While The Queenslander relies on traditional filtration devices for water quality management, it is the arrangement (and the management) of those components that provides the system with its productive edge.
The nutrient-rich water leaves the fish tank through a tank overflow (which draws from the bottom of the tank) and flows into a sedimentation and clarifier tank.
The sedimentation and clarifier tank is fitted with filter mats which trap all sedimentary solids and much of the suspended solids, too.
The water then flows into a duckweed tank where its velocity decreases sharply – and any smaller sedimentary solids are allowed to settle out.
The duckweed also provides for some bio-remediation in that the plants have a fondness for ammonia (particularly in its more toxic un-ionised form).
The sediment that accumulates on the floor of the duckweed tank is vacuumed out weekly (at the same time that the duckweed is harvested).
The water then enters a grow bed filled with expanded clay pebbles which traps any remaining suspended solids. (The management of this grow bed is central to the enhanced operation of The Queenslander and is discussed more fully in my next post).
The water drains from the grow bed into a sump tank. A trickling bio-filter is mounted above the sump tank. A pump is located in the sump tank.
While some of the flow from the pump returns to the fish tank, the rest of it is diverted to the trickling bio-filter which drains back into the sump tank.
The constant recirculation of the water in the sump tank through the bio-filter ensures that the water is both clean and very well aerated.
Another important benefit of the trickling bio-filter is that, in the event of a disease or infestation in either the fish or the plants, I can disconnect the fish tank from the growing systems. This means that each organism can be treated without detriment to the other.
Mounting the bio-filter over the sump tank (rather than over the fish tank) has reduced pumping head by up to a metre which means that we can now move more water for the same cost…….or the same amount of water at lower cost.
The liquid waste that results from cleaning the clarifier pads, duckweed tank and the grow beds contains valuable nutrients which will be recovered and returned to the system. It is pumped to an aerobic digester where brisk aeration of the water mineralises the solids.
Once the air supply to the aerobic digester is turned off, the sludge settles out very quickly. The nutrient-rich liquor can then be decanted and returned to the system. The spent sludge is good for the worms or compost heap.
In my next post, I describe how grow bed management is used to support component location in the cost effective removal of solid wastes.