Mechanical Filtration Abstracts
Full Abstract
Sand filters provide the primary mechanism for the mechanical filtration of recycled water. Sand is a good filtration media but suffers from biofouling and biocoagulation of the filter bed, leading to compaction and wormhole channelling of un-treated water through the filter. Activated filter media (AFM) is manufactured from glass as a raw material. The product has been engineered to prevent biofouling, compaction and channelling. The leading accredited filter media laboratory in Europe has tested the mechanical filtration performance and back-wash efficiency of both AFM and high quality silica sand. The results are discussed and optimised filter bed operational criteria are established. |
Introduction to Bead Filter Technologies An
Alternative Filtration for Life Support Systems Tim Pfeiffer, PhD, Aquaculture Systems Technology, LLC Watch Video (Login required) Full Abstract
Bead filters are expandable granular media filters and use plastic floating beads to capture the solids while simultaneously providing a large surface area (1300 m2/m3) for the attachment of nitrifying bacteria. The beads are capable of capturing 100% of particles greater than 50 microns per pass and a large portion of smaller particles. Bead filters were designed to reduce the water use associated with sand filters in recirculating aquaculture systems. Compared to sand filters the reduced head loss through a bead filter represents a savings of approximately 28% for similar system designs using sand filters. The savings in backwash water loss is approximately 75% of the amount used for sand filters, and bead media have been shown to have a life span of over 10 years. Bead filters have been used for a variety of aquatic animals, clams, and oyster seed production. In recent years, acceptance of bead filter technology by the aquarium and zoological communities has grown. Bead filters have been used on sea lion, otter, elephant, alligator, and polar bear exhibits. Bead filter have also been applied to many backyard Koi water gardens throughout the world. |
Microscreen Drum Filtration
John C. Christiansen, EHDD Architecture Watch Video (Login required) Full Abstract
Microscreen drum filters have been used in water/wastewater and aquaculture systems for decades and now have considerable presence in zoos. But only recently have a small number of aquariums and oceanariums used them to either replace or supplement granular media filters. While corrosion and biofouling may impact both operation and service life, drum filters have the benefits of low head requirements and a low water demand for backwashing. They also function continuously at relatively fixed flow rates. These features may provide substantial system performance and life cycle cost benefits. But with only gravity flow operation, inability to remove particulates smaller than their mesh size and lack of surface area for biological filtration, a fundamental shift in life support system design may be essential to meet water quality requirements, especially for large exhibits. This shift may include the rearrangement of building elements to move life support equipment to where the system can maximize the use of gravity instead of pump head, with increased capital costs. But the potential for substantial energy and water savings with such a system is high. |