Effectiveness of bulking agents for co-composting penicillin mycelial dreg (PMD) and sewage sludge in pilot-scale system

Penicillin mycelial dreg (PMD) has a distinguishing characteristic of the high content of penicillin residue and nutrients. The existing handling of PMD used as feed additive of livestock and poultry is facing a direct challenge of penicillin transportation into environment due to the inadequate absorption through the digestive system. This work aims at examining the feasibility of co-composting of PMD with sewage sludge (SWS) in a pilot-scale system and evaluating the effect of four bulking agents. Seven treatments were co-composted over a 32-day period in 390-L reactors using the same PMD and SWS with different bulking agents, corresponding to the seven formulas (T-1: PMD + SWS + RS; T-2: PMD + SWS + WS; T-3: PMD + SWS + RS + SD; T-4: PMD + SWS + WS + SD; T-5: PMD + SWS + SD; T-6: PMD + SWS + RS + WS; control: PMD + SWS). The parameters monitored over this period included temperature, organic matter (OM), TN, NH₄ ⁺–N, NO₃ ⁻–N, pH, EC, penicillin residue, as well as germination index (GI). The results showed that co-composting PMD and SWS with BA is feasible. The highest rate of OM mineralization was observed in T-3, while below 30 % for T-2, T-4, and T-5. Furthermore, the SD addition resulted in both the increase in the duration of thermophilic stage and maximum temperature and the decrease in TN losses, particularly in T-3, suggesting that the formula of the T-3 is very suitable option for the co-composting of PMD and SWS.