There are many factors that may cause cloudy or turbid water. Cloudy water can also be referred to as having high levels of turbidity. The most common causes of turbidity are organic matter, and/or colloidal solids that are too small and too fine to settle out properly. These suspended particles can cause problems with disinfection processes, and also be an indicator of bacterial activity in the water. Turbidity is measured in NTU’s, (Nephelometric Turbidity Units). The turbidity of drinking water should always be less than 1 NTU. Most treated city water is less than .2 NTUs.
A very effective method to remove turbidity is with reverse osmosis (‘RO”) or ultrafiltration (“UF”) membrane systems. RO and UF systems can be used by homeowners, small communities and commercial sites to reduce turbidity and produce crystal clear water less than 0.1 NTUs.
Another low cost option is to use a whole house cartridge filter. These filters are large size filter cartridge systems which come in various micron ratings and can filter down to the 1 micron size. One option frequently used by homeowners with cloudy water is to use a backwashing sediment filter, followed by a 1 or 5 micron filter cartridge system.
There are many factors that may cause colour in water. The most common causes are iron, manganese, tannins, organic matter, and/or colloidal solids that are too small and too fine to settle out properly.
If the colour is from tannins or humic acids, then a tannin filter might be applicable. These filters remove dissolved colour by ion-exchange, using anion exchange media. The units we use regenerate with rock salt (sodium chloride). While these are called tannin filters, they are really ion-exchange units. Frequently we see shallow wells, or wells under the influence of surface run-off water, achieve high levels of tannins during heavy rainy periods.
Sometimes tannins are accompanied with iron or manganese. Water high in iron or manganese can sometimes be red, rust coloured, brown, tan, black, or greenish in colour. Oxidation, followed by a well-designed iron filter can be very effective at removing tannin and these oxidized iron particles.
Iron and Manganese
Iron and manganese are often found in a dissolved state in well waters, and the water appears clear when first drawn. Upon exposure to air, or after the addition of oxidants (such as chlorine bleach or ozone), this ferrous iron is oxidized (“rusted”) to the ferric state to form insoluble particles. The water then looks orange or yellow, or in the case with manganese, brown or black.
The role of pH is very important in iron treatment. Generally, if the pH of the water is acidic (or less than 7.0), it must be corrected with a special type of neutralizing filter of the iron filtration system. It is usually best to test for pH right at the water source, and not depend on laboratory analysis for pH, since in some cases the pH can raise after sampling, giving false results.
The term “water hardness” originally referred to the ability of water to precipitate soap and form soap scum. Soap is precipitated (or brought to the “surface”) by water containing high levels of calcium and magnesium. The “harder” the water the less soap will dissolve in the water.
Water hardness minerals are commonly treated with a water softener system that uses an ion-exchange resin and regenerates with salt. For residential and commercial applications these are the most effective as they remove the hardness minerals from water. The media within the filter is a “cation” resin. Using water, sodium in salt (NaCl) is swapped for the calcium in the water. In nitrate the chloride (Cl) is swapped for the nitrate in the water. Thus, in water softening sodium is added to the water. Sodium levels should be checked to ensure they do not exceed the maximum allowable value of 150mg/l. Current advice from the UK Department of Environment is that softened water should not be used for drinking and an unfiltered drinking supply should be taken off prior to a water softener.
There are many devices on the market that purport to eliminate the effects of water hardness by the use of electrical fields, magnetism, catalytic metals and other materials. These are called No-Salt Water Conditioners and do not remove hardness from the water, but treat minerals to prevent scale build-up.
In well water, odours are commonly the result of sulfur bacteria, or compounds of iron, manganese, and sulfates. For example, hydrogen sulfide gas (“rotten-egg odour”) commonly occurs in well water as a result of decaying organic matter and the activity of sulfates and various species of sulfur or iron bacteria.
Plumbed-in activated carbon filters work on the same principle as the jug filter to remove chlorine and organic substances but are not so effective on inorganics such as salts and metals. They consist of a filter head for connection to the water supply with a detachable bowl housing a filter cartridge incorporating a mechanical filter, which excludes grit, dirt, sand and so on.
The effectiveness of an activated carbon filter can be extended through additions to the basic filter material and different types of cartridge are now available, capable of removing or reducing a variety of additional substances. Activated carbon filters are also often used as the main element of a larger combination filter system, capable of removing heavy metals and nitrates.
Bacterial growth can occur in filters if they are left unused for a long period of time, as they would be, for instance, at a holiday home. Any treated water not used immediately should be refrigerated.
All filter cartridges should be changed regularly, in accordance with the manufacturer’s instructions. The maximum filter cartridge life recommended by BRITISH WATER is 6 months for standard filters
The primary causes for nitrate contamination in groundwater are failed or overloaded or improperly constructed and located septic systems, animal waste and fertilizer. Water that comes in contact with these sources will absorb nitrate and carry it down into the soil eventually ending up in the groundwater.
If a consumer chooses to reduce nitrate levels, there are several plumbed-in drinking water filters available to do the job. Be aware, though, that there are many types of drinking water filters available, with different capabilities and only some will remove or reduce nitrate.
Nitrate removal filters use the ion exchange principal as with water softening
If you are on your own private well you can choose to either remove the nitrate through out the house, or purify at one or more faucets. Since bathing in nitrate is usually thought of as a health threat, it can more practical and less expensive to treat for nitrate at one tap, often the kitchen sink.
The higher the TDS, the less palatable the water is considered to be. Sea water ranges from 30,000 to 40,000 ppm. Many brackish ground water supplies contain private well water with a TDS of 1500 – 5000 ppm. In some cases the levels exceed 7000 ppm. Generally, one wants a TDS of less than 500 ppm for household use.
In our experience, it appears that folks can tolerate for general household use, soft clean water with a TDS of up to 1500 ppm. When the levels start to exceed 1500 ppm, most people start to complain of dry skin, stiff laundry, and rapid corrosion of piping and fixtures. White spotting and films on surfaces and fixtures is also common at these levels and can be very difficult or impossible to remove.
TDS affects taste, and waters over 500 – 600 ppm can have an alkaline taste. When the levels top 1500 ppm, most people will report the water tastes very similar to weak alka-seltzer.
TDS is removed by distillation, reverse-osmosis or electrodialysis. Increasingly most desalination projects, both large and small are accomplished with reverse-osmosis. Depending on the water chemistry, reverse osmosis systems are the most popular, given their low cost and ease of use. For point of use, at one faucet, distillers work very well also, and produce very high quality water, but require electricity and higher maintenance than reverse osmosis systems.
Tannins in well waters form from humic acid, which is one of the major components of humic substances (or Natural Organic Matter (NOM). These are the dark brown constituents of soil organic matter. They can also be found in peat, coal, many upland streams and ocean water. Tannins are astringent, bitter-tasting plant polyphenols that bind and precipitate proteins. The word tannin refers to the source of tannins used in tanning animal hides into leather; however, the term is widely applied to refer to brown colour in water, caused by decaying organic substances.
Tannins can be removed by tannin filters. These filters remove tannin by ion-exchange, using anion exchange media. The units we use regenerate with rock salt (sodium chloride) in the same way water softeners function. Frequently we see shallow wells under the influence of surface run-off water, achieve high levels of tannins (turning the water brown) during heavy rainy periods. Tannin filters are often an excellent relatively low-cost technology to use for this type of problem, if the actual cause of the problem (such as sealing off the well from the surface) cannot be achieved.
A very effective method to remove tannin colour is by using ultrafiltration (“UF”) membrane systems. UF systems can be used by homeowners, small communities and commercial sites to reduce turbidity and produce crystal clear water less than 0.1 NTUs. Care must be taken to properly pretreat the water if UF is used if iron, manganese or hardness minerals are present.
In some cases, by pretreating the water with chlorine or ozone, direct filtration can be used.
Low pH or acidic water can cause corrosion of copper pipe fittings. In extreme cases the copper the water dissolves from pipework can react with soaps causing water to turn blue and with hair dyes giving unpredictable results, e.g. blondes go green.
Treatment is accomplished by neutralizing the water with the use of a neutralizer filter. The filter uses a media in the filter which corrects the acidic nature of water without the need for mixing or dosing of chemicals. The media slowly reacts with water and the filter media is topped up, usually once a year
Often the pH is less than 5.0. Treating this type of water requires using a soda ash feeder, and in some cases injection of sodium hydroxide.
Coliform bacteria are common in the environment and are generally not harmful. However, the presence of these bacteria in well water or spring water usually indicates that the water may be contaminated with germs that can cause disease.
E. coli, is a type of faecal coliform bacteria commonly found in the intestines of animals and humans. E. coli is short for Escherichia coli. E. coli comes from human and animal wastes. The presence of E. coli in water is a strong indication of recent sewage or animal waste contamination. Sewage may contain many types of disease-causing organisms.
If the contamination is a recurring problem, try to identify the source of the problem (such as a defective well seal, or cracked casing) and fix it. You can also install a disinfection unit.