Observations on the Accretion Experiment at Palm Jumeirah

Professor Joe Valencic

December 13, 2004

Overview: An experimental set-up of two pyramid-shaped steel reinforcing bar structures was deployed at a depth of 3 meters off Zebra Station in Palm Jumeirah on September 13, 2004. Power to the accretion experiment was supplied from shore using and Alpine 50 DC battery charger regulated to an output of 10 amps. The purpose of this experiment was to determine the rates of accretion on each of the two test pyramid-shaped structures places at different distances from the anode.

The experiment was under the direction of Professor Wolf H. Hilbertz, co-founder of Biorock Inc., who invented the mineral accretion process to create structures in seawater. Biorock technology is a process of electrodeposition of mineral in the seawater known as mineral accretion. In general, this technology uses electricity to “grow” limestone rock on artificial steel reef frames. It has also been shown to increase the growth rates of corals and other reef organisms.

In this technology and our experimental setup, two electrodes are supplied with a low-voltage DC current from a battery charger. Electrolytic reactions at the cathode (a negatively charged electrode) cause minerals naturally present in seawater, primarily calcium carbonate and magnesium hydroxide, to build up or accrete.

Results: A recent SCUBA dive to the two pyramid-shaped accreting structures permitted video, digital still and measurements of the accretion formed since the experiment was started. The results include:

1. Very rapid accretion rates that are influenced by the higher than normal salinity of the test area in the Arabian Gulf (45 ppt vs 34 ppt in normal ocean seawater.

2. Fastest growth rates on the pyramid placed closest to the Anode. The closest point anode to cathode was 1.5 feet or approximately 0.5 meters. It was at this point the greatest accretion took place.

3. The accretion on the pyramid closest to the anode (0.5 meters distant) had an accretion rate that was 83% higher than the pyramid located further away (approximately 2.5 meters distant)

4. The diameter of the accretion over the 3/8” steel rebar was 3.89 cm on the pyramid closest to the anode and 2.86 cm on the pyramid further away from the anode.

5. A diamond-shape steel extrusion was welded onto one side of each of the pyramids. The remaining diamond-shaped openings were accreted more heavily on the pyramid closest to the anode with the opening reduced to 1 cm x 3 cm. The remaining diamond-shaped openings were less accreted on the pyramid further away from the anode to an opening size of 2 x 4.5 cm.

6. The hardness of the accretion on the two structures appeared to touch to be of similar hardness. The one exception is the heavily accreted lifting eye at the top of the pyramid closest to the anode. This 7 cm lifting eyehole was accreted such that an opening of only 1 cm occurred on the pyramid closest to the anode and 4 cm on the pyramid distant from the anode. The very heavy accretion on the close pyramid structure broke off upon touch exposing the bare steel structure underneath. Bubbles were observed at the exposed blackened steel indicating the accreting process was continuing.

Conclusion: The accretion experiment has successfully demonstrated that not only accretion but also very high accretion rates are possible in the Arabian Gulf where ocean salinities are approximately 30% higher than that of the open ocean. The next logical phase of the test would be to add live corals and monitor their growth rates.

Documentation: The following pictures were taken with a Sony 5 Mega Pixel digital camera:

General pyramid shape of the accretion experimental structures. The rear face has an extruded, diamond pattern steel plate attached. The white covering is the accreted material that has accumulated over a 3/8” steel reinforcing bar.

Structure closest to the Anode Structure distant to the Anode

Structure closest to the Anode Structure distant to the Anode

Structure closest to the Anode Structure distant to the Anode

Close up view of accretion of diamond-shaped extruded steel

plate on the structure closest to the anode.

Heaviest accretion observed at a location closest to the anode at 0.5 meters.

Accreted material was very hard to the touch. Notice the diamond-shaped openings are almost entirely covered. The width of the alternate colored/black stripes on the reference rod is 0.75 inches or approximately 2 cm.

On pyramid closest to the Anode, the bottom of the structure was beginning to accrete into the substrate. This provides documented proof that the accreted structure

will bond or “grow” into the reef structure or caprock that it is placed upon.

On pyramid closest to the anode, very heavy accretion was noted near the top-lifting eye.

The only “soft” accretion was observed at the top of the lifting eye. The exposed black steel started to re-accrete immediately as evidenced by the gas bubbles. Anode below.