[[File:Susana logo.png|right|90px|alt=Susana logo.png|link=http://www.susana.org/en/]]This article is based on a [http://www.susana.org/en/resources/library/details/1229 433 factsheet] that makes a plea for a sanitation system approach where technologies are categorised based on their “product-process” characteristics and then linked into logical systems using a “Flowstream” concept. Technologies are grouped and used to construct seven logical systems. This method for organising and defining sanitation systems helps facilitate informed decision making and consideration of an integrated approach.
=== 1. Introduction: the need for a systems approach ===
Technology choice should be based on determining the best possible and most sustainable solution within an urban or rural context. There is often a prevailing assumption that centralised water-based sewer system can be the solution in all urban and peri-urban contexts. Site specific considerations such as the scarcity of fresh water, farmers’ demand for treated wastewater or excreta-based fertiliser, or lack of technical skill and institutional or socio-economic barriers to such centralised sewer systems are often neglected (Luethi et al., 2011). [[File:Schematic.jpg|thumb|right|200px|Figure 1: Schematic of school toilets connected to biogas settler and anaerobic baffled reactor at Adarsh College, in Badlapur, India (source: N. Zimmermann, 2009)jpg|link=https://www.flickr.com/photos/gtzecosan/6730198271/in/photolist-]]
The options: to change the basic design or to consider alternative sanitation technologies to take into account the specific on site conditions are often overlooked or not investigated. As a result, in spite of significant investments, a number of latrines are found to be either dysfunctional or malfunctioning and the unsatisfied users have reverted to open defecation or the use of unsanitary pits latrines. In addition, the focus is often on the construction of ''toilets'' alone with little consideration given to the management of the generated ''faecal sludge'', including its collection, transport, treatment and possible reuse or disposal.
=== 2. Systemising sanitation systems ===
The main objective of a sanitation system is to protect and promote human health by providing a clean environment and breaking the cycle of disease transmission, as well as to preserve the dignity of users - particularly women and girls. In order to be sustainable, a sanitation system has to be not only economically viable, socially acceptable, and technically and institutionally appropriate, it should also protect the environment and the natural resources (SuSanA, 2008).
Sanitation systems can be distinguished by:
*being water-reliant or non-water reliant for the transport of excreta and wastewater (Cruz et al., 2005) (Tilley, Zurbruegg, 2007)
*on-site and off-site treatment
*various degrees of separation of incoming wastes.
In the following table seven distinctly different sanitation systems are described based on the categorisation from the EU-funded NETSSAF project (Network for the development of Sustainable approaches of large-scale implementation of Sanitation in Africa). They all have their place and application, and not one of them is per''se'' better than the other.
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=== 3. Description and evaluation of technology components ===
[[File:Vertical flow wetland.jpg|thumb|right|200px|Figure 2: Vertical flow constructed wetland in the “Olympic forest park” located north of the city centre of Beijing, Peoples Republic of China, 2008 (source: J. Germer, 2008)]]
In all the recent publications that have described sets of typical sanitation systems (Cruz et al., 2005), (IWA, 2005), (Tilley, Zurbruegg, 2007), (Tilley et al., 2008), (DWA, 2010) a certain procedure was applied to characterise technologies: along with the description of the sanitation system, each technology (or technological component) is discussed and described. The technology is grouped according to its role in the process (i.e. the function that it serves) while on the other hand it is also sub-divided according to the flowstreams that it deals with. The technological components and the complete sanitation systems need to be discussed and evaluated with respect to specific sustainability criteria. Examples for such criteria are given in Table 2.
[[File:Vertical flow wetland.jpg|thumb|right|200px|Vertical flow wetland.jpg]] In all the recent publications that have described sets of typical sanitation systems (Cruz et al., 2005), (IWA, 2005), (Tilley, Zurbruegg, 2007), (Tilley et al., 2008), (DWA, 2010) a certain procedure was applied to characterise technologies: along with the description of the sanitation system, each technology (or technological component) is discussed and described. The technology is grouped according to its role in the process (i.e. the function that it serves) while on the other hand it is also sub-divided according to the flowstreams that it deals with. The technological components and the complete sanitation systems need to be discussed and evaluated with respect to specific sustainability criteria. Examples for such criteria are given in Table 2. <br/> {| width="329" cellspacing="0" cellpadding="5" border="1" width="329" style="width: 800px"
|+ Table 2: Sustainability criteria used to evaluate and compare technological components & complete sanitation systems
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<br/> === 4. Acknowledgements<br/> ===
=== 4. Acknowledgements ===
SuSanA factsheet: Capacity development for sustainable sanitation. April 2012. [http://www.susana.org/en/ susana.org]
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