By: T.L. Provin, Extension Soil Chemist; and J.L. Pitt, Extension Associate, The Texas A&M University System
That water you’re drinking — or sprinkling onto your flowers, or using to irrigate your crops, or providing to your livestock — what’s in it? Is it safe? Does it taste good? Is it beneficial for people, plants and animals? If not, what can be done to improve it?
One way to learn about the contents of your water is to send a sample to a laboratory to be analyzed. The lab will test the water and send you a report about its contents. Water analysis is conducted by governmental agencies and by private companies.
But sometimes it is difficult to understand the reports that labs send to consumers. What do the results mean? What characteristics of your water can cause problems? And what can be done to make it safer, tastier or more usable?
To help you understand the lab analysis of your water, on the following pages are tables of common components and properties measured in water. The tables include the sources of water contaminants, problems that can be caused by those contaminants, suggestions for how to correct them and the safe levels of each in water for household use, for irrigation and for livestock. After the tables are explanations of commonly used terms and water treatment methods.
The U.S. Environmental Protection Agency (EPA) has set safety standards for drinking water. The EPA Primary Drinking Water Standard is a legally enforceable standard that applies to public water systems. Such systems must meet this EPA standard.
The EPA Secondary Drinking Water Standard is a nonenforceable guideline regulating contaminates that may affect the appearance or taste of your drinking water. Public water systems do not have to meet this standard.
Most U.S. public water sources are safe. But problems have been found in some areas, and in many cases they can be alleviated. If you have questions about your water, contact your local health department.
Water Terms and Abbreviations
10-4 cancer risk: the concentration of a contaminant in drinking water indicating an estimated lifetime cancer risk of 1 in 10,000.
Acid feeder: a system that dispenses a preset concentration of acid (usually sulfuric acid) into the water stream to reduce pH and to eliminate calcium and magnesium carbonate deposits. Most acid feeders are used in irrigation systems, greenhouses or other non-household/drinking water systems. Acid feeders are often available only to professional installers or specialty supply stores.
Activated alumina: aluminum oxide that is highly porous and has a large surface area. It is used to adsorb impurities such as beryllium, selenium or thallium from water.
Aeration: a process in which air is bubbled or otherwise mixed into water to oxidize specific reduced contaminants such as iron and manganese. This process may be used in ponds or tanks, where much nonpotable (not for drinking) water is to be treated, or in semienclosed spray chambers. The efficiency of aeration depends on the amount of oxygen absorbed into the water and the amount of time allowed0 for the precipitation of contaminants.
Most aeration systems require sediment filters to remove the particulates generated during oxidation. Spray systems are often available only to professional installers or in specialty supply stores.
AL (action level): the trigger point at which remedial measures are to take place.
Anion: an ion or group of ions with a negative charge because they have gained one or more electrons.
Cation: an ion or group of ions with a positive charge because they have lost one or more electrons.
Charge balance: a calculation of the ratio of negative charges (anions) to positive charges (cations). Ideally, water will have a charge balance of 100, which indicates that it has an equal number of anions and cations. This number can differ significantly from 100 if sediment, organics or other substances are present.
Chlorination: a process by which reduced chlorine (includes chlorine gas and hypochlorite, the active ingredient in chlorine bleach) is injected into water to oxidize inorganic (iron, manganese, etc.) or organic (microorganisms) constituents. The equipment required for this process generally requires professional installation.
Coagulation/filtration: the act of collecting like dissolved, suspended and non-settleable particles from water into a mass through chemical treatment and the subsequent removal of the mass through filtration.
Contaminant: any physical, chemical, biological or radiological substance or matter in water.
Corrositivity: the reaction between water and metal surfaces. Corrosive water can increase the levels of copper, lead and zinc in the water; deteriorate household plumbing; and stain laundry, basins and drains. Also, the deterioration of metallic plumbing fixtures often makes the water taste bitter or metallic.
Deionization: a process to treat water using resins saturated with various anions and cations. As water passes across the resin, the ions “exchange.” The ions in the water are replaced by those on the resin. There are two major groups of ion exchange systems: mixedbed units and water softeners (explained below). Most mixed-bed exchange units reduce the salt content of the water.
Because of the high costs of resins or consumables required to regenerate the resins, deionization is typically reserved for a final polishing of previously treated water. Deionized water is normally used for laboratories or saltwater aquariums.
Distillation (steam): a process in which water is heated to its vapor point and steam is then the collected. Salts and other nonwater substances with higher vapor points (208 to 215 °F) remain in the heating chamber or are flushed from the heating element in wastewater. Some organics with vapor points similar to or lower than water may be concentrated in the final product.
Because of the energy costs and low recovery of water, distillation is often limited to laboratory use. The equipment for large-scale production is generally not available to the general public. However, small-volume (1-gallon) tabletop models are available.
DWEL (drinking water equivalent level): the concentration of a contaminant in drinking water at which a lifetime of exposure to it will not cause adverse, carcinogenic health effects, assuming that all the exposure to the contaminant is from drinking water.
Electrodialysis: the passage of anions or cations through a permeable membrane under the influence of an electrical gradient.
HA (health advisory): the estimated concentration of a substance below which there will likely be no observable health effects.
- One-day HA: The concentration of a chemical in drinking water that is not expected to cause adverse noncarcinogenic effects for up to 1 day of exposure, based on a 10-kg (22- pound) child.
- Ten-day HA: The concentration of a chemical in drinking water that is not expected to cause adverse noncarcinogenic effects for up to 10 days of exposure, based on a 10-kg (22-pound) child.
- Lifetime HA: The concentration of a chemical in drinking water that is not expected to cause any adverse noncarcinogenic effects for a lifetime of exposure.
LED10 (lower limit on effective dose10): the dose of a chemical needed to produce an adverse effect in 10 percent of those exposed to the chemical, compared to a control group of people not exposed.
MCL (maximum contaminant level): the highest amount of a specific contaminant allowed in the water delivered to any customer of a public water supply. MCLs are based on the levels of contaminants that cause adverse health effects.
MCLG (maximum contaminant level goal): the concentration of a contaminant that experts believe a person can safely drink over his or her lifetime. Although the EPA does not enforce the MCLG, it is used to set the enforceable drinking water standards.
Micrograms per liter (µg/L): 0.001 mg/L or parts per billion (ppb) concentration of a substance in water.
Milligrams per liter (mg/L): parts per million (ppm) concentration of a substance in water.
Millirems per year (mrem/yr): an equivalent unit of radiation a body or organ receives (0.001 rem, where rem is roentgen equivalent man).
(N)PDWR [(National) Primary Drinking Water Regulations)]: legally enforceable standards that apply to public drinking water systems.
(N)SDWR [(National) Secondary Drinking Water Regulations)]: nonenforceable guidelines regulating contaminants that may cause cosmetic effects such as skin or tooth discoloration; aesthetic effects such as taste, odor or color in drinking water; or technical effects such as damage to equipment or reduced effectiveness for treatment of other contaminants. The EPA recommends but does not require that public water systems comply with secondary standards. Individual states may elect to adopt them as enforceable standards.
Oxidation: a process in which oxygen or another element or compound (poor in electrons) reacts with a reduced element or compound (rich in electrons) and acquires one or more electrons. Normally, this reaction converts the reduced material to a more treatable/management form. The best example of this process is the aeration of water to convert iron to a more easily treated form. The oxidizing agents used to treat water include chlorine, hypochlorite and potassium pemanganate. Homeowners should consult with a reputable water treatment professional on system design and installation because chemical oxidation systems are complex and spray systems can introduce biological contaminants into the water.
Picocuries per liter (pCi/L): a common unit used to measure radioactivity.
Polyphosphate feeders: a system that introduces a polyphosphate solution into a water system to protect the plumbing from corrosive or other metalrelated problems. The polyphosphate coats the plumbing, forming a protective barrier against dissolved oxygen and other corrosive materials. Because these systems are expensive and require considerable design expertise, they should be installed by water treatment professionals.
- ppm: parts per million.
Public water system: any system that provides water to the public for human consumption.
Radionuclides: radioactive particles that occur naturally in areas where there are uranium and radium deposits.
Reverse osmosis (RO): a procedure in which water is forced through a semipermeable membrane with openings that are about the size of water molecules. The membrane allows the water to pass through but rejects the contaminants in it.
Reverse osmosis can remove salts, bacteria, sugars and other particles whose molecules are bigger than those of water. Contaminants that are collected on the membrane are back flushed and washed out of the system as waste.
Because dissolved iron and manganese can significantly reduce the life of a membrane life, they should be removed through other treatment procedures before the water is entered into an RO system. Similarly, water with more than 20 ppm of calcium and magnesium should be softened to reduce the formation of lime scale on the membrane. Also, it is vital that particulates be removed to maintain and extend the life of the membrane.
Most RO units sold in retail stores operate on household water pressure and contain RO membranes that are sensitive to chlorine or other oxidizing agents. These oxidizers are commonly removed, along with dissolved organics, by activated charcoal.
Waters high in salt often require higher pressure “pump” systems. This type of unit is often available only to specialty distributors and/or professional installers.
Rfd (Reference dose): the estimate of the daily dose of a substance that a person can ingest over a lifetime and suffer no adverse health effects. This estimate, formerly called the acceptable daily intake (ADI), includes a conservative safety margin.
Salt: an organic or inorganic compound that is subject to dissociation when water is added, resulting in a distinct increase in specific anions and cations.
Sediment/precipitate filter: a filter that removes suspended solids by trapping particles between media pores. The filter may be made of numerous materials, including sand, pleated paper, porous disks, porous aggregates, spun paper and other fibers. The effectiveness of each filter depends on the average particle retention size and the estimated amount of water that can be filtered. In turn, these sizes and estimates depend greatly on the initial water quality, water pressure and length of time since the last filter change.
Many user-installable filter cartridges are available from home centers and hardware stores. Sand filters and other non-cartridge systems are normally available only through professional installers, as they can introduce diseasecausing agents if introduced improperly.
SOC (synthetic organic compound): a man-made compound that contains carbon (and is hence called organic) and that is nonvolatile. Regulated SOCs include atrazine, chlordane, 2,4-D, lindane, and glyphosate.
Soda ash feeder: a system in which sodium carbonate is fed into water to raise water pH. Typically, these systems are placed near the water source and treat all the water used by the home. Soda ash feeders are often available only to professional installers or specialty supply stores.
Submicron filtration: the process of removing particles from a solution that are less than 1 millionth of a meter by passing the solution through a porous medium.
SWDA (Safe Drinking Water Act): the law authorizing the EPA to establish a cooperative program among local, state and federal agencies for drinking water. The federal government’s primary role under this act was to develop national drinking water standards to protect public health and welfare.
TT (treatment technique): the mandatory minimum technique with which public water systems must be treated.
Ultrafiltration: the process of removing particles from a solution under pressure by passing it through a porous medium that has larger pore sizes than submicron or RO filtration systems.
URTH (unreasonable risk to health): the level above which long-term exposure to a substance may present significant health risks.
VOC (volatile organic compound): a man-made compound that contains carbon (and is hence called organic) and that readily evaporates or votilizes. Regulated VOCs include benzene, vinyl chloride, toluene and xylene. Water ratings:
- Acceptable — Under normal management, the water should not pose any long-term problem for the intended use.
- Limiting — A higher than normal level of management or treatment is needed to use the water for a given application.
- Very limiting — The water needs such significant management or treatment that it may not be economically or technically feasible for the intended use.
Water softener: a system that uses cation exchange resin to remove calcium, magnesium, iron and manganese from water. Such systems typically use a sodium chloride salt brine to saturate the resin with sodium. As the water is treated, calcium and magnesium are exchanged for sodium. The result is simply a trade of cations, not a reduction of salt.
The size of the water softener should accommodate the water hardness and daily water usage to minimize the number of resin regeneration cycles required per week. Some systems are designed to use potassium instead of sodium, thus providing softened water without raising sodium levels. Water softeners are commonly available in home centers as well as from professional installers.
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