Fresh Perspectives on the Assessment of Sewage Sludge Management
Doktorsavhandling, 2015

Sewage sludge management and its role in closing nutrient cycles have received considerable attention in recent years. This thesis quantified phosphorus flows in Gothenburg, Sweden, under current and possible future waste management practices, and aimed to improve the assessment of wastewater and sludge management from an environmental and human health perspective through blending risk assessment (RA) and life cycle assessment (LCA). A review of previous environmental assessment case studies revealed inconsistent use of terminology regarding what is meant by integration, combination, hybridisation, or integrated use of RA and LCA. To facilitate a better understanding and more transparent communication of the nature of a given case study, this thesis proposed a design space that outlines choices to be made when blending RA and LCA. For the assessment of human health effects, this thesis suggests that a case study should only be referred to as a combination or integration of RA and LCA if it addresses two distinct perspectives: risks for specific members of a given human population (RA perspective) and overall impacts for a given human population (LCA perspective). RA and LCA can also be blended by transferring model elements from one framework to the other. This thesis explored the transfer of elements of quantitative microbial risk assessment (QMRA) to an LCA framework in order to account for adverse effects of pathogens on human health. Such practice was found to be adequate, but it is important to ensure that exposure pathways and parameters are chosen in accordance with the principles applied in the LCA study of which the assessment is a part. Also, in the context of sewage sludge management, the consideration of non-routine operation scenarios in LCA may be warranted. This thesis also explored different models to assess human health effects related to chemical contaminants in the context of land application of sewage sludge. The different model variants investigated provided different burden of disease estimates for individual chemical contaminants, but an aggregate burden of disease estimate of the same order of magnitude. Overall, this thesis emphasises the importance of explicitly contemplating which type of question relevant to sewage sludge management can be answered by quantitative assessment tools such as RA and LCA.

life cycle assessment

biosolids

land application

sewage sludge

pathogen risk

risk assessment

life cycle impact assessment

human toxicity

wastewater

chemical risks

10:an, Kemigården 4, Chalmers University of Technology
Opponent: Dr. Reinout Heijungs

Författare

Robin Harder

Chalmers, Kemi- och bioteknik, Kemisk miljövetenskap

Current agricultural production relies heavily on mineral fertiliser containing phosphorus mined from phosphate rock. Phosphorus and other nutrients are subsequently dissipated to the environment through various pathways. Many municipalities are facing increasing pressure to adapt waste management infrastructure in order to better close nutrient cycles. In waterborne sanitation systems, phosphorus is concentrated in sewage sludge, the residual material left after collection and treatment of wastewater. This thesis focuses on quantifying phosphorus flows in Gothenburg, Sweden, through material flow analysis, and on improving the assessment of wastewater and sewage sludge management options from an environmental and human health perspective through blending risk assessment and life cycle assessment. In particular, the work presented in this thesis explored how to account for adverse effects of pathogens on human health in life cycle assessment. Furthermore, different ways to model and predict human health effects related to chemical contaminants in the context of land application of sewage sludge were explored. Finally, this thesis also emphasises that the current debate about sewage sludge management, which essentially is about optimising existing waterborne sanitation systems, might be too narrow. Coping with the challenge of closing nutrient cycles in the long run requires different questions and different ways of thinking.

Drivkrafter

Hållbar utveckling

Ämneskategorier

Vattenteknik

Miljövetenskap

ISBN

978-91-7597-294-7

Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 0346

10:an, Kemigården 4, Chalmers University of Technology

Opponent: Dr. Reinout Heijungs