Department Urban Water Management

Generation and Assessment of Sanitation Systems for Strategic Planning (GRASP)

To select an appropriate and sustainable sanitation system is a complex multi-criteria decision-making problem. As novel technologies emerge, it becomes increasingly difficult to identify the best option. Structured decision-making (SDM) can tackle such complex situations by combining environmental engineering and multi-criteria decision analysis (MCDA). So far, most of research focuses on the selection procedure assuming that a set of options to choose from is already given. This project aims at developing (1) a systematic method to identify locally appropriate sanitation options at the structuring phase; and (2) a simulation model to quantitatively compare sustainability indicators of a broad range of sanitation options at urban scale.

Project description

The general aim of this project is to improve sanitation planning by providing systematic methods to identify more appropriate and sustainable sanitation system decision options.

These methods should (i) consider entire sanitation systems from the user inerface to the point of (re-)use or disposal; (ii) be applicable for a broad range of conventional and novel technologies and system configurations (networked, distributed, on-site); (iii) consider sustainability as a multi-dimensional issue; and (iv) be applicable to expanding urban areas in developing countries. The resulting methods integrate themselves into a structured decision-making (SDM) framework such as community-led urban environmental sanitation (CLUES) or Sanitation21. In order to be applicable to novel concepts and expanding urban areas in developing countries, the methods should allow dealing with different types of uncertainties.

Specific  objectives:

  1. To develop a systematic method for the generation of locally appropriate sanitation system decision options at the structuring phase of the decision-making process.
  2. To develop a generic model for the quantification of performance indicators to compare a broad range of sanitation technologies and system configurations.
  3. To test and validate the developed methods in two application cases in rapidly growing urban areas of developing countries.


Much was invested to improve sanitation coverage worldwide over the past decades. However, the high number of inoperative facilities worldwide shows quite dramatically that there are some substantial deficits with the non-technical issues of the implementation. Conventional sanitation planning approaches have been top-down, expert-driven and focusing on toilet infrastructure provision and leaving out other important aspects such as wastewater treatment downstream or user acceptance. This has led to inappropriate technology choices, lack of ownership and a high number of failing facilities. The situation is particularly challenging in expanding urban areas of developing countries, where most of the global population growth is currently taking place. We claim that the problem will be reduced if sanitation planning is improved by providing more appropriate and sustainable sanitation system options.

A sanitation system is a set of technologies, which in combination manage human excreta and wastewater from the generation to final reuse or disposal.

Construction of simplified sewerage connected to a constructed wetland in Nala (Nepal). The system design was an outcome of the application of CLUES. This system turned out to be the preferred option considering the different environmental, social and financial objectives of the stakeholders.
Source. C. Lüthi (2011)


Sustainable sanitation systems not only provide appropriate technologies to protect the human health and the environment; they are also socially acceptable, and financially and institutionally viable. SDM can assist decision-makers to clarify trade-offs between different decision options by combining multi-criteria decision analysis (MCDA) and environmental engineering. However, decisions are only as good as the decision options presented. So far, the identification of decision options was based on expert assessment, often randomly assembled. The current rapid technological development in the field of sanitation requires a more systematic procedure that provides input for the decision-making process.

Sustainability challenges us to shift the focus from basic infrastructure provision towards more systematic approaches including optimal resources utilization and closing material cycles at the lowest possible level. This means we have to consider various technical, financial, social and environmental criteria. Currently there is a lack of generic models to quantify such diverse indicators for sanitation systems others then sewer-based ones at the scale of a urban settlement. A substance flow model based on mass balances to estimate material use and emissions could provide relevant performance indicators at scale.

A sanitation system is a set of technologies that in combination manage and treat human excreta and wastewater from the point of generation to the final point of (re-)use or disposal. Source: D. Spuhler (2015)


To generate locally appropriate sanitation systems options (objective 1), methodologies from the field of product development will be applied, which are based on attributes to pre-select the locally appropriate options from all the potential sanitation technologies. A generic set of appropriateness attributes will be developed, which can be used for rapid appraisal of any conventional or novel sanitation technology already at the structuring phase of decision-making. This step will be followed by the combination of locally appropriate technologies to form entire systems using the compatibility-based procedure developed at Eawag.

For objective 2, a model-based approach will be used to measure substance flows and to quantify indicators such as nutrients, water, energy, pathogens, and costs for different system options at the scale of an urban settlement. The model will allow capturing the whole range of technologies and system configurations (including distributed systems) and will complement existing models, which are focusing on sewered systems only and thus are not appropriate for typical situations in developing countries.

The methods will be tested and validated in two application cases in Nepal and Ethiopia (objective 3). This will provide information on the potential of conventional and novel sanitation options to fulfill sustainability objectives relevant for the decision-making process. Given the context of expanding urban environments and the focus on novel technologies, uncertainty will be considered and recommendations will be provided how to deal with different types of uncertainties throughout the whole process.

Dhulikel Hospital (Kathmandu University Teaching Hospital) wastewater treatment plan during expenasion in 2008. It was the first wetland treatment system in Nepal constructed in 1997. The system is designed for 90 m3/d (hospital and staff quarters) and consists of two three phase systems in parallel (anaerobic baffle reactor, horizontal wetland, vertical wetland) followed by a sludge drying bed. Maintenance is undertaken by the Dhulikhel Hospital Engineering department and funded through the hospital’s annual budget. The treated wastewater is discharges into the existing channel. The sludge from the drying bed is used as fertilizer. Source: ENPHO (2008)

Overview on activities

This projects aims at improving sanitation planning by providing the methods (1) to systematically generate locally appropriate sanitation system options for the structuring phase of the decision process; and (2) to quantitatively compare the performance of a broad range of sanitation technologies and systems in a given context as input into the structured decision making. The developed methods are validated in two cases in Nepal and Ethiopia. Source: D. Spuhler (2015)


Dorothee SpuhlerDr. Eng. Environment ETH, Postdoctoral ResearcherTel. +41 58 765 5628Send Mail


Environmental and Public Health Organization (ENPHO), Kathmandhu, Nepal, Link

Arba Minch University (AMU), Ethiopia, Department of Water Supply and Environmental Engineering

University for Natural Ressources and Life Science (BOKU), Vienna, Institute for Sanitary Engineering and Water Pollution Control, Link

Institut für Automation und Kommunikation (ifak), Magdeburg, Department for Water andEnergy, Link

Related projects

Guidelines for Community-Led Urban Environmental Sanitation Planning (CLUES). Link

Compendium of Sanitation Systems and Technologies 2nd Edition. Link

Onsite Treatment (OST). Link

Sustainable Network Infrastructure Planning (SNIP). Link