Safe resource recovery – managing microbial hazards of wastewater reuse systems

In 2050 it’s projected that the world population will have increased to 9.7 billion. This future scenario puts demand on food production and provision of clean water as well as of infrastructure for sanitation and waste. In the age of depletion of natural feedstock’s it is necessary to find ways to optimise reuse and recycling of waste to achieve a more sustainable food production. The majority of the nutrients brought into households with the food ends up in the sewage fraction, causing environmental problems when released to water bodies as untreated or only partially treated wastewater.

A sewage system where the different fractions (urine, faeces and bath-, dish- and washing- water) are separated at the source (similar to how solid waste is separated at household level) enables a more optimised management enabling a high degree of nutrient reuse. In general such reuse save primary energy, decreases greenhouse gas emission and prevent eutrophication. For these more concentrated fractions, treatment can be optimised regarding both resources and risks. When recycling the nutrients in excreta it is important to prevent disease transmission where containment and treatment of excreta is the best measure to ensure the safe reuse.

My research objective is to advance our knowledge on how to best manage microbial risk when reusing resources from waste water fractions. In my research, I have in particular focused on ammonia sanitisation, which is a treatment technology that is based on that toxic concentrations of NH₃ is reached in the material, either naturally present or from additions. In my lecture I will present how the process parameters of ammonia sanitisation affects pathogen inactivation and experiences from implement the technology at different scales, from treating 1000 m³ of black water in Sweden to treating a single defecation in the Peepoo toilet in Kibera, urban slum in Nairobi. What level of treatment that is needed for a safe use is often context specific and risks from reusing excreta may have to be put in perspective. Quantitative microbial risk assessment is a tool that can be used to assess different aspects related to utilisation of human excreta in food production. For example in an QMRA paired with environmental sampling for a case in Uganda we could see that faecal sludge reuse was not the only source of pathogens on produced vegetables and that for a safe food production faecal sludge treatment need to be complemented with also other measures. To promote the reuse of resources in waste without compromising human, animal or environmental health, I aim continue to investigate how to manage emerging microbial risks as well as evaluate the role of different waste management systems on disease prevention.