Influence of algae on organic micropollutants removal by hybrid ultrafiltration and eco-adsorption

This study evaluates the efficiency of a novel eco-adsorbent produced from drinking water treatment sludge for the first time applied within a hybrid ultrafiltration process. It was employed to remove selected organic micropollutants (OMPs) from algae-containing water. A lab-scale pilot unit (30 L/h), equipped with the inline coagulant and adsorbent dosing was utilized. Experiments were performed with both artificial water enriched either with Chlorella vulgaris or Arthrospira platensis in different growth phases and natural reservoir water. Two dosing strategies for eco-adsorbent (20 mg/L) and coagulant (2 mg Al³⁺/L) were investigated: (i) alternating the dosing of every 5 minutes, and (ii) continuous simultaneous dosing throughout the filtration cycles. The presence of algae (2-6 × 10 8 cells/L; chlorophyll a 6–12 µg/L) affected median removal of OMPs in different ways depending on both the algae and the OMP type. A. platensis reduced ibuprofen removal by more than 25% regardless of dosing mode, while C. vulgaris increased caffeine removal by 30–40% for both dosing modes. Algae age negatively affected median removals of ibuprofen and caffeine for continuous dosing when C. vulgaris was in the stationary growth phase, while for diclofenac same happened in the matrix with A. platensis. Real natural reservoir water (2-3 × 10 5 cells/L; chlorophyll a 1–7 µg/L) showed lower removal rate than artificial lab water with algae for all compounds, most probably because of presence of terrestrial dissolved organic carbon. Overall, for this kind of matrix median removal was 8–53% for ibuprofen, 24–43% for caffeine and 14–89% for diclofenac. Findings highlighted that the process should be optimized on-site by long-term testing.