T butanol

For SEM images, the culture medium was aspirated from the PDMS-chip, and spheroids were washed 3X with PBS. They were then fixed with a mixture of 2.5% glutaraldehyde (FUJIFILM Wako Laboratory Chemicals) and 2% formaldehyde for 1 h at room temperature and washed with PBS one more time. Fixed spheroids were treated with 1% osmium tetroxide (OsO₄) solution (Electron Microscopy Sciences, Hatfield, USA) in PBS for 1 h at 4 °C, washed with Milli-Q water and dehydrated by successive treatment with 30%, 50%, 70%, 90% ethanol solution (FUJIFILM Wako Laboratory Chemicals), for 5 min each, followed by washing 3X with 100% ethanol solution, 5 min each, at room temperature. Ethanol was exchanged with t-butanol by washing the spheroids 2X with 100% t-butanol (Sigma-Aldrich). The samples were first kept at 4 °C for 1 h, transferred to −30 °C for 1 h, and finally lyophilized in a freeze dryer overnight (pressure = 10 Pa, temperature = −45 °C). The SEM images were obtained from a Miniscope TM-1,000 SEM (Hitachi, Tokyo, Japan).

The precursor salt Ce(NO₃)₃·6H₂O (analytical grade, CAS number: 10277-43-7) and sulfamethoxazole (SMX, C₁₀H₁₁N₃O₃S, 99+%, CAS number: 723-46-6) were purchased from Sigma-Aldrich (St. Louis, MO, USA). Sodium persulfate (SPS, Na₂S₂O₈ 99%, CAS number: 7775-27-1) was purchased from Scharlau (Barcelona, Spain). Most of the experiments were carried out in ultrapure water (UPW: pH = 6.5). Other matrices included (i) commercially available bottled water (BW: pH = 7.7, conductivity 355 μS cm⁻¹, containing (in mg L⁻¹): 237 bicarbonate; 3.7 chloride; 7.8 sulfate; 1.1 nitrate; 75.5 calcium; 5.1 magnesium; 2.1 sodium; and 0.65 potassium ions); (ii) secondary treated wastewater (WW) taken from the University of Patras campus treatment plant (pH = 8, conductivity = 1.682 mS cm⁻¹, total organic C = 2.46 mg L⁻¹, chemical oxygen demand = 48.53 mg L⁻¹, total suspended solids = 22 mg L⁻¹, [Cl⁻] = 262.41 mg L⁻¹, [PO₄³⁻] = 14.98 mg L⁻¹, [HCO₃⁻] = 278 mg L⁻¹, [Br⁻] = 165.64 mg L⁻¹, [Ca²⁺ ] = 112 mg L⁻¹); and (iii) UPW spiked with various water constituents such as humic acid (HA: CAS number: 1415-93-6), bicarbonate (CAS number: 144-55-8), chloride (CAS number: 7647-14-5), sodium azide (NaN₃: CAS number: 26628-22-8), t-butanol (CAS number: 75-65-0), and methanol (CAS number: 67-56-1); all these were purchased from Sigma-Aldrich (St. Louis, MO, USA).