Water Quality Metrics

by

Tanja Srebotnjak

• LAST REVIEWED: 28 August 2018
• LAST MODIFIED: 28 August 2018
• DOI: 10.1093/obo/9780199363445-0102

Introduction

Water is a critical resource for sustaining life on earth. Water quality and quantity are closely linked, as a decline in water quantity is typically associated with deteriorating water quality, while water of poor quality limits its usability. Water quality has important environmental, societal, and economic implications. Good water quality contributes to healthy ecosystems, while pollution can negatively affect aquatic species survival, shift the nutrient balance in water bodies, change the physical and chemical composition of the water, and reduce the amount of sunlight penetrating the water, thus changing patterns of aquatic plant growth and the decomposition of organic matter. For society, water quality is closely linked to human health. The contact, ingestion, or inhalation of polluted water can cause acute and chronic health problems. Worldwide, the number of cases of waterborne diseases related to unsafe water and sanitation is estimated to be in the millions. Diarrheal cases alone cause an estimated two million deaths annually, most of them in young children. In addition, poor water quality and inadequate sanitation can negatively impact food security, the livelihoods, and educational opportunities, especially for the poor. Governments, therefore, typically regulate water quality for different water uses and environmental objectives. The United Nations and its partner organizations specified Sustainable Development Goal 6: Ensure access to water and sanitation for all. From an economic perspective, water quality impacts many sectors, including agriculture, manufacturing, and tourism. Managing water quantity and quality sustainably is critical for human well-being and prosperity and this recognition led to the scientific study of water quality indicators and metrics. Typical parameters used to assess water quality can be divided into physical (e.g., temperature, color, taste, turbidity), chemical (e.g., electrical conductivity, major cations and anions, pH, metals, phosphorus, and organic material), and biological (e.g., fecal coliform). Water quality indices then aggregate subsets of these parameters in ways that are useful for determining the usability of the water for specific purposes, e.g., bathing, irrigation, desired ecological condition, and determining trends over time and space. In particular, to make judgments about whether water meets certain regulatory or desired ecological criteria, water quality indices (WQI) incorporate threshold values or rating curves. Since water quality depends on many local environmental factors and its measurement can serve a multitude of purposes, numerous approaches have emerged. Many of these have seen nuanced adaptations to fit particular situations.

General Overviews

There are numerous general reference sources available on water quality measurement. They range from the technical guides for sampling and measuring specific water quality parameters to scientific texts on the ecological, physical, chemical, and biological processes that influence water quality at local sites to watershed scales. Among the practical guides is Standard Methods for the Examination of Water and Wastewater by the American Public Health Association in 2017. In its twenty-third edition it is a widely used source for analyzing natural waters, water supplies, and wastewaters. A very accessible and broad overview is given by Boyd 2015. Goel 2006 focuses on the causes and mechanisms of water pollution and how it can be mediated; this publication is suitable for non-technical readers. Considering its importance for human health and well-being, numerous texts focus specifically on drinking water quality. The American Water Works Association 2011 covers state-of-the-art technologies and methods for water treatment and quality control. De Zuane 1997 reviews a wide range of parameters, including physical, chemical, microbiological, carcinogenic, and ionizing radiation metrics, from public health, regulatory, and treatment perspectives. Spellman 2017 takes a life cycle approach to water. Starting at the source, it tracks and explains the processes used to ensure drinking water safety, including water extraction at source, treatment, and distribution to the tap, and ultimately its use and reuse. Written for an engineering audience, Benjamin and Lawler 2013 explains the fundamental physics, chemistry, and mathematics of water and wastewater treatment processes. Dodds 2002 focuses on the freshwater ecology community and couples discussions of water quality parameters with limnology, ecology, and freshwater ecosystem management.

• American Public Health Association, American Water Works Association, Water Pollution Control Federation, and Water Environment Federation. 2017. Standard methods for the examination of water and wastewater. Washington, DC: American Public Health Association.

  This publication is mainly for practitioners, such as laboratory technicians, and describes more than four hundred laboratory methods for the analysis of dissolved solids, metals, free and total chlorine, odor, taste, disinfection by-products, radionuclides, total organic carbon, total and fecal coliform and other parameters. The methods explained reflect the best available, generally accepted procedures for analyzing water, wastewater, and related water quality aspects.

• American Water Works Association. 2011. Water quality & treatment: A handbook on drinking water. 6th ed. New York: McGraw-Hill.

  This book provides comprehensive and current coverage of technologies and methods for water treatment and quality control. The book’s chapters cover topics such as drinking water standards, regulations, goals, and health effects, a broad range of physical, chemical, and biological water treatment processes, as well as issues related to corrosion and deposition control, quality control in distribution systems, and options for the management of wastewater treatment plant residuals.

• Benjamin, M. M., and D. F. Lawler. 2013. Water quality engineering: Physical/chemical treatment processes. Hoboken, NJ: John Wiley & Sons.

  This publication describes the fundamentals of physical and chemical treatment processes for water and wastewater. It uses many examples to illustrate water treatment challenges and step-by-step mathematical calculations.

• Boyd, C. E. 2015. Water quality: An introduction. Cham, Switzerland: Springer.

  DOI: 10.1007/978-3-319-17446-4

  This book explains the basic aspects of water quality, focusing on the physical, chemical, and biological factors influencing water quality. It draws on a variety of disciplines, including chemistry, biology, mathematics, physics, engineering and resource management, while providing sufficient depth to highlight the key mechanisms and processes.

• De Zuane, J. 1997. Handbook of drinking water quality. New York: John Wiley & Sons.

  This is a handbook of the most important water quality parameters and the processes for sampling and monitoring them. It also includes a chapter on federal regulations relating to surface and groundwater.

• Dodds, W. K. 2002. Freshwater ecology: Concepts and environmental applications. San Diego, CA: Academic Press.

  This book presents a broad and current discussion of freshwater ecology starting with the basic chemical and physical properties of water to presenting mainstream concepts of community ecology and ecosystem relationships relevant for continental waters.

• Goel, P. K. 2006. Water pollution: Causes, effects and control. New Delhi: New Age International.

  This book covers virtually all aspects of water pollution and is geared toward readers with backgrounds or interests in environmental science, life sciences, environmental engineering, pollution control, and regulatory mechanisms.

• Spellman, F. R. 2017. The drinking water handbook. Boca Raton, FL: CRC Press.

  DOI: 10.1201/9781315159126

  This book traces the steps, and processes involved, for water to reach the consumer’s tap as safe drinking water, including extraction at source, quality treatment, delivery, and treatment for release back into the environment, and economic issues. In doing so, the book covers important concepts and regulations and identifies current problems with the water supply.