Elimination of Micropollutants during Post-Treatment of Hospital Wastewater with Powdered Activated Carbon, Ozone, and UV
A pilot-scale hospital wastewater treatment plant consisting of a primary clarifier, membrane bioreactor, and five post-treatment technologies including ozone (O-3), O-3/H2O2, powdered activated carbon (PAC), and low pressure UV light with and without TiO2 was operated to test the elimination efficiencies for 56 micropollutants. The extent of the elimination of the selected micropollutants (pharmaceuticals, metabolites and industrial chemicals) was successfully correlated to physical-chemical properties or molecular structure. By mass loading, 95% of all measured micropollutants in the biologically treated hospital wastewater feeding the post-treatments consisted of iodinated contrast media (ICM). The elimination of ICM by the tested post-treatment technologies was 50-65% when using 1.08 g O-3/gDOC, 23 mg/L PAC, or a UV dose of 2400 J/m(2) (254 nm). For the total load of analyzed pharmaceuticals and metabolites excluding ICM the elimination by zonation, PAC, and UV at the same conditions was 90%, 86%, and 33%, respectively. Thus, the majority of analyzed substances can be efficiently eliminated by zonation (which also provides disinfection) or PAC (which provides micropollutants removal, not only transformation). Some micropollutants recalcitrant to those two post-treatments, such as the ICM diatrizoate, can be substantially removed only by high doses of UV (96% at 7200 J/m(2)). The tested combined treatments (O-3/H2O2 and UV/TiO2) did not improve the elimination compared to the single treatments (O-3 and UV).