Ammonia Stripping Explained Brochure (PDF 602 KB)

AMMONIA STRIPPINGBRANCH ENVIRONMENTAL CORP. 2WATER TREATMENTzRemoval of Ammonia.zAir Stripping.BRANCH ENVIRONMENTAL CORP. 3HOW DOES IT WORK?In a waste stream, ammonium ions exist in equilibrium with ammonia.1. Below pH 7, virtually all the ammonia will be soluble ammonia ions.2. Above pH 12, virtually all the ammonia will be present as a dissolved gas.3. The range between 7 and 12, both ammonium ions and dissolve gas exist together. 4. Percentage of dissolved gas increases with temperature and pH. Where temperature and pH favor removal of ammonia from solution.BRANCH ENVIRONMENTAL CORP. 4AIR TO WATER RATIOz At any given temperature and pH, we can determine the amount of air necessary to provide an adequate flow for the ammonia. z Generally, the higher the temperature, the lower the air flow.BRANCH ENVIRONMENTAL CORP. 5STRIPPER DESIGNIn the stripper, the pH and temperature are adjusted before the water enters the stripper.As the water is distributed over the internal packing media, it is broken up into small droplets which create a tremendous amount of surface. Air enters the bottom of the tower from a fan and travels upward through the packing. Since the ammonia is partially present as a dissolved gas, some of the ammonia transfers from the water to the air. BRANCH ENVIRONMENTAL CORP. 6FACTORS FAVORING HIGH EFFICIENCY1. High pH.2. High temperature.3. High air flow.4. Greater packed bed depth.BRANCH ENVIRONMENTAL CORP. 7TYPICAL PACKING MEDIABRANCH ENVIRONMENTAL CORP. 8TYPICAL OPERATING CONDITIONSWhile a range of operating conditions is possible, the most common designs are either pH 11 with low temperature water or warming the water to approximately 120°F (with heat recovery) and pH as low as 9.5.BRANCH ENVIRONMENTAL CORP. 9WHAT TO DO WITH AMMONIA?Once the ammonia is removed from the wastewater, there are three possible methods of disposal.1. Air dispersal.2. Concentration as ammonium sulfate or equal.3. Thermal destruction.BRANCH ENVIRONMENTAL CORP. 10AIR STRIPPER ONLYThe simplest system involves pH adjustment with air discharged directly to atmosphere.Advantage:1. Low initial cost.2. Low operating cost.Disadvantage:Removal efficiency is limited byoperating temperature.BRANCH ENVIRONMENTAL CORP. 11CLOSED LOOPWhere higher temperatures are preferred to get better efficiency, a closed loop can be used. In the closed loop, the air is sent to an absorber where concentrated ammonium sulfate is formed. The clean air is then recycled back to the stripper.Advantages:1. No air emissions2. Conservation of energy.Disadvantages:1. Higher initial cost.2. Higher operating cost.3. Must dispose of concentrated ammonia sulfate.BRANCH ENVIRONMENTAL CORP. 12Closed Loop SchematicBRANCH ENVIRONMENTAL CORP. 13THERMAL DESTRUCTIONThe air containing ammonia can be treated to meet air pollution control regulations if they will not allow the ammonia to be released. One method to do this is our catalytic oxidation system. The air is sent to the catalytic oxidizer where it is heated up to an operating temperature of approximately 550°F. As the ammonia passes over the catalyst, it is converted to nitrogen and water. The exit gas is innocuous and can be release directly to the atmosphere with no difficulty. Advantages:1. If regulations will not allow release of ammonia, oxidizer will provide control.2. No need to deal with concentrated ammonium sulfate.Disadvantages:1. Higher initial cost.2. Higher operating cost.BRANCH ENVIRONMENTAL CORP. 14Schematic-Stripper with Thermal DestructionBRANCH ENVIRONMENTAL CORP. 15TYPICAL STRIPPERS