Organic micropollutant degradation in sewage sludge during composting under thermophilic conditions

Degradation of 12 common organic micropollutants in sewage sludge representing bactericides, flame retardants, fragrances, vulcanizers, and plasticizers (part of many common products) during thermophilic composting was investigated. Micropollutant concentrations, compost temperature, water content, and organic matter content were measured over 24 days in a full-scale compost windrow made from digested sewage sludge, yard waste, and horse manure. Composting took place indoors, and the windrow was turned several times during the experimental period. Concentrations of all 12 micropollutants decreased during composting, and degradation was statistically significant for 7 of the 12 micropollutants. Metabolites (galaxolidone and methyl-triclosan) were produced from two micropollutants (galaxolide and triclosan) during composting, indicating microbial degradation. Pollutant concentrations early in the experiment were more variable than those experienced for the chemical method development. This was likely due to compost heterogeneity. After the second compost turning, concentrations became more stable as compost became more homogeneous.