Water Quality
By Kenton Shepard
DRINKING WATER SOURCES
70% of drinking water in the US comes from either deep or shallow groundwater sources. Despite the fact that microorganisms are typically less of a problem in groundwater because it’s been filtered by soil and rock, it still must be disinfected before use as drinking water. Although natural filtration takes place as precipitation seeps down through layers of soil and rock, because water is a powerful solvent, it can also pick up other types of contaminants such as dissolved minerals, some of which must be removed by treatment.
Drinking water also comes from surface water sources such as lakes, reservoirs, rivers and canals. Surface water contamination can consist of a variety of pollutants washed into sources by storm water, including biological, chemical and mineral contaminants and sediment.
WATER CONTAMINATION
The Hydrologic Cycle
Contamination begins as water on earth goes through a continuous cycle called the Hydrologic Cycle. It proceeds like this..
- Through plant transpiration and surface evaporation (which together are called evapotranspiration) processes (which purify water), water enters the atmosphere where it exists as water vapor and ice crystal formations we call “clouds”.
- As water falls back to earth as rain, it begins the contamination process by dissolving and absorbing elements from the atmosphere. Some of the falling water reacts with the carbon dioxide in the air to form carbonic acid, which increases its solvent properties. A few of the contaminants water picks up from the atmosphere are…
- Bacteria
- Dust
- Molds
- Industrial airborne effluents such as lead, mercury and Strontium 90
- Water reaching the ground flows across and through the surface, collecting chemicals leached from minerals and decayed vegetation along with a variety of other man-made and naturally-occurring contaminants. What types of contaminants are collected by water depend upon…
- the region
- whether the water remains on the surface
- what potential contaminants lie in the waters path.
- what potential contaminants exist in the soil and underground materials through which water seeps on its way to recharging aquifers.
Source
The Hydrologic Cycle
The Contaminants
Many, many contaminants exist and the following list is designed to provide only a basic introduction to some of the more common.
- Bacteria, Viruses and Cysts: Not typically a problem in municipally-treated water, some types may cause serious health issues even at low levels and can be an issue in well water. These contaminants include e-coli, giardia and cryptosporidium and are often associated with human and animal waste.
- Pesticides, Chemicals, Pharmaceuticals and Detergents: Found in both municipal water supplies and well water, this group is huge and growing. Many are not tested for, have not been studied and no provision exists to remove them from drinking water.
- Heavy Metals: Most often found in wells, heavy metals such as mercury, lead, cadmium and copper can accumulate in the human body and represent a significant health concern in certain areas.
- Chlorine (CL2): Chlorine gas is one of the primary disinfectants used by municipalities to disinfect drinking water. An alternative, chloramine, is created by bonding CL2 to ammonia. The introduction of chlorine to drinking water over 100 years ago effectively ended diseases such as cholera and dysentery.
Although there is disagreement within the scientific community over the effects of chlorine found in water on the human body, it is known to combine with organic compounds naturally occurring in water to form contaminants called trihalomethanes (tri-Hay-loh-MEH-thanes). This is the reason for the switch to chloramine although there is also some concern about residual ammonia with the use of chloramine.
- Nitrates (NO3): Typically present near agricultural communities and found in both municipally-treated and well water, Nitrates represent a health hazard to humans. They interfere with the transfer of oxygen in the human bloodstream and are considered to be a prime source of blue baby syndrome.
- Hydrogen Sulfide (H2S): Recognized by its “rotten egg” smell, hydrogen sulfide is not typically an issue in water treated by municipalities, but can be found in well water. H2S can cause the following issues…
- may cause migraine headaches even at low levels.
- may stain silverware and household plumbing fixtures or items.
- may indicate other contaminants requiring treatment.
- pH (acidity/alkalinity): pH is not a contaminant but can effect water quality by influencing the impact of other contaminants present in water which may effect water’s potable or corrosive properties.
- Total Dissolved Solids (TDS): TDS levels reflect the levels of non-H2O in water which can affect its potability, aesthetics and taste. TSD levels also are used as indicators by water treatment specialists. It is considered a contaminant at levels above 500 parts per million (ppm).
- Calcium Bicarbonate (CaCo3) and Magnesium Bicarbonate (MgMo3): determine water hardness. Although not strictly contaminants, excessively hard water (water with high levels of either of these compounds) can have significant effects on home systems or components such as the following…
- Appliances such as water heaters may experience build-up which effects their efficient operation and shortens their lifespan.
- Hard water causes build-up in showers and tubs and spots on kitchenware.
- Experts are divided concerning the effects of hard water on the human body.
- Iron (Fe): can cause a number of problems, depending on the type of iron present…
- Ferrous Iron: Although it’s clear when dissolved in water (typical state) ferrous iron turns yellow or reddish brown when exposed to air.
- Ferric Iron: found as particles in water which settle to the bottom of containers and oxidize to orange or red.
- Organic Iron: Seldom found in municipally-treated water, may give well water a yellowish color, stain laundry or produce poor taste or odor in drinking water.
- Iron Bacteria: Iron-eating bacteria give water a gelatinous or scummy appearance.
- Radioactivity: Found mostly in well water, radioactive contaminants are elements such as uranium, radium 226, 228 and radon.
COMMUNITY WATER SUPPLIES
Public Drinking Water Treatment
Drinking water in the U.S. comes from a variety of sources both public and private. Supply for a community water system might follow a route something like this…
Precipitation drains down a watershed to a reservoir where it’s stored to be used as needed. From the reservoir it’s first screened to remove debris such as sticks and leaves, then pumped through pipes to a series of containment areas in which different treatments may be applied depending on what contaminants must be removed, neutralized or adjusted.
Purification may include some or all of the following:
- Natural bacterial action- helps purify water
- PH adjustment- helps make other treatment methods more effective and reduces the risk of lead from pipes or solder being dissolved into drinking water.
- Flocculation is a process in which water is clarified by the introduction of very tiny particles called precipitants into water where they’re allowed to sink slowly to the bottom. As they sink, they begin to stick together in a process similar to coagulation. Other particles suspended in the water also adhere to these particles, resulting in their removal.
- Sedimentation- allows solids to further settle out.
- Filtration- may consist of sand or membrane filters though which water moves by gravity or applied pressure.
- Disinfection- typically the last step in water purification, water is held in a clear well while a strong oxidant such as one of various forms of chlorine are dissolved in the water and over time act as a disinfectant. Levels are kept to just above 1 part per million (PPM) until just before water is delivered to customers.
Source: EPA
Community water treatment system
Text Links to the water treatment system:
Coagulation
Sedimentation
Filtration
Disinfection
Storage
After use in a home, water is typically discharged to a wastewater system (or, in remote areas, to an on-site septic system). Wastewater collection systems transport the water used for toilet flushing and other household uses to a sewage treatment plant, where the wastewater is treated (consisting of aeration, bacterial decomposition, settling of solids, and disinfection) before it is discharged to a receiving water body.
PRIVATE HOME WATER SUPPLIES
Source
Water Well Overview
Most private home water is supplied from a well located on the property. Deciding on an appropriate water treatment for a home well depends on what contaminants are likely to be found. Considerations include the type of well and surveying the area for possible contaminant sources such as septic systems, agriculture, livestock, mining or any other potential source of chemical, radioactive, mineral or biological contaminant. Filters types already installed in homes may also provide clues to what contaminants might be present.
Many health departments will perform a potable water test for bacteria for a nominal fee. Testing requires filling a small bottle according to simple instructions and delivering it to a laboratory.
Local companies providing well inspection services may also have suggestions about what contaminants to test for. Unless accurate information about filter maintenance is available, home buyers may want to replace filter media or have filters tested for effective operation.
PRIVATE HOME WATER TREATMENT and FILTRATION SYSTEMS
Types of home water treatment systems.
Filters are affected by local water chemistry and maintenance quality and often, similar-looking filters will not reduce or remove the same contaminants. Confirming effective filter operation and filter purpose requires special knowledge and lies beyond the scope of a general home inspection.
The best way to deal with existing filters is to contact the manufacturer for advice on filter effectiveness and maintenance.
 = Effectively Removes  = Significantly Reduces  = Minimal or No Removal
* when combined with activated carbon in same filter / system
** At high contaminant levels, filter life will be reduced significantly. Manganese greensand (whole house iron reduction filter) or KDF filter is recommended for Hydrogen sulfide.
*** Even though reverse osmosis is effective in removing bacteria and viruses, it is not recommended that your rely upon reverse osmosis solely if your water is contaminated with bacteria or viruses. Ultraviolet (UV) purification is also recommended.
Whole House Filter- also called a “silt” filter, an easily-replaceable filter in a clear, plastic canister installed in the main water supply pipe, they remove or reduce sediments (rust, sand, silt and dirt). These canisters may use one of several filter types, some of which may remove chlorine.
Source: Kenton Shepard
Whole House Water Filter
Carbon (Activated Charcoal)- Charcoal is “activated” by providing it with a positive electrical charge so that it attracts and holds negatively-charged particles. These filters are designed to expose contaminants to as much filtration media as possible by providing a large internal surface area. Activated charcoal contains over 13,000 square feet of internal surface area per pound.
The charcoal filter should be replaced on a schedule recommended by the manufacturer, but which may vary according to levels of contaminants in water.
Carbon (charcoal) filters are most effective at removing chlorine, sediment, many chemicals including Volatile Organic Compounds (VOC’s) and improving water taste and odor.
 
Source Source
Carbon water filter views
Reverse Osmosis (RO)- These filters work by forcing water through a semi-permeable membrane which prevents contaminants from passing through. Although RO filters will remove bacteria and viruses, they will not remove VOC’s and for this reason are often used in conjunction with carbon filters.
Source
Reverse osmosis filter
RO filters require around 24 hours to filter 5 gallons of drinking water, which must then be stored. These systems waste up to 9 gallons of water for each gallon of drinking water produced. Because of their slow flow rate, they provide drinking/cooking water only and are not suitable as whole-house filters.
Ultra-violet (UV)- These filters consist of an ultra-violet light bulb encased in a canister. As water is routed past the bulb, the ultra-violet light destroys the DNA of living microbes.
Although UV light is capable of killing microorganisms such as bacteria, viruses, molds, algae, yeast, and cysts like cryptosporidium and giardia, it will not remove chemical contaminants. For this reason water is sometimes first routed through carbon filters.
Problems with UV filters include degradation of the light source over time due to mineral adhesion to the bulb, or water cloudiness which reduces light penetration. UV bulbs need replacement at least once a year or more depending on the chemical and mineral content of the water.
Source: Kenton Shepard
An ultra-violet filter canister with a ballast
Ceramic filtration- screens particles through a porous filter manufactured using is Diatomaceous Earth, a fossil substance made up of tiny silicon shells left by trillions of microscopic, one celled algae called diatoms which have inhabited the waters of the earth for the last 150 million years. Removes a number of biological pathogens. Over time, buildup on the filter will reduce water flow through the filter, requiring periodic cleaning and eventual replacement. Ceramic water filters have a low flow rate.
Learn about other water filter types.
Sources for More Information
- State-by-state reports on drinking water quality
- Water Quality Association (WQA) is a resource and information source, a voice for the industry, an educator for professionals, a laboratory for product testing and a communicator to the public. Use their water information Library.
- National Sanitary Foundation (NSF) has been answering consumer questions about drinking water for more than a quarter century. To learn more about common contaminants, Water Quality/Consumer Confidence Reports (CCR), or any of the other drinking water subjects shown below, simply click on that topic.
- EPA Drinking Water Contaminants
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