Sven and Sebastiaan used STAN2.5. This is how the publishers, TU Vienna, Institute for Water Quality, Resource and Waste Management, describe the program
STAN (short for subSTance flow ANalysis) is a freeware that helps to perform material flow analysis according to the Austrian standard ÖNorm S 2096 (Material flow analysis – Application in waste management).
After building a graphical model with predefined components (processes, flows, system boundary, text fields) you can enter or import known data (mass flows, stocks, concentrations, transfer coefficients) for different layers (good, substance, energy) and periods to calculate unknown quantities. All flows can be displayed in Sankey-style, i.e. the width of a flow is proportional to its value. The graphical picture of the model can be printed or exported. For data import and export Microsoft Excel is used as an interface.
Specialists have the possibility to consider data uncertainties. The calculation algorithm uses mathematical statistical tools such as data reconciliation and error propagation.
STAN2.5 allowed Sven and Sebastiaan to respectively study the flows of Nitrogen and Water in the city of Maputo and with these results discussed the viability of some development scenarios. These included the city-wide implementation of rain-water harvesting versus reduction of non-revenue water; or the impact of doubling the volume of treated faecal sludge versus conveying all sewer collected in the city-center to a (fully-functional) the wastewater treatment plant. The work is really interesting and does provide valuable insight on how to manage the water and water and sanitation sector in a city like Maputo. In the next few weeks I am expecting to publish an extended abstract of their work.