1. A Diagrammatic Representation of the iAVs Operating Cycle
How iAVs Works
A Diagrammatic Representation of the iAVs Operating Cycle
Gary Donaldson

2. Fish provide the metabolic wastes that become nutrients that feed the plants - so iAVs starts with a fish tank.
Fish Tank
- viewed from side
Fish Tank
- Viewed from side
iAVs starts with a fish tank (fish provide the nutrients that feed the plants)....
The Fish Tank should have a cone (or wedge) shaped bottom so that solids collect within reach of the pump.

3. Fish Tank Sand Biofilter
....and a sand biofilter in which plants are grown.
Fish Tank
(viewed from the top)
Sand Biofilter
(viewed from the top)
....and a sand biofilter in which plants are grown.

4. Furrows are created in the sand bed – to ensure the even distribution of water and fish wastes across the beds – and to keep the plant crowns out of the water…and away from the fish wastes.
Furrows
Furrows are created in the sand bed – to ensure the even distribution of water and fish wastes across the beds – and to keep the plant crowns out of the water…and away from the fish wastes.

5. 00:00:00 A timer-controlled pump is located in the fish tank.
Timer Operated Pump
A timer-controlled pump is located in the fish tank.

6. At predetermined intervals, the pump raises water from the fish tank to the sand biofilter/grow bed.
00:00:01
At predetermined intervals, the pump raises water from the fish tank to the sand biofilter/grow bed.
The times shown in this presentation are indicative rather than prescriptive. They will vary according the precise particle size range of the sand, the capacity of the water pump and the specific circumstances of the system operator.

7. 00:00:02 The water enters the bed and makes its way along the furrows.
In a new bed, the water will often soak into the sand before it flows the full length of the furrows. A detritus layer will develop in the days/weeks following the start up – and this will assist the water to extend its reach along the furrows.

8. As the water moves along the furrows, it percolates down through the sand – leaving the particulate wastes trapped on the surface.
00:01:00
As the water moves along the furrows, it percolates down through the sand – leaving the particulate wastes trapped on the surface.

9. Within about 15 minutes, the beds are saturated
Within about 15 minutes, the beds are saturated...and water is draining freely from the bottom of the sand bed and back into the fish tank – by gravity.
00:15:00
Within about 15 minutes, the beds are saturated...and water is draining freely from the bottom of the sand bed and back into the fish tank – by gravity.

10. At about 20 minutes, the furrows are filled to a predetermined level (100% saturation) and the pump stops…and the bed begins to drain.
00:20:00
At about 20 minutes, the water reaches a predetermined level (100% saturation) and the pump stops…and the bed begins to drain.

11. Air is drawn into the bed…
As the bed drains, a full charge of fresh air is drawn into the sand...to provide oxygen to the soil microbes and plant roots.
Air is drawn into the bed…
As the bed drains, a full charge of fresh air is drawn into the sand...to provide oxygen to the soil microbes and plant roots.
…as the water recedes.

12. This cyclical gaseous exchange is analogous to the ‘scavenge’ effect in an internal combustion engine. Just as a piston draws air into the cylinder on the induction stroke, the draining water creates a vacuum that draws oxygen-rich air into the sand providing energy for the soil microbes.
This cyclical gaseous exchange is analogous to the ‘scavenge’ effect in an internal combustion engine. In the same way that a piston draws air into the cylinder on the induction stroke, the draining water creates a vacuum that draws oxygen-rich air into the sand providing energy for the soil microbes.

13. At around the 30-minute mark, most of the water will have drained from the bed back into the fish tank.
00:30:00
At around the 30-minute mark, most of the water will have drained from the bed back into the fish tank.

14. 5%
An amount equal to about 5% of the total pore volume will be retained in the sand – bound by hydrostatic pressure.
An amount equal to about 5% of the total pore volume will be retained in the sand – bound by hydrostatic pressure.

15. The irrigation process – about 30 minutes to flood and drain and 90 minutes at rest – is repeated every two hours during daylight.
02:00:00
The irrigation process – about 30 minutes to flood and drain and 90 minutes of oxygen availability – is repeated every two hours during daylight.

16. 2018 Mark R McMurtry PhD and Gary Donaldson
Copyright Notice
2018 Mark R McMurtry PhD and Gary Donaldson
All rights reserved. Apart from fair dealing for the purposes of study, research, criticism or review, as permitted under the Copyright Act, no part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise without the written permission of the authors.
While every precaution has been taken in the preparation of this presentation, the authors assume no responsibility for errors and omissions. Neither is any liability assumed for damages resulting from the use of the information contained therein.
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