Circular management of sewage sludge for the sustainable dewatering and reuse of biosolids: an experimental study

Wastewater treatment generates a by-product material known as sewage sludge. In many countries, most of the produced sludge is disposed in landfills, following a linear management strategy that is based on mechanical and chemical methods for limited dewatering and daily transportation to landfills. This strategy is rather expensive and unsustainable and possesses several environmental risks such as groundwater pollution, insufficient sludge drying and stabilization, high carbon footprint etc. Ecological engineering concepts and technologies can provide a circular sludge management strategy that focuses on the utilization of this valuable by-product with the smallest possible environmental impact.

This work will present an ongoing large research study that investigates different technologies and methods towards transforming this organic by-product to a beneficial material with the minimum environmental impact. Specific tasks of the project are:

• A setup of 16 pilot-scale units of the sustainable technology of Sludge Treatment Wetlands for sewage sludge treatment. The pilot units have different operation and construction properties, such as planted/unplanted, presence of earthworms, different substrate thickness, different loading rates, in order to eventually result in a highly efficient and optimized design configuration.
• Composting of sewage sludge along with the reed biomass from the constructed wetlands
• Production of biochar using sewage sludge and reed biomass as raw materials

 

The experimental results of the first operational year of this project will be presented.

The studied circular model for sludge management will be evaluated regarding the reduction of greenhouse gas emissions due to the non-use of mechanical dewatering methods, avoidance of high energy and chemicals consumption, and cessation of daily transport and disposal in landfills. The various organic materials that are produced will be assessed based on their quality properties and will further be tested by application to tomato crops for the estimation of yield improvement. Ultimately, an assessment of the economic, technical, environmental and social parameters of all methods and material cycles and studied management scenarios, will be carried out in order to determine the optimal circular management strategy.