5.0
Design
5.1
Aquaculture Centre
5.1.1
Schematic plan
5.1.2
Engineering specifications
To comply
with the above points the ground level was raised by 1.5 metres
by the importation of and compaction of 250mm layers of silty-sandy
clay.
Twelve engineered
nursery ponds featuring an average surface area of 300 square
metres were constructed using sustainable materials including
bentonite lining and bezinal coated gabions infilled with aggregate.
5.1.3
Water Extraction
Water is extracted
at a rate of 1000 litres per minute from The River Don by using
an ex-colliery, diesel generated pump, housed in the pumphouse
illustrated to the left of the picture below.
Future research
will focus upon the feasibility of converting the pump to a renewable
energy powered system that could possibly comprise of solar, wind
or biogas driven energy.
River water travels via 110 metres of 10cm diameter steel pipe
to the inlet reed bed.
5.1.4
Intake Reedbed
To achieve
the initial concept of optimum water quality the ecological treatment
of source water was recognised prerequisite to conform to best
practice of sustainable aquaculture at the Earth Centre.
The principle aim of this element is to efficiently reduce the
organic loading of the source water using a vertical flow system
designed to consider the following:
* Space restriction
in masterplan design specifications and a high flow rate of pumped
source water at 1m3 per minute
* A relatively
low organic loading (average Biological Oxygen Demand at 10 mg/l)
* An educational
exhibit to display varying methods of reed filtration i.e. in
this case a Vertical Flow Reed Bed
Once completed
the four beds will cover 1000 m2. Each bed is in operation for
one day and then drained and allowed to rest for the next three
days before being used again.
The beds
are 0.6 m deep with pea gravel on the surface and limestone gravel
underneath. The water is sprayed onto the bed from surface pipes
and trickles down through the gravel to the drainage pipes underneath.
As the water passes over the surface of the gravel the bacteria
consume many of the pollutants and any suspended particles present
in the water are filtered. The water leaves the beds via the outlet
pipe at the top of the stream (ringed yellow circle in the picture
below).
5.1.5
Open Water Channels
It was acknowledged
that an open water circulation system is essential to interpret
the progression of water through the varying stages of the demonstration
fish farm.
Reed bed cleansed
water flows through open ditches designed to consider natural
flow forms (or eddies that) reintroduce dissolved oxygen to the
water, previously decreased by the biological action of the reed
beds. The multi purpose ditchwork also creates a rich 'brook'
type habitat with a variety of water plants and amphibians. Water
insects are attracted to the running water and larvae swept into
the culture foods to assist natural feeding regimes.
The intermittent
planting of wetland plants furthers the cleansing of water on
it's journey to the nursery ponds, this includes a large stand
of watercress located in a stepped area, which is particularly
useful increasing the efficiency of the uptake of water borne
nitrates.
5.1.6
Nursery Ponds
Water circulation
in the nursery ponds utilises a parallel delivery system whereby
each pond is individually fed by to a maximum of 0.1 m3 per minute
of clean water if required.
The lining material was a pre-hydrated bentonite matting which
effectively discouraged the upward transport of toxins from the
coal spoil below.
The liquid fish waste returns via a separate circuit to flow into
the outlet treatment lagoon. The benefits of a parallel method
are the isolation of any outbreaks of fish diseases to an individual
pond.
The liquid
fish waste returns via a separate circuit to flow into the outlet
treatment lagoon. The benefits of a parallel method are the isolation
of any outbreaks of fish diseases to an individual pond unlike
a 'series system' where all the ponds are linked to the same 'flow
through 'circuit.
5.1.7
Outlet Reedbed
Fish farming
is a polluting industry and it is necessary to clean the water
we use before being discharged back into the river. Treatment
of outlet fish culture water is via settlement and a wetland horizontal
flow ecological filtration process to reduce BOD, Ammonia, Nitrate
and Suspended Solid levels .
This was arranged
in a natural wetland surrounding is to illustrate plant beds multi-functional
purpose of water filtration, plant production and habitat conservation.
The intention
was to also create a natural wetland surrounding, for aesthetic
purposes and for the production and cyclic harvesting of water
plants
The clean
water in the lagoon can also be used to irrigate a variety of
horticultural initiatives on the site or finally discharged cleaner
than previously extracted.
5.1.8
Biological design
The foremost
consideration for the biological pond design was the combination
of existing practical and productive aquacultural methods with
the increased utilisation of natural aquatic food chains.
The development
of a controlled littoral (emergent aquatic plant) zone is a significant
factor for the bio-structure of vegetable (phytoplankton) and
animal (zooplankton) infrastructure. Not only does this provide
a food source, but contributes to the breakdown of organic chemicals
via bacteriological actions. This in turn reduces toxic organic
and chemical concentrations to acceptable water quality levels
for freshwater cultured organisms.
5.2
Hatchery and Aquatic Ecology Centre
Incorporates
an attractive, practical design comprising of a 15m x 10m sustainable
timber and glass building, partly below ground level with insulation
and solar energy features.
An average optimum temperature of 18° Centigrade also utilises
the hatchery for temperate (and exotic) species culture. There
is an extensive solar gain which also contributes to the stimulation
and growth of algae as a first stage fry food. The energy saving
building design extends fry production facilities from six to
twelve months.
River water
is pumped to an external planted tank running the length of the
building and a series of stop taps control the gravity feed and
added aeration of water running to the internal tanks. The internal,
flexible working configuration, creates an opportunity for visitor
observation towards the developing stages of freshwater fish production.
The hatchery
is also the base for pond dipping equipment from the adjacent
'community pond'. Here a variety of interpretative instruments
such as microscopes, 'touch and feel' troughs and literature both
expressive and electronic can be found.
5.3
Circle Tip Wetland Site
5.3.1 Characteristics
The underlying
land was previously liable to extensive flooding and has over
the years been raised with various spoil materials:
An average
cross section is as follows:
Top soil 200mm - 300mm
Coal spoil (comprising of sandstone, coal fines, red ash , slag,
etc..) 500mm- 1100 mm
Sandy clay greater than 2000mm
5.3.2
Engineering specifications
The overlying
flat scrubland area was excavated with heavy machinery to an average
depth of 500mm. The resultant spoil was transferred to create
raised islands planted with trees and shrubs. A further 8000m2
of fish stock ponds were dug to an average depth of one metre
and seeded with emergent plant species.
Tests on
the impermeability of coal spoil indicated a figure of 10-9 m/sec
relative to clay at 10 -11 m/sec. Fringed areas were top soiled
and left to naturally regenerate.
5.3.3
Biological design
The United Kingdom is rapidly losing wetland habitats due to land
demand, loss of agricultural and commercial exploitation. Even
where successful conservation schemes do exist the financial burden
of maintenance must be met from dwindling funds. It is further
recognised that a well-established wetland is said to be up to
50 times more productive than similar grassland and up to 8 times
more productive than a similar area of cultivated land.
This innovative design considers eco-sensitive production and
maintenance of conservation wetlands and is used to demonstrate
to landowners that 'conservation does and can pay'. While recognising
the habitat requirements of a variety of plants, birds and animals
- a series of fish ponds has been constructed within the wetland.
Plants and fish can be sporadically harvested in this system and
regular maintenance to the productive areas assists in discouraging
the transition of wetland to terrestrial habitats.
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