The Sound Economics of Wastewater Gardens®
Cost reduction and longer life-time
- While initial investment and installation of constructed wetlands
may be equal or higher than some conventional sewage treatment plants
(STP - See *) (or over 50% lower), depending on the country, labour
cost, materials, on the type of plants chosen (mature or budding at
start of operation) as well as on the nature of the project, operating
and maintenance costs are typically 90-95% lower than for
high-tech, mechanically based STPs (see *)
|* There are different types
of conventional STPs (Sewage Treatment Plants). On a small scale, compact system are increasingly available, with an enhanced septic tank system (2 or several chambers, in some cases with an air pump to accelerate oxygenation) and on a larger scale STPs often provide treatment by Extended
Aeration Biological Systems, Activated Sludges, RBC, and Hybrid
systems), with a different cost for each system.
For example: Extended Aeration Systems costs around 15% less
that Biological Systems in installation, while running costs
are typically around 10 times more expensive.
- While different types of conventional STPs have varying initial
capital costs and maintenance expenses, all have much higher operating
and refitting/repair expenses (conventional STPs typically need
refitting after 5-10 years of service).
- WASTEWATER GARDENS®
have a life cycle of minimum 20 years, which is 2-3 times that
which might be expected of an STP, especially in tropical
conditions; most conventional sewage treatment systems will have
a lifetime of at best 10 years, after which time significant or
complete parts replacement must be considered.
Being natural systems, there are no monthly and/or
yearly costs of expensive chemical additives, while WWG systems
also provide insurance against inflation of maintenance costs (parts,
electricity, service, chemicals, etc.).
WWG systems are designed to rely completely on
gravity-flow, with little or no machinery being used; costs of pumps,
electricity, replacement of parts and technician labor for maintenance
are removed, unless natural gravity doesn't allow free flow of water.
In addition to sewage water treatment and ability
to release into the environment purified water, the WASTEWATER
GARDENS® can supply part or all
of the landscaping needs without need of additional potable water
or fertilizer - part or all of the landscape being watered
by otherwise wasted water -, which in some sites can represent significant
The discharge water from the WWG being much lower
in organic compounds (BOD) and suspended solids, problems with important
quantity of water having to be released into the environment, with
attendant problems of soils absorption capacity in the leachfields,
are greatly reduced ; WWG discharge water will much less likely
clog soils and leachdrains remain effective for a much longer time,
Using constructed wetlands / WWG systems
as an economical incentive
Constructed wetlands can
be a low-cost and effective solution by providing a sustainable
solution to the problem of how to deal with sewage by generating
useful and saleable products from the effective use of the wastewater.
The "sludge" (solids pumped from the primary treatment / for ex.
septic tank) can be picked-up and composted, which kills any potential
pathogenic bacteria, and will produce beneficial organic fertilizer.
The constructed wetland and secondary subsoil
irrigation can be used to grow crops such as fast-growing timber,
cut flowers, medicinal plants and herbs, fiber for handicraft manufacture
can also be created to deal with sludge from septic tank pumpout
trucks, an effective way in utilizing this material which otherwise
is expensive to treat and dispose of. This service, combined with
the use - or sale - of compost and the harvested products grown
on the WWG, can help defray the costs of construction and operation
of a treatment system such as WWG.
are built with local labor and local materials rather than importing
expensive machinery and/or chemical products; both initial capital
investment and operating costs reflect and contribute to local,
regional and national economies.