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

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 m3 each and two horizontal flow constructed wetland (subsurface and surface flow) of 36 m2 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 (BOD5). Constructed wetlands reached 35% TSS removal and 70–80% of TCOD and BOD5 removal. Average effluent concentrations for the first and second year of operation were 49 and 28 mg TCOD l−1, 29 and 15 mg BOD5 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%.