Many authorities continuously strive to reduce excess sludge production, and the operational costs of sludge treatment and disposal in wastewater treatment facilities by environmentally friendly approaches. As a part of resource recovery within the circular economy framework, the land application of stabilized wastewater sludge (as biosolids) is considered a sustainable and low-cost sludge disposal option. Prior to the beneficial reuse of biosolids, anaerobic digestion has been recognized as a well-known and preferred technology worldwide for sludge stabilization and renewable energy production. However, releasing emerging micropollutants into the environment via land application or disposal of biosolids creates potential ecological and human health risks. These contaminants may only be partially eliminated, and transformed into their transformation products (or metabolites) during wastewater and sludge treatment processes. For this reason, wastewater sludge is considered as an endpoint for many emerging micropollutants and their possible transformation products due to their limited biodegradability and physiochemical characteristics. Of a broad range of emerging micropollutants, pharmaceutical and personal care products (PPCPs) have been frequently detected in wastewater sludge at high levels due to their widespread usage in daily life and their refractory nature. Then, these PPCPs have been reported to accumulate in biosolids and biosolid-amended agricultural soils.
There is limited knowledge on the occurrence and behavior of PPCPs, and their transformation products in solid matrices due to the highly complex nature of solid matrices and the difficulties encountered during their quantitative analysis. Therefore, the detection and reduction of these problematic chemicals in solid matrices have become a priority topic for many authorities.
Developing energy-efficient biomass-based technologies can help to solve growing worldwide environmental concerns. As an emerging thermal pretreatment technology, a radio frequency heating operating at a frequency of 13.56 MHz is a novel and energy-efficient system for sludge disintegration and bioenergy recovery. The EU-funded RADIOFREPOLIS project investigated the removal and transformation of PPCPs from biosolids by applying this custom-designed/built radio frequency sludge pretreatment followed by anaerobic digestion to produce eco-friendly and high-quality organic residues for beneficial reuse of sludge.
This project's action has allowed controlling the release of these emerging contaminants into the environment and increased bioenergy to move towards a better net energy balance of the overall process. RADIOFREPOLIS project successfully demonstrated that an innovative, sustainable, and energy-efficient technology, such as anaerobic sludge digestion combined with a custom-designed RF pretreatment, can be used to manage the wastewater treatment sludge contaminated with emerging micropollutants.
