GLOBAL AQUATICS

After the removal of solids, the most import water quality concern is the removal of ammonia and nitrites. The process considered the most effective to accomplish this is known as "Bio-filtration". This works through the use of bacteria colonies which are found in nature. A bio-filter will usually contain two different types of bacteria which work together to complete a process known as "Denitrification.".

In simple explanation each animal is a part of of a chain which takes ammonia, which is the element that fish and fish waste creates and they turn it into an different form. The first bacteria consume the ammonia and they excrete nitrite. The second bacteria colony consumes the nitrite and excrete a nutrient.

The purpose of the device known as the biofilter is to provide the area where thebacteria can accumulate and then have the effluent from the re-circulating system flow pass them so they can feed. Since the bacteria will stick to almost anything, the media that has been used by system designers has been everything from plastic shotgun wads to plastic hair curlers. Some companies make special coring just for this purpose. For over twenty years we at Global Aquatics have studied the various designs for biofilters, the media, the applications and water flows through the filter and past the bacteria. What we found was that although the filter would work for awhile, in almost every case, sooner or later the media became clogged with very small suspended particulate from the fish waste that was not removed prior to going to the filter, and one of two things happened. (It is almost impossible to remove 100% of the particulate prior to biofiltration). First the waste would begin building up on top of the media and sometimes along the sides of the vessel. At this point the denitrifaction bacteria started to loose clean places to live and their population began to drop. Next the waste would begin to attract aerobic bacteria which would deplete the biofilter of the oxygen the denitrification bacteria needed for survival. In time, the biofilter no longer served it's intended purpose at all, but instead became a BOD (Bio Oxygen Demand) generator. This action not only failed to remove the original ammonia and nitrite from the water, but actually created more as it digested the particulate. The obvious answer to this problem as described by the designers was, "You need to back flush it periodically to clean the waste out." The problem with this theory is that it can not be done without also removing the denitrification bacteria as well. Now you have an inactive biofilter and by the time the bacteria are able to rebuild their population back to the required numbers it is time to clean the filter again.

The "Up-Welling" biofilter developed by Global Aquatics over comes this problem. Thanks to it's unique internal design and the fact that the effluent enters through the bottom and exits through the top, the effluent is passing by the bacteria at a very low speed, giving them lots time to be in contact with the water. Also, since the effluent is not coming in from the top and there are no flat surfaces in the media, suspended solids entering the filter can only pass through, there is no where for them to settle. Also the bottom of the filter is designed to allow for settlement of some of this particulate and is quickly back flushed from the filter without disturbing the bacteria on the media.

The biofilter in an S-92 intensive system is located between the hydroponic clarifier and the next stage in the total filtration process which is optional to the system owner. Placed between the biofilters and the pumps returning the filtered water to the fish grow out tanks an ozone injection tower can be installed for those applications requiring low turbidity water in their growing system. Following this is a foam fractionator if that too is required. The important point to make here is, in all applications found within S-92 designs, at least 50% of all water flow within the system is created by gravity. In the chain of events just explained, water is only pumped one time. First into the bottom of the biofilters. From there, gravity carries it through the ozone injection tower and through a foam fractionator. Once again saving vast amounts of money by cutting down on pumps and electricity needs.

aquatic@iximd.com

All information found throughout these pages are the exclusive property of Global Aquatics Ltd. and may not be copied or distributed without the expressed written permission from the owners of this intellectual property.