1. What are the three basic causes of water corrosively toward metals: Three basic characteristics of water that promote corrosion are: 1) oxygen content, 2) acidity and 3) electrical conductivity. High oxygen content, high conductivity (i.e., high TDS) and low pH will each make water more corrosive. High alkalinity in water can also contribute to greater corrosion. The rate of corrosion may also increase with higher temperature and higher flow rate.
2. The Safe Drinking Water Act extends Federal Standards over all water systems with 15 or more service connections or that serve 25 or more people.
3. Water does not significantly compress or change in volume under pressure as does air.
4. Algae are a major source of taste and odor problems. Algae are simple forms of plant life and are commonly present in surface supplies.
5. Major factors affecting the growth of algae are temperature, nutrients, sunlight and dissolved carbon dioxide.
6. A bad taste and rotten egg odor in water is caused by the presence of hydrogen sulfide.
7. The finer the media, the shorter the filter run because more suspended material will be collected in the bed. When coarse media is used, the suspended material penetration is usually deeper, longer filter runs can be expected and there may be less removal of the finer turbidity particles.
8. The chlorine demand goes up because the turbidity may contain substances that react with (use up) chlorine. Turbidity also interferes with disinfection by preventing the chlorine from killing bacteria buried within the suspended material.
9. Softening water through the use of ion exchange equipment does not change the majority of the factors which affect corrosion: Oxygen content, acidity, alkalinity, total minerals, water temperature or water flow rate, nor does it significantly increase electrical conductivity.
10. Theoretically lime-soda softening cannot reduce hardness below 26 mg/l as CaCO3 because of the solubility of CaCO3 (calcium carbonate or lime). Due to slow reaction rates, waters softened by the lime-soda ash processes usually have from 85 to 140 mg/l (about 5-8 gpg) of residual hardness as calcium carbonate.