The James Hutton Institute, together with RSK ADAS and Aqua Enviro, were contracted by Scottish Government to deliver a project that will extend current guidance (on how sewage sludge is used on land restoration sites) to include agricultural land. The project is reviewing data on the characteristics of sewage sludge relevant to human health and environmental impact, measuring the odour potential of sludge from different treatment processes, and comparing these with existing regulatory and best practice controls to understand where there might be gaps. Engaging with community groups is a key part of understanding where those gaps might be, and how they can be closed.
While sewage sludge is a valued source of plant nutrients as well as organic matter, it does contain various potentially hazardous agents that need to be managed appropriately. Around 70,000 tonnes of sewage sludge are spread to land in Scotland each year. While this represents less than a quarter of one percent of all organic materials spread to land, a significant body of work has been undertaken over the decades with the aim of investigating and managing environmental safety, potential impacts on the food-chain, and possible human health implications. These studies, and the development of legislative and other 'good' practice, have by and large been the basis for the management of the chemical and pathogenic risks associated with sewage sludge.
During the last 10 years, various so called 'emerging' contaminants have been identified in sewage sludge. It has also become apparent that wider health and well-being issues, including the impact of malodour, have largely been ignored by previous investigations. Therefore, a re-assessment of the chemical and pathogenic safety was commissioned that also included impacts from malodour on health and well-being (this project).
To date we have used mathematical techniques to estimate risks to human health via the food-chain and inhalation routes for more than 60 'emerging contaminants' including organic substances, pharmaceuticals and personal care products; as well as considering microplastics and pathogens. We have also built a computer model that explores the relationships between sewage sludge products and handling, weather conditions, distance, etc. and impacts of malodour.
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