Biodegradation kinetic constants and sorption coefficients of micropollutants in membrane bioreactors

Abstract

In order to elucidate the capability of biomass developed in membrane bioreactors (MBR) to degrade and sorb emerging micropollutants, biodegradation (kbiol) and sorption (ksor) kinetic constants as well as solid-liquid partition coefficients (Kd) of 13 selected pharmaceutical and personal care products (PPCPs) were determined with MBR heterotrophic biomass adding a pulse (100 ppb of each compound) and following the liquid and solid phase concentrations over time. The results obtained were compared to literature data referring to conventional activated sludge (CAS) systems. Two experiments were performed: one in the MBR itself and the second one in a batch reactor with the same type and concentration of biomass as in the MBR. Overall, both biodegradation and sorption coefficients were in the same range as previously reported by other studies in CAS systems, indicating that MBR biomass does not show better capabilities for the biological degradation and/or sorption of PPCPs compared to the biomass developed in CAS reactors. Therefore, the higher PPCPs removal efficiencies found in MBRs are explained by the high biomass concentrations obtained at the long sludge retention times at which this type of reactors are usually operated.

Removal of Antibiotics in Biological Wastewater Treatment Systems—A Critical Assessment Using the Activated Sludge Modeling Framework for Xenobiotics (ASM-X)

“…Through scenario simulations, we suggested that improved biotransformation kinetics resulted from a step increase of k Bio , in agreement with previous findings for diclofenac. 33 In previous studies at SRT > 100 d, 175,176 estimated k Bio values for SMX for laboratory-and pilot-scale MBRs were found comparable to CAS (see Table S4 for comparison). This may though be considered as limited evidence of the influence of extended SRT on biotransformation kinetics of SMX.…”

Hazardous events in membrane bioreactors – Part 2: Impacts on removal of trace organic chemical contaminants

“…In contrast, the most biotransformable compounds (caffeine and paracetamol with K biol = 106-240 L.gMLSS -1 .d -1 ) [46,47] were less affected by the organic carbon shock. The removal of ibuprofen that has a K biol varying from 1.3 to 49.3 L.gMLSS -1 .d -1 [46,48] was also just slightly reduced by the organic carbon shock. These results are consistent with previous findings from the above shock load experiments.…”

“…The less readily biotransformable compounds (ketoprofen with K biol = 0.03 L.gMLSS -1 .d -1 and gemfibrozil with K biol = 0.06 L.gMLSS -1 .d -1 ) [46,50] were shown to suffer a significant reduction in removal efficiency by the organic carbon shock. Naproxen featuring K biol varying from 0.06 -5.45 L.gMLSS -1 .d -1 [46,48,49] also experienced a considerable decrease in removal efficiency after introducing the organic carbon shock. In contrast, the most biotransformable compounds (caffeine and paracetamol with K biol = 106-240 L.gMLSS -1 .d -1 ) [46,47] were less affected by the organic carbon shock.…”

Occurrence and environmental implications of pharmaceuticals in Chinese municipal sewage sludge

“…The presence of pharmaceuticals in sludge from East China was significantly different from those in North or West China (Table 1), indicating differences in prescription practices for healthcare. The different regional climate presents an additional factor affecting the presence of individual compounds in sewage sludge, as temperature plays a key role controlling their sorption or degradation processes (Fernandez-Fontaina et al, 2012). Family income may also exert some influences on the presence of some pharmaceuticals in sewage sludge (Table 1) by different consumption pattern of medicines and investment in sewage treatment plants (Zhang et al, 2008).…”