There are several things in life that we take for granted. Water is very often one of them. Each of us uses this vital liquid, the most common substance on earth, everyday. And we rarely think twice about it.
However, the water we use for cooking, drinking, and countless other domestic tasks will quickly catch our attention when there is some sort of problem.
Fortunately, some of the most obvious water problems are also the easiest to solve. The problems in this report are aesthetic. Although they are not considered harmful to health, they do affect the look and taste of the water, and may cause it to be undrinkable by some people's standards. Addressing these water quality problems is therefore important. Issues such as taste and odour, colour, and turbidity (cloudiness) are all aesthetic water problems, and all have relatively simple solutions. This report will discuss each of these problems in turn, EPA standards regarding aesthetic problems, and finally present treatment technologies to solve them.
In order to treat these problems, we must first look at their source. Water is known as the universal solvent. Before it reaches a consumer's tap, it comes into contact with many different substances, such as gases, minerals, and organic matter. Water picks up traces of these substances, and unfortunately, some of them may cause taste, odour, colour, or turbidity problems for the consumer.
Turbidity: Cloudy Water
At one time or another, most consumers have encountered water that appears cloudy or foggy. This characteristic is due to turbidity: the presence of finely divided solid particles in water. These particles may be inorganic mineral matter which does not dissolve, or organic matter that has been picked up as the water flows over and through the ground. The particles cause the scattering and absorption of light rays, which gives the water a cloudy appearance.
Whether turbidity is due to suspended organic or inorganic matter, it can cause staining of sinks and fixtures, and the discoloration of laundered fabrics. Inorganic turbidity can have an abrasive effect on plumbing systems and may cause physical wear or erosion on pipes and fittings. Turbidity is most commonly found at taps whose source is surface water from lakes, streams, or ponds.
Taste and Odour
Another set of problems that will quickly catch a consumer's attention is objectionable tastes or odours present in water. These two senses appear to work in unison, which makes it difficult to separate taste and odour.
A common characteristic of water from public systems is the chlorine taste and odour, which is often quite noticeable. Many public water systems treat water with chlorine to disinfect it. Although this is an important step in the treatment of water because it destroys disease-producing bacteria and other harmful organisms that may be in present in water, there is no doubt that excess chlorine from the disinfection treatment step can make the water objectionable.
In other cases, water with a high mineral concentration may have an unpleasant soda or salty taste, and a metallic taste may be produced by the presence of iron or manganese in water.
Many people have also encountered water that contains hydrogen sulphide gas, which creates an objectionable odour. So-called 'sulphur water' not only produces the obnoxious 'rotten egg' odour, but is also corrosive to plumbing and can cause the rapid tarnishing of silver. Even very low concentrations of hydrogen sulphide are detectable because of the strong odour.
Various taste and odour conditions are caused by the presence of organic matter in water. Even when the amount of organic matter is very low, unusual tastes and odours such as musty, fishy, or earthy smells may be found.
It is important to note that tastes and odours affect drinking water as well as the foods and beverages prepared with the water.
In some home water supplies, a yellowish coloration may be present. This colour condition is organic in nature, but presents no health hazard. It is caused by the presence of microscopic suspended particles.
This colouration occurs in regions where the water passes through marshlands and has percolated down through peaty soils. It is most likely to be found in the Highlands of Scotland and other moorland areas; and is more common in surface water supplies and shallow wells than in deep wells.
Humic acids, often referred to as tannins, are the real cause of the colour condition. Often the colour is not highly visible in a glass of water, but can frequently be noticed when water is drawn for a bath. The white porcelain background of the tub can highlight even the slightest discolouration.
A more severe colour condition may be caused by the presence of iron in the water. Depending on the type and state of the iron, the water may or may not be clear when it is first drawn. Water with dissolved iron may appear clear when it is first drawn, but may turn a brown-red colour when it stands exposed to air or when it is heated. Water with precipitated iron may have a reddish colour or red particles when it is first drawn.
The disadvantages of water containing significant amounts of iron are obvious. It can leave brown-red stains on fixtures and dishes, as well as discolour laundry. It is also unappealing for drinking.
The U.S. Environmental Protection Agency (EPA) sets federal guidelines for contaminants that may adversely affect the aesthetic quality of drinking water. These Secondary Maximum Contaminant Levels (SMCL's) apply to any contaminant in drinking water which may adversely affect the odour or appearance of the water, and consequently may cause people to discontinue its use in favour of another supply, or otherwise adversely affect 'public welfare.'
SMCL's differ from national primary (health related) maximum contaminant levels (MCL's) in that they are not federally enforceable. Instead, the SMCL's offer guidance to water quality based on odour, aesthetics, or appearance; the primary MCL's are established by the EPA based upon potential adverse health effects.
If the water in a consumer's home has these problems with turbidity, taste, odour, or colour, what can be done? Fortunately, there are several products available that can be directly installed in the home to treat these problems. Point-of-Use (POU) and Point-of-Entry (POE) technologies can treat water in the home and reduce these problems.
A process that is effective in reducing most of these aesthetic problems is the use of an activated carbon filter. These filters are specially designed for the removal of solid particles from the water. Activated carbon is a unique material known for its ability to absorb (bind to its surface) soluble organic compounds and certain gases. This quality makes it especially suited for use in water treatment and allows it to act as a fine screen which traps solid particles, but allows the water to pass through. Activated carbon filters are available in three forms: solid block, precoat, and granular.
Carbon filters may either attach directly to the tap, or may be installed under the sink; filters for the whole house may also be used to treat staining and odour problems.
Most taste and odour problems can be reduced with the use of an activated carbon filter. To combat the taste and odour problem of excess amounts of chlorine, for example, many consumers install a filter at the kitchen tap. The filter adsorbs the excess chlorine, and produces a tasty, clean water for cooking and drinking.
Turbidity may also be removed with an activated carbon filter, or a particulate filter. The particulate filter will trap the fine particles that cause a cloudy appearance, and its use will result in a clear, clean appearance.
The problem of hydrogen sulphide in water is more complex than many other odour problems. If the concentration of hydrogen sulphide is very low, then an activated carbon filter may be used. For greater concentrations, an iron removal filter should be effective in correcting the problem. For high concentrations of hydrogen sulphide, a chlorination system with activated carbon filtration would likely be the best solution. Chlorine is potentially harmful, and must be handled carefully. We recommend you consult a professional.
(RO) Another treatment technique commonly used in the home is a process called reverse osmosis (RO). In this process, the water to be treated is forced against a semi permeable membrane, which rejects contaminants suspended in the water. The membrane permits the new water to pass to a holding tank where it is then available for use. RO is effective in treating water that has a metallic taste, as well as reducing numerous other health contaminants. It is also often paired with an activated carbon filter.
Distillation is also often used for water treatment. A distillation system raises the water temperature to boiling. The water turns to vapour, leaving behind contaminants that have been dissolved in it, as well as microscopic solids, microorganisms, and organic materials. The clean water vapour enters a condenser where it is cooled, and returned to its liquid state. This process produces a clean, clear water with a distinctive clarity.
To treat water that is coloured as a result of humic acids, an anion exchange resin may be used. The resin absorbs the organic bodies that cause the discolouration, and will leave behind clear water.
For colour problems that are due to low or moderate levels of dissolved iron, a household water softener may remove the impurity. The soluble iron is removed from the water by ion exchange, in the same way that hardness is removed by a water softener.
If much of the iron is already precipitated, or the iron concentration is too high for a water softener, an iron removal filter should be used. The filter forms a barrier that prevents the continued passage in the water.
Whether a water problem involves turbidity, taste, odour, or colour, the first step to its treatment is to have the water tested. Testing determines the precise cause of the problem so the ideal treatment may be applied.
When the safety of the water is in question, it should be tested by a state certified, EPA certified, or other reputable laboratory. Testing for turbidity, taste, odour, or colour problems may be performed in the home by a professional water treatment dealer.
Before purchasing a product, become an educated consumer. Determine what water problems the proposed product reduces, and to what level. Check the product's performance capabilities, maintenance provisions, and warranty.
Aesthetic water problems have easily applied and proven solutions. Don't settle for unappealing water. This article first appeared in the WaterReview Technical Brief.