Biological Filtration Abstracts
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Pre-Nitrification via Temporary Process Loop: A Means to Reduce Exhibit Construction Time
Dave Cohrs, University of Utah, National Aquarium Watch Video (Login required) Full Abstract
Establishing stable ammonia-oxidizing (AOB) and nitrite-oxidizing bacteria (NOB) populations to adequately process nitrogenous wastes in a new aquatic animal life support system typically requires three to six weeks and much longer at temperate to polar temperatures. AOB/NOB colonization of biological media typically begins after system commissioning and adds three to six weeks to construction time before animal introduction can commence. AOB/NOB populations can be established by building a pre-nitrification process loop concurrent with aquatic system fabrication, effectively reducing the construction schedule by three to six weeks. The pre-nitrification loop consists of a sump with a pump that feeds water to filtration components containing appropriate substrate for AOB/NOB growth. These biological reactors in turn supply water back to the sump to complete the closed loop. The sump has significantly less volume than the final aquatic system (10% or less), so daily dosing with a nitrogen source, such as urea, is readily and economically achieved. In 2013, the National Aquarium, Baltimore, applied this technique during the construction of a 275,000-gallon mixed species exhibit. Using regular water quality measurements (ammonia, nitrite, alkalinity, pH and salinity) incremental increases in daily urea additions were calculated for the 30,000-gallon pre-nitrification system. After characteristic ammonia and nitrite peaks, a stable concentration of daily nitrogen input, equivalent to a fully stocked system, was achieved, in less than one month (26 days). Thereafter the filters were fed a stable maintenance dose of urea until the final life support system was connected, at which point daily urea doses were reduced to offset nitrogen input from food fed to stocked fishes. Urea was introduced immediately prior to the sand filters and no ammonia or nitrite was detected in the exhibit, allowing maintenance of AOB/NOB populations without risk to the fishes. |
Nitrification in Marine Aquarium Systems
Timothy A. Hovanec, Ph.D., DrTim's Aquatics, LLC Watch Video (Login required) Full Abstract
Biodegradable carbon pellets such as Polyhydroxyalkanotes (PHAs), have many uses in the filtration of public aquarium display waters because of their ability to serve as both a consumable carbon source and bacterial substrate. They can be used anaerobically as an external carbon source to transform dissolved nitrate-nitrogen into gaseous nitrogen ( N2), or aerobically as a carbon source to promote bacteria assimilation resulting in reduced concentrations of nitrogen (both ammonia-nitrogen and/or nitrate-nitrogen) and phosphate, creating a nutrient limited environment without the risk of producing hydrogen sulfide. Recent research shows the assimilation of ammonia-nitrogen in soft, acidic waters where biofiltration is typically inhibited due to low pH, occurs at similar volumetric conversion rates as seen in biofilters operating at optimal pH (6.8 to 8.0). Further, recent research has shown that the introduction of a biodegradable carbon source also can help to eliminate ammonia spikes in newly started biofilters and/or help reduce the impact of shock loading resulting from the fast acclimation of the assimilation process (days) versus traditional nitrification (weeks). Operated anaerobically, nitrate removal rates are between 1.0 - 3.5 g NO3 --N/L pellets/day compared to aerobic removal of nitrate/ammonia between 0.250-0.750 g NO3 --N/L pellets/day. Aerobic PHA consumption rates (15-20 g-PHA consumed/g-N removed) are 5-8 times higher than anaerobic consumption rates (2-3 g-PHA/g-N). As a result, anaerobic designs are favored for larger operations with control/monitoring capabilities. Aerobic operations can be operated passively and are more appropriate for smaller individual tank systems. |
Aquaponics: Emerging Technologies for
In Situ Nutrient Mitigation - An Overview Stewart McDaniel, Pentair Aquatic Eco-Systems Watch Video (Login required) Full Abstract
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Open and Semi-Open Systems the
Atlantis Case Study Corry M. Cloward, PE, Cloward H2O Watch Video (Login required) Full Abstract
The Atlantis Resort contains one of the largest displays of marine life in the world. Built in three major phases, the life support systems adopt different methods of water supply and water treatment. Each phase used either fully open or semi-open systems and there are different advantages and challenges that each system type presented. The type of animals displayed, as well as site-specific opportunities for sourcing and disposal of seawater, were a major factor in the selection of water treatment processes. Water temperature control was a key consideration for system design. There have been successes throughout the operational history of the system, as well as some challenges that have been addressed with post-construction modifications. |