Spencer Bowen and Dr. Randy Lewis, Department of Chemical Engineering
The goal of this project was to design and install one bio-toilet system before the end of May 2011 in cooperation with the inhabitants of the Uros Islands on Lake Titicaca, Peru. The system is composed of two parts: the bio-toilet infrastructure and the treatment of waste. This proposal focuses on waste treatment. The bio-toilet infrastructure was developed in tandem via another project. There are several bio-toilet and waste treatment designs useful for land applications1; however, the unique challenge of this project was to develop a system that will be able to serve the people living on man-made, floating reed islands.
A functional waste treatment system was extremely important because the Uros Islands did not have any sanitary waste disposal facilities. By providing these basic needs, this project improved islanders’ standard of living and decreased contamination of their water source. Nelson Lujano, a leader on Utama (one of the Uros Islands) with whom we have weekly contact, has told us that having a toilet system on their island was the highest priority for their community. Mr. Lujano stated that the islanders were willing to pay 70 $US for a toilet system even though their average family income is only $30 US per month. The final cost ended up around 50 $US. Each of the 42 Uros Islands is home to approximately 20 people (3-8 families), and they were anxious to have a toilet on their island.
A simple but reliable waste treatment system was required to meet the needs of the islanders and protect Lake Titicaca from further contamination. The lake is not only an internationally recognized landmark; it is also the only water source for the islanders. The physical bio-toilet infrastructure will separate the urine from solid wastes. Urine is sterile when uncontaminated by feces, and can be used directly as fertilizer in dilute concentrations2, so the bulk of the waste treatment system will deal with the treatment of solid waste. Aerobic decomposition of solids uses microbes and worms to break down the solid waste quickly and without odor, which is important because the majority of the islander’s income comes from tourism and an odiferous toilet system would severely hamper the islanders ability to maintain their traditional lifestyle. The primary difficulty in ensuring aerobic decomposition is the oxygen permeation of the waste. Our system focused on developing a system of rapid aerobic decomposition of solid waste. Aerobic decomposition is much faster than the anaerobic decomposition that occurs in septic tanks and other sewer systems. Therefore, one of the biggest challenges of the project is to maintain aerobic decomposition in a system that is suitable for man-made, reed islands.
Our initial designs for the composting portion involved a waste collection barrel that would double as the decomposition chamber. We performed multiple decomposition tests using material from the primary clarifier at the Provo Water Treatment Facility, however, due to budget and size constraints, 55 gallon barrels were not viable for implementation on the Uros islands. Eventually, the entire system was almost completely redesigned, ultimately using a 5 gallon bucket as the waste receptacle and a simple compost heap for the waste treatment portion of the system. Most of the time actually in Peru was spent instructing the islanders on the principles behind the bio-filter toilet and helping them construct their own units. The principles of compost heaps were taught, but may require additional encouragement to be fully implemented. There is another group of engineers headed to the same islands May 2012, so we anticipate receiving feedback on the long-term status of the system. While we were there, 4 full toilet units were constructed with materials provided by the islanders, and the leaders of almost all 42 Uros Islands were instructed in toilet construction and given manuals in both Spanish and English describing the process and principles. While the waste treatment part of the project was not as fully implemented as we would have liked, the project as a whole was extremely successful and very well received.
This project was a rare opportunity for us to work on a true multi-disciplinary team to gain international real-world experience. Unlike typical classwork, we interacted with engineers from different disciplines to solve real problems that met the needs of real communities, thereby enriching our educational experience. We also learned to solve a real need by applying problem solving skills and failure mode analysis as we worked together with islanders to design a system that meets their needs. This experience really was the highlight of my four years at BYU, and was the first thing I did in any class that really made a difference in the lives of others. It was truly an amazing experience.
References
- Jenkins, J. The Humanure Handbook. 3rd. White River Junction, VT: Chelsea Green Publishing, 2005.
- Kirchmann, H. “Human urine-chemical composition and fertilizer use efficiency.” Nutrient Cycling in Agroecosystems, 1994.