Biodegradation of glucose and paracetamol and process optimisation with open mixed microbial cultures in lab-scale sequencing batch reactors

In the context of biological wastewater treatment, this study investigated xenobiotics (man-made chemicals) biodegradation and process optimisation to maximise sustainability. Lab-scale sequencing batch reactors (SBRs) fed with paracetamol (model xenobiotic) and glucose (model biogenic substrate) each as only carbon source (feed concentration 1 g L−1) were run in a range of HRTs (hydraulic retention time, range 0.5–2 d) and SRTs (solids retention time, range 1–28 d). For both substrates, the removal of COD (chemical oxygen demand) increased as the SRT increased, reaching 97 % for glucose and 86 % for paracetamol. At the lowest HRT, the high solid losses with the effluent caused a reduction in the SRT with worse substrate removal. The fraction of the removed COD which was converted into biomass increased for lower SRT and overall the best performance for sustainability (compromise between substrate removal, energy consumption and plant footprint) was observed with HRT 1 d and SRT 11–12 d. The experimental data were modelled using two different approaches: linearisation of a continuous-flow model and non-linear parameter fitting with a periodic steady-state SBR model. The results indicated faster growth rate and slightly higher growth yield for glucose than for paracetamol.