Tassal Tasmanian Salmon, an Australian salmon farming company, backed away from plans to dump treated wastewater from salmon pens into...
Brushing Up on Water Chemistry 101
This article is part one of a three-part series addressing
water chemistry basics.
Basic water chemistry, terminology and applications can be very complicated and not seem so basic to individuals without a chemistry background. This series of articles will help shed light on the chemistry of water and the mysteries that it can contain, plus explain the technologies used to treat water so the purchaser can make an educated attempt to find the right solution for a particular application. There are no cut-and-dry formulas for water treatment and certainly no cure-all for every application or problem, but with an understanding of how water works and the technologies developed to treat water, a person can utilize his resources to come up with solutions for his particular need or application.
Water need not be obfuscated by the complexity that many
treatment professionals portray about the technologies. However, the general
public should not try and treat water with over-the-counter remedies, since
many times without proper knowledge, education or experience these remedies
will not work to their satisfaction and not achieve the desired result. The
store shelves are full of water treatment products, but unless the raw water
and application are understood, the problems will not be solved.
Water is a universal solvent and will dissolve everything it
touches to some degree, taking with it impurities, organics and man-made
chemicals. Everyone has a different use or expectation of water, whether it is
a health official, industrial firm, hospital, farmer, homeowner or scientist.
Each user has special requirements in terms of water quality and when these
requirements are not met, trouble begins. To provide the right water for any
demand depends on several factors, the analysis of the raw water, the
employment of the end use and the nature and amounts of these impurities as
well as the tolerances permissible. Water quality may prove unacceptable or
unsatisfactory for certain requirements but may be quite favorable for other
instances. To treat water economically, the raw water and end use always must
Webster defines this fascinating substance we call water, as
“a liquid, which descends from clouds in rain that creates rivers, lakes,
seas, etc. Pure ordinary water is (H2O) consisting of hydrogen (11.1888
percent) by weight and oxygen (88.812 percent). It is very slightly
compressible. Its maximum density at 39.2º F or 4º C is the standard
for the specific gravities of solids or liquids, and its specific heat is the
basis for the calorie and British thermal unit (BTU) of heat. It freezes at
32º F or 0º C.”
The term pure water is ambiguous and has different
connotations to individuals in various fields. A bacteriologist, for example,
is apt to regard “pure water” as a sterile liquid with no living
bacteria in it. A chemist would classify water as “pure” when it
possesses no minerals, gaseous or organic impurities. Obviously, “pure
water,” as described here is likely to be found only in laboratories and
even then only under ideal conditions.
The U.S. Environmental Protection Agency (EPA) provides
practical standards for water of its suitability for drinking or potability in
the Primary Drinking Water Regulations and for aesthetic considerations in the
Secondary Drinking Water Regulations. These regulations take into consideration
adequate protection of water against the effects of contamination through
natural processes and through artificial treatment. The list of standards set
requirements for bacterial count, plus physical and chemical characteristics.
It is almost impossible to find a source of water that will meet the basic
requirements for a public water supply without requiring some form of
treatment. The general requirements are that it shall not contain any
disease-producing organisms, be colorless and clear, good tasting and free from
odors and preferably cool, be non-corrosive, free from objectionable gases or
minerals which cause staining, and that it be plentiful and low in cost.
Potable, or safe water is not necessarily usable or useful for many purposes
and may require treatment of another sort to render it useful to home, industry
or a scientist.
Water supplies vary from area to area and each are generally altered from a geographical standpoint and environmental aspects that cause these variations. The hydrological cycle causes this phenomenon as a complete sky to earth circuit is pursued by water in nature. As the largest water purification system known to man, the water cycle (See Water Definitions: hydrologic cycle)
cleanses the air and picks up impurities from the Earth’s crust. This
vapor provides protection against extremes of heat and cold and the cleansing
effects leaves water with undesirable minerals and man-made contaminants that
cause problems, thus requiring treatment.
As the water falls through the air, a weak acid is formed
that reacts with vegetation, limestone, granite and sand. Only 30 percent of
the precipitation that falls to the ground finds its way into lakes, rivers and
oceans or percolates into the ground. The other 70 percent is evaporated and returns to the atmosphere almost immediately to start over in the process of cleansing the earth. The geographical areas that this acid falls on creates various degrees of impurities and the atmospheric content the water fell through causes different complications for water treatment professionals.
Sources from which water is drawn provide other
complications for treatment. Each water source, whether it is a lake, river,
well or municipal system, has its own unique set of contaminants that must be
dealt with. Couple these with applications of various natures such as home,
industry, commercial and agricultural and the water treatment professional has
his work cut out for him. In the ensuing articles of subsequent nature, such
technologies as ozonation, ionization, filtration, aeration, distillation,
ultraviolet light and reverse osmosis will be discussed and examples of each
will be presented along with the outcomes of how they faired in the application
they were used to treat. Contaminants such as hardness, iron, hydrogen sulfide
and manganese, will be reviewed. So, come along for an educational journey
above and below the earth’s surface to find out more about water and how
water treatment professionals deal with this life sustaining substance.
Part 2 of this article will appear in the June issue and
part 3 in the July issue.