The total area of the earth is composed of 2/3 water, making it one of the most plentiful and most important resources available. Without potable water, humankind cannot survive.
Pure water consists of two parts hydrogen and one part oxygen, chemically combined to form pure water. The only pure source of water is the earth’s atmosphere (sometimes called the hydrological cycle). Impure water from the earth’s oceans, lakes, rivers and surface evaporates into the atmosphere then condenses to form rain droplets which are totally pure. The above process operates basically the same as a man-made still, which evaporates all the impurities from the water, then returns the condensates into pure water. If this process did not exist, there would likely not be enough potable water to support the earth's population.
The pure water vapor – which forms in the earth's atmosphere as clouds – begins to pick up impurities. As it begins to fall to the earth in the form of rain, snow, etc., impurities are immediately absorbed. A little of everything found in the atmosphere (dust, micro-organisms, gases, etc.) is absorbed on the way to the surface.
Rain or snowfall then finds its way to various sources of water supplies on the earth's lakes, rivers, oceans or it may seep into the ground and become part of an underground stream or lake.
CHARACTERISTICS OF VARIOUS WATER SOURCES
After the water picks up impurities in the atmosphere and percolates through the ground, it comes into contact with carbon dioxide and then forms carbonic acid. This dissolves some of the mineral content of the soil or rock it contacts, thus adding these minerals to the water.
Water from streams may be turbid due to the presence of silt, clay, etc. However, in larger surface water, a greater amount of self-purification takes place through aerobic digestion, plant life, fish, etc. and the quality of the water could change to a great degree.
Normally picks up the minerals it flows through. As a general rule, water from deep wells contains a higher mineral content and is less likely to contain organics or turbidity. Water from shallow wells is usually lower in mineral content and may be subjected to pollution or other bacteria which is available from various sources nearby (e.g. spring run-off through forests and hills, plants, industrial wastes, etc. which will all pass various bacteria into the water).
Impurities in water are divided into two classifications:
1. DISSOLVED SOLIDS
Solids which naturally dissolve into water. NOTE: Gases may also dissolve into water unless they combine chemically with other impurities. They will be released into the atmosphere upon boiling and are not truly classified as dissolved solids. Upon evaporation, only the dissolved solids would remain in the actual mineral form and then can be analyzed by actual weight of the various elements.
2. SUSPENDED SOLIDS
Consist of clay, mud, silt, etc. and will not dissolve into water naturally but remain as such in their present state.
Water treatment and pollution control is one of the largest and most important industries in the modern day world. As can be seen from the preceding information, water treatment is a very broad and varied field and chemical analysis of certain water supplies is virtually impossible to completely break down. In time, humankind may discover additional information regarding the field of water treatment and the entire cycle of the earth's largest and most important single resource. The following sections will attempt to clarify some of the more common problems and solutions presently available.
GRAINS PER GALLON - GPG
1/7000 of a pound - normally used in relation to hardness.
PARTS PER MILLION - PPM
One part dissolved material in one million parts of water. Used as a measurement for iron, manganese, TDS, hydrogen sulfide, chlorides, sulfates and tannins.
MILLIGRAMS PER LITER - MG/L
For our purpose, same as PPM Normally used for a more accurate measurement or where small quantities of certain elements cause big problems in relation to iron, manganese, sulphur, nitrates and silica.
CONVERTING GPG TO PPM OR MG/L
1 gpg = 17.1 PPM (mg/l)
TOTAL DISSOLVED SOLIDS - TDS
The weight of solids, per unit volume of water, which are in true solution. Can be determined by the evaporation of a measured volume of filtered water and determination of the residue weight. A common alternative method to determine TDS is to measure the conductivity of water.
A characteristic of natural water due to the presence of dissolved calcium and magnesium. Water hardness is responsible for most scale formation in pipes and water heaters and forms insoluble "curd" when it reacts with soaps. Hardness is usually expressed in grains per gallon (gpg), parts per million (PPM) or milligrams per liter (mg/l), all as calcium carbonate equivalent.
Iron that is oxidized in water and is visible. Also called red water iron.
Iron that is dissolved in water. Also called clear water iron.
pH is a measure of the intensity of the acidity or alkalinity of water on a scale from 0 to 14, with 7 being neutral. When acidity is increased, the hydrogen ion concentration increases, resulting in a lower pH value. Similarly, when alkalinity is increased, the hydrogen ion concentration decreases, resulting in higher pH. The pH value is an exponential function so that pH 10 is 10 times more alkaline than pH 9 and 100 times more alkaline than pH 8. Similarly, a pH 4 is 100 times more acid than pH 6 and 1000 times more acid than pH 7.
For correct sizing and application of water conditioning equipment, a water analysis is required. A basic water analysis includes tests for the following:
- TDS (Total Dissolved Solids)
Water samples should be taken as near the source as possible and represent the average water condition. Clean containers must be used. When performing the analysis, the test equipment must be clean and rinsed with the test water and the test water should be between 68ºF and 77ºF (20ºC and 25ºC). Use rubber stops as supplied. Do not use your fingers as contaminants and acids could affect test results.
Additional tests can be performed for tannins and hydrogen sulfide (H2S). The test for H2S must be performed on-site for accurate results. Special tests can be performed for chlorides, sulfates and alkalinity by specified laboratories. If it is suspected the water supply is contaminated with coliform bacteria or nitrates, a sample must be collected in an approved sterilized container and submitted to a government approved laboratory. Iron bacteria will not be detected with the standard iron test and can be tested for by a government approved laboratory.
If the TDS is over 1000 PPM and hardness is less than 30% of the TDS, a complete water analysis should be performed to discover what other contaminants exist in the water.
If a contaminant exceeds the limits detectable by any test method, the raw water sample can be diluted with distilled water until a reading can be taken. A calculation must then be performed to determine the actual degree of contamination. All test chemicals are susceptible to age and extreme temperatures. Proper storage techniques and expiry dates should be observed.
The Water Analysis Report must be completed accurately to determine the correct equipment to recommend for the water problem(s) being experienced.
Water with a total hardness of 1.0 gpg or more as calcium carbonate equivalent.
Less than 1.0 gpg.................... Soft
1.0 - 3.5 gpg........................... Slightly hard
3.5 - 7.0 gpg........................... Moderately hard
7.0 - 10.5 gpg......................... Hard
More than 10.5 gpg................. Very hard
A characteristic of natural water due to the presence of dissolved calcium and magnesium. Water hardness is responsible for most scale formation in pipes and water heaters and forms insoluble "curd" when it reacts with soaps. Hardness is usually expressed in grains per gallon (gpg), parts per million (PPM) or milligrams per liter (mg/l) all as calcium carbonate equivalent.
Any water which contains less than 1.0 gpg (17.1 mg/l) of hardness minerals, expressed as calcium carbonate equivalent.
Any water that is treated to reduce hardness minerals, expressed as calcium carbonate equivalent.