Chemistry: Water Pollution
Phosphates in Water Pollution

Phosphates may be created by substituting some or all of the
hydrogen of a phosphoric acid by metals. Depending on the number of
hydrogen atoms that are replaced, the resulting compound is described as
a primary, secondary or tertiary phosphate. Primary and secondary
phosphates contain hydrogen and are acid salts. Secondary and tertiary
phosphates, with the exception of those of sodium, potassium and
ammonium are insoluble in water. Tertiary sodium phosphate is valuable
as a detergent and water softener. The primary phosphates tend to be
more soluble.
Phosphates, which are an important component to metabolism in
both plants and animals, help in the first step in oxidation of glucose
in the body. Primary calcium phosphate is an ingredient of plant
Phosphates have caused increasing attention recently. The focus
is on the environmentally harmful effects in household detergents.
Wastewater, from laundering agents, contains phosphates, which are said
to be a water pollutant.
Most laundry detergents contain approximately 35% to 75% sodium
triphosphate (Na5P3O10), which serves two purposes. Providing an
alkaline solution (pH 9.0 to 10.5) is necessary for effective cleansing
and also to tie up calcium and magnesium ions found in natural waters
and prevent them from interfering with the cleansing role of the
Eutrophication is the progressive over-fertilization of water,
in which festering masses of algae\'s blooms, choking rivers and lakes.
Phosphorus compounds act as a fertilizer for all plant life, whether
free-floating algae or more substantial rooted weeds, and are implicated
in eutrophication. Many countries control phosphate levels, whereas
Switzerland has banned the use of phosphates.
The marine environment is both fragile and more resistant than
the terrestrial ecosystem. It is fragile for the reasons that nutrients
are generally present in very low concentrations, permanently consumed
by living organisms and pollutants diffuse rapidly.
Lakes and rivers are extremely complex ecosystems. Nutrients are
taken up by both algae and rooted weeds. The weeds act as a shelter for
fish larvae and zooplankton, both of which eat algae and are, in turn,
eaten by larger fish. Scientists have concluded that unpolluted lakes
can absorb surprisingly large amounts of phosphates without uncertainty.
When a fertilizer, such as a phosphate, is added more algae will grow,
and consequently will the populations of zooplankton and fish.
Difficulties only arise when the lake is already impure. Zooplankton are
sensitive to their environment and many substances are toxic to them. If
any of these substances, including phosphates, are present the
zooplankton population cannot increase. Adding phosphates to this
polluted system will case algae growth. The floating masses cut off the
light supply. Weeds die and decompose using up dissolved oxygen, and
causing sulfurous smells and plagues. Deprived of shelter and food, the
fish larvae starve. The lake is well on the way to catastrophe.
Without wetlands there would be a minimal amount of fresh
drinking water due to the fact that wetlands filter the waters of our
lakes, rivers and streams, sequentially reducing contamination of water.
The plant growth in wetlands removes phosphates and other plant
nutrients washed in from the surrounding soil, consequently restricting
the growth of algae and aquatic weeds. This growth is a serious problem
in some of Canada’s major waterways, where dead and decaying algae
deprive the deeper waters of their oxygen.
Researches at Lancaster University have studied lakes whose
plant and animal life has been killed by acid rain. The excess acid in
the lakes can be neutralized easily by adding lime, but this makes the
waters rich in calcium. Life will gradually return to the lake but, as
these lakes should have low calcium levels, it will not be the same kind
of life that existed in lakes before pollution. The answer, they have
concluded, is to add phosphates.
These phosphates work by shielding the water. This depends upon
nitrate ions in the lake. Contradictory, these ions also are produced by
acid rain, contain oxides of nitrogen from combustion sources. These
fertilizers do not alter the pH level of the water. Instead, they
stimulate the growth of plants. The plants absorb the dissolved
nitrates, generating hydroxide ions, which in return neutralize the
excess acid.
Removal of phosphates from detergent is not likely to slow algae
growth in containing substances. It may actually prove disastrous. Its
replacement with