sterilising the water flow

Two, three phase Onga pumps (Model 142) bring water from the 40 tonne tanks into the hatchery system (Figure 6).  The Ultraviolet Steriliser (Ultra Pure Model 85k) provides treatment that leaves no residue in the seawater due to the use of light (Figure 7).  However it is the combination of methods that removes bacterially produced toxins, pesticides, heavy metals, etc.  Each of the production tanks have disinfected saltwater and freshwater on tap.





The freshwater pump Onga Model JS110 delivers freshwater throughout (Figure 6).  Freshwater is supplied from the underground bore and is stored in the cement freshwater tank.  It is utilised for cleaning purposes and the adjustment of salinity to farm parameters prior to shipment of postlarvae.

Figure 6 Onga Pumps Model 142 & JS 110

Figure 7 Ultraviolet Sterilisation Unit

All pipes and drains of the hatchery are positioned with a sloping gradient from front to rear, to allow for complete drainage.  Chlorination of the saltwater pipes takes place prior to a production run and can be scheduled intermittently during operation. 

The Mass Algal Culture Room has three submersible pumps:-

(i)                  KSB AMA – Drainer 301.1;

(ii)                Gundfos KP Basic 300A;

(iii)               Grundfos KPC 300A

These transfer algal cultures along three pipes in the ceiling to the Larval and Nursery areas (Figure 8). 

Figure 8 Mass Algal Culture Room

The Finfish Production Unit has a Davey Electric Transfer Pump Model XF 221 with a flow rate of 13,500 litres per hour for recirculating water from the Swirl Separator to the Biological Filter (Figure 9).

Figure 9 Davey Electric Transfer Pump

As the primary mechanical filter, the Swirl Separator (Aquasonic Model FGSS80) enables solids to be removed by centrifugal action via a central drain.  Water quality is improved by the removal of approximately 50% of solids (Figure 10). The moving bed biological filter system has a vessel volume of 1,130 litres and a biofilm surface area of 280 square metres.  The high surface area to volume ratio ensures effective biological assimilation.  Aeration is applied with water flow to ensure circulation of the moving bed media.  Nitrifying bacteria require optimum conditions of oxygen, temperature and pH. Their role in the system is converting ammonia into more harmless nitrate which is an aerobic process.  Bioculture (BCC100) is a formulation of three pure strains of bacteria used to inoculate the moving bed filter (Aquasonic Model LSB560) (Figure 11).  The dose rate is 100ml per 5000 litres of water.  Start-up ammonia (Marine Start) is added to the system to a level of 1ppm as “feed” for the bacteria, and this level is maintained for seven days.  A test kit is required for ammonia and nitrite.  When the ammonia levels reach zero, stocking of fish can begin

Figure 10 Swirl Separator

Figure 11 Moving Bed Filter