Dear Colleagues,

This Special Issue in the journal of Sustainability is dedicated to quantitative assessment of decentralized sanitation systems serving small and remote communities and developing regions, to support the United Nations (UN) Sustainable Development Goal #6 “Clean Water and Sanitation”, one of the 17 goals of the UN 2030 Agenda for Sustainable development that requires urgent attention and action through a global partnership between all developed and developing countries. In 2017, the health and living conditions of 4.2 billion people suffered from a lack of safely managed sanitation ¹.

In small and remote communities and developing regions, decentralized wastewater treatment systems including onsite and cluster sanitation systems are commonly used and preferred over centralized wastewater treatment plants (WWTPs) due to financial restrictions and resource limitations ². Some examples include (but are not limited to) traditional septic systems; innovative and alternative onsite wastewater treatment systems (I/A OWTS) such as nitrogen removing biofilters (NRBs), sand filters, aerobic treatment units, wetlands, and peat-based systems; and waste stabilization ponds (WSPs). Conventional septic systems are suspected as sources of nutrients, pathogen, and emerging contaminants of concern (EC) and are linked to health issues in communities where drinking water is supplied from onsite water resources ^3–6.

However, the current literature lacks sufficient information to fully support these implications and provide a framework for the suitability of designs and legislative regulations and enforcement ³. In addition, the current guidelines are developed through data-based approaches leading to rule-of-thumb designs and thus have resulted in heterogeneous and inconsistent application on a global scale. The use of data- or model-based approaches can provide a grounding for a globally consistent application of research and regulation on decentralized sanitation systems, which can ultimately support evidence-based designs that are focused on site-specific conditions of each service region. Moreover, in deterministic design procedures, the safety factor has been used to account for the associated uncertainty. More stringent environmental regulations warrant integration of a more in-depth uncertainty analysis, as a part of risk assessment, to identify sources accurately ⁷. 

As such, the aim and scope of this Special Issue has been defined as follows:

• Case studies of “traditional technology optimization” or “new technology development and validation” using appropriate sample population and real-time data;
• Analysis and case studies of technology development in small, remote, and Indigenous communities, including northern and cold climates;
• Fate and transport of EC in traditional and innovative decentralized sanitation systems;
• Characterization of wastewater sources in small and remote communities using big data, with a specific focus on determining EC and wastewater strength of “green” households where conservative water use strategies are practiced;
• Greenhouse gas (GHG) emissions from decentralized sanitation systems;
• Cost analysis and life cycle assessment (including social life cycle assessment) of traditional and innovative decentralized sanitation systems using innovative quantitative assessment techniques (e.g., data mining and machine learning).

Other innovative research in the general area of quantitative assessment of decentralized sanitation systems may also be considered.

Dr. Roya Pishgar
Prof. Dr. Angus Chu
Dr. Kerry Black
Guest Editors

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• big data
• decentralized sanitation systems
• developing countries
• emerging contaminants of concern (EC)
• innovative/alternative onsite wastewater treatment systems (I/A OWTS)
• life cycle assessment
• sanitation
• small and remote communities