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

fertilizer.

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

detergent.

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 borax will definitely be disastrous. Scientists are

unsure of borax role in plant growth. It is not required by algae and

other micro plants, but it is essential to higher plants. However in

excessive quantities, about 5 micrograms of boron per gram of water,

boron severely damages plant life. Highly alkaline substances, gel

proteins and sodium hydroxide is hazardous substances.

Another concern is the fact that each year thousands of children swallow

detergents resulting in serious injuries or death.

In conclusion, the only way to overcome the disastrous effects

of phosphates is to find an alternate. However, an acceptable substitute

for phosphates has not yet been found. Washing only with synthetic

detergents would require so much detergent that the cost per wash would

increase significantly. Another alternative is the substitution of

synthetic nonionic detergents for ionic detergents in use. Nonionic

detergents are not precipitated by Calcium of Magnesium ions. This

would reduce the risk contaminating our lakes and rivers.