You have already seen that potassium permanganate is used in treating water.   However, the following chemicals are also used in water treatment. 

Lime

At the end of the aeration basin, we add lime, also called calcium hydroxide (CaOH). Water is capable of dissolving anything (including plastic, glass and metal), so we need to change the chemistry of the water so that is not longer corrosive.  When we add the lime, it forms a protective coating inside of the pipes.  This helps protect our pipes since the water must dissolve the lime before it gets to the pipe.

Aluminum Sulfate (Alum)

t may seem strange, but we make the water dirty to make it clean.  To help do this we add alum, also called aluminum sulfate (Al₂SO₄^-3).  The alum works like a little magnet.  The aluminum ion is positively charged, and many viruses, bacteria, and dirt are negatively charged.  Like a magnet which attracts things with an opposite charge, the alum attracts these small particles in the water.  The resulting "clumps" are called floc particles.  As floc particles grow, they become large enough to be seen in the water.  They may appear to be little snowflakes in the water.

Ferric Chloride

Both Ferric Chloride and Aluminum Sulfate can be used interchangeably since both chemicals serve the same function.

Polymer (Cat-Floc TL)

If you try to pick up too many paper clips with a magnet, some will not stick to the magnet.  This is because the magnet is not strong enough to hold the outer paper clips.  If you were to put the paper clips and magnet into a plastic bag, then all of the paper clips could be held together.  We have the same problem with the floc particles that you would have with the paper clips.  Once the floc particles are formed, they are fragile and can be torn apart.  So, we add a cationic (positively charged) polymer to make the floc particle stronger.  Just like the plastic bag, the polymer forms a protective coating on the outside of the floc particle. Because the polymer does not like to be added to the water, and it branches out and surrounds the floc particle.  This make the floc particle much more stable.  Cat-Floc TL is added early in the treatment process.

Polymer (POL-EZ 675)

POL-EZ 675 is an anionic (negatively charged) polymer.  It is added to water late in the treatment process and forms a layer on the top of the water in the filter.  It attracts the particulates going through the filter and keeps them in the filter rather than letting them pass through.  This layer does not pass through the filter media and is removed from the filter media during a filter backwash. 

Chlorine

In streams and lakes, bacteria and other pathogenic (disease causing) organisms are present.  In order to make sure that these organisms are not present in tap water, the water must be disinfected to inactivate the harmful organisms.  We use Chlorine (Cl₂) to accomplish this important job.  Chlorine works by attacking the organisms through a process called oxidation.  The exact way that chlorine works to inactivate the harmful organisms is not fully known.  One theory maintains that chlorine exerts a direct action against the bacterial cell, thus destroying it.  Another states that the toxic characteristic of chlorine inactivates the ENZYMES which enable living microorganisms to use their food supply.  As a result, the organisms die of starvation.

Sodium Hydroxide (NaOH)

Sodium Hydroxide is strong caustic chemical used in treatment processes to neutralize acidity, increase alkalinity, or to raise the pH value.  It is also know as caustic soda, sodium hydrate, lye, or white caustic.

Fluorosilicic Acid (Fluoride)

Fluoride was approved by popular vote and is now required by Salt Lake Valley Health Department Regulation #33.  The Metropolitan Water District of Salt Lake & Sandy began adding fluoride as required on October 1, 2003.  Your tap water now has 1.0 mg/l fluoride.

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