Fate of parasites and pathogenic bacteria in an anaerobic hybrid reactor followed by downflow hanging sponge system treating domestic wastewater.

Treatment of domestic wastewater in a pilot-scale upflow anaerobic hybrid (AH) reactor (0.9 m(3)) in combination with downflow hanging sponge (DHS) system (1.3 m(3)) was investigated. The combined system was operated at a hydraulic retention time (HRT) of 6.0 h for AH and 3.2 h for DHS system. The total process achieved a substantial reduction of COD(total) resulting in an average effluent concentration of only 39 ± 12 mg/l. Moreover, 90 ± 7% of ammonia was eliminated in the DHS system. Nitrate and nitrite data revealed that 49 ± 3.2% of the ammonia removal occurred through nitrification process. The removal efficiency of total coliform (TC), fecal coliform (FC), and fecal streptococci (FS) was relatively low in the AH reactor. The major portion of TC, FC, and FS was removed in the DHS system resulting to an average count of 1.7 × 10(5) ± 1.1 × 10(2)/100 ml for TC, 7.1 × 10(4) ± 1.2 × 10(2)/100 ml for FC, and 7.5 × 10(4) ± 1.3 × 10(2)/100 ml for FS in the final effluent. Likely, the combined system was very efficient for the removal of protozoological species such as sarcodins (Entamoeba cysts), flagellates (Giardia cysts), and ciliates (Balantidium cysts). This was not the case for coccidia (Cryptosporidium oocysts), where 36.4 and 27.3% were detected in the effluent of AH and DHS system, respectively. Only 10% of intestinal nematode and cestode ova were recorded in the effluent of AH reactor and were completely removed in the DHS system.