Abstract:
Treating the wastewater from the kitchen before discharging it into the
environment is vital in preserving natural resources such as groundwater, surface
water, soil, etc. However, in most cases, kitchen wastewater is discharged into the
environment without any treatment in developing countries like Sri Lanka,
especially in rural areas. Hence the study objective is to examine the feasibility of
treating kitchen wastewater by implementing constructed wetlands suitable for rural
areas in the north-western province of Sri Lanka. A pilot-scale horizontal
subsurface flow constructed-wetland constructed, with the dimension of 1.8 m x
1.6 m x 0.6 m in length, width, and depth, respectively. The selected native plants
were planted into the constructed wetland, watered, and maintained for thirty days.
After 30 days, the freshwater supply was stopped and wastewater generated from
the kitchen was sent into the constructed wetland. The hydraulic retention time was
maintained at three days. The water quality parameters such as Biochemical
Oxygen Demand (BOD) and Hydrogen Ion (pH) were tested in influent and
effluent samples using the standard laboratory procedures and were compared with
the standard set by the Central Environmental Authority (CEA) and the World
Health Organization (WHO). BOD levels in the raw kitchen wastewater and treated
wastewater were observed to be in the range of 125.5 - 147.5 mg/l and 9.5 – 13.0
mg/l respectively. The BOD5 levels of the effluent were within limits set by the
CEA and WHO standards. The pH level in the raw kitchen wastewater and treated
wastewater were observed to be in the range of 8.54 - 8.83 and 6.38 - 6.83
respectively. The effluent’s pH values moved toward the neutral phase and were
within the range of CEA standards. The overall removal efficiency in BOD and
pH was 91.9% and 24.9% respectively. This type of constructed wetlands with
native plants can be a technically feasible, low-cost solution to treat kitchen
wastewater in rural areas of Sri Lanka.
