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This article is a comprehensive review of the literature dealing with the transfer of carbon dioxide to water where no chemical reactions are taking place. It reviews the studies related to the absorption and desorption kinetics, mass-transfer rates, effect of the contactor geometry, effect of water salinity, and the effects of temperature and pressure on the process in conventional reactors or the more recently common membrane contactors. The available data show inconsistent trends and an abundance of system-and geometry-specific correlations/models to predict the mass-transfer performance, which may explain the inefficient design of most industrially available contactors. Furthermore, no agreement can be found in the literature on the effect of temperature and pressure of the system, as well as the presence of additives in the water, on the solubility of CO 2 .

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Over the past decade, several citizen science projects have been launched, with a smaller subset addressing citizen scientists' involvement in water quality monitoring. Most of these projects were conducted in developed countries and focused on qualitative assessment and measurements of a limited number of water quality parameters. Moreover, data generated by citizen scientists were mainly for monitoring purposes and rarely resulted in remedial measures. In this work, a collaborative citizen science approach involving local citizens and university researchers was applied to assess the groundwater quality in a Lebanese village. Using a mobile laboratory, winter and summer sampling campaigns were conducted and 12 physical, chemical and biological water quality parameters were tested. Results indicated that the data generated by the citizen scientists were comparable with those generated by university researchers for the majority of physical and chemical water quality parameters. However, the bacteriological test results showed a marked difference and may be attributed to the complexity of the testing procedure and quality of testing material. The collaborative and participatory approach resulted in building local capacity and knowledge and in the formation of a locally elected water committee which will be responsible for continuous monitoring of the groundwater resources.

The reuse of treated wastewater, whether direct or indirect, can raise public concerns as a result of the overall risk perception. As such, community acceptance plays a significant role in the implementation of alternative water systems. Public attitudes towards water reuse are highly influenced by perceived health risk, religious prohibition, political issues, and the degree of human contact with recycled water. In most of the Mediterranean countries, wastewater is reused to different extents either within planned or unplanned schemes. Unfortunately, there are few in-depth studies of the socio-cultural aspects of reuse projects in developing countries, and Lebanon is no exception. Accordingly, this research will comprehensively tackle the issue of public knowledge, perceptions, and acceptance from different perspectives in an effort to provide national baseline information on wastewater reuse that is needed for future regulatory and developmental projects. As such, a survey was developed, tested, and administered. Results showed an inverse relation between the degree of human contact with the treated wastewater and public acceptance. People were found to be more inclined towards reuse for purposes with minimal human contact such as landscaping and agriculture with opposition when it came to use for personal use. Moreover, the results showed a general lack of trust in governing institutions and authorities, which could explain perceived health risks and perceptions of risk resulting from system failure. Overall, the willingness to use treated wastewater was found to vary as a function of the "disgust factor," religious beliefs, and perceptions of a high risk towards contracting waterborne diseases. The disgust towards reuse of treated wastewater was found to be a strong predictor affecting willingness to reuse whereby those who believed it is disgusting to reuse treated wastewater were found to be on average, three times less likely to reuse treated wastewater as compared to those who did not declare disgust. Similarly, a significant association was found between religious beliefs and respondents' willingness to use treated wastewater. Interviewees who thought treated wastewater reuse is not religiously accepted were, on average, twice less likely to use treated wastewater as compared to those who did not believe that reuse contradicts with their religious beliefs. Additionally, people's perceptions on associating the spread of water-borne diseases with reuse were found to be significant. Those who perceived that reusing treated wastewater would lead to diseases and affect the human health, were on average, twice less likely to accept reuse. Developing a comprehensive strategy that integrates increasing awareness and knowledge, setting policies related to water reuse, building public trust and communication channels, increasing public participation/engagement in decision making, and developing a sustainable management framework is thus crucial before any investments are made in reclaimed water-reuse projects.

Pharmaceuticals comprise an extensive group of compounds whose release into the environment has potential adverse impacts on human health and aquatic ecosystems. In many developing countries the extent of the problem and the occurrence of pharmaceuticals in water bodies are generally unknown. While thousands of tons of pharmaceutical substances are used annually, little information is known about their final fate after their intended use. This paper focuses on better understanding the management of human-use pharmaceutical wastes generated at the residential level within the Administrative Beirut Area. A survey encompassing 300 households was conducted. Results revealed that the majority of respondents were found to dispose of their unwanted medications, mainly through the domestic solid waste stream. Willingness to participate in a future collection program was found to be a function of age, medical expenditure, and the respondents' views towards awareness and the importance of establishing a collection system for pharmaceutical wastes. Respondents who stated a willingness to participate in a collection program and/or those who believed in the need for awareness programs on the dangers of improper medical waste disposal tended to favor more collection programs managed by the government as compared to a program run by pharmacies or to the act of re-gifting medication to people in need. Ultimately, collaboration and coordination between concerned stakeholders are essential for developing a successful national collection plan.

This study investigates the use of a novel static mixer to intensify the physical absorption of CO2 in water. To assess the efficiency of this tubular reactor, the temporal variation of absorbed CO2 was tracked along the reactor using three methods, namely, inline pH measurements, direct CO2 measurements using a CO2 analyzer, and titration. The effect of varying the liquid and gas flow rates on the mass transfer performance was investigated and analyzed. This article focuses on a comparison between the three methods of measurements to highlight differences in their results and sources of error. The findings demonstrated the reliability of the titration technique in quantifying dissolved CO2 concentrations when compared to the other two methods. In addition, it was found that the measured volumetric mass transfer coefficients, k L a, for this reactor were several orders of magnitude larger than those reported using conventional reactors such as mechanically agitated tanks and bubble columns. The values of k L a reached a maximum of 0.83 s–1 at low specific energy consumption rates (≈0.016 kWh/t) within 0.35 s of residence time in the reactor/contactor.

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