Emerging organic compounds as markers of the degradation of groundwater qualitative and quantitative equilibrium in a context of rapid urban expansion

With the neo-metamorphosis of the residential landscape worldwide and sluggish sanitation strategies in urban environments, rudimentary on-site sanitation systems remain commonly used, especially in developing countries, despite the risks of groundwater contamination. The effective management of such water resources relies on assessment of the sensitivity of anthropized aquifers to man-made impact, including groundwater behavioural alteration, in terms of both quality and quantity. Associated with tracking of changes in land use, this study proposes an approach involving emerging organic contaminants (EOCs) as indicators of the alteration of groundwater balance due the exposure of shallow aquifers to the risks of infiltration of untreated wastewater from soak pits. This methodology was applied to the shallow aquifer beneath the urban agglomeration of Grand-Sfax (Tunisia). Combined with an updated follow-up of groundwater piezometric fluctuations in relation with inputs from surface contamination sources, the spatialisation of contamination levels by EOCs provided a clear delineation of the most impacted aquifer zones. This approach revealed a significant link between the continuous rise in piezometric levels by contributions from untreated inputs and the accumulation of high levels of contamination in groundwater. The understanding of EOC underground pathways allowed the determination of the fates and processes responsible for the diffusion of contamination throughout the studied aquifer. The ability of groundwater to reflect population life style and the use patterns of such organic molecules was also assessed. Besides revealing the legacy of persistent contamination, this approach involving EOCs as tracers with different levels of persistence provided a spatial observation of the aquifer exposure to continuous contamination processes. This approach made it possible to develop a conceptual presentation of aquifer vulnerability to urban pressures and to predict the effects of subsequent expansion of unplanned urbanisation on groundwater quality.

A review of how decision support tools address resource recovery in sanitation systems

Globally, there is increasing interest in recovering resources from sanitation systems. However, the process of planning and implementing circular sanitation is complex and can necessitate software-based tools to support decision-making. In this paper, we review 24 decision support software tools used for sanitation planning, to generate insights into how they address resource recovery across the sanitation chain. The findings reveal that the tools can address many planning issues around resource recovery in sanitation including analysis of material flows, integrating resource recovery technologies and products in the design of sanitation systems, and assessing the sustainability implications of resource recovery. The results and recommendations presented here can guide users in the choice of different tools depending on, for example, what kind of tool features and functions the user is interested in as well as the elements of the planning process and the sanitation service chain that are in focus. However, some issues are not adequately covered and need improvements in the available tools including quantifying the demand for and value of resource recovery products, addressing retrofitting of existing sanitation infrastructure for resource recovery and assessing social impacts of resource recovery from a life cycle perspective. While there is scope to develop new tools or to modify existing ones to cover these gaps, communication efforts are needed to create awareness about existing tools, their functions and how they address resource recovery. It is also important to further integrate the available tools into infrastructure planning and programming processes by e.g. customizing to relevant planning regimes and procedures, to move them beyond research and pilots into practice, and hopefully contribute towards more circular sanitation systems.

Pharmaceuticals in source separated sanitation systems: Fecal sludge and blackwater treatment

This study investigated, for the first time, the occurrence and fate of 29 multiple-class pharmaceuticals (PhACs) in two source separated sanitation systems based on: (i) batch experiments for the anaerobic digestion (AD) of fecal sludge under mesophilic (37 °C) and thermophilic (52 °C) conditions, and (ii) a full-scale blackwater treatment plant using wet composting and sanitation with urea addition. Results revealed high concentrations of PhACs in raw fecal sludge and blackwater samples, with concentrations up to hundreds of μg L^-1 and μg kg^-1 dry weight (dw) in liquid and solid fractions, respectively. For mesophilic and thermophilic treatments in the batch experiments, average PhACs removal rates of 31% and 45%, respectively, were observed. The average removal efficiency was slightly better for the full-scale blackwater treatment, with 49% average removal, and few compounds, such as atenolol, valsartan and hydrochlorothiazide, showed almost complete degradation. In the AD treatments, no significant differences were observed between mesophilic and thermophilic conditions. For the full-scale blackwater treatment, the aerobic wet composting step proved to be the most efficient in PhACs reduction, while urea addition had an almost negligible effect for most PhACs, except for citalopram, venlafaxine, oxazepam, valsartan and atorvastatin, for which minor reductions (on average 25%) were observed. Even though both treatment systems reduced initial PhACs loads considerably, significant PhAC concentrations remained in the treated effluents, indicating that fecal sludge and blackwater fertilizations could be a relevant vector for dissemination of PhACs into agricultural fields and thus the environment.

Generation of sanitation system options for urban planning considering novel technologies

The identification of appropriate sanitation systems is particularly challenging in developing urban areas where local needs are not met by conventional solutions. While structured decision-making frameworks such as Community-Led Urban Environmental Sanitation (CLUES) can help facilitate this process, they require a set of sanitation system options as input. Given the large number of possible combinations of sanitation technologies, the generation of a good set of sanitation system options is far from trivial. This paper presents a procedure for generating a set of locally appropriate sanitation system options, which can then be used in a structured decision-making process. The systematic and partly automated procedure was designed (i) to enhance the reproducibility of option generation; (ii) to consider all types of conventional and novel technologies; (iii) to provide a set of sanitation systems that is technologically diverse; and (iv) to formally account for uncertainties linked to technology specifications and local conditions. We applied the procedure to an emerging small town in Nepal. We assessed the appropriateness of 40 technologies and generated 17,955 appropriate system options. These were classified into 16 system templates including on-site, urine-diverting, biogas, and blackwater templates. From these, a subset of 36 most appropriate sanitation system options were selected, which included both conventional and novel options. We performed a sensitivity analysis to evaluate the impact of different elements on the diversity and appropriateness of the set of selected sanitation system options. We found that the use of system templates is most important, followed by the use of a weighted multiplicative aggregation function to quantify local appropriateness. We also show that the optimal size of the set of selected sanitation system options is equal to or slightly greater than the number of system templates. As novel technologies are developed and added to the already large portfolio of technology options, the procedure presented in this work may become an essential tool for generating and exploring appropriate sanitation system options.