A survey of national groundwater supplies conducted from June
1998 to June 1999 found that arsenic (As) concentrations
exceeding 0.010 mg/L are widespread in the United States. In
January 2001, the US Environmental Protection Agency published a
final rule to lower the As maximum contaminant level from 0.05 to
0.010 mg/L. To meet this new standard, many utilities may need to
upgrade current facilities or investigate new treatment options. They
also need an accurate appraisal of the ability of existing treatment
technologies to consistently reduce As to low levels.
The authors conducted a year-long study to evaluate the
performance of five full-scale facilities for removing As from raw
water. The two coagulation-filtration plants evaluated consistently
achieved low levels of As. However, when one facility
changed its coagulant from alum to polyaluminum chloride, average
removal efficiency plunged from 84 to 43%, a reduction that
might be attributable to difference in pH. Of the two iron-removal
facilities, one consistently reduced As concentrations; addition of
a coagulant, however, should help improve the other plant's As
removal. The lime-softening plant was unable to consistently
reduce As to low levels, but raising the operating pH through
increased lime dosage may improve removal efficiencies.
Conventional treatment technologies are capable of removing
As from water supplies to levels < 10 ug/L. To ensure optimal As
removal, however, treatment processes may need modifications.
Utilities intent on optimizing As removal must consider the effect
these modifications may have on system performance and costs,
as well as other performance issues that may be triggered by
changes in water chemistry. Includes 33 references, tables, figures.
| Edition : | Vol. 94 - No. 9 |
| File Size : | 1
file
, 1.1 MB |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 14 |
| Published : | 09/01/2002 |
