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.

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Anthropogenic greenhouse gas emissions change earth’s climate by altering the planet’s radiative balance. An important first step in mitigation of climate change is to reduce annual increases in these emissions. However, the many suggested means of limiting emissions rates have led to few actual changes in policy or behavior. This disconnection can be attributed in part to the difficulty of convening groups of stakeholders with diverse values, the polarizing nature of current political systems, poor communication across disciplines, and a lack of clear, usable information about emission mitigation strategies. Here, electronically facilitated ethical deliberation, a method of determining courses of action on common goals by collaborative discussion, is used to evaluate Pacala and Socolow’s climate change stabilization strategies based on economic, technological, social, and ecological impacts across a wide range of spatial and temporal scales. Few previous analyses of climate mitigation strategies include all of these factors; rather, short-term technological feasibility studies and economic cost–benefit analyses predominate. After accounting for tradeoffs among disparate criteria, strategies involving end-user efficiency (e.g., efficient buildings and vehicles), wind, and solar power rank highest, while carbon capture and storage, hydrogen fuel cells, and biofuels options rank lowest. This electronically facilitated deliberation method offers an alternative to oppositional debate or cost–benefit analysis for assessing strategies where both quantitative and qualitative factors are important, information from disparate disciplines is relevant, and stakeholders are geographically dispersed.

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