Sanitation system and technical components
Understanding the sanitation system:
A sanitation system considers all components required for the adequate management of human wastes: the users of the system, the toilet infrastructure, the collection, transport, treatment, and management of end products (human excreta, solid waste, grey water, storm water and industrial wastewater). Each system represents a configuration of different technology components that carry out different processes on specific waste flows and have particular management, operation and maintenance conditions. Starting at the household level with waste generation, a system can include storage and potentially also treatment and reuse of the different waste streams. However, it might not be feasible to manage the human waste on-site, and therefore it is necessary to transport the waste to a larger jurisdiction, where it is usually treated in large installations.
The different sanitation systems can be classified according to three criteria: wet <--> dry, as well as the various degrees of separating waste flowstreams and the spatial level of treatment (on-site <--> off-site). These divisions allow for the identification of 7 main systems, which are illustrated in seven templates. Each system template includes various system alternatives. The elements of the system are: products, processes, flowstreams and technologies. To know more about the templates, click on the different components below.
What are products?
A product has classically been known as a “waste”, however the sustainable sanitation approach considers the option of reusing the water, the nutrients and energy present in the human excreta. Each product passes through different process steps in its lifecycle, or along its “flowstream” and differs in its characteristics due to mixing or separating different waste materials. Sometimes the flowstream can have the same name as the product, if no products are combined into the same flowstream. Because each product is so unique, it is important then that the technologies comprising the sanitation system are product-appropriate. Products that are presented in the system diagrams are summarised below (by EAWAG/SANDEC/NETSSAF).
What are processes?
What are flowstreams?
This describes the path that the product takes as it moves from the point of generation to the point of disposal: from “cradle to grave”. It could be described as the lifecycle of the product as it passes through the various process steps, which transform and transfer the product to its ultimate release into the environment. Click here for more information about the different flowstreams and their own products and description (by EAWAG/SANDEC/NETSSAF).
Show me the sanitation system templates!
The different sanitation systems can be clasified according to three criteria:
- Wet” and “Dry”, refers to the use or non-use of water for flushing.
- Degree of product separation (source segregation) into various flowstreams.
- Spatial level of treatment (on-site <==> off-site).
These divisiones allow for the identification of 7 main systems. “Wet” and “Dry” indicate the presence of flushing water for the transport of excreta. This however only gives a certain indication of how wet or dry the collected waste materials will be. Although flushing water might not be used (and would not therefore qualify as a “Dry system”) a system may nevertheless contain anal cleansing water, urine flushing water, or even greywater (by EAWAG/SANDEC/NETSSAF).
| No. | System name | Flowstreams |
| 1 | Wet mixed blackwater and geywater system with offsite treatment |
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| 2 | Wet mixed blackwater and greywater system with onsite treatment |
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| 3 | Wet blackwater systems (blackwater separated from greywater) |
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| 4 | Wet urine-diversion system |
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| 5 | Dry greywater-separate system |
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| 6 | Dry urine and Greywater diversion system |
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| 7 | Dry all mixed systems |
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What are the technical components? (only English version)
For each conventional and innovative sanitation technology there is a brief description and, where possible, a reference. The technology components are grouped according to process (i.e. the function that they serve) and sub-divided according to flowstream. Click here to download the file with technology components description.
The following document presents a detailed description of the sanitation systems, their elements and the technical components associated. Click here to download it (Eawag/Sandec/NETSSAF, 2007).
Pre-selection:
A set of criteria that is considered critical when using a holistic approach to assess sanitation systems shall be used to compare the various alternatives. The following table includes a comprehensive list of evaluation criteria to provide decision-makers with a complete overview of the existing aspects of sanitation systems (click here to download it). These include (1) health criterion, (2) environmental and resource criteria, (3) technical and operational criteria, (4) financial and economical criteria, (5) social, cultural and gender criteria.
The sanitation planning team might need to consult sanitation experts to select from the given set of criteria those parameters relevant to their community's profile. Furthermore, its open for the experts to select a rating system that better suits the local framework. However, an option for the qualitative comparison would be the use of the following descriptors (see table). The whole range of technologies for the flowstreams and processes step are assessed using comparative judgements. The “worst” technology for one flowstream and process step receives a “--" evaluation and the “best” technology a “++”.
An example of the assessment of the different technology components carried out by experts can be found clicking just here. This document serves as a reference for the evaluation and comparison of sanitation systems.
Another option could be the "expert selection" using key (strong criteria). For more details click here.
At this stage, no decision about the system(s) considered best has to be made, thus the criteria shall only facilitate the comparison of the alternatives.
The product of this sub step should be a short list of feasible sanitation options given the local context (social, financial, environmental). This pre-selection list shall be based not only on the expert experiences, but also on user functional demands as well as the requirements from the service providers´s point of view. At this stage it is expected that each selected potential system configuration is linked with logical, appropriate technologies for each process and each product to generate locally-appropriate system solutions. This document should be easy to understand by non-specialists, since the stakeholders are rarely sanitation experts.