Water Contaminants
1). Alkalinity
The alkalinity of natural waters is associated with the carbon dioxide, bicarbonate, carbonate, and hydroxide components. These factors are characteristic of the source of water, and the natural processes taking place over any given time. For particular industrial and domestic use, it is often desirable to change these characteristics by treatments such as aeration, neutralization, softening, etc. The particular treatment and the extent to which it is employed will depend upon the end use of the water.
2). Ammonia (Ammonia Nitrogen)
Ammonia nitrogen is present in various concentrations in many surface and ground water supplies. Any sudden change in the amount of ammonia in a supply which has been of rather constant composition is cause for suspicion. A product of microbiological activity, ammonia nitrogen is sometimes accepted as chemical evidence of sanitary pollution when encountered in natural waters.
Ammonia is rapidly oxidized in natural water systems by special bacterial groups that produce nitrite and nitrate. The oxidation requires that dissolved oxygen be available in the water. Ammonia is an additional source of nitrogen as a nutrient which may contribute to the expanded growth of undesirable algae and other forms of plant growth thus overloading the natural system and causing pollution.
3.)Carbon Dioxide
Carbon Dioxide is present in water supplies in the form of dissolved gasses. Surface waters generally contain less than 10 mg/L. Free carbon dioxide, while some groundwater may easily exceed that concentration. Corrosion is the principal problem caused by high concentrations of carbon dioxide in water.
Aquatic plant life depends upon carbon dioxide in water for growth. Microscopic plant life suspended in the water – called phytoplankton – as well as large rooted plants- utilize carbon dioxide in the photosynthesis of plant materials (starches, sugars, oils, proteins etc.) the carbon in all of these material comes from the carbon dioxide.
When the oxygen concentration in waters containing organic wastes is reduced, the carbon dioxide level rises. The rise in carbon dioxide makes it difficult for fish to use the limited amount of oxygen available to them. To take on fresh oxygen, the fish must first discharge the carbon dioxide in their blood stream, and this is a much slower process when there are high concentrations of carbon dioxide in the water itself.
4). Phosphorus
Phosphorus is an important nutrient for aquatic plants. The amount found in water is generally not more than 0.1 mg/L unless the water has become polluted from waste water sources or excessive drainage from agricultural areas. When phosphorus is present in excess of the concentrations required for normal aquatic plant growth, a process called eutrophication occurs. This create a favorable environment for the increase in algae and weed nuisances. When algea die, oxygen is used in the decomposition, and fish kills often result. Rapid decomposition of dense algae scums with associated organisms give rise to foul odors and hydrogen sulfide gas.
5). pH
The pH is an Index of the acidic, basic, or neutral nature of the water. Most natural waters have a pH of 5.0-8.5. The acidic, freshly fallen rain may have a pH of 5.5 – 6.0. when this rainwater comes in contact with soil and minerals containing weakly basic materials, the water may become slightly basic with a pH value of 8.0-8.5. Waters more acidic than 5.0 and more basic than 8.5-9.0 should be viewed with suspicion. Acid mine drainage and the introduction of acid or basic industrial wastes are generally the cause of this.
6.) Nitrate
Nitrogen is essential for plant growth, but the presence of excessive amounts in water supplies presents a major pollution problem. Nitrogen compounds may enter the water as nitrates or be converted to nitrates from agricultural fertilizers, sewage, and industrial wastes. Nitrates in large amounts can cause “blue babies” (methemomglobinemia) in infants less than 6 months of age. Nitrates in conjunction with phosphates stimulate algae growth with all of the related difficulties associated with excessive algae growth.
7). Dissolved Oxygen
Oxygen is vital to the life cycle common to water. It is essential to keep organisms living, to sustain species reproduction, and for the development of populations. Oxygen is soluble in water, although the solubility decreases as temperature increases. Salt water holds less oxygen than fresh water. Oxygen can enter the water by direct absorption from the atmosphere, or from plant respiration. It is removed from water by organism respiration and by organic decomposition. During respiration and decomposition, animals and plants consume oxygen and produce carbon dioxide. Organic wastes may overload the natural system and cause a serious depletion of the oxygen supply in the water. Waters rich in nutrients produce large amounts of algae which, upon decomposition, deplete the oxygen supply. Fish kills are often associated with this process called eutrophication.
Standards for dissolved oxygen vary, but a general requirement for fresh water fish is no less than 4.0 mg/L for warm water fish populations, and 5.0 mg/L for cold water fish populations.
8). Iron
Most natural water s contain some iron. Its presence may vary from the smallest trace to very large amounts in water which is contaminated by acid mine wastes. For domestic use, the concentration should not exceed 0.2 mg/L. High concentrations of iron can be removed by chemical processes such as oxidation, and lime softening.
9). Hardness
Hardness of water is a function of the total concentration of Magnesium and Calcium ions. Calcium and Magnesium may be added to a natural water system as it passes through the ground containing large amounts of these mineral deposits. Water containing small amounts of these ions is termed “soft”. Water containing large amounts is termed “hard”.
From the domestic standpoint, hard water consumes excessive quantities of soap, and forms curds and deposits on hair, fabrics, and glassware. Drinking water standards determine water with a total hardness between 0 – 60 mg/L is considered :soft”, from 60 – 120 mg/L medium hard”, 120-180 “hard”, and anything above 180 mg/L “very hard”
Questions
1). For the Nitrate, pH, Dissolved Oxygen, and Phosphate tests performed, provide the Q value from graphs provided, and the overall rating (i.e. excellent, good etc.)
Test / Q value / ScoreHardness
Ammonia
Nitrate
Phosphate
pH
Dissolved Oxygen
Carbon Dioxide
2). Give 2 domestic problems associated with water hardness.
3). Which dissolved gas is a product of organism respiration?
4.)Which dissolved gas is a product of plant respiration?
5). What are the two major ways that oxygen can enter the water?
6). As the temperature of a body of water increases, what would you expect to happen to the concentration of dissolved gases?
7). What is eutrophication?
8). What potential water contaminant is responsible for “blue babies”?
9). Give 3 contaminants that can give rise to an increase in algae population.
10). How does a high Carbon Dioxide concentration effect fish respiration?
11). Provide the Dissolved Oxygen level found for your water sample. Is it enough to support a fish population?
12). In your own words, describe the overall quality of your water sample. Would you drink it? Would you bathe in it?