Residues of disinfectant sodium dichloroisocyanurate impedes the attenuation of antibiotics and antibiotic resistance genes during goat manure aerobic composting.

Aerobic composting is an effective pathway for the resource utilization of livestock waste; successful treatment achieves not only efficient nutrient conversion but also attenuates hazardous contaminants like antibiotics and antibiotic resistance genes (ARGs), thereby reducing the safety risks associated with waste application. As a globally prevalent livestock disinfectant, Sodium dichloroisocyanurate (NaDCC) inevitably accumulates as residues in manure. However, whether these residues compromise the microbial mitigation of antibiotics and ARGs during composting remains unclear. Here, we investigated how NaDCC residues impact antibiotic attenuation and ARG dynamics during goat manure composting. NaDCC showed no obvious influence on temperature dynamics or major physicochemical properties throughout composting, but significantly increased electrical conductivity during the thermophilic phase. Addition of NaDCC notably reduced antibiotic removal efficiency from 98.6% to approximately 73.6%. Furthermore, NaDCC reshaped ARG dynamics, suppressing relative abundance in the thermophilic phase but triggering a distinct "rebound" in the maturation phase (an increase in relative abundance compared to the control group). During this phase, stronger correlations between ARGs and mobile genetic elements were detected, and the disinfectant resistance gene qacEdelta was significantly correlated with multiple ARGs, indicating residue-driven co-selection. These findings indicate that NaDCC residues hinder bioremediation and facilitate resistance spread, effectively turning an antibacterial practice into a pollution retention risk. Therefore, optimizing disinfectant usage and composting strategies is essential to mitigate these biological hazards.