Sanitation System Methodology

We began our work on the sanitation system by outlining key objectives:

  • Research anaerobic baffled reactor (ABR) systems and wastewater disposal options.
  • Determine the applicability of an innovative ABR system to the VPUU facility.
  • Work with stakeholders to design an adapted ABR system with separate systems for the greywater and blackwater, which will be used for research and testing purposes.
  • Build a sanitation system that will satisfy the immediate needs of the VPUU facility and allow for future development.

Developing a plan for the innovative sanitation system that would be implemented at the VPUU office site began with research into existing sewerage system plans. Specifically, our team focused on the development of an anaerobic baffled reactor. Once preliminary research was conducted, communications with Dr. Kevin Winter, a professor of geographical sciences at UCT, provided the team with additional information and design options. The combination of Internet research, past work by the WPI CTPC, and discussions with Dr. Winter, supplied information necessary for the design process.

Communications with our VPUU liaison, urban planner Kathryn Ewing, as well as other professionals, provided the information necessary to determine the system’s usage. Knowing the estimated daily usage of the ablutions facilities is one of the most critical design parameters for the system. The VPUU was uncertain as to the number of people who will use the system, stating that it will be moderately used by the live-in caretaker, office employees, and occasional visitors. We designed the system to accommodate an excess usage, which will account for an increase in users of the system and allow for future expansion. Monitoring the system is crucial to avoid overuse of the system.  Other important design considerations included function, construction, maintenance, finance, security, and future plans for the system. Once this information was received, we began to determine feasible design options.

To produce the most sustainable results and cleanest effluent, we decided to treat grey and blackwater separately. This requires two sanitation systems, each with a way to store the wastewater and a way to dispose of it. Next, we decided that the most sanitary way to dispose of blackwater would be to first promote anaerobic decomposition of solids as much as possible, making an ABR preferable (DEWATS, 1998). Taking construction processes into consideration, we decided it would be more feasible to purchase pre-made septic tanks than to design and make our own with concrete blocks or other materials. Leach fields were chosen as the most practical and beneficial way to dispose of wastewater after it has been filtered through the tanks. Although soakaways are most commonly used in South Africa, we chose to construct leach fields because they release filtered wastewater over a larger area and have more potential for future sustainable projects, such as growing grass.

Once our team consulted UCT, who concurred with our design plans, we submitted a proposal to our VPUU sponsor for approval. We found little design guidance for sanitation systems that separate grey and blackwater, so it will be crucial that the approach is monitored by UCT and WPI to assess how well it works.  After the plans were finalized, a construction timeline was determined. Collaboration with the VPUU, tank supplier 4EVR Plastics, and our team was needed before construction could take place. William Trom, VPUU Operation and Maintenance head, identified local labourers to help with construction and our team managed the process on-site. The VPUU was responsible for inspecting and approving all work, making final decisions throughout the project, including changes to the final designs for encasing the tanks in concrete. The WPI CTPC and the VPUU shared the costs for the project.


Cost Analysis [120 MB]

Determining Tank Size [108 KB]

Determining Leach Field Size [428 KB]

Operations Manual

Our team wrote an Operations Manual for the VPUU, in order to explain the systems and to ensure they are properly operated and maintained. This manual includes drawings and details step-by-step procedures on how to empty the greywater tank and how to determine when the blackwater tanks need to be pumped, as well as daily and monthly procedures that should be followed. We also list precautions that the VPUU should take to guarantee proper use of the facility, including installing grates on the drains for the basins and showers and supplying toilet paper for the toilets.

In order to test the system, we installed access points at various places in the piping. The manual details how to collect water samples from these points, which can be used to monitor the success of the system. Additionally, our team recommends that the VPUU install a chalkboard in the facility to monitor how many people are using the basins, showers, and/or toilets on a daily basis. When designing the system, the VPUU specified relatively modest, though unknown initial use, and monitoring to obtain actual usage information is advised.