Alkalinity The capacity of water to neutralize acids by the water’s content of
carbonates, bicarbonates, hydroxide, and other compounds, also known as buffering capacity.
Alternative energy Energy derived from nontraditional sources (e.g., compressed
natural gas, solar, hydroelectric, wind).
Ammonia nitrogen Elemental nitrogen present in the form of ammonia (NH 3 ).
Ammonia stripping It is a physicochemical desorption process for removing
ammonia content from a wastewater by a gas-stripping operation. In the process,
wastewater at elevated pH is pumped to the top of a packed tower with a
countercurrent flow of air drawn through the bottom openings. Free ammonia
(NH 3 ) is stripped from the falling water droplets into the air stream, which is then
discharged to the atmosphere. Lime or caustic soda is added prior to the stripping
to raise the pH of the wastewater to the range of 10.8 to 11.5, converting
essentially all ammonium ions to ammonia gas, which can then be stripped by
air. Process controls required for the operation are the proper pH adjustment of
the influent wastewater, and maintenance of proper air and water flows. Ammonia
removal efficiency is highly dependent on air temperature and air/water ratios. As
the air temperature decreases, the efficiency drops significantly. For instance, the
ammonia removal efficiency can be 75% at air temperature of 10
C, while the
ammonia removal efficiency can be 90–95% at air temperature of 20
C. Very
poor ammonia removal efficiency will be experienced in cold weather location
(0 to 10
C). The influent wastewater should always be clarified before stripping.
Residual ammonia in the ammonia stripping effluent can be removed by
breakpoint chlorination. The countercurrent flow ammonia stripping process is
technically and economically feasible for a wastewater containing about
10–100 mg/L of ammonia.
Ammonification A biochemical or chemical process in which soluble organic
nitrogen is converted to ammonia.
Anaerobic (a) An environmental condition in which free, dissolved, and combined
oxygen is unavailable in an aqueous environment (i.e., dissolved oxygen ¼ 0 mg/
L); (b) A condition in which atmospheric or dissolved molecular oxygen is NOT
present in the aquatic (water) environment.
Anaerobic bacteria They are bacteria that live and reproduce in an environment
containing no “free” or dissolved oxygen. Anaerobic bacteria obtain their oxygen
supply by breaking down chemical compounds, which contain oxygen, such as
sulfate (SO 4
2À ).
Anaerobic digestion This is a biological destruction process for destroying biodegradable organic sludge (biosolids) in the absence of molecular oxygen, or under
anaerobic conditions. It is a three-stage sludge stabilization process for sludge
volume reduction: (a) hydrolysis stage: breakdown of particulate matter and large
macromolecules; (b) acid formation stage: fermentation of the soluble organic
matter formed in the first reaction to volatile acids; (c) methanogenesis stage:
conversion of the volatile acids to the stable end produces, such as methane gas,
carbon dioxide gas, and water. Four anaerobic digestion operational modes are
available: (a) standard rate digestion mode, or one stage, unheated, and unmixed;
12 Glossary of Natural Resources and Environmental Pollution Control
427
carbonates, bicarbonates, hydroxide, and other compounds, also known as buffering capacity.
Alternative energy Energy derived from nontraditional sources (e.g., compressed
natural gas, solar, hydroelectric, wind).
Ammonia nitrogen Elemental nitrogen present in the form of ammonia (NH 3 ).
Ammonia stripping It is a physicochemical desorption process for removing
ammonia content from a wastewater by a gas-stripping operation. In the process,
wastewater at elevated pH is pumped to the top of a packed tower with a
countercurrent flow of air drawn through the bottom openings. Free ammonia
(NH 3 ) is stripped from the falling water droplets into the air stream, which is then
discharged to the atmosphere. Lime or caustic soda is added prior to the stripping
to raise the pH of the wastewater to the range of 10.8 to 11.5, converting
essentially all ammonium ions to ammonia gas, which can then be stripped by
air. Process controls required for the operation are the proper pH adjustment of
the influent wastewater, and maintenance of proper air and water flows. Ammonia
removal efficiency is highly dependent on air temperature and air/water ratios. As
the air temperature decreases, the efficiency drops significantly. For instance, the
ammonia removal efficiency can be 75% at air temperature of 10
C, while the
ammonia removal efficiency can be 90–95% at air temperature of 20
C. Very
poor ammonia removal efficiency will be experienced in cold weather location
(0 to 10
C). The influent wastewater should always be clarified before stripping.
Residual ammonia in the ammonia stripping effluent can be removed by
breakpoint chlorination. The countercurrent flow ammonia stripping process is
technically and economically feasible for a wastewater containing about
10–100 mg/L of ammonia.
Ammonification A biochemical or chemical process in which soluble organic
nitrogen is converted to ammonia.
Anaerobic (a) An environmental condition in which free, dissolved, and combined
oxygen is unavailable in an aqueous environment (i.e., dissolved oxygen ¼ 0 mg/
L); (b) A condition in which atmospheric or dissolved molecular oxygen is NOT
present in the aquatic (water) environment.
Anaerobic bacteria They are bacteria that live and reproduce in an environment
containing no “free” or dissolved oxygen. Anaerobic bacteria obtain their oxygen
supply by breaking down chemical compounds, which contain oxygen, such as
sulfate (SO 4
2À ).
Anaerobic digestion This is a biological destruction process for destroying biodegradable organic sludge (biosolids) in the absence of molecular oxygen, or under
anaerobic conditions. It is a three-stage sludge stabilization process for sludge
volume reduction: (a) hydrolysis stage: breakdown of particulate matter and large
macromolecules; (b) acid formation stage: fermentation of the soluble organic
matter formed in the first reaction to volatile acids; (c) methanogenesis stage:
conversion of the volatile acids to the stable end produces, such as methane gas,
carbon dioxide gas, and water. Four anaerobic digestion operational modes are
available: (a) standard rate digestion mode, or one stage, unheated, and unmixed;
12 Glossary of Natural Resources and Environmental Pollution Control
427