REMOVAL OF ARSENIC AND BORON FROM GEOTHERMAL BRINES
D. C. Christensen, Research Engineer
J. A. McNeese, Research Engineer
Battelle-Northwest Laboratories
Richland, Washington 99352
INTRODUCTION
This study is one facet of a large project aimed at providing the most cost-effective
method for disposal of arsenic- and boron-laden wastewater from a geothermal power
plant.   Although this method did not prove to be entirely cost-effective, the approach and
findings are of interest for future applications and investigations.
The geothermal wells in question are in the Ahuachapan fields of El Salvador.   Electrical power is presently being generated in the fields.   As a result of power production, there
is a significant amount of water entrained in the steam production wells containing large
amounts of boron and arsenic.   When released into the environment, these two contaminants can cause serious pollution problems.
This report details the results of a literature review evaluating the technology of boron
and arsenic removal; the experimental work related specifically to the Ahuachapan brine
and a proposed treatment process.
LITERATURE REVIEW
In recent years it has been discovered that many trace elements are readily released
from sediments into the water column and bioconcentrated by organisms up through the
food chain.   Some of these trace contaminants are confirmed as toxic at low levels and
others are suspected of being carcinogenic through exposure [ 1 ].   The following discussion will focus on the arsenic and boron elements separately.
Arsenic
Arsenic accumulates in plants and aquatic organisms, but it is not known to have toxic
effects on man after consumption of these plants or organisms as food [2].   Acute chronic
arsenic poisoning has occurred from ingestion of polluted drinking water [3,4].
The primary stimuli for dose-response research on arsenic has come from:   (a) a history
of arsenic poisoning; (b) industrial arsenic use; (c) clinical application of arsenic and (d)
use as chemical warfare agents [5].
Some of the principle methods found in this review for the removal of arsenic included
ion exchange, pH adjustment and lime precipitation, physical adsorption on bone chars,
adsorption on metal hydroxide floes and adsorption onto clays.
The ion exchange equilibrium of arsenic ions with VARION anion exchange resins was
studied in 1974 at Veszprem, Hungary where 90% removal of a 40-mg/l As solution was
achieved [6].
An arsenic removal efficiency of 99.96% was demonstrated with the lime precipitation
process on solutions containing about 2400 mg/1 total arsenic [7,8].   In conjunction with
lime, the same researchers investigated iron salt enhancement in precipitation and demonstrated 100% removal of arsenic for ratios of Fe:As equal to 5:1 and greater [7].
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