Constructed wetlands and sand filter applied as onsite post-treatment of anaerobic effluent

Abstract

This paper evaluates constructed wetlands and sand filter technologies applied as onsite post-treatment of anaerobic effluent, under environmental conditions of Southern Brazil. Three different onsite systems were evaluated, as follow: onsite system 1 (septic tank – ST followed by horizontal flow constructed wetlands – HFCW) with five years operation; onsite system 2 (ST followed by sand filter – SF) with three years operation and onsite system 3 (anaerobic pond – AP followed by vertical flow constructed wetland – VFCW) with one year operation. HFCW shows an average potential removal of 82, 84, 16, 50 and 90% of chemical oxygen demand (COD), biochemical oxygen demand (BOD), NH4+-N, PO43−-P and SS, respectively. Clogging phenomena occurred in the HFCW after three years operations with an average of 11 gSS m−2 d−1 loading rate applied. SF shows an average potential removal of 83, 88, 73, 76 and 88% of COD, BOD, NH4+-N, PO43−-P and SS, respectively. VFCH shows an average potential removal of 72, 80, and 71% of COD, NH4+-N, and SS, respectively, and also a very good nitrification (25 mgNO3−-N L−1 in the treated effluent) considering the high average COD loading rate (41 gCOD m−2 d−1) and average SS loading rate (15 gSS m−2 d−1) applied.