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Different Solutions For
Different Purposes
Reed Bed Treatment
Systems, constructed wetlands for waste water treatment
Reed-bed systems are
bio-mechanical installations and clean so called household-water from toilets,
washing basins and washing machines. After treatment in reed bed systems the
water can reach almost drinking-water quality, good enough to drain into rivers,
lakes and infiltrate into groundwater. Reed-bed systems cost about 1/3 of a
conventional water treatment plant, but require about 3 times more space.
The function of a reed-bed system:
1. The sewage will be pre-cleaned mechanically through screens, grit chambers or
sedimentation tanks where the solid organic residues will be separated from the
water. The sludge has to be taken out from time to time and can be used as
organic fertilizer.
2. The pumping station comprises two main pumps (one as a reserve pump) which
alternate in operation.
3. The reed bed treatment system (Root Zone Method) combines aerobic and
anaerobic decomposition processes in a substrate layer. The polyethylene lined
and refilled basins are planted with special plants.
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 due to soil constituents. This is most important for
phosphate and ammonia binding. Some of the wastewater nitrogen is released out
of the artificial ecosystem to the atmosphere as nitrogenous gases
(de-nitrification).
Through intermittent loading of the reed beds a radical change of oxygen regime
is achieved. After water saturation by feeding with the distribution system a
drainage network at the base collects the purified water. The pore space of the
substrate is refilled with air thus enabling aerobic decomposition processes.
Another part of oxygen transfer into the rhizosphere happens through a special
helophyte tissue in the plant stems and roots (aerenchym) from the air.
Clogging effects of the filter substrates (soil, sand, gravel) are prevented by
the continuous growth and decay of roots and rhizomes of the plants and the
thereby remaining soil macropores. In this manner, long-term water transport
into the soil matrix is guaranteed.
The substrate, which is filled in the sealed earth basins, is a site-specific
mixture of selected components determined by aspects of hydraulic conductivity
and physical and chemical properties. The substrate mixture is a single case
decision of planning further depending on the composition of sewage, whether
municipal or industrial. |
By means of high evapotranspiration of the marsh plants the waste water tends to
increase pollutant concentrations, thus improving the efficiency of the
microbial degradation process. These artificial wetlands reduce both pollutant
concentrations and the water volume.
Besides proper designing, construction and planting of these artificial
wetlands, specialists should supervise the initial phase of the ecosystem
development to avoid malfunctions of the total pollution control concept.
See more details... |
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