Management of milking wastewater as a significant control point of microbial pollution in the environment

Introduction and Objective.Milking wastewater (MW) is an under-recognised reservoir of antibiotic resistant bacteria (ARB) and antimicrobial resistance genes (ARGs).The aim of the study is to evaluate MW as a point source pollutant for the presence of ARB and ARGs, to develop a treatment plant, and to address current legislation.Materials and Method.Milking wastewater was analysed for the total number of bacteria, Enterococcus spp., Staphylococcus spp., Enterobacterales, and Clostridium perfringens.Microbial identification by MALDI-TOF MS was followed by antimicrobial susceptibility testing and detection of ARGs.Wastewater samples were also tested for the antimicrobials presence using immunochromatographic tests.An on-site two-chamber MW treatment plant was designed with consideration of its costeffectiveness and profitability.The system incorporated filtration through a mixture of fine sand and 10% kaolin, or a fine sand filter bed, yielding hydraulic conductivity coefficients of 5.13 10-6 m/s and 5.36 10-5 m/s, respectively.The treated effluent was considered suitable for activities not requiring tap water quality.Results.Escherichia coli and Enterococcus spp.were identified as ARB.PCR confirmed the presence of ARGs conferring resistance to -lactams (cphA, bla 11 , bla TEM1,2 ) and chloramphenicol (cfr).Milkling wastewater samples also tested positive for chloramphenicol.Conclusions.To mitigate environmental contamination, regulations should be established for the release of bioactive substances, with penalties imposed for non-compliance with recommended safety measures.