accretion The increase in size of an inorganic body by the addition or accumulation of particles ACCU Air sampler by Rupprecht Patashnick AccuguardM Automated pH electrode cleaning and calibration module by bie. Accu-Mag Electromagnetic flow meter by USFilter/Wallace Tiernan accumulation zone The upper part of a glacier where net gain in ice exceeds the accumulator A tank installed in a circulating water system to allow for fluctuations in flow, temperature, pressure, or other variations in operation. AccuPac Cross-corrugated surface media for biological wastewater treatment by Brentwood Industries. Inc Accura- flo Flumes for measuring flows by Composite Structures Accu-TabTM Tablet chlorination system by Hammonds and PPG Industries, Inc Accuvac Chemical reagents in vacuum vials for chemical analysis of fluids by Hach Co ACE rule See"Any Credible Evidence rule(Ace rule). acetaldehyde An organic chemical formed during the disinfection of water, most commonly associated with the use of ozone as disinfectant. Chemical formula is Ch.CHo acetic acid A weak, organic acid contained in vinegar and used in the manufactur f organic chemicals and plastics. Also called"ethanoic acid. Chemical for mula is Ch cooH acetone A colorless, volatile liquid used in organic synthesis and as a commercial solvent. Chemical formula is CH, COCH ACFM Actual cubic feet per minute ACFTD Air cleaner fine test dust. Dust used to calibrate particle counters ACGIH American Conference of Governmental Industrial Hygienists ACH (1) See"air changes per hour(ACH). (2) See"aluminum chlorohydrate (ACH) AC American Concrete institute acid (1)A substance that can react with a base to form a salt. (2)A substance that can donate a hydrogen ion or proton acid deposition See“ acid rain?” acid mine drainage Drainage of water from areas that have been mined for coal or other mineral ores, usually having a low ph due to contact with sulfur- bearing material acid neutralizing capacity (ANC) Measure of the ability of water or soil to resist changes in pH acid rain Precipitation having an unusually low pH, generally attributed to the absorption of sulfur dioxide pollution in air. Also known as"acid de acid shock The biological disruption of an aquatic system that results from rapid acidification acid-forming bacteria Microbes that can metabolize complex organic compounds under anaerobic conditions, leading to the production of methane acidic The condition of water or soil that contains a sufficient amount of acid substances to lower the ph below 7.0accretion The increase in size of an inorganic body by the addition or accumulation of particles. ACCU® Air sampler by Rupprecht & Patashnick. Accuguard™ Automated pH electrode cleaning and calibration module by BIF. Accu-Mag Electromagnetic flow meter by USFilter/Wallace & Tiernan. accumulation zone The upper part of a glacier where net gain in ice exceeds the net loss. accumulator A tank installed in a circulating water system to allow for fluctuations in flow, temperature, pressure, or other variations in operation. AccuPac® Cross-corrugated surface media for biological wastewater treatment by Brentwood Industries, Inc. Accura-flo® Flumes for measuring flows by Composite Structures. Accu-Tab™ Tablet chlorination system by Hammonds and PPG Industries, Inc.. Accuvac Chemical reagents in vacuum vials for chemical analysis of fluids by Hach Co. ACE rule See “Any Credible Evidence rule (ACE rule).” acetaldehyde An organic chemical formed during the disinfection of water, most commonly associated with the use of ozone as disinfectant. Chemical formula is CH3CHO. acetic acid A weak, organic acid contained in vinegar and used in the manufacture of organic chemicals and plastics. Also called “ethanoic acid.” Chemical for￾mula is CH3COOH. acetone A colorless, volatile liquid used in organic synthesis and as a commercial solvent. Chemical formula is CH3COCH3. ACFM Actual cubic feet per minute. ACFTD Air cleaner fine test dust. Dust used to calibrate particle counters. ACGIH American Conference of Governmental Industrial Hygienists. ACH (1) See “air changes per hour (ACH).” (2) See “aluminum chlorohydrate (ACH).” ACI American Concrete Institute. acid (1) A substance that can react with a base to form a salt. (2) A substance that can donate a hydrogen ion or proton. acid deposition See “acid rain.” acid mine drainage Drainage of water from areas that have been mined for coal or other mineral ores, usually having a low pH due to contact with sulfur￾bearing material. acid neutralizing capacity (ANC) Measure of the ability of water or soil to resist changes in pH. acid rain Precipitation having an unusually low pH, generally attributed to the absorption of sulfur dioxide pollution in air. Also known as “acid deposition.” acid shock The biological disruption of an aquatic system that results from rapid acidification. acid-forming bacteria Microbes that can metabolize complex organic compounds under anaerobic conditions, leading to the production of methane. acidic The condition of water or soil that contains a sufficient amount of acid substances to lower the pH below 7.0