Water quality

[1][2] It is most frequently used by reference to a set of standards against which compliance, generally achieved through treatment of the water, can be assessed.

[3] Over time, there has been increasing recognition of the importance of drinking water quality and its impact on public health.

[4] The understanding of the links between water quality and health continues to grow and highlight new potential health crises: from the chronic impacts of infectious diseases on child development through stunting to new evidence on the harms from known contaminants, such as manganese with growing evidence of neurotoxicity in children.

Water drawn directly from a stream, lake, or aquifer and that has no treatment will be of uncertain quality in terms of potability.

[11] Communities that lack these clean drinking-water services are at risk of contracting water-borne and pollution-related illnesses like Cholera, diarrhea, dysentery, hepatitis A, typhoid, and polio.

[12] These communities are often in low-income areas, where human wastewater is discharged into a nearby drainage channel or surface water drain without sufficient treatment, or is used in agricultural irrigation.

The most familiar of these is probably the presence of calcium (Ca2+) and magnesium (Mg2+) that interfere with the cleaning action of soap, and can form hard sulfate and soft carbonate deposits in water heaters or boilers.

[15] The necessity for additional calcium and magnesium in water depends on the population in question because people generally satisfy their recommended amounts through food.

Toxic substances and high populations of certain microorganisms can present a health hazard[17] for non-drinking purposes such as irrigation, swimming, fishing, rafting, boating, and industrial uses.

Given the landscape changes (e.g., land development, urbanization, clearcutting in forested areas) in the watersheds of many freshwater bodies, returning to pristine conditions would be a significant challenge.

Sampling of water for physical or chemical testing can be done by several methods, depending on the accuracy needed and the characteristics of the contaminant.

[21] Scientists gathering this type of data often employ auto-sampler devices that pump increments of water at either time or discharge intervals.

More complex measurements are often made in a laboratory requiring a water sample to be collected, preserved, transported, and analyzed at another location.

[26] The threat of disease increases hugely due to the large numbers of people living close together, often in squalid conditions, and without proper sanitation.

[27] After a natural disaster, as far as water quality testing is concerned, there are widespread views on the best course of action to take and a variety of methods can be employed.

The key basic water quality parameters that need to be addressed in an emergency are bacteriological indicators of fecal contamination, free chlorine residual, pH, turbidity and possibly conductivity/total dissolved solids.

[28][29] After major natural disasters, a considerable length of time might pass before water quality returns to pre-disaster levels.

[30] IWMI developed protocols for cleaning wells contaminated by saltwater; these were subsequently officially endorsed by the World Health Organization as part of its series of Emergency Guidelines.

Filtration of soil particles from the water sample before acid addition, however, may cause loss of dissolved metals onto the filter.

Because direct measurements of water quality can be expensive, ongoing monitoring programs are typically conducted and results released by government agencies.

[33] Tools available to the general public include on-site test kits, commonly used for home fish tanks, and biological assessment procedures.

In the early 21st century, a variety of sensors and remote monitoring systems have been deployed for measuring water pH, turbidity, dissolved oxygen and other parameters.

Biological monitoring metrics have been developed in many places, and one widely used family of measurements for freshwater is the presence and abundance of members of the insect orders Ephemeroptera, Plecoptera and Trichoptera (EPT) (of benthic macroinvertebrates whose common names are, respectively, mayfly, stonefly and caddisfly).

The SASS aquatic biomonitoring tool has been refined over the past 30 years and is now on the fifth version (SASS5) which has been specifically modified in accordance with international standards, namely the ISO/IEC 17025 protocol.

Environmental lawyers and policymakers work to define legislation with the intention that water is maintained at an appropriate quality for its identified use.