|
|
|
|
The reed bed system is a self contained,
artificially engineered, wetland ecosystem for treatment and
recycling of sullage, sewage and industrial effluent. It is
designed to optimize the microbiological, chemical and
physical processes naturally occurring in the reed bed.
Wetland plants, such as reeds, transfer atmospheric oxygen
down through their roots in order to survive in waterlogged
conditions. This creates both aerobic and anaerobic soil
conditions, allowing a rich microbial diversity comprising of
bacteria and fungi use organic pollutants as a food source,
breaking down a wide range of organic chemical products. So,
chemical are not simply stored in the reed bed and are
actually degraded into harmless smaller components. Other
contaminants comprising of heavier metals are transformed from
a toxic, mobile state into fixed state by complex chemical
reactions in the soil. Also adsorption capacity of soil acts
as a buffer for peak or shock effluent loads.
The
complexity of microbial life and powerful reactions within the
root zone of the soil based reed bed system results in
extraordinary water cleaning or treatment capacity.
|
|
Components of
reed bed system |
|
Resembling
a beautiful garden of flowering wetland plants, the reed bed
system comprises of the following components;
· A
sedimentation tank
· A
reed bed consisting of
- Filling
media
- Acclimated,
aerobic, anaerobic and facultative bacteria & fungi
- Selected
indigenous wetland plants (phragmite species)
Combing mechanical filtering, chemical
precipitation and biological degradation in one step, the
system effectively removes suspended solids and organic matter
in the form of BOD and COD
|
|
Working
of Reed bed system
|
|
After primary settling in the
sedimentation tank, the breakdown of contaminants is
achieved by the controlled seepage of wastewater through
the root zone of the selected wetland plants. Organic
pollutants are broken down as a food source by
microorganisms and the plants, while the other
contaminants, such as metals are fixed in the humic acid
(via cation exchange bonds) in the soil or mineral
substrates in which the plants are rooted. During this
process suspended solids, BOD and COD are reduced to an
acceptable level. |
 |
|
|
This method requires a detention
period of at least six hours but provision of eight hours
detention time is preferable. Hence, an effective and
efficient treatment of wastewater is produced within the Reed
bed in a sustainable and natural manner. There is no ongoing
electricity cost to run pumps and air blowers, the
power source is the sun which powers the plants through the
natural process of photosynthesis.
The system will not clog up over time as the design ensures
that the rate of breakdown exceeds the rate of loading in the
Reed bed, so the performance of a reed usually increases not
decreases, over time. Biomass is removed and not permitted to
clog the voids of the gravel bed. This treatment involves a
careful and continuous thinning of the growth so that
biological activity does not get reduced. The reed so removed
can be utilized and they have considerable commercial value.
|
|
The Role of
Plants |
|
The specially
selected plant species( Phragmite species e.g. Phragmite
karka and Typha angustus) with in the Reed bed have
the following three main functions:
|
· They
provide the means for secondary restructuring of the soil
system. The very extensive root and rhizome system
creates channels for the water to pass through and also
keeps the soil open through the constant growth. |
|
· The
roots of the aquatic plant introduce atmospheric oxygen
down into the body of soil, facilitating the diversity of
microorganisms to flourish around the plant roots. It is
essential for the effective breakdown of various organic
and inorganic compounds. |
|
· The
plants are capable of taking up a certain amount of
nutrients from the wastewater itself.
|
|
|
Features of
the Reed Bed System |
|
1. Operation
and maintenance free: The reed bed system has no
mechanical/moving parts. There is also no wastage of
energy since mechanical aeration is not needed. |
|
2. Clean
and efficient: Since all chemical, physical and
biological changes occur underground, there are no strong
odours or sludge formation. |
|
3. Self-sustaining
and long lasting: Once installed and become
operational, the reed bed system can sustain itself for
more than 40 years. |
|
4. Adaptability:
The reed bed systems are suitable for concentrations from
a few mg/l 20,000 mg/l of COD and 400 mg/l of nitrogen.
Their capacity varies from about 1m3/day to more than
10,000 m3/day. |
|
5. Can
handle difficult effluents: As the reed bed system has
diversity of microbes and the wetland and the plants, it
can adapt itself to diverse types and varying shock loads
of effluents, including difficult waste waters containing.
·
Organic compounds like Chlorinated hydrocarbons,
dyes and sulphur
containing aromatics. |
|
·
Nitrogen compounds such as ammonia and nitrates. |
|
·
Sulphur compounds like sulphides and sulphates |
|
·
Heavy metals and pathogens |
|
|
Applications |
|
The reed
bed system is effective in treating effluent from
- Rural areas
- Food processing industry
- Breweries
- Animal husbandry
- Sullage and sewage from residential,
institutional and industrial
complexes.
- Chemical industry
|
|
Benefits |
|
· It offers a low cost, low maintenance and
sustainable solution to effluent
problems. |
|
· A
single reed bed system is able to treat effluents from a
number of sources. |
|
· This
method requires smaller space as compared to conventional
modes of wastewater treatment including trickling filters. |
|
· The
operational cost of this mode is also less, as no trained
staff is required for its operation. |
|
· The
treated effluent can be safely used for irrigation and the
crops grown have higher yield and do not create any health
problem. |
|
|
|
|
|
