Management and Disposal of Sewage Sludge

Dear Colleagues,

The focus of this Special Issue is on the management and disposal of sewage sludge. Historically, sewage sludge has been identified as a problematic waste due to its odour, pathogen content, sheer volume and potential proximity to urban and sub-urban areas. Irresponsible management and disposal of sewage sludge can lead to point source or diffuse pollution of ground water and surface water bodies, potential contamination of agricultural crops and the gradual build-up of heavy metals in soils. This has led to a number of legal restrictions on how sewage sludge can be disposed of – prompting water utilities to investigate a number of possible alternatives to sea disposal, landfilling and land-spreading of untreated sludge.

As the concepts of resource efficiency, the circular economy and the waste hierarchy exert an increasingly influence on society, a major shift has occurred in the attitudes and practices associated with sewage sludge management and disposal.

Sewage sludge is no longer being perceived as a problematic waste, but as a potentially valuable resource. The nitrogen and phosphorus contents are now perceived as being potentially valuable fertiliser instead of a possible eutrophication risk. The organic matter content is now considered as a potential soil conditioner, feedstock for methane production or combustible fuel instead of an odorous and putrescible health risk.

Now that the perception issues are being improved, companies are faced with a wide range of choices of how exactly to improve their sewage sludge management. Each region has its own legislative landscape and each sewage treatment plant has its own site-specific logistical challenges and opportunities. There is no one optimum solution to sewage sludge management but, by building up evidence in the literature on a case-by-case basis, it will be possible to create a mosaic of scientifically validated and real-life experiences that can serve as a practical road-map for the entire industry.

The following topics are of particular interest for this Special Issue are:

1. The government perspective: Development and subsequent impact of regional/national/international legislation relating to sewage sludge disposal and management.
2. The water utility perspective: Strategies and decision making processes for deciding how to approach sewage sludge management and disposal. Associated cost-benefit analysis, life cycle costs, life cycle environmental impacts and lessons learned.
3. The technical perspective-1: Possible future developments and the state-of-the art in advanced treatment for land-spreading of sewage sludge (e.g., anaerobic digestion, composting, lime stabilisation with alkaline wastes).
4. The technical perspective-2: Possible future developments and the state-of-the art in thermal treatment of sewage sludge (e.g., thermal drying, mono-incineration, co-incineration, gasification).
5. The technical perspective-3: Niche processing of sewage sludge to produce moderate to high-value products (e.g., fertilizer, activated carbon, bio-based feedstocks).
6. A holistic perspective: Comparison of different sewage sludge management options in specific cases from a life cycle assessment perspective.

Dr. Shane Donatello
Guest Editor

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