WWW.WAS.ORG • WORLD AQUACULTURE • MARCH 2016 53 two systems by inserting a 10.2-cm diameter PVC cap into each bulkhead fitting. Mark the location of the hole for the first 10.2cm diameter bulkhead on the far side of one of the tanks, being careful to leave sufficient space on all sides of the hole to install the bulkhead fitting fastening ring. Cut this hole and then mark the location of the corresponding hole on the adjacent tank. After installing the bulkhead fitting, connect the two sumps with two 10.2-cm diameter PVC male adapters and a short length of PVC pipe. On the opposite wall of the sump tanks, mark and cut holes for 7.6-cm diameter bulkhead fittings. Join the two adjacent tanks with a single 7.6-cm diameter bulkhead fitting. For the bulkhead connecting the two tanks within the one system, use an additional bulkhead gasket to insure that water will not leak between the two tanks. One final hole was cut for a 1.9-cm diamter bulkhead fitting in the wall opposite the 7.6-cm diameter bulkhead fitting to connect the water pump to the water supply system. Water Treatment Components. After preparing the sump tanks, add the associated water treatment components for each bank of tanks. Install immersion heaters on the lip of sump tanks (Fig. 6). Attach the heater so that as much of the element as possible remains submerged in the sump tank water. For solids capture, a polycarbonate tray for a restaurant supply company nests in the top access hole on the first sump tank. The tray was drilled with multiple 1.3-cm diameter holes across the bottom in a grid pattern to allow water to pass (Fig. 7). Two layers of filter material were placed on top of the holes to capture solids. For solids capture in the collection trays, cut bulk polyester HVAC filter media to size. This material is inexpensive, easy to cut and may be reused by simply cleaning the solids with the spray of a hose. If collection filters are cut slightly smaller than the tray, when they become clogged, water will still flow into the sump tank instead of overflowing onto the floor, keeping the system running. Biofiltration media was added to the inboard sump tank. We determined that Bio-Fill™ (a shredded plastic bio-media) was not suitable because the water pump pulled the media toward the intake. Bio-ball media floats well and can be excluded from the pump with a 1.3-cm mesh Vexar® screen inlet cover. Aeration is provided by a single linear piston air pump that also provides air to other systems within the laboratory. Air is delivered to racks through 6-mm vinyl tubing from a 2.5-cm diameter PVC pipe manifold that extends around the perimeter of the room. The sump of each bank of the rack system is supplied with air from two 7.6 cm × 3.8 cm, medium-pore diffusers. There are no air diffusers in individual holding tanks. An external mag drive pump was connected to the sump through a 1.9-cm diameter bulkhead. Two 1.9-cm diameter true unions, a drain plug and 1.9-cm ball valve were added to expedite changing the water pump in the event of failure (Fig. 8). A bypass cartridge filter was mounted beneath the bottom shelf of the rack. The bypass feature is invaluable for saving space by eliminating the need for a separate bypass circuit and control valves and for the ease of changing filter cartridges because it is not necessary to shut down the system to perform this maintenance operation. The cartridge filter housing was mounted to the assembled shelving unit with fiberglass U-channel pipe clamps, 6-mm nylon bolts and two wooden mounting or spacer blocks (Fig. 9). The mounting blocks were used to space the cartridge from the bottom of the shelf for ease of rotating the filter bypass top when filters need to be changed. (CONTINUED ON PAGE 54) FIGURE 7. Representation of solids capture tray with layered filter material and holes for overflow. FIGURE 8. External mag drive pump with true unions, cleanout plug, ball valve and cartridge filter. FIGURE 9. Mounting block and location of cartridge filter mount.
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