Assessing the role of domestic phosphorus emissions in the human phosphorus footprint
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Societal phosphorus (P) use is unsustainable; P is vital for food security and its increase in the ecosphere is the single greatest cause of water quality degradation on the planet. The following thesis focuses on the role domestic P emissions play in the human P cycle with an aim to support management in reducing the individual P footprint. Measurement of the P composition of private sewage system (PSS) effluent was used to assess domestic P emissions from properties located within the Loch Leven catchment, in East Scotland, UK. This thesis shows PSS treatment type (i.e. level of additional treatment further to a single settling tank) does not reduce effluent P concentration, challenging the efficacy of policies aiming to reduce P pollution from PSS by technological solutions. Using a questionnaire, assessment of domestic and PSS maintenance behaviours of 156 PSS users indicated reductions in P emissions may be achieved through behavioural change. To understand the impact of behaviour on the human P footprint, a novel method using 31P nuclear magnetic resonance (NMR) spectroscopy was successfully developed to identify P compounds related to human behaviour (e.g. washing machine use) in PSS effluent. An assessment of the impact of behaviours on the human P footprint of ten individual households was conducted. Thesis findings conclude PSS desludging reduces concentrations of orthophosphate in PSS effluent; 85% of the variation in total soluble P in PSS effluent can be explained by ‘desludging frequency’ and ‘washing machine use’. Furthermore, PSS users feel responsible for correctly maintaining their PSS, but are potentially not maintaining them effectively or have poorly installed or inadequate systems, and do not know how to reduce domestic P emissions. A need for better public education on PSS maintenance and how to reduce domestic P emissions is required. This work highlights a critical need to integrate social sciences with natural sciences to tackle unsustainable P use.