Stipendrapport: Closing the Nutrient Loop with Ecological Sanitation in Nepal

Sabina Maharjan

This study attempts to recommend a suitable and sustainable solution for the sanitation problem in Nepal.

Figure 1   Effluent with no or little treatment of Guheshwori wastewater treatment plant mixing with already polluted river. Source: (Maharjan, 2020)

The sanitation solution in Nepal has mostly been focused on hygiene education and construction of toilets and septic tanks. Also, only a small number of houses are connected to the treatment plant and therefore most houses end up disposing the wastewater directly into the rivers and other water bodies. In addition, the treatment plant discharges the effluent into the environment with little or no treatment, and then get mixed with already polluted river contributing to more environment pollution problem rather than solving them.

With a shift in thinking from nutrient removal to nutrient recovery, focus is now on pathways to recover these nutrients successfully. Therefore, this study recommended ecological sanitation systems as promising for Nepal because ecological sanitation is a circular economy, a closed nutrient loop sanitation system, and a “waste to resource” concept. It is a concept of recycling the plant-essential nutrients, like Nitrogen, Phosphorus and Potassium contained in the excreta, as a fertiliser into the agriculture farm. In human excreta, these nutrients are found in water-soluble ionic form making it readily available for plant uptake and has been studied since late 1990s.

Moreover, energy can also be recovered from human excreta in the form of biogas. Biogas is a waste-to-energy technology that uses organic waste such as cattle manure, food waste, agricultural waste, and human excreta, separated or combined, for cooking or to produce electricity. Slurry as a by-product of the biogas production process can also be used to increase soil fertility. For example, urine as a fertilizer is suitable especially to plants with high nitrogen demand such as grain, grass crops, oil plants, spinach, cauliflower, corn, lentils, red beans, and soybeans.

Despite the benefits, application of human excreta in agriculture has also been associated with health and environmental risks and other socio-cultural issues. If not handled properly, human faeces can be responsible for most WASH-related diseases as one gram of faeces contain about 100 million bacteria some of which are pathogenic. Faeces must be hygienized either by a dehydration or compositing process before its application. The anaerobic digestion yielding biogas can also contribute to the necessary hygienization of the excreta whereas source separated urine has been found to be a safe and efficient fertilizer. Ecological sanitation users must also be aware that improper use of any toilet system may threaten public health and pollute the environment despite the benefits ecological sanitation system has. These problems can best be avoided by awareness of the ways of using the toilets and adopting the appropriate treatment processes before the application of excreta in the nutrient recovery or energy recovery as well. Moreover, people need to transform the misconception of excreta as waste and dirt to view it as a resource and treat the excreta properly to produce a safe fertilizer product supplemented by biogas generation.

Figure 2 ecosan toilet. Source: Maharjan, 2020