Efficiency of continuous flow CPC reactor in removing indicator bacteria and E. coli O157:H7 from hospital wastewater effluents

Chlorination of sewage effluent produces numerous carcinogenic byproducts. Solar disinfection, may be a good alternative, particularly in regions with high solar radiation, such as the central parts of Iran. This research was aimed to investigate the efficacy of a Compound Parabolic Concentrator reactor in eliminating fecal indicator bacteria and E. coli O157:H7 from effluents. Aqueous solution and hospital wastewater effluent with turbidities of 2 and 50 NTU were subjected to sunlight in a 2.5 L continuous flow CPC reactor. Parameters such as UVA and IR of solar radiation, reactor temperature, and bacterial counts at different retention times were determined and analyzed. In both aqueous solution and real effluent, temperatures exceeding 55 °C were achieved within a retention time of approximately 20 min. E. coli O157:H7 was removed earlier than E. coli and the coliform group. Although a slight increase in turbidity correlated with a temperature rise, more extended retention times were required for bacterial removal. In the real effluent, the HPC bacterial count decreased from 5.5 to 1.6 logarithmic units. In summary, the CPC reactor demonstrated remarkable efficiency in removing E. coli O157:H7 and fecal indicator bacteria from hospital wastewater effluent with a turbidity of about 50 NTU. This effectiveness was observed under conditions where UVA and IR levels, as well as UVA dosage, were approximately 45, 1200 W/m², and 8.3 × 10⁶ µW-s/cm², respectively. The bacterial destruction was so severe that even after 48 h, regrowth did not occur.