Elucidating the removal of organic micropollutants on biological ion exchange resins.

Biological ion exchange (BIEX) refers to operating ion exchange (IX) filters with infrequent regeneration to favor the microbial growth on resin surface and thereby contribute to the removal of organic matter through biodegradation. However, the extent of biodegradation on BIEX resins is still debatable due to the difficulty in discriminating between biodegradation and IX. The objective of the present study was to evaluate the performance of BIEX resins for the removal of organic micropollutants and thereby validate the occurrence of biodegradation. The removals of biodegradable micropollutants (neutral: caffeine and estradiol; negative: ibuprofen and naproxen) and nonbiodegradable micropollutants with different charges (neutral: atrazine and thiamethoxam; negative: PFOA and PFOS) were respectively monitored during batch tests with biotic and abiotic BIEX resins. Results demonstrated that biodegradation contributed to the removal of caffeine, estradiol, and ibuprofen, confirming that biodegradation occurred on the BIEX resins. Furthermore, biodegradation contributed to a lower extent to the removal of naproxen probably due to the absence of an adapted bacterial community (Biotic: 49% vs Abiotic: 38% after 24 h batch test). The removal of naproxen, PFOS, and PFOA were attributable to ion exchange with previously retained natural organic matter on BIEX resins. Nonbiodegradable and neutral micropollutants (atrazine and thiamethoxam) were minimally (6%-10%) removed during the batch tests. Overall, the present study corroborates that biomass found on BIEX resins contribute to the removal of micropollutants through biodegradation and ion exchange resins can be used as biomass support for biofiltration.

Removal of micropollutants by fresh and colonized magnetic powdered activated carbon.

This study evaluated the adsorption capacity and rate constants for 9 micropollutants (MP) on fresh and aged magnetic powdered activated carbon (MPAC) as a magnetically separable alternative to conventional PAC for drinking water treatment. MPAC with mass fractions of 10%, 38% and 54% maghemite nanoparticles were compared to bare PAC and pure maghemite in batch adsorption experiments. Pure maghemite alone did not adsorb significant amounts of MP and when normalized to PAC content, no significant differences of MP adsorption between MPAC and PAC were observed. Freundlich constants KF (normalized to PAC content) ranged between 2.3-37 µg/mg (L/µg)1/n for all MP and adsorbents. Pseudo-second order rate constants for MP decreased with increasing maghemite content ranging between 0.2-2.7 mg/µg/min for bare PAC and 0.02-2.19 mg/µg/min for MPAC. Residual adsorption capacities of 90-days old colonized adsorbents were 10 times lower than for fresh adsorbent. At typical concentrations of 3.5 g colonized adsorbent/L found inside reactors, kinetics were still fast and removals of all MP except sulfamethoxazole exceeded 90% within 5 min.