Detection and removal of spp. cysts and spp. oocysts by anaerobic reactors in Brazil.

The discharge of raw wastewater into the environment can be a contamination source of spp. cysts and spp. oocysts. The UASB (Upflow Anaerobic Sludge Blanket) reactor is the most popular technology applied for wastewater treatment in Brazil, nevertheless there is little information concerning its capacity for (oo)cyst removal. In this context, this study investigated the occurrence and removal of spp. cysts and spp. oocysts by three different UASB reactors ( Reactor A, B, and C) treating different wastewater types. In the wastewater influent, the concentration varied from 493.3 to 14,000 cysts·L for spp. and from 'not detected' to 53.3 oocysts·L for spp. The (oo)cyst concentration increased after the anaerobic treatment in Reactors A and B, while spp. log-removal of 0.5 ± 0.2 was found in Reactor C. The increment in (oo)cyst concentration may happened due to the inefficacy for (oo)cyst removal by the specific UASB reactor and/or due to the reduction of matrix interference for reactor effluent samples in the detection method. The results suggest that hydraulic retention time (HRT) may be the key parameter for spp. removal by the UASB reactor. Furthermore, no parameter analysed (physical-chemical and indicator microorganisms) showed a common correlation with the (oo)cyst concentration in the three UASB reactors. Considering that official data of cryptosporidiosis and giardiasis cases are rarely reported in Brazil, monitoring spp. cysts and spp. oocysts in wastewater could be an alternative to estimate the occurrence of diseases in the served population.