A universal empirical equation to estimate the abundance of carbapenem-resistant genes during aerobic digestion of wastewater sludge

This research was funded by the Natural Sciences and Engineering Research Council of Canada, Discovery Grant program and Jarislowsky Chair Funds awarded to Professor Banu Örmeci.

Peer Reviewed

Carbapenem-resistant genes (CRGs) exist in wastewater and accumulate in wastewater sludge. Due to the potential threat posed by the CRGs, it is important to quantify CRGs and predict their removal and discharge concentrations during aerobic sludge digestion. Nonetheless, gene quantification is tedious, error-prone and expensive. This study aims to develop multiple regression models to estimate CRGs from sludge parameters that are routinely measured for the monitoring and design of aerobic sludge digesters. Batch reactors were operated at mesophilic and thermophilic temperatures for 20-35 days. Sludge samples were periodically taken during aerobic digestion. Three CRGs (blaGES, blaOXA-48 and blaIMP-27) together with 16S rRNA and integron class 1 genes were quantified. Aerobic digestion reduced the abundance of all target genes. Multiple regression modelling was conducted in linear (LM) and non-linear (NLM) modes. Sums of squared errors of the LM models were 0-0.048, whereas those of the NLM models were 0–0.003. Adjusted R2 ranges of the LM and NLM models were 0.774–0.931 and 0.986–1, respectively. Overall, the NLM models predicted the abundance of target genes more accurately than the LM models. NLM models may be used to modify the design and operational parameters of aerobic sludge digesters.