State of the art reed bed technology adapted to Middle East-conditions:
Raw sewage (without any sedimentation)is being discharged via macerator pump onto Stage A reed beds (filtration, suspended solids removal, sludge mineralization). Filtered sewage outflow from Stage A is pumped into Stage B reed beds(biological treatment, nitrification, disinfection), prior to reuse for landscaping or agricultural purposes.
A basic description and a video of the integrated sewage sludge and wastewater treatment by a sequence of vertical flow constructed wetlands is given here.
Stage A is used to filter the suspended solids from the wastewater. The reed plants grow through the overlying organic solids on the surface and develop numerous roots and shoots within the substrate. This leads to a forced dewatering, drying and mineralization of the organic solids. The organic solids volume declines to about 10 % of the initial volume. The filter bed and the accumulated solids are kept unblocked due to the continuous growth of rhizomes and stems of the reed plants, which also increase the permeability of the deeper solid layers.
The biological reed bed treatment step (Stage B) combines aerobic and anaerobic decomposition processes in a substratum layer. The wastewater percolates the filter substrate vertically to the bottom drains. Besides the microbial and fungal decomposition of organic matter and pollutants in the rooted substrate matrix, chemical and physical precipitation, adsorption and filter processes occur. Some of the wastewater nitrogen is released out of the artificial ecosystem as nitrogenous gases (denitrification).
Reed bed total sewage effluent quality & quantity, if Middle East design criteria are followed:
COD < 50 mg/l
BOD < 5 mg/l
TSS < 5 mg/l
TP < 5 mg/l
NH4-N < 1 mg/l
TN < 30 mg/l
Total sewage effluent recovery > 80 %