uses of water in addition to benefits like:

Protect Human Health

There are many health risks that polluted water pose on human health. Most of the pollution is linked to domestic sewage that contains solid waste, bacterial contaminants, and plastics.

Industrial waste also contains hazardous elements like toxic metals Contaminated water is the primary cause of water-borne diseases, especially in developing countries. The water has also been linked to cardiovascular illnesses and neurological disorders as well as respiratory diseases and various types of cancer.

Promote Tourism

Coastal territories are popular tourist spots for bathers and enthusiasts of water sports. Water quality standards ensure that these water bodies are safe for tourist use and help to boost the industry. Water quality also influences ecotourism by protecting the habitats of wildlife and plants.

Discouraging Future Costs

It is more economical to protect wetlands from contamination than to address it once it has taken place. Pollution is also a complicated affair as it will reach the downstream populations. Territories may be forced to address contamination that happened in another region.

Cultural and Religious Significance

In some territories, some religious and cultural beliefs and practices are linked to water bodies. Rivers, lakes, and oceans provide populations with pride, where they rely on the wetlands for day-to-day activities. It is, therefore, paramount to protect aquatic resources for the people that live around water bodies as well as the beneficiaries of the water supply.

How to Measure Water Quality?

Several parameters are used to determine water quality, including:


The water temperature can be determined by devices like thermocouples, digital temperature sensors, and thermometers. Temperature has a significant effect on organisms that inhabit or reproduce in water since they can only tolerate a particular temperature range.

If this range is exceeded, their growth and reproduction will be affected, and they can die. Temperature also influences the rate of photosynthesis and oxygen levels.

Bacteria and macro-invertebrates

Bacteria are measured to analyze the risk of falling risk from interacting with the surface waters of a water body. Bacteria find their way into water through the wastes of warm-blooded animals, and their presence relates to the presence of pathogens.

Organisms like leeches and prawns play a significant role in the food web and are therefore good indicators of pollution.


PH conveys the alkalinity or acidity of water and is determined on a scale of 1 to 14. Tap water is typically neutral, while most organisms will thrive in a PH between 6 to 9. Pollution can easily alter the PH of the water and increase the amount of ammonia in water.

PH supports many biological processes in animals, which is why the delicate PH balance in wetlands should be maintained. PH is measured by water test kits or PH sensors for more accurate values.

Dissolved Oxygen

Dissolved oxygen (DO) estimates the level of oxygen available to the aquatic flora and fauna and is given as percent saturation or mg/L. A DO level of less than 6 mg/L is undesirable and harmful for plants and animals. Low DO levels are linked to the excessive presence of nutrients in the water and other forms of organic matter.


Turbidity determines water clarity, and the higher the measurement, the dirtier the water. Turbid water appears cloudy due to suspended fine sediments in the water column. Light penetration is often poor in these kinds of waters, and it affects aquatic life and recreational activities. Causes of water turbidity include land disturbance and the erosion of river banks.

Hazardous Substances

Toxic substances often find themselves in water bodies via pollution, and they pose health risks. Some of these substances, like mercury, accumulate in human tissues over time and cause health issues. Other toxic elements include ammonia, lead, copper, and arsenic.

How to Purify Drinking Water?

There are many purification techniques that homeowners can use to make water safe for consumption. They include simple methods like boiling and using chlorine drops to more sophisticated practices like the use of ultraviolet light.

Water filters remain one of the most effective purification methods. These systems typically use activated carbon to absorb contaminants, since it has been shown to remove around 81 pollutants as well as unpleasant tastes and odors. The inner filter cartridge should be replaced periodically to ensure it is effective.


Water quality standards ensure that a water body’s use is clearly spelled out, and it is protected accordingly. Different countries have legal guidelines and bodies that enforce the regulations.

These standards not only ensure that the water is safe for human health but also promote ecotourism and the cultural significance of various wetlands.


This is George, the Aquaman, editor at AquaMantra. I'm a water quality analyst by profession, and used to work at one of the largest water bottler company.
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