Septic Tank Combined with Anaerobic Filter and Conventional Uasb – Results from Full Scale Plants

Anaerobic digestion is an important alternative for domestic wastewater treatment, especially in warm climate regions. Two full-scale anaerobic schemes were investigated: septic tank combined with anaerobic filter (STANF) and conventional UASB reactors. Treated effluents from these systems were subjected to disinfection by chlorination. The operational performance of 56 full-scale plants (36 STANF and 20 UASB) provided a realistic view. Findings showed that the plants operated with low OLR (< 2.0 kg COD/m.day). Despite this, the removal of organic material was below values suggested by the literature (around 60% for COD). A removal of 4.0 Log10 units of total coliform and E. coli can be reached with residual chlorine (RCL) of at least 2.0 Cl-Cl2/l. Although UASB plants have performed better, improvement of maintenance is needed in both treatment configurations.