Performance of an anaerobic digester-constructed wetland system for a small community

Abstract

This paper describes the operation of an anaerobic digester-constructed wetland system treating the overall effluent of a rural community of about 30 inhabitants. The system comprised two identical upflow anaerobic digesters of 3.6 m 3 each and two horizontal flow constructed wetland (subsurface and surface flow) of 36 m 2 each. The four units were connected in series. Anaerobic digesters provided a high total suspended solids (TSS) removal (80–90%), about 65% removal of total chemical oxygen demand (TCOD) and 40–50% removal of biological oxygen demand (BOD 5). Constructed wetlands reached 35% TSS removal and 70–80% of TCOD and BOD 5 removal. Average effluent concentrations for the first and second year of operation were 49 and 28 mg TCOD l −1, 29 and 15 mg BOD 5 l −1 and 23 and 20 mg TSS l −1. During the second year of operation, the overall system reached faecal coliforms removal of 2.1 log units, total nitrogen removal of 52% and total phosphorus removal of 38%.