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Phosphorus:  Chemical Reactions of Phosphorus and Its Importance

Abstract:  Aluminum sulfate reacts with phosphates to create aluminum
phosphate and a sulfate.  The conversion of the phosphate to aluminum
phosphate is very important because this allows the phosphate to be easily
extracted.  This manipulation is used today in industrial waste treatment
sights.  The removal of phosphates is very important for if phosphates are
not removed, they plague bodies of water by feeding algae which clog the
surface waters and eventually effect every living and nonliving thing in
that environment.

Chemical Process:  The reactions which occur are the following:

Aluminum sulfate(alum) in combination with wastewater can flocculate
phosphorus.  The Flocculation that happens with aluminum sulfate addition
is the formation of aluminum phosphate particles that attach themselves to
one another and become heavy and settle to the bottom of a clarifier.  The
aluminum sulfate and phosphorus mixture can then be withdrawn, thereby
removing the phosphate or phosphorus from the wastewater flow.

Industrial Applications:  The application of this reaction to the
industrial world consists of a set of processes to filter out the phosphate.
 The setup is the following: Purpose:  Restrict phosphates to aluminum
phosphates for easier disposal of phosphorus.

     The first step in phosphorus removal is the Rapid Mix.  In this stage,
alum and waste or water runoff(known as effluent) is blended together as
rapidly as possible with the use of a high-speed mixer called a "flash
mixer."  After this instant mixing, a slower moving process called
coagulation and flocculation follows to allow the formation of a floc.
These processes occur in a Flocculation Chamber. This floc consists of
suspended and colloidal matter, mainly including the aluminum phosphate. 
Next, the effluent travels to a clarifier in which sedimentation occurs. 
The heavier aluminum phosphate settles to the bottom then pumps at the
bottom of the clarifier pump out the aluminum phosphate via pipes. This
aluminum phosphate is then disposed.  Currently, there are no economical
uses for aluminum phosphate.
     Also, this chemical process is similar to the process used by laundry
detergents.  Many detergents contain synthetic phosphates, called
tripolyphosphates(TTPs).  These chemicals cling to grease and dirt
particles(alum in the previous example), keeping them in suspension until
the wash water is flushed out of the washing machine.

Impact on Society: This reduction in phosphorus is very important. This
added phosphorus disrupts the natural cycle of phosphorus. One result of
this is an algal blooms, or exponential growth in algae. When algal blooms
occur, the surface of a freshwater lake is clouded with an almost finite
amount of bacteria because of an increase in a nutrient.  In this case an
increase in phosphate, a favorite for algae.  This deprives the bottom of
the lake by cutting off light.  A dense mat of algae choke off the lake. 
Also, phosphates are nutrients for plantlife. When fall approaches, or when
phosphate levels are decreased, the algae die and fall to the bottom,
changing the bottom from a silt, sand and clay bottom to a sand gravel and
rock bottom.  When the plants die, they are degraded by aerobic bacteria,
which can deplete dissolved oxygen, killing aquatic organisms.  As oxygen
levels drop, anaerobic bacteria resume the breakdown and produce noxious
products.  All of this impairs navigation, fishing, swimming and
recreational boating.
     Total phosphorus removal through filters after using alum as a
filtering aid achieves 70 to 95 percent efficiency.  Phosphates must be
filtered out before the water or wastes are dumped back into bodies of
water.

                               Glossary

Flocculation:  The gathering together of fine particles to form larger
particles.

Effluent:  Wastewater or other liquid -- raw, partially or completely
treated -- flowing from a basin, treatment process, or treatment plant.

Coagulation:  The use of chemicals that cause very fine particles to clump
together into larger particles.  This makes it easier to separate the
solids from the liquids by setting, skimming, draining or filtering.

Floc:  Groups or clumps of bacteria and particles or coagulants and
impurities that have come together and formed a cluster.

Colloidal:  Very small and finely divided.  Referring to solids. Does not
dissolve and remains dispersed in a liquid for a long time due to small
size.

Algal blooms:  Rapid growth of algae in surface waters due to increase in
inorganic nutrients.

                             Bibliography

Kerri, Kenneth D. Advanced Waste Treatment.  Sacramento, Ca.: CSU,

Sacramento, 1987.

Adams, Melinda.  Environmental Science.  Redwood City, Ca.:  The
Benjamin/Cummings Publishing Company, Inc., 1991.