Maturity and security assessment of pilot-scale aerobic co-composting of penicillin fermentation dregs (PFDs) with sewage sludge

• Feasibility of co-composting of PFDs with sewage sludge was assessed.
• Compost product achieved an acceptable level in maturity.
• Almost 100% of the residual of penicillin was removed during the composting process.
• Log copy number of β-lactam resistance genes in the compost increased remarkably.
• Sewage sludge was not an appropriate co-compost material for PFDs composting.

In this work, penicillin fermentation dregs (PFDs) and sewage sludge (SWS) were co-composted to analyze the possibility of recycling nutrients in PFDs. The temperature was maintained above 55 °C for more than 3 days, and the final electrical conductivity (EC), pH and C/N all met the national standards in maturity. A nearly 100% removal of the residual penicillin was achieved, and the seed germination index (GI) increased from 0.02% to 83.54 ± 3.1% by the end of the composting process. However, monitoring the quantity of antibiotic resistance genes (ARGs) showed that the logarithm of the number of copies of blaTEM increased from 4.17 ± 0.19 at the initial phase to 8.92 ± 0.27 by the end of the composting process, which means that there is a high risk for land use when using PFD compost products.