Conceptualising global water challenges: A transdisciplinary approach for understanding different discourses in sustainable development.

Global challenges impact upon substantial numbers of people in different locations and inform policy at multiple levels under the United Nation's Sustainable Development Goals (SDGs). An aspect of the SDGs framework is the stated inter-relationship between SDGs and local, regional and global partnerships for research and development. In response to dissatisfaction with existing approaches to addressing such complex problems the purpose of this paper is to propose a problem-language-context (PLC) model as a way of framing sustainable development challenges; and in so doing create a heuristic that allows challenges such as water security to be understood using a logically consistent framework. Such an approach builds on a growing transdisciplinary innovation literature that strives to generate knowledge that is problem-focused and inclusive of both scientific and societal stakeholders. The utility of the PLC model is then examined using a case study review carried out on a body of evidence - the United Nations World Water Development Reports (WWDRs) 2003-2019. The result of this review suggests that such problem framing can be of value in revealing the implicit (and sometimes contradictory) assumptions held by policy makers, practitioners and researchers. The main conclusion is that a transdisciplinary approach is one way of better understanding some of the conflicting viewpoints evident in discipline-based approaches to sustainable development, global water challenges and water security.

UVC inactivation of MS2-phage in drinking water - Modelling and field testing.

UVC disinfection has been recognised by the WHO as an effective disinfection treatment to provide decentralized potable water. Under real conditions there are still unknowns that limit this application including the influence of suspended solids and natural organic matter. This work aims to investigate the influence of two key parameters, suspended solids and natural organic matter, on the efficiency of UVC disinfection of surface water to achieve the drinking water quality requirements established by the WHO for point of use (POU) technologies. Kaolinite (turbidity agent) and humic acids (HA, model of organic matter) were used in a factorial design of experiments (Turbidity from 0 to 5 NTU, and HA from 0 to 3.5 mg/L) to investigate their effect on UVC inactivation of MS2 phage in surface water. A collimated beam (12 W) and a commercial UVC disinfection flow system (16 W) designed to provide drinking water at households were used. The UVC flow system both in the laboratory and in the field was able to achieve the reduction requirements established by WHO (LRV >3.5 for all tested conditions), confirming the good performance of the studied UVC disinfection system. The results found in the lab were used to establish a numerical model that predicts the disinfection rate constant as a function of water turbidity and transmittance at 254 nm (confidence level>95%). The model permitted to elucidate the critical effect of low concentrations of HA in reducing the inactivation rate by 40% for 3.5 mg/L-HA compared with 0, the non-significant detrimental effect of turbidity lower than 5 NTU, and the lack of synergistic effects between both parameters at these levels. The UVC flow system was also tested in the field, in Tzabalho, Chiapas (Mexico), and Antioquia (Colombia), with spiked MS2 into natural surface water. This investigation opens a potential application to monitor the performance of UVC systems with surface water by monitoring transmittance at 254 nm as a tool to control UVC domestic systems to deliver safe drinking water in a household without the need of expensive and laborious biological monitoring tools.