4. Conclusions
The domestic wastewater of a small community was successfully
treated for organic matter, suspended solids, nitrogen, phosphorus
and coliform removal in horizontal (HSSF-CW) and vertical
(VSSF-CW) sub-surface flow constructed wetlands operated in series.
Anaerobic pretreatment decreased the organic matter and
suspended solids loading in the constructed wetlands. Operation of
the two-stage constructed wetland system provided advantages
over single systems such that removal of organic matter and suspended
solids as well as denitrification were mainly achieved in
HSSF-CW, whereas nitrification and phosphorus removal were
mainly achieved in the succeeding VSSF-CW. The whole treatment
system including anaerobic pretreatment achieved on average up
to more than 95% organic matter and 90% nitrogen removal
resulting in effluent COD and TN concentrations below 20 mg/L
with a specific wetland surface area of only about 1 m2 per person.
The treated domestic wastewater met the discharge standards for
organic matter and suspended solids parameters. Discharge from
the system can also be used for irrigation if it is disinfected properly
via chlorination. The study showed that hybrid constructed
wetland system with anaerobic pretreatment can be considered as
an alternative for small communities.