Composting Domestic Sewage Sludge with Natural Zeolites in a Rotary Drum Reactor
The research paper investigates the effects of adding natural zeolites to the composting process of domestic sewage sludge using a pilot-scale rotary drum reactor. The study focuses on three types of commercial natural zeolites: mordenite and two clinoptilolites (Klinolith and Zeocat). Key findings include that mordenite resulted in the highest carbon removal (58%), while clinoptilolites significantly reduced ammonium losses. All zeolites effectively removed heavy metals, achieving 100% retention of nickel (Ni), chromium (Cr), and lead (Pb), and over 60% retention of copper (Cu), zinc (Zn), and mercury (Hg). The study highlights that the addition of 10% Zeocat produced compost compliant with Spanish regulations, and leaching tests indicated low metal concentrations in zeolite leachates (<1 mg/kg), suggesting that the final compost could be safely applied to soil. The research emphasizes the potential of zeolites to enhance the composting process by improving organic matter degradation, controlling ammonia emissions, and retaining heavy metals, thus addressing environmental concerns associated with sewage sludge disposal.
This research paper is significant in the field of waste management and environmental technology, particularly in addressing the challenges of sewage sludge disposal. With European cities producing over 10 million tons of sewage sludge annually, effective treatment methods are crucial. The study contributes to ongoing discussions about sustainable waste management practices by demonstrating how natural zeolites can enhance composting processes, improve compost quality, and mitigate heavy metal contamination. The findings offer practical benefits for agricultural applications, as they provide a pathway for producing safe compost from sewage sludge, thus promoting recycling and reducing environmental pollution.
