Organics

Ammonia stripping with waste heat

 

The Ammonion® Process has been developed to offer an alternative route to ammonia stripping from that of pH adjustment. With pH adjustment the wastewater stream is dosed with lime or caustic soda to raise the pH to above 11. This will convert ammonium ions to ammonia gas. Air or steam is then passed through the wastewater, typically in a packed column or plate tower at a ratio of approximately 3,000:1. The effluent is dosed with acid to reduce the pH to acceptable discharge levels.

 

With the Ammonion® Process no chemical additions are required, apart from a minor addition of anti-foam liquid. The single requirement is for waste heat with which to drive the chemical reactions. Such waste heat can be derived from combustible waste gases, an engine exhaust, excess plant steam or any other source where energy is available for disposal.

 

 

Key features

• high-rate ammonia removal with no added ph adjustment chemicals
• single-pass systems can achieve > 98.5% ammonia removal
• minimal plant footprint: removal rates of up to 840 kg nh3-n/m2/day

 

Key data

• Flow rates available: 50 to 2,000 cubic metres per day
• Energy requirements: Approximately 450 MJ of energy is required per cubic metre of leachate treated. This is equivalent to 25 cubic metres of landfill gas with 50% methane. A 1MW electrical engine will provide adequate waste heat in its exhaust (at~50% of electrical power) to treat 80 - 100 cubic metres per day of leachate
• Pre-treatment requirements: Coarse filtration for solids over 2 mm diameter
• Land requirements: This is as much a function of the process capacity as the actual process selected. As an indication of land requirements, a 200 cubic metre per day ammonia stripper will occupy approximately 120 square metres

Ammonia is found in raw domestic sewage in concentrations of about 30 mg/litre. In leachate from landfill sites and other organic wastewater streams it may rise to several thousands of milligrams per litre. It is necessary to remove ammonia from discharged water for three reasons:

 

• Ammonia is toxic to fish. Lethal concentrations range from 2.5 to 25 mg/l.
• As ammonia is biologically oxidised to nitrate it exerts an oxygen demand on the receiving water. This can reduce the oxygen in the water to a point where aquatic life forms cannot survive.
• Ammonia acts as a fertiliser, causing the profuse growth of stringy bacteria and/or fungi and generally disrupting the natural environment.

 

The Ammonion® Process has been run for over a combined 100,000 hours of compliant operation. The process has been demonstrated as consistently reliable and effective.

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