Arsenic (As) is common in US raw water
sources, particularly in groundwater of
the midwestern and western states.
Most water utilities meet the current
As maximum contaminant level (MCL) of 50
ug/L, but if the MCL is lowered to 10 ug/L,
cost-effective As removal will be critical to an
increased number of water utilities.
Groundwaters that have high As concentrations
sometimes also contain moderate to
high concentrations of ferrous iron (Fe).
When conventional water treatment methods
are used to remove the soluble Fe by oxidizing
it to hydrous ferric oxide, As is also
removed. Thus, this paper discusses optimizing
As removal at water treatment plants that
remove Fe.
Common dissolved substances, including
bicarbonate, silica (Si), and phosphate
(PO4
3-) interfere with As removal by iron
oxide. This study was undertaken because the
effects of bicarbonate and Si on As removal
were not well known. However, these substances
are present in all source waters and
may affect As removal at many water treatment
plants. Holm shows how a widely used
chemical-equilibrium computer model can be
easily modified to predict such interferences.
The article also describes experiments that
were designed to simulate the effects of bicarbonate,
Si, and PO4
3- on concurrent Fe and
As removal. According to the author, if a
source water contains As and Fe, it may be
possible to improve As removal by lowering
the pH. He also points out that the computer
model may be useful in designing processes
such as Fe removal or ferric chloride coagulation
to remove As. Includes 50 references, table, figures.
| Edition : | Vol. 94 - No. 4 |
| File Size : | 1
file
, 440 KB |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 8 |
| Published : | 04/01/2002 |
