Biological performance and trace organic contaminant removal by a side-stream ceramic nanofiltration membrane bioreactor

Abstract

This study evaluated the performance of a side-stream ceramic nanofiltration membrane bioreactor (NF-MBR) system with respect to basic water quality parameters as well as trace organic contaminant (TrOC) removal efficiency. The results show a stable biological performance of the continuous NF-MBR system with high effluent quality (total organic carbon < 4 mg L-1 and NH4 +-N below the detection limit). Significantly higher performance by this NF-MBR in comparison to the conventional microfiltration/ultrafiltration MBR regarding the removal of a large number of TrOCs was observed. TrOC removal efficiency depended on their hydrophobicity and molecular features. All hydrophobic compounds (LogD pH=6 > 3) were well removed (>85%), except diazinon (59 ± 7%). Hydrophilic compounds containing electron donating groups were also well removed (>90%). By contrast, hydrophilic compounds containing electron withdrawing groups were poorly removed (8-54%). Most of the 40 TrOCs investigated in this study did not accumulate in the sludge. Only three hydrophobic compounds, namely amitriptyline, triclosan and triclocarban showed considerable accumulation in sludge (>500 ng g-1). Mass balance indicated biodegradation/transformation as the most significant TrOC removal mechanism by this NF-MBR. were well removed (>85%), except diazinon (59 ± 7%). Hydrophilic compounds containing 24 electron donating groups (EDGs) were also well removed (> 90%). By contrast, hydrophilic 25 compounds containing electron withdrawing groups (EWGs) were poorly removed (8 -54%). 26

Understanding the mechanisms of trace organic contaminant removal by high retention membrane bioreactors: a critical review

“…In addition to the use of high retention membranes that allows effective retention of pollutants including TrOCs, HR-MBRs may have different features compared to the conventional MBR configuration (Figure 1a Figure 1c) and nanofiltration (NF)-MBR ( Figure 1d) have been investigated to-date (Luo et al 2017b, Phan et al 2016b, Wijekoon et al 2014b).…”

“…As mentioned before, three configurations of HR-MBR, namely membrane distillation bioreactor (MDBR), forward osmosis (FO-MBR) and nanofiltration (NF-MBR) have been investigated to-date (Fernandez-Fontaina et al 2012, Luo et al 2017b, Phan et al 2016b, Wijekoon et al 2014b. Depending on the physicochemical properties of TrOCs and the type of HR-MBR configuration, removal of TrOCs by HR-MBRs can range between 90-99% (Table 2).…”

“…In general, simple structured TrOCs without branched/multi chain alkyl groups are readily biodegraded compared to structurally complex TrOCs due to their resistance to microbial degradation. Similar to conventional MBR, TrOCs containing strong electron withdrawing functional groups (EWG) such as carboxyl, halogen and amide are resistant to biodegradation, and their degradation is also poor and/or unstable in HR-MBR (Phan et al 2016b, Wijekoon et al 2014b. For instance, atrazine, carbamazepine and diclofenac are resistant to biodegradation due to the presence of EWGs (i.e., halogen and amide) in their structures (Nguyen et al 2013a).…”

“…TrOCs containing strong EWGs such as atrazine, carbamazepine and primidone; (ii) consistently high removal (80-90%) of hydrophobic TrOCs containing electron donating groups (EDGs) such as steroid hormones; and (iii) poor to moderate removal (30-80%) of hydrophilic TrOC containing both EWGs and EDGs (Luo et al 2017a, Phan et al 2016b, Wijekoon et al 2014b. Limited degradation of some TrOCs by the activated sludge highlights the significance of high retention membranes in effective TrOC removal for producing a high quality effluent.…”

The fate of trace organic contaminants during anaerobic digestion of primary sludge: A pilot scale study

“…. Most studies of aerobic treatment demonstrated a good biotransformation of these seven biodegradable TrOCs, except for some variation in the case of trimethoprim and sulfamethoxazole(Luo et al, 2014;Phan et al, 2016;Wijekoon et al, 2013). Compared to aerobic treatment, it is speculated that the negative redox potential can enhance the biodegradation of sulfamethoxazole and trimethoprim(Alvarino et al, 2014;Narumiya et al, 2013;Yang et al, 2017) Xue et al (2010).…”