From Dictionary of Water and Waste Management, Second Edition
AAFEBR acid mine drainage
AAFEBR
Anaerobic attached film expanded bed reactor, i.e. an expanded bed biofilm reactor operated anaerobically.
AAO process, A2O process
An adaptation of the A/O process . It is an activated sludge process that can achieve nitrification, denitrification and biological phosphorus removal as well as BOD removal. The three stage process involves an anaerobic zone of about one hour retention followed by an anoxic zone of similar size and finally an aerobic (oxidation) zone of 4 to 6 hours retention ( see Figure A.1). In the process the third zone is used for BOD removal and nitrification. The recycle from the end of the third (aerobic) zone back to the inlet of the second (anoxic) zone results in the nitrate being mixed with the wastewater in the anoxic zone and the nitrate is denitrified to nitrogen gas. The return activated sludge from the sedimentation tank is fed back to the start of the anaerobic zone. The first zone is required in order to obtain biological phosphorus removal. The percent removal can be in excess of 95% for nitrogen and 90% for phosphates.
Figure A.1: AAO process, flow diagram.
AAS
Atomic absorption spectrometer.
abattoir wastewater
See meat processing wastewater.
abiotic
Description of the non-living part of an ecosystem.
ablation
Removal. The opposite of accumulation.
A B process
A wastewater treatment process used in Europe that uses two acti vated sludge plants in series, i.e. aeration tank, sedimentation tank. Each sedimentation...
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