The  following description of "Hard" water was used  as  part  of  
presentation  to  a company describing the benefits  of  treating 
their  incoming water from a well, used to clean parts  prior  to 
painting and plating. 

                          Water Supply

What  is considered normally good, mineral laden, drinking  water 
is  not  always  good process water. All  ground  water  supplies 
contain a a certain amount of dissolved minerals. In those  areas 
where  the  ground water is predominantly limestone,  rain  water 
dissolves significant amounts of calcium and magnesium carbonate. 
This  is caused by the fact that the rain water starts out  rela-
tively  pure,  and on it's way through the air,  dissolves  large 
quantities  of carbon dioxide from the air. Carbon  dioxide  gas, 
when  dissolved in water forms carbonic acid and causes the  rain 
water to be slightly acidic (did you ever hear of putting a rusty 
nail  in Coca-Cola?). This "acidity" is then neutralized  as  the 
rain  filters  through  the limestone  changing  the  water  from 
slightly "acidic" to slightly "alkaline". Because most waters are 
not completely alkaline, they contain a mixture of carbonates and 
partially neutralized carbonic acid known as bicarbonates.

Over the years , these particular dissolved minerals have  become 
known  by the trouble they cause. Calcium and magnesium,  because 
they  retard  the action of soaps and detergents,  got  the  name 
"hardness".  They leave their evidence in wasted  cleaners,  soap 
film  and insoluble sludge. Carbonates and  bicarbonate,  because 
they  are the opposite of acids, got the name "alkalinity".  When 
found  with  calcium and magnesium, alkalinity  forms  a  tightly 
adherent  sludge  called "hardness scale" that is found  in  most 
pipes,  water  heaters, untreated boilers,   cooling  towers  and 
industrial washers. 

The  most  common form of treatment is  softening,  where  "soft" 
sodium carbonates are exchanged for the "hard" calcium and magne-
sium carbonates. This however does not reduce the total amount of 
material  that  is dissolved in the water. An  alternate  method, 
known  as  "dealkalization", takes the process one  step  further 
where  "soft"  hydrogen carbonates are exchanged for  the  "hard" 
calcium  and magnesium carbonates. The hydrogen carbonates,  also 
known  as carbonic acid, (carbon dioxide dissolved in water)  are 
then  removed from the water by passing through an air  stripper. 
The  resulting  water is substantially reduced in  both  hardness 
andalkalinity.  The water is then close in comparison to  typical 
fresh lake, brook or rain water.  

This  process is about half the capital cost of D.I.  (deionized) 
water  and substantially less expensive to operate.  It  provides 
many production benefits by improving chemical ability to  clean, 
thereby  decreasing chemical consumption and cost. It would  sig-
nificantly  reduce  sludging  and scaling in all  stages  of  the 
washer. 


Dave Wright - Texo Corporation




