This research investigated the possibility of transferring phosphorus from human urine into a concentrated form that can be used as fertilizer in agriculture. The community of Siddhipur in Nepal was chosen as a research site, because there is a strong presence and acceptance of the urine-diverting dry toilets needed to collect urine separately at the source. Furthermore, because the mainly agricultural country is landlocked and depends on expensive, imported fertilizers, the need for nutrient security is high. We found that struvite (MgNH(4)PO(4)·6H(2)O) precipitation from urine is an efficient and simple approach to produce a granulated phosphorus fertilizer. Bittern, a waste stream from salt production, is a practical magnesium source for struvite production, but it has to be imported from India. Calculations show that magnesium oxide produced from locally available magnesite would be a cheaper magnesium source. A reactor with an external filtration system was capable of removing over 90% of phosphorus with a low magnesium dosage (1.1 mol Mg mol P), with coarse nylon filters (pore width up to 160±50 μm) and with only one hour total treatment time. A second reactor setup based on sedimentation only achieved 50% phosphate removal, even when flocculants were added. Given the current fertilizer prices, high volumes of urine must be processed, if struvite recovery should be financially sustainable. Therefore, it is important to optimize the process. Our calculations showed that collecting the struvite and calcium phosphate precipitated spontaneously due to urea hydrolysis could increase the overall phosphate recovery by at least 40%. The magnesium dosage can be optimized by estimating the phosphate concentration by measuring electrical conductivity. An important source of additional revenue could be the effluent of the struvite reactor. Further research should be aimed at finding methods and technologies to recover the nutrients from the effluent.

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Increasing metropolitan solid waste and absence of concrete information sources is a developing worry in urban areas of developing countries like in Kathmandu Metropolitan City (KMC) in Nepal. Two goals of this study were: (1) to estimate household solid waste generation and its composition; and (2) to assess the socioeconomic factors impacting on household waste generation. Using stratified sampling, 288 families were chosen from the 32 wards of KMC for household survey. The quantification of total waste and its composition was undertaken for each household using digital weighing scales. Socioeconomic variables affecting household waste generation were analysis by using regression model. The rate of household waste generation in KMC was found 0.3 kg/capita/day and total household waste generation was found 413 tonnes/day. Household waste comprised of 51% organic and 49% recyclable comprising 5% paper and paper products, 3% glass, 1% metal, 19% plastic, 13% textiles, 4% rubber and leather and 4% other waste. As organic waste constitutes more than half proportion of total solid waste, it should deal appropriately, if not it will create serious health and environmental hazards. Household size and income had a positive impact on waste generation; both were statistically significant and thus are important indicators in forecasting solid waste generation trends. Finding from this study will help concerning authority to formulate sustainable solid waste management plan in KMC and beyond.

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