ID Water/WW Operator flashcards

36 cards. Read the term and the definition here. The deck at the top of this page is optional.

CT value

Product of disinfectant residual concentration in mg/L and contact time in minutes. Required CT rises with colder water, higher pH for chlorine, and greater target log inactivation.

Log inactivation

Reduction expressed as log(N0/N). One log is 90 percent, two logs is 99 percent, three logs is 99.9 percent, and four logs is 99.99 percent removal or inactivation of the target organism.

Combined filter effluent turbidity

Compliance turbidity measured after all filters blend. Conventional plants must stay at or below 0.3 NTU in 95 percent of monthly measurements and never exceed 1 NTU.

Detention time formula

Detention time equals basin volume divided by flow rate. Keep units consistent, for example gallons divided by gallons per minute gives minutes; baffling reduces actual versus theoretical time.

Chloramine residual

Formed by reacting chlorine with ammonia, usually at a chlorine-to-ammonia-nitrogen ratio near 5:1 by weight. It persists longer than free chlorine but is a much weaker disinfectant.

Lead action level

The 90th-percentile lead concentration of 0.015 mg/L in tap samples. Exceeding it triggers corrosion control treatment, public education, and possible source water replacement.

Copper action level

The 90th-percentile copper concentration of 1.3 mg/L. Copper leaching is controlled mainly by pH adjustment and corrosion inhibitor addition rather than by treatment removal.

Hardness as CaCO3

Calculated as 2.497 times calcium mg/L plus 4.118 times magnesium mg/L. It indicates the sum of divalent cations and influences scaling, softening needs, and corrosion control.

Langelier Saturation Index

LSI equals measured pH minus the saturation pH. Values near zero are balanced, negative values indicate corrosive tendencies, and positive values indicate scale-forming tendencies.

Turbidity and pathogens

Turbidity is not a direct pathogen measure, but particles shield microorganisms from disinfection. Low filtered turbidity is required because it correlates with effective filtration and microbial barrier performance.

Surface water treatment rule

Requires filtration and disinfection for most surface sources, with combined removal and inactivation targets set by pathogen type, such as 3-log Giardia and 4-log virus.

Distribution dead ends

Pipes with no through flow accumulate sediment and lose disinfectant residual. Flushing, looping, or valve changes restore flow and help keep detectable residual throughout the system.

Backflow prevention

An air gap or reduced-pressure zone assembly stops reverse flow of contaminants into the potable system. Devices require testing at installation and at intervals set by state rule.

Jar test purpose

A bench-scale test that mixes coagulant at several doses and pH values to identify the dose producing the lowest settled turbidity before full-scale chemical feed changes.

Filter media backwash

Reversing flow expands the bed to break up and carry away captured solids. Expansion is typically 15 to 25 percent, and wash rates must avoid media loss or mudball formation.

Alkalinity and corrosion

Alkalinity buffers pH changes and, with calcium, drives carbonate scale formation. Low alkalinity water tends toward corrosion, while high alkalinity can support protective scale.

BOD5 definition

Biochemical oxygen demand measured over five days at 20 degrees Celsius. It estimates biodegradable organic matter consumed by microorganisms and is a core secondary treatment permit limit.

Ultimate CBOD estimate

Carbonaceous BOD exerted by day five is roughly 60 to 70 percent of the ultimate value, so ultimate CBOD approximately equals BOD5 divided by about 0.68.

Total suspended solids

Solids retained on a filter, distinguishing them from dissolved solids that pass through. TSS is a primary permit parameter and indicates treatment performance and effluent quality.

Volatile suspended solids

The fraction of suspended solids burned off at about 550 degrees Celsius, approximating organic material. MLVSS estimates active biomass in aeration basins for loading calculations.

Sludge age (MCRT)

Mean cell residence time equals solids mass in the aeration basin divided by solids leaving the system per day. It governs nitrification, sludge production, and settling characteristics.

Food-to-microorganism ratio

F/M equals BOD mass entering per day divided by MLVSS mass in the aeration basin. Low ratios favor nitrification; very low or very high ratios can cause poor settling.

Hydraulic loading rate

Flow divided by surface area, expressed as gallons per day per square foot or cubic meters per square meter per day. It sizes clarifiers and checks whether overflow rates exceed design.

Solids loading rate

Applied solids mass per unit area per day, using influent plus recycle flow times MLSS divided by clarifier area. Exceeding design rates causes solids carryover in the effluent.

Nitrification oxygen demand

Oxidizing ammonia to nitrate consumes about 4.57 mg oxygen per mg nitrogen. It also consumes about 7.14 mg alkalinity as CaCO3 per mg nitrogen, which can depress pH.

Denitrification benefit

Converting nitrate to nitrogen gas recovers roughly half the oxygen used in nitrification and returns alkalinity. Anoxic zones use influent carbon to drive this reaction.

Pipe slope percent

One percent slope equals 0.01 feet per foot, or one foot of fall per 100 feet. Minimum grades keep velocity high enough to prevent solids deposition in collection mains.

Self-cleansing velocity

Typically about 2 feet per second at design flow, which keeps grit and solids moving. Lower velocities allow deposition; much higher velocities can scour and damage pipe.

Infiltration versus inflow

Infiltration enters through defective pipes, joints, and manholes from groundwater. Inflow is direct stormwater entry, often through improper connections, and spikes during rain events.

Activated sludge return rate

Return activated sludge is conveyed from clarifier to aeration to maintain MLSS. The return rate, often 50 to 150 percent of influent flow, balances solids inventory and clarifier depth.

Effluent chlorine CT

Residual chlorine concentration times contact time in the disinfection channel. Permits set a coliform limit plus minimum residual and contact time at peak flow conditions.

Sludge volume index

SVI equals settled sludge volume in mL/L after 30 minutes times 1000 divided by MLSS in mg/L. Roughly 80 to 150 indicates good settling; higher values suggest bulking.

Anaerobic digester stages

Hydrolysis and acidogenesis break down organics to acids, acetogenesis forms acetate, and methanogenesis produces methane. Methanogens are slow and sensitive to pH and temperature swings.

Pump horsepower formula

Water horsepower equals flow in gallons per minute times head in feet divided by 3960. Brake horsepower equals water horsepower divided by pump efficiency as a decimal.

Grit removal purpose

Grit chambers slow flow so dense inorganic material settles while lighter organics stay suspended. Removing grit protects pumps and digesters from abrasion and accumulation.

Ammonia toxicity to fish

Un-ionized ammonia is the toxic form and increases with pH and temperature. Effluent limits may be set as total ammonia nitrogen with seasonal or pH-dependent caps.