Since 1930, Publix has grown from a single store into the largest employee-owned grocery chain ripple liquor the United States. Currently, we are not able to service customers outside of the United States, and our site is not fully available internationally. Upon your arrival, you may plan your grocery trips, find weekly savings, and even order select products online at www.
Since 1930, Publix has grown from a single store into the largest employee-owned grocery chain in the United States. Currently, we are not able to service customers outside of the United States, and our site is not fully available internationally. Upon your arrival, you may plan your grocery trips, find weekly savings, and even order select products online at www. Concerns about cold temperature nitrification usually arise when water temperature in the biological treatment system drop 5 degrees Celsius or below. At this temperature the nitrifying bacteria responsible for oxidizing ammonia tend to go dormant. If you operate an activated sludge plant in New Hampshire this is usually not a huge problem since most aeration basins here probably don’t get much colder than 7 to 8 degrees Celsius during the dead of winter.
A common process control technique for dealing with cold temperatures is to increase your solids inventory. This helps to insure you will maximize the number of nitrifiers in the system. For the aerated lagoon operator, however, complying with ammonia limits is more of a challenge. Temperatures of 0 degrees Celsius are not uncommon, especially when the ice is 2 feet thick. Anything left alive in that environment, including the nitrifiers, are going to be moving pretty slowly.
Significant research has been devoted to understanding lagoon nitrification and finding ways to manipulate lagoons so that they can nitrify year round at 0 degrees Celsius. That may be asking a lot, but the stakes are high. The conventional approach to achieving ammonia limits is to convert the lagoon to activated sludge, which is guaranteed to nitrify all the time. One research project under way at the Exeter, New Hampshire aerated lagoon system seeks to increase the nitrifier population so that the lagoons have at least a fighting chance. Exeter is a worst case scenario, with summer ammonia limits of 1. Since nitrifying bacteria are not free swimming organisms, they must be provided with a home upon which to grow. The second media was the thought of Scott Butler, Chief Operator of the Exeter lagoons and responsible for the day to day operations of the pilot plant.
3M scrubbing pad material manufactured by the 3M Company of St. This is the same material used on the bottom of floor scrubbing machines and on abrasive kitchen sponges. The media and frames are immersed in a 4,000 gallon rectangular storage tank. The tank is divided down its length by a center dividing wall, effectively creating two separate tanks out of one. Both tanks are separated into 5 individual compartments through the use of cross baffling. They pilot plant operates in a plug flow mode and receives its influent from the discharge pipe of the final lagoon via submersible pump.
Flow rates for winter operation are designed to be low, averaging 0. This provides a detention time of approximately 1. The influent and effluent from both tanks are monitored for typical nitrification on a regular basis. The pilot plant went online on October 12, 1999. As of this writing, thirteen weeks of certified lab results for ammonia have been received, covering the period from October 28, 1999 through January 20, 2000. The results show that both media have consistently produced an effluent containing less ammonia than found in the lagoon. With the exception of week 9, the 3M media regularly outperformed the Biomatrix media.
During December, weeks 6 through 10, lagoon effluent ammonia concentration steadily increased as lagoon temperatures dropped. The pilot plant results of the same period held fairly steady. As January arrived, lagoon temperatures plummeted and lagoon ammonias continued to increase. For the first 2 weeks of January, which corresponds to week 11 and 12 of the project, the pilot plant did remarked well. Pilot plant temperatures averaged around 2. 5 degrees Celsius for these two weeks. The relatively mild winter that we had been experiencing turned bitterly cold.