Water quality overall is determined on how a variety of characteristics such as turbidly and pH (among others) are measured against federally mandated regulations. Every six years the drinking water standards get more and more lengthy. Drinking water standards are regulations that EPA sets to control the level of contaminants in the nation's drinking water. These standards are part of the Safe Drinking Water Act's "multiple barrier" approach to drinking water protection, which includes assessing and protecting drinking water sources; protecting wells and collection systems; making sure water is treated by qualified operators; ensuring the integrity of distribution systems; and making information available to the public on the quality of their drinking water. With the involvement of EPA, states, tribes, drinking water utilities, communities and citizens, these multiple barriers ensure that tap water in the United States and territories is safe to drink. In most cases, EPA delegates responsibility for implementing drinking water standards to states and tribes.
EPA sets up monitoring schedules for each possible contaminant. Monitoring schedules differ according to the type of contaminant, the type of source water used to produce drinking water, and the population served by the public water system. Each regulation outlines the requirements that systems must follow. It is the job of state and local governments to make sure their utilities follow the new regulations, thus ensuring a safe drinking water for the general public.
There are several ways water quality at a basic level can be measured. This is primarily done at the closest possible point to the water source, an 'in the field' form of testing. The quality of water here is determined by making measurements or by taking samples of water and testing them for acidity (pH), color, dissolved oxygen and turbidity (a measure of the suspended particles in the water). Such tests give a water utility operator a basic, general interpretation of the conditions of a water source.
Samples are also taken at this time such as suspended materials, bottom sediment, or biota. These samples are typically brought back to a laboratory or send out to one for physical, chemical, and microbiological analyses. The concentrations of metals, nutrients, pesticides, and other substances are measured in the laboratory. Laboratories analyze public water systems’ (PWSs) water samples and provide the PWSs with information on the quality of their water. Water sample types analyzed and purposes of analysis: Source water samples are analyzed to check for contamination and determine general water quality characteristics that influence the treatment processes; process water samples are analyzed to provide key information relevant to treatment optimization; finished water samples are analyzed to verify the water meets health-based and aesthetic standards and periodically check for contaminants that are not regulated in drinking water.
Another way to obtain an indication of the water quality is through biological testing. This test determines, for example, whether the water or the sediment is toxic to life forms or if there has been a fluctuation in the numbers and kinds of plants and animals. Some of these biological tests are done in a laboratory, while some basic ones are carried out at the stream or lake.
Every year utilities gather more data about their water quality and with the best technology available to them, strive to deliver the highest quality of water available to its customers. This is done through testing at a field level as well as in-depth testing in the laboratory.