ASABE Technical Library - Abstract
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Technological Issues
Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org
Citation: No Citation available.Authors: Ray, Chittaranjan
Keywords: Pesticides, Removal mechanisms, Point of Treatment, Water treatment plants(WTPs), Point of use, Osmosis, Carbon filters, Consumption
Water treatment plants (WTPs) use a variety of unit operations for water treatment.
However, most unit operationsincluding aeration, coagulation, flocculation, sedimentation,
and sand filtrationdo not remove pesticides such as atrazine (Lykins et al., 1986; Miltner
et al., 1989; Koga et al., 1992). Unit operations at WTPs typically are not used to treat
domestic water supplies, with the exception of sorption, membrane filtration, and ozonation
as used for the point-of-use (POU) devices. The following is a brief discussion of some
removal studies at WTPs.
Many WTPs use ozonation as a method of disinfection against microbial pathogens.
Adams and Randtke (1992b) studied the removal of atrazine from drinking water via
ozonation. An ozonation facility built for atrazine removal may not be economically feasible;
however, atrazine removal at existing or planned ozonation facilities can provide additional
treatment benefits. In a pilot plant study, Lykins et al. (1986) found that ozone significantly
reduced the atrazine concentration by an average of 83 percent. Koga et al. (1992) found
that ozonation in conjunction with hydrogen peroxide treatment was effective in decomposing
resistant pesticides such as atrazine, simazine, and dichlorvos. Kearny et al. (1984) showed
that ozone, along with ultraviolet light, can effectively reduce atrazine from waste and
rinsate when atrazine is present near its saturation concentration. Somich et al. (1990) and
Adams and Randtke (1992a) showed that ozonation preceding biotreatment can be effective
in reducing the atrazine concentration from the rinsate. In the study by Adams and Randtke
(1992a), the concentration of atrazine in raw water ranged from less than 0.1 to 5.0 g/L.
Atrazine was spiked into all samples so that the concentration ranged from 3.8 to
11.4 g/L. At the same time, the dissolved organic carbon of water samples ranged from 2.4
to 7.3 mg/L. Ozone was added to these waters at concentrations ranging from 0.5 to
2.6 mg/L, and the time for reaction was up to 40 minutes. Samples were taken at regular
intervals for measuring atrazine and its ozonation byproducts. The rate constant for
degradation was first order and was faster at pH 9 than at pH 5. The ratio of rate constants
at 25 and 15C was 2.2. The types and concentrations of degradation products were not
reported.