INTEC   05402
INSTITUTO DE DESARROLLO TECNOLOGICO PARA LA INDUSTRIA QUIMICA
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Combination of photocatalysis and biological oxidation for the degradation of pharmaceuticals in water
Autor/es:
O. M. ALFANO; A. MANASSERO. ; M. L. SATUF; K.A. VILLÓN
Lugar:
Buenos Aires
Reunión:
Congreso; The Fifth International Symposium on Environmental Biotechnology and Engineering; 2016
Resumen:
Many pharmaceutical compounds are incompletely removed by conventional processes in wastewater treatment plants, and they are released into natural waters. These compounds are suspected to cause toxic effects on living organisms even at very low concentrations. Because of their continuous input and accumulation in the environment, they are considered as persistent micropollutants. Particularly, clofibric acid (CA), the active metabolite of the lipid regulator clofibrate, is hardly biodegradable and it has been detected in surface waters. Chemical oxidation by photocatalysis can be employed as a pre-treatment step to enhance the biodegradability of wastewaters containing CA, which could then be treated by a biological process with lower costs. This study focuses on the degradation of CA by using a combined treatment of immobilized TiO2 photocatalysis and biological oxidation.Photocatalytic experiments were carried out in a fixed-bed reactor filled with TiO2-coated glass rings. The reactor was cylindrical with two flat, borosilicate glass windows. It operates in a closed recirculating circuit driven by a peristaltic pump. Illumination was provided by two sets of four black light UV lamps, placed on both sides of the reactor. The catalyst (TiO2 P25 from Evonik) was immobilized on the glass rings (5 mm x 5 mm) by the dip-coating technique. Experiments were carried out employing rings with 1, 2 and 3 catalyst coatings, and different levels of irradiation (100%, 77%, and 37%). Each run lasted 6 hours. Along the treatment, the concentration of CA and its main intermediate, 4-chlorophenol (4-CP), were measured by HPLC. The biodegradability of the samples collected at different stages of the photocatalytic process was evaluated by means of the ratio BOD5/COD (5-days biochemical oxygen demand/chemical oxygen demand). Biological oxidation was carried out in a laboratory-scale reactor operated in a batch mode. This reactor was mounted on an orbital shaker and it was inoculated with freeze dried bacteria, taken from a commercial consortium called Bi-Chem SM 700 of Sybrom Chemical. Along the biological treatment, the toxicity of the samples and the concentration of 4-CP were assessed. Toxicity was evaluated by means of the Microtox® acute toxicity test. The highest degradation rate of CA in the photocatalytic reactor was obtained with rings with 3 catalyst coatings and 100 % irradiation level. After 6 h of treatment, CA was fully degraded, but the main intermediate 4-CP still remained in the solution. The BOD5/COD ratio of the sample was enhanced from 0.2 to 0.7, indicating that this effluent could be subjected to a consecutive biological treatment. After 7 days of biological oxidation, the complete removal of 4-CP was achieved, and the toxicity of the sample was significantly reduced, as evidenced in the decrease from 75% to 22% of the inhibition of the bioluminescence of Vibrio fischeri (Microtox® test).