Ozone Resistance, Water Permeability, and Concrete Adhesion of Metallic Films Sprayed on a Concrete Structure for Advanced Water Purification

The occurrence of sulfonamide and macrolide antimicrobials, as well as trimethoprim, was investigated in conventional activated sludge treatment. Average daily loads in untreated wastewater correlated well with those estimated from annual consumption data and pharmacokinetic behavior. Considerable variations were found during a day, and seasonal differences seem to occur for the macrolides, probably caused by a higher consumption of these substances in winter. The most predominant macrolide and sulfonamide antimicrobials were clarithromycin and sulfamethoxazole, respectively. In the case of sulfamethoxazole, the main human metabolite, N4-acetylsulfamethoxazole, was included as an analyte, accounting for up to 86% of the total load in untreated wastewater. The results obtained illustrate the importance of considering retransformable substances, for example human metabolites, when investigating the behavior and fate of pharmaceuticals. Average concentrations of sulfapyridine, sulfamethoxazole, trimethoprim, azithromycin, and clarithromycin in activated sludge ranged between 28 and 68 microg/kg of dry weight. Overall the sorption to activated sludge was shown to be low for the investigated antimicrobials, with estimated sorption constants for activated sludge below 500 L/kg. Elimination in activated sludge treatment was found to be incomplete for all investigated compounds. In final effluents, the median concentrations for sulfamethoxazole and clarithromycin were 290 and 240 ng/L, respectively.

The behavior of fluoroquinolone antibacterial agents (FQs) during mechanical-biological wastewater treatment was studied by mass flow analysis. In addition, the fate of FQs in agricultural soils after sludge application was investigated. Concentrations of FQs in filtered wastewater (raw sewage, primary, secondary, and tertiary effluents) were determined using solid-phase extraction with mixed phase cation exchange disk cartridges and reversed-phase liquid chromatography with fluorescence detection. FQs in suspended solids, sewage sludge (raw, excess, and anaerobically digested sludge), and sludge-treated soils were determined as described for the aqueous samples but preceded by accelerated solvent extraction. Wastewater treatment resulted in a reduction of the FQ mass flow of 88-92%, mainly due to sorption on sewage sludge. A sludge-wastewater partition coefficient (log Kd approximately 4) was calculated in the activated sludge reactors with a hydraulic residence time of about 8 h. No significant removal of FQs occurred under methanogenic conditions of the sludge digesters. These results suggest sewage sludge as the main reservoir of FQ residues and outline the importance of sludge management strategies to determine whether most of the human-excreted FQs enter the environment. Field experiments of sludge-application to agricultural land confirmed the long-term persistence of trace amounts of FQs in sludge-treated soils and indicated a limited mobility of FQs into the subsoil.

A study was conducted to examine the influence of hydraulic retention time (HRT) and solid retention time (SRT) on the removal of tetracycline in the activated sludge processes. Two lab-scale sequencing batch reactors (SBRs) were operated to simulate the activated sludge process. One SBR was spiked with 250 microg/L tetracycline, while the other SBR was evaluated at tetracycline concentrations found in the influent of the wastewater treatment plant (WWTP) where the activated sludge was obtained. The concentrations of tetracyclines in the influent of the WWTP ranged from 0.1 to 0.6 microg/L. Three different operating conditions were applied during the study (phase 1-HRT: 24 h and SRT: 10 days; phase 2-HRT: 7.4 h and SRT: 10 days; and phase 3-HRT: 7.4 h and SRT: 3 days). The removal efficiency of tetracycline in phase 3 (78.4 +/- 7.1%) was significantly lower than that observed in phase 1 (86.4 +/- 8.7%) and phase 2 (85.1 +/- 5.4%) at the 95% confidence level. The reduction of SRT in phase 3 while maintaining a constant HRT decreased tetracycline removal efficiency. Sorption kinetics reached equilibrium within 24 h. Batch equilibrium experiments yielded an adsorption coefficient (Kads) of 8400 +/- 500 mL/g and a desorption coefficient (Kdes) of 22 600 +/- 2200 mL/g. No evidence of biodegradation for tetracycline was observed during the biodegradability test, and sorption was found to be the principal removal mechanism of tetracycline in activated sludge.