Douglas Drennan
Douglas Drennan
Douglas Drennan received a B.S. in Biology and Chemistry, and then continued on to get a Masters Degree in Aquaculture. His first job was working for a small community college in the Mississippi delta teaching catfish aquaculture. Concurrently Douglas was working with a Mississippi consortium operating and collecting data to determine the economic feasibility of growing catfish indoors in a recirculating aquaculture system. While doing research, he met Dr. Ron Malone a professor at Louisiana State University who operated the Civil Engineering Aquatic Systems Laboratory. Dr. Malone had just invented the Propeller-Washed Bead Filter and Douglas was able to obtain the third Propeller-Washed Bead Filter in existence for his “AquaTank” Project.
In 1991, Douglas went to work for Dr. Malone researching bead filters at L.S.U. In 1995, Douglas took a job working for the company that originally manufactured Dr. Malone’s bead filters, and after less than a year he acquired the Licensing Rights for the Bead Filters and formed Aquaculture Systems Technologies, LLC. The company’s primary product is Propeller-Washed Bead Filters (PBF’s). These filter range in size from 3 cubic feet to 450 cubic feet and have flow rates from 30 gallons per minute to 1500 gallons per minute. The distinguishing feature of the PBF technology is the use of embedded high speed propellers which are used to periodically agitate and fluidize the beads to effect the backwash. Compared to sand filters the PBF filters lose very little water during backwash, utilize low-head energy efficient pumps and are resistant to clogging and channeling. Shortly after founding AST in 1995 one of Douglas’s first sales was for 180 Model PBF-25’s to Archer Daniels Midland to be used in food fish production, and he has never looked back. In addition to PBF Filters, AST also offers a full line of Bubble-Washed Bead Filters (BBF’s), automated backwash controllers for both PBF and BBF filters and has recently introduced a new patented bead filter technology called a PolyGeyser “Drop” Bead Filter.
Aquaculture Systems Technologies is both a manufacturing company, and a cutting edge research company that is continually seeking to improve its patented Bead Filter Technologies. Since founding the company in 1995 Douglas has been very successful obtaining reach funds through both the U.S. Department of Agriculture and the U.S. Department of Commerce’s Small Business Innovative Research Programs. Technologies which AST has been able to bring to market as a direct result of these grants include the roto-molded plastic Model PBF-3, three cubic foot Propeller-Washed Bead Filters, automated bead filter backwash controllers, enhanced nitrification bead media which can increase the nitrifying capacity of a bead filter by up 50%, PolyGeyser Drop Bead Filters, and a computer automated system for producing algae for feeding larval shrimp, oysters and zooplankton. Ongoing research is focused on improving single pass solids capture of particles in the 5-10 micron range in bead filters by manipulating bead size and shape. This research is being conducted by mixing Arizona Test Dust with water and forming a test solution with a known particle size distribution from 1 to 200 microns. The test solution is passed upward though a column of floating bead media. Water samples are taken before and after the solution passes through the bead bed. The water samples are then analyzed using a Beckman Coulter Particle Size Analyzer and the percent removal in both the 5-10 and 20-50 micron ranges is determined. This same test is being carried out with three different bed depths and at four different flow rates to determine the effect of bed depth and flow rate on the percent removal. Note all tests are being conducted on a single pass basis to date, while our filters are typically operated on a recirculating basis. Douglas will be a key speaker at the upcoming 5th International Conference on Recirculation Aquaculture in Roanoke, VA, presenting a paper entitled “Enhancement of Fine Solids Capture in Recirculating Aquaculture Systems through Media Selection” and invites serious Koi enthusiasts to register and attend! AST also recently received funding for a study entitled “Passive Self-Regulating Denitrification Technology for Aquaculture”. Denitrification or the removal of nitrate is extremely important in marine aquaculture as well as in large aquariums which re-use their water for extended periods of time.
AST’s bead filter technologies are currently in use by some of the largest and most prestigious facilities around the world. These include ADM’s Tilapia Farm, one of the largest indoor fish farms in the US, Miami Metro Zoo’s new Asian Aviary, the Koi Pond located in the City of Phoenix AZ’s Japanese Friendship Garden, London Zoo, Hubbs-SeaWorld Research Institute, Mote Marine’s new sturgeon facility and Harbor Branch Oceanographic Institute-- to name a few. They even built three huge 450 cubic foot PBF filters that were 16’ diameter x 22’ tall for the U.S. Fish and Wildlife Service to be used at a cold water salmonid hatchery in New Mexico. In typical fish farming operations the filters are designed to mitigate the waste loading from fish tanks stocked at a density of over one pound of fish per two gallons of water.
Douglas is just finishing a new filter called a Drop Bead or PolyGeyser Filter which takes maximum advantage of the EN Bead Media. The Polygeyser Filter stands apart from AST’s other Bead Filter technologies primarily through its automatic pneumatic backwash mechanism. Water is introduced below a bed of packed EN bead media, traveling upward through the filtration chamber where mechanical and biological filtration takes place. Simultaneously, air is introduced into the air charge chamber at a constant, predetermined rate to achieve the desired backwash frequency. Once the charge chamber has reached capacity, the pneumatic trigger fires, releasing the entrained air from the charge chamber into the filter chamber below the media bed. The sudden release of air from the charge chamber causes the beads to mix, roll and “drop” as the air agitates the beads. The sludge falls down to the bottom of the filter and is drained, while the bacterial colonies keep working. This design trades more frequent, gentle wash cycles for the more vigorous, occasional ones of the PBF filter systems, and achieves equally excellent water quality.
So – how did Douglas get into Koi? Douglas purchased the rights for large Propeller-Washed Bead Filters and started Aquaculture Systems Technologies, while Burt Nichols of Water Garden Gems had previously acquired the rights to certain models of Bubble-Washed Bead Filter designs. Deciding it was better to work together than compete; Douglas and Burt became good friends and continue to work together applying the technology developed for high density fish culture to keeping Koi. In fact, you can usually find them sharing a booth at Koi Shows around the country.
Douglas and Burt are constantly striving to upgrade/improve the bead filter technologies. An example of this is the introduction of the “Pump Assisted Backwash” plumbing scheme for Bubble-Washed Bead Filters in which the circulation pump is utilized to suck/pump the backwash water from the filter. By using the pump to suck the dirty water from the filter, the water is pulled from the filter faster resulting in the air being sucked into the filter faster and hence a significantly more robust backwash. A complete explanation, schematic and parts list for this plumbing scheme are available on AST’s website (www.BeadFilters.com). Filter owners can plumb the improvements themselves rather than pay for an expensive upgrade. Additionally, in the last several years most of the BBF Filters have undergone a major face-lift. All filters are now one piece- no more separate bases, additionally the polyethylene spin weld fittings have been replaced with molded in aluminum fittings and the inlet and outlet screens enter horizontally and are equipped with unions for ease of maintenance.
While Koi applications are currently only 15% of Douglas’s market, he sees a tremendous opportunity for growth in this area. Many high-end Koi ponds are using his Propeller-Washed Bead Filters. Aquaculture System Technologies’ filters were all developed and design recommendations put forth based on quantifiable science, and use the lessons learned from fish production applications. AST has also simplified filter sizing by developing a hydraulic Koi pond sizing criteria that takes into account your pond volume and estimated fish loading—they have even developed an Online Inter-active Filter Sizing Assistant that is available on their website.
Aquaculture Systems Technologies, LLC currently has 10 employees and it is growing!. Nick Schatz the Sales Manager has a Master’s Degree in Marine Biology from the University of Maine, Pradyot Deshpande the Research Director has a Master’s Degree in Civil and Environmental Engineering from Louisiana State University and Douglas Drennan the owner and founder of AST has a Master’s Degree in Aquaculture from Mississippi State University. AST is the world leader in Bead Filter Technologies and Research and is recognized as one of the leaders in the area of biofiltration and solids capture for recirculating aquaculture systems. AST also continues to make in-roads into new industries such as zoos, aquariums and even municipal wastewater. “It is our goal to continue to improve our Bead Filtration Technologies using sound science and research” says Douglas which should please may Koi keepers by knowing that AST is constantly raising the bar for improved filtration for Koi ponds.