Historically, there is evidence to suggest that communities in the developing world have used plant-based materials as one strategy for purifying drinking water. In this study, the coagulant properties of Opuntia spp., a species of cactus, are quantitatively evaluated for the first time. Opuntia spp. was evaluated for turbidity removal from synthetic water samples, and steps were made toward elucidating the underlying coagulation mechanism. In model turbid water using kaolin clay particles at pH 10, Opuntia spp. reduced turbidity by 98% for a range of initial turbidities. This is similar to the observed coagulation activities previously described for Moringa oleifera, a widely studied natural coagulant. Although it has been reported that Moringa oleifera predominantly operates through charge neutralization, comparison of zeta potential measurements and transmission electron microscopy images of flocs formed by Opuntia spp. suggest that these natural coagulants operate through different mechanisms. It is suggested that Opuntia spp. operates predominantly through a bridging coagulation mechanism. Once optimized, application of these readily available plants as a part of point-of-use water treatment technology may offer a practical, inexpensive, and appropriate solution for producing potable water in some developing communities.
A large part of the Virginia Department of Transportation's (DOT) maintenance effort comprises the implementation of its anti-icing program. Earlier research confirmed that Virginia DOT captures a large volume of salt-laden storm water runoff at its 300-plus salt storage facilities throughout the state and that disposal options for this water are limited and costly. Although Virginia DOT is implementing recommended management options to reduce the quantity of salt water captured, this research was undertaken to determine the possibility of recycling salt-contaminated storm water runoff for brine production. Laboratory and field tests were conducted using bench-scale brine generation equipment. In the laboratory phase, brine was produced by using tap water, applying different hydraulic retention times and temperatures. Storm water runoff from a storage pond without any previous treatment was used in the field phase. Results show that the optimum conditions for brine production are low hydraulic retention time (high flow rates) and high temperatures. The total suspended solids present in the storm water runoff did not diminish the quality of brine in the field tests. Economic and environmental benefits can be obtained by applying this recycling strategy.
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