Fresh water may come from either a surface or ground source and typically contains less than 5 000ppm TDS
Brackish water contains between 5 000 and 25 000ppm of TDS. Its sources can either be natural fresh water alone or mixed with seawater.- Brackish water differs from open seawater in the biological activity.- Within harbours, bays and estuaries differences can exist in the amount and type of constituents present in the water. The main constituents are the salinity and the silt. Extensive seasonal variations in these are observed.
Potable water is natural fresh water that is made safe for drinking purposes by filtration, extensive treatment and/or disinfection.-World Health Organisation (WHO) issues the guidelines for the allowable limits of various constituents in potable water. Many countries also have their own standards.
Distilled or Demineralised Water
The minerals can be removed by Reverse Osmosis, Distillation or Ion Exchange processes.- Water quality is described by specific conductivity.- When the specific conductivity reduces to <0.1µs/cm (Microsiemens Per Centimetre), it is expressed in resistivity (MΩ.cm) – for ultra pure water.
Cooling water require treatment against excessive scaling or corrosion.- This may include anything from natural water to seawater and may comprise either an open- or closed- loop system or a once through system.
Boiler Feed Water
The Boiler Feed Water requires to be softened or demineralised or combination of both. Based on boiler pressure it may be required to be de-aerated. It may potentially include recovered steam condensate.
This is a general term commonly used to describe water used for process purposes in various industries.- This can vary from simple filtered water to several times purified ultra pure water (UPW).
This is a term used to describe water which is used for general purposes such as washing, flushing, cleaning of process equipment and gardening.
By definition waste water is any water that has been adversely affected in quality by human influence.- Water that results from industrial process or manufacture of goods are classed as industrial waste water.- Industrial waste water contains contaminants that are specific to the industry and unit operations.
The waste water from residences and institutions carrying human waste, washing water, food preparation wastes, laundry waste and other waste products, are classed as domestic or sanitary sewage.- Waste water from shops/stores and community service establishments, is termed commercial wastes is included in the sanitary or domestic sewage category if their characteristics are similar to household flows.
Grey & Black Water
Grey water is the waste water that comes from the laundry, bathroom faucets, baths and showers.- Black water is the waste water that comes from the toilet, kitchen and garbage disposal.- Municipal domestic sewage is the combined mixture of all grey and black water.
Seawater typically contains about 35 000ppm TDS or 3.5% salinity. The salinity may be reduced due to dilution by rivers with fresh water or due to concentration by solar evaporation in small bodies of water.- Seawater contains impurities such as Boron, Barium, Strontium and various micro marine organisms.
Common Water Problem
Whether fed from a municipal source, a borehole, a river, or the ocean, all water supplies contain dissolved mineral salts, microbiological contaminants and other materials. The amounts present determine the final analysis of the water, and ultimately whether the water is suitable for its intended application. In order to provide quality water for domestic and industrial use, the impurities that exceed acceptable levels have to be identified. Water treatment equipment should never be installed without a detailed water analysis. In this section, we discuss common water problems, how to identify them, the affects they can have on drinking and process water, and the most effective ways we can treat them.
Bacteria & Viruses
The human body contains certain amounts of coliforms and E. coli bacteria. In normal concentrations, these bacteria are not harmful. Most E. coli are harmless. Some strains, however, may cause illness such as diarrhoea, cramps, nausea, headaches or other symptoms. The presence of E. coli or faecal coliform in a drinking water sample may indicate human or animal faecal contamination. There are a number of methods for effective bacteria removal, which includes Chlorination, Ultraviolet Disinfection, Ozonation, Reverse Osmosis and certain types of Filtration.
Fluorides in water can be harmful to humans and animals, depending on the concentration. Excess amounts of fluoride in the water can cause a condition known as ‘endemic dental fluorosis’ during the period of tooth formation. This condition leads to dark brown staining of teeth. Conversely, low concentrations of fluoride (such as those found in most toothpastes) help protect against tooth decay. The most effective way to remove fluoride is using Reverse Osmosis.
Iron & Manganese
Iron is a problem usually associated with borehole water supplies. Iron can be found in 2 states. Water containing ‘Ferrous’ iron is usually clear when it comes out of the ground, but becomes cloudy or red when it comes into contact with air, converting the iron to its ‘Ferric’ state. Traces of ferric iron can often be seen through the red stains found on basins, baths, toilets and staining on laundry. Manganese is usually found in the same water supplies as iron. Even small concentrations of manganese can cause brown or black stains to appear. Specialized Iron Removal Filters can be used to remove iron & manganese from water supplies.
In most water supplies, the presence of excessive nitrate levels is as a result of pollution by organic matter. Usually, excessive nitrates are only found in borehole supplies. An example would be where a borehole and a septic tank are too close to one another. Concentration of nitrates in excess of 10 ppm in drinking water supplies can cause cyanosis (blue baby). Cyanosis results on a poisoning of the blood, decreasing its ability to effectively carry oxygen through the body. Nitrate removal is most effectively carried out using a Reverse Osmosis System, usually combined with a Water Softener.
The pH scale is used to express the acidity or alkalinity of water. The pH scale ranges from 0 to 14. A pH of 7.0 is neutral, indicating a balance between acidity and alkalinity. Values < 7.0 indicate increasing acidic strength. Conversely, values > 7.0 indicate increasing alkaline strength. Waters with pH < 7.0 tend to cause iron or copper pick-up in piping systems and often lead to staining problems. Blue or green staining will be seen if the piping is copper, and red or brown stains can be expected if the piping is iron. The lower the pH, the greater the tendency of the water to cause corrosion. Excess acidity in water is treated by neutralizing the acidity the through the addition of alkaline minerals. ENBITEC’s Filter Systems can be filled with neutralizing media, which slowly dissolves as the water passes over the media bed, adding a small amount of hardness to the water. This additional water hardness may mean that a water softener is recommended. The ideal pH range is 6.5 – 8.5.
Sodium can be found in almost all water supplies. Low concentrations of sodium have no effect on the taste or quality of drinking water, but as the sodium levels increase, the water will become more corrosive, and the taste will become unpleasant. Usually taste starts becoming apparent at around 500 ppm of sodium. Sodium can be removed using a Reverse Osmosis Process, Deionization Process, or by Distillation.
Excessive levels of sulphates will often lead to a metallic or medicine-like taste, and will act as a laxative. Sulphatecan be achieved by means of Reverse Osmosis, Deionization, Distillation process.
Taste & Odours
Tastes and odours are generally considered as the same problem, except for tastes caused by mineral salts. For example, water with high chloride content will have a salty taste but will probably not have any odour. A properly treated water supply should contain no trace of objectionable taste or odour. There are a number of tastes and odours that may exist in your water supply. Most often, these are caused by excessive chlorine, but can also include a musty or mouldy smell, or oil, gas or rotten egg odours. For each different type of bad taste or odour there is likely to be a different set of distinct problems and recommendations for treatment. Chlorine, mouldy or musty tastes and odours can usually be removed using an Activated Carbon Filter. Rotten eggs smells result from traces of hydrogen sulphide in the water, and will usually need to be oxidized or ozonised to effectively remove them.
Total Dissolved Solids
Total Dissolved Solids (TDS) is the name given to the sum of all the mineral compounds dissolved in a water supply. For the most part, TDS is made up of calcium, magnesium and sodium. High TDS levels can lead to a number of problems, ranging from a salty or brackish taste, to a decrease in the effectiveness of Water Softeners and other water treatment equipment. For domestic and most industrial water supplies, the maximum recommended TDS level is 500 ppm. Reverse Osmosis is the most commonly used process for the reduction of Total Dissolved Solids.
Excess hardness is one of the most common water problems on any water supply. Hard water can be used for most domestic applications, however it is unsuitable for industrial use. Using hard water can result in:- Excess use of detergents and other cleaning chemicals.- Scale build-up on heating elements and in industrial heating and cooling systems resulting in reduced lifespan of heating systems.- Higher electrical costs.- White deposits on glass, vehicles and other smooth surfaces in contact with water. Whilst there are a number of scale removal systems available, hard water can be most effectively treated using an Ion Exchange Water Softeners. Water softeners use an ion exchange process to remove the majority of calcium and magnesium ions from the water supply. During the exchange process, the calcium and magnesium ions are replaced by sodium ions, generated from a sodium chloride/water solution (brine) made in the system’s brine tank. For domestic purposes, the recommended hardness levels are 120-200 ppm. For industrial purposes, hardness should not exceed 50ppm.
Water Purification & Filtration Methods
Water Purification/Filtration is the process of removing undesirable chemicals, materials, and biological contaminants from contaminated water. The goal is to produce water fit for a specific purpose. Most water is purified for human consumption (drinking water) but water purification systems may also be designed for a variety of other purposes, including meeting the requirements of medical, pharmacology, chemical and industrial applications.