Shit-Flow Diagram

The Shit-Flow Diagram serves as a tool for professionals and practitioners to characterize and compare the various functional elements of a sanitation system at a more generalized level and from different perspectives. This diagram illustrates a central sewer, OSWT and open defecation. There are obviously other systems, such as decentralized systems or variations on sewer and on-site, but it serves to highlight safety in a way that is useful. In actuality, the functional elements and their component technologies are system dependent and exhibit a lot of variability across system types. Some functional elements may be combined and/or be co-located, or each may be implemented separately in separate locations. Some of these component technologies are common and have been in use for decades or more; others are more recent innovations attempting to solve environmental issues such as wastewater discharges that pollute coastal waters, unsafe human wastewater management, or regional challenges where limited infrastructure, resources and even cultural barriers exist. The challenges are multifaceted and vary across regions and cultures. But wherever the system is implemented, to be successful, the criteria for sanitation system technology must:

  • Be healthy and safe for the populations they serve
  • Be sustainable and maintainable
  • Not pollute the environment at any stage from collection through disposal/reuse
  • Complete the sanitation process by appropriate disposal of the treated waste and/or reuse of the waste treatment products
Infographic showing example of a shit-flow diagram. Wastewater starting from Containment with arrow pointing to emptying, then arrow pointing to transport, then arrow pointing to treatment, then arrow pointing to reuse and disposal.

The flowchart shows 11% of waste points arrow to WC connected to sewer. One arrow points to Leakage which points to non treated water, adequately treated water and not treated water. Another arrow points the WC connected to Sewer straight to Non treated water and adequately treated water.

the other 88% of waste water arrow points to On-site sanitation facility which points to three paths. 1) safety emptied then arrow points to legally dumped and illegally dumped. The legally dumped is then pointing to paths that are either adequately treated or not treated. 2) Another path that wastewater follows for on-site sanitation facility points to not safety emptied. 3) the last path that wastewater follows for on-site sanitation facility points to closed when full and relocated. 

The rest of wastewater (1%) is open defecation.

Following the results of the flow chart, residential environment accounts for 39% of waste water. 1% arrow from open defecation, 38% arrow from not safely emptied waste.

The drainage system accounts for 14% of wastewater. 5% arrow from illegally dumped from safely emptied, on-site sanitation facility. 7% from non treated waste that was safely emptied and legally dumped from On-site sanitation facility.

3% of wastewater results from receiving waters. 2% arrow from non treated waste that was safely emptied and legally dumped from On-site sanitation facility. 1% arrow from non treated wastewater leakage from WC connected to wastewater.

Bottom right corner shows result of 46% of wastewater safely managed. 54% of wastewater unsafely managed.
Example of a shit-flow diagram (Source: Hawkins, P., WaterAid)

Sometimes local conditions and resources are so constrained that only the most innovative and resource sensitive solutions are viable. In other situations, resources are not constrained but other barriers prevent investment in healthier systems. Additionally, sustainability and maintainability are critical as even well designed and implemented sanitation systems can fall into disrepair and leak pollutants into groundwater and subsequently degrade the environment and pollute coastal waters. There are other tools (as discussed in GRASP Generation & Assessment of Sanitation Systems for Strategic Planning) that support planning and design of systems that weigh the technology options in the context of applicable criteria and stakeholder preferences (see Sustainable Sanitation diagram below).

Infographic of Decision-making process for implementing a sustainable sanitation system.

Triangle line connecting three ideas: 1) Growing number of technology options with a water drop and a curved arrow inside. 2) Differing stakeholder preference with clipart of two people. 3) Multiple Criteria of sustainable sanitation: a) health aspects. b) environment and natural resources aspects. c) Technology and operation aspects. D) Finance and economic issues E) socio-cultural and institutional aspects with a clipart of a checklist.
Decision-making process for implementing a sustainable sanitation system (Source: Spuhler, D., Eawag)