Phosphate is an important, non-substitutable nutrient for all life forms and is essential in ensuring universal food security. In the past, waste water treatment works (WWTW) typically installed effluent polishing technologies to eliminate phosphate and lower concentrations of both nitrogen and phosphate to below regulatory levels. More recently, there has been a global shift towards treating waste water as a "water-carried waste", presenting opportunities for both nutrient and energy recovery. South Africa is yet to embrace this shift, as it battles to provide universal access to basic sanitation needs and is faced with massive infrastructure maintenance and upgrading backlogs in the sanitation sector. Mature phosphate recovery technologies that produce high quality struvite for use in food production do exist. However, there is little evidence to indicate that similar phosphate recovery techniques would be economically viable or socially accepted in South Africa. Therefore, this dissertation sets out to investigate the viability of a simpler and cheaper phosphate recovery technology. The dissertation addresses the hypothesis that the South African market is better suited for low quality struvite for use in secondary (non-food) markets and that this would be cheaper than both traditional chemical precipiation (phosphate elimination) methods and highquality struvite production. This dissertation attempts to answer two key questions derived from this hypothesis by means of two separate methodologies. A qualitative methodology explores socio-technical issues to understand the potential of sewage-recovered struvite in the South African markets. This sets out to explore: What space there is for fertilizer production (such as struvite) from human waste in the South African markets? The second research component uses standard engineeirng economic methods, to investigate the potential for centralized recovery of nutrients through the conceptual design and a techno-economic pre-feasibility assessment of two phosphate recovery options at the largest WWIW in the Western Cape. These options are contrasted with a more traditional chemical precipitation process. Expert interviews revealed that although most stakeholders recognized the importance of phosphate recycling in tackling food security and achieving sustainable water and nutrient cycles. However, it is believed by the industry experts that the South African organic market and its consumer may not be ready for fertilizers produced from human waste to be used in food production. Better acceptability could be experienced within the inorganic fertilizer production market, regardless of source, if struvite is proven to be safe and a purification process is identified. More feasible markets could lie within ornamental plant fertilization, commercial fertilizer production and fertilizer use within closed community gardens. Therefore, there is potentially a larger market for lower grade struvite. The techno-economic assessment reveals that the digestate stream at the 200 ML/ day WWfW has the potential to produce -470 kg/d of struvite fertilizer, which only recovers 1-3% of the plant costs in 20 years. Revenue is subject to prices on the South African fertilizer market; and as it stands, the selling price of struvite for both low- and high-grade treatment is significantly lower than the cost of recovering them. Net present costs of R76,2-, R25,4- and RSl ,2 million were calculated for retrofit projects for high-grade struvite, low-grade struvite and chemical precipitation respectively. From this perspective and as hypothesized, low-grade struvite production is the most attractive process option. The establishment costs for chemical precipitation showed to be the most economical, with a CAPEX of R2,5 million, 10 and 30 times less than that of low-grade and high struvite production; which is within the Cape Flats planned budget for a nutrient treatment facility. Although this is the most common treatment technique in South Africa, it is the least sustainable process option resulting in the formation of a toxic by-product that must be disposed of in offsite landfills - an important factor that cannot be overlooked. The high capital costs and unprofitable operations of struvite, production are attributed to the high flowrate to phosphate loading ratio experienced at the CFWWTW. Other WWIWs with a more concentrated waste water profile, may yield better economics. However, unless the value of struvite increases, the cost of running the additional plant will not be recovered. Yet again, production does fall within the cost bracket for struvite production at R8,90/kgP removed. Hence investment may be justified from this angle. If a WWIW is to reduce effluent phosphate loading to within regulated standards, low-grade struvite production has thus been shown to be the most ecologically and economically sustainable option from a life-cycle-costs perspective. From a social stand-point, the experts interviewed believe that the South African food market could resistance fertilizers derived from human waste, hence potentially ruling in favour of low-grade struvite for use in secondary nonfood markets. Although it is a simple process, it is not cheaJ:>; the capital investment is 10 times that of South Africa's more familiar chemical precipitation route. Municipalities will have to consider the lower operating costs, as well as the environmental benefit of producing a useful phosphate fertilizer over the immediate capital costs.

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