Water treatment department
In this
department the equipment to control and eventually improve the water quality is
installed. It is a very difficult department to design well, especially when
much equipment is needed (Fig. 21.13). In several established farms this
department looks a mess. When planning, it is important to allow sufficient
space. The department will, in all proba-
bility, be
changed and modified several times. It is advantageous to include several
valves in the system so that water flows can easily be stopped and sent in
different directions. It must be possible to remove all the individual pieces
of equipment without having to shut off the inlet water supply to the farm.
The amount of equipment
needed in this department varies with the quality of inlet water and therefore
the need to treat it. In this department equipment is typically installed for:
· Aeration
· Disinfection
· Oxygenation
· pH control
· Removal of
suspended solids
· Heating and
cooling.
If using a central re-use system,
the equipment for ammonia removal and the re-use pumps may also be placed here.
Before starting to plan a
water-treatment department on a new farm, it is always recommended that a flow
chart be drawn that includes the different free water surfaces to prevent
mistakes. It is quite normal to site the water treatment department in two
rooms, a machine room and a water treatment room. Equipment for oxygen
production together with equipment for heating and cooling can be placed in the
machine room. In the water treatment room there are large free water surfaces
and therefore high humidity, so proper ventilation is necessary here. Examples
of equipment placed in this room include that for aeration, ammonia removal and
solids removal. By having two rooms, the expensive mechanical equipment can be
placed in a separate room with lower humidity.
It is advantageous to locate some
equipment close to the water inlet or where the water transfer pipe to the
farms starts. This ensures some exposure time before the inlet water reaches
the farm. When using ozone as a disinfectant, or when adding chemicals for
changing the pH, it can be done in the inlet and the need for a large retention
basin inside the farm avoided.
There are advantages in having a
feeder tank as a last step before the water reaches the production system. This
will ensure equal pressure in the inter-
nal pipelines. At the same time,
the pressure will not be too high. High pressure in the internal pipelines will
create a lot of noise in the pipes and valves in the production hall. In
addition, it may be necessary to use pipes and parts of a higher pressure
class, which is more expensive. A feeder tank is also a suitable place to
install the alarm sensors, because the level will immediately drop when there
is trouble with the water supply (Fig. 21.14); some reaction time is also
achieved if the water flowdrops, depending on the volume of the header tank.
The disadvantages of using a feeder tank are that it is necessary to lift the
water to a higher level, if no pressurized water is available. For this reason
sea-water is sometimes sent directly through channels or pipes into the
production room.
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