Civil Engineering January/February 2021 | Vol 29 No 1

22 January/February 2021 Civil Engineering with the contents often illegally disposed of in the open environment. Working on the same premise as Uber, residents can now use text messages to order the services of private drainage operators who have registered on the system and compete on auction to claim a desludging request. Based on GPS tech- nology, the system has also enabled the Senegalese government to collect valuable information to improve evaluation and monitoring for sanitation planning. “For example, they now know how often the septic tanks are being emptied; how many trips are being undertaken by the operators; and exactly where the faecal sludge is being disposed. This infor- mation has also facilitated the regulation of the many operators, while the platform has provided an entry point for more pri- vate sector participants in the desludging industry, creating employment opportuni- ties and further potential to drive down the costs of drainage,” says Tompkins. In addition, the Dakar city government has created an enabling environment for private operators to manage and operate these decentralised wastewater treat- ment systems, thereby improving both livelihood opportunities for citizens and self-regulation of the faecal sludge service delivery chain. In India, which is among the world leaders in new sanitation technologies, de- centralised sanitation systems are having a profound positive impact on the living conditions of low-income communities. A case in point is a system that is treating around 50 kℓ/day of the total wastewater from the Kuchhpura slum in Agra, India. This cost-effective, easy-to- maintain solution has reduced biological oxygen demand by 61%, chemical oxygen demand by 64%, and total-dissolved solids by 94%, and has immense potential to be adapted for areas in Africa. The wastewater is received from five clusters via a common drain. Separated from solid waste via a screen chamber, wastewater enters three chambered septic tanks where it undergoes primary treat- ment. Secondary treatment is undertaken in nine chambered baffled anaerobic reactors which are filled with gravels. The wastewater is then sent to a filter bed that is filled with white river pebbles, red stones, and gravels, and planted with Canna indica for root zone treatment. Notably, the treated wastewater is used by the community for horticulture and irrigation, helping to create many open green spaces in this area. CIRCULAR APPROACH This new thinking around sanitation goes further by focusing on producing many end products from faecal sludge as part of the circular economy. Tompkins says that studies undertaken in Senegal, Ghana, and Uganda, have demonstrated that there are five groups of end products that can be derived from processing faecal sludge, and that there is a viable market for them that varies from city to city. These products include dry sludge as fuel for combustion; biogas from anaerobic digestion of sludge; protein derived from sludge processing for use as animal feed; dried sludge as a component in building materials; and treated sludge as a soil conditioner or organic fertiliser. In South Africa, faecal sludge from VIP toilets is being extruded to produce pallets using Latrine Dehydration Pasteurisation, or LaDePa, technology that was developed by eThekwini Water and Sanitation and Particle System Separation. According to Septein et al. in their 2018 1 paper on the LaDePa process, the pellets are dried using infrared radiation to destroy pathogens, including E. coli, Salmonella, Shigella and Vibrio cholerae. Notably, this unique method of drying faecal sludge also reduces the mass and volume of the material and, in so doing, lowers the costs associated with its trans- portation, handling and storage. As part of a pilot phase, these dried and pasteurised pellets will be sold as an agricultural product. According to Septein et al., “this can be considered one of the most natural routes of reuse as the use of human excreta in agriculture closes the loop of the nutrient cycle,” while the dried faecal sludge can also be used as a biofuel in line with the circular economy. At the same time, an innovative means of treating faecal sludge was recently commissioned in Durban, South Africa. It involves harvesting black soldier fly larvae, which eat human faecal waste, to reduce the waste after composting it with a combination of food and faecal origin for further processing into a branded nutrient product for the agricultural market. Based upon Agriprotein’s black soldier fly larvae technology, the system was developed by Khanyisa Projects via a grant from the Bill & Melinda Gates Foundation (BMGF). Notably, this new thinking around sanitation has also created immense op- portunity for increased private sector par- ticipation, in addition to local livelihoods. As the nucleus of the new circular economy, experts such as Dhesigen Naidoo, CEO of the Water Research Commission , believe that sanitation could possibly produce the world’s next ‘unicorn’ – a privately held start-up com- pany with a market of over US$ 1 billion. This revenue would be generated from the removal of microconstituents; the engineering of microbial pathways and Lilies in the Okavango basin