About 2.5 billion people in developing countries, more than one third of the world's population, lack access to basic sanitation facilities (UNICEF/WHO, 2012). As a result, 3.4 million people, mostly children, die every year from diseases contracted through direct and indirect contact with pathogens found in human excreta (WHO, 2001). The low sanitation coverage in developing countries is primarily due to the lack of affordable sanitation technologies. In addition, the lack of skilled personnel and technical capacity contribute to this problem.
Modified Anaerobic Digestion (ModAD) technology has the potential to address the sanitation challenges in developing countries. Laboratory results showed that the technology has the potential to be developed into an effective waste treatment system (Garoma and Williams, 2013). ModAD technology has produced residual biosolids with fecal coliform (FC) bacteria less than 2 million per gram of solids and volatile solids (VS) reductions greater than 38%. The residuals meet US Environmental Protection Agency (USEPA) requirements for FC and VS reductions, thus these biosolids can be applied to soil as fertilizer (USEPA, 1995). In addition, the technology recovers biogas as a fuel for energy.
The ModAD technology has the potential to be developed into a reliable, affordable, and sustainable waste treatment technology thus can be adopted in developing countries. It can be built from locally available resources (e.g., brick, cement, and stone), does not require chemical additions, works at ambient temperature, does not require complex monitoring equipment, and can be operated and managed by individuals with minimal training. The system uses two alternating reactors, allowing longer digestion periods. This makes the biosolids free of foul odor and safe for manual handling, where access to vacuum trucks is limited. The ModAD technology can also be used to collect, contain, and treat waste in the same reactor, making it suitable for rural and urban communities with no sewer connections.
The ModAD technology is versatile and the design can be modified to fit for communities of all income levels. Furthermore, it can be scaled to treat waste at any size facility, from a group of households at rural communities to a high rise building in big cities.
The ModAD process is developed at San Diego State University (SDSU) with a grant from the Bill and Melinda Gate Foundation (BMGF), and we are currently seeking additional funding to field test the technology.