Question Answer
This taste and odour removal method removes taste and odour compounds by oxidation, such as soluble ferrous iron, but is not as effective in removing organic compounds? Aeration
Why is organic compound removal by oxidation less successful than other methods? Because aeration does not allow for complete oxidation of organic compounds
List three aeration processes used to remove taste and odour problems? Forced Draft Aerators; Cascade and Spray Aerators; and, Reaction Basins
This taste and odour control method is a strong oxidizing agent that can effectively destroy many taste and odour causing compounds; it is added to sedimentation basins and preceded by aeration? Potassium permanganate
This taste and odour control method uses the process of adsorption to remove offensive compounds from water? Activated carbon
Why is activated carbon able to adsorb large quantities of compounds? It has an extremely high surface-to-weight ratio (lots surface area)
How are offensive taste and odour compounds held by activated carbon (list three forces)? Physical (predominant), chemical, and electrical forces
In the removal of taste and odour compounds, this substance is used as an oxidizer where the use of chlorine produces additional undesirable taste and odour problems? Chlorine dioxide
When chlorine is added to water it first combines with organic and inorganic compounds to form chlorine compounds. The total dosage needed to satisfy the reactions with these compounds is called the? Chlorine demand
XXXSome of the chlorine compounds created when chlorine is first added to water have? Disinfecting properties
The total of the chlorine compounds having disinfectant properties plus the remaining free chlorine (or uncombined chlorine) is termed the? Chlorine residual
In normal waters having pH values near 7.0, what is the ratio of hypochlorous acid and hypochlorite ions? Equilibrium (one-to-one ratio)
Following the addition of chlorine, it initially reacts with these types of agents (organic/inorganic)? Reducing agents (oxidation)
Which inorganic substances initially react with chlorine when it is first added to water (list two)? Hydrogen sulfide and ferric iron
As the volume of chlorine increases in water, following reduction with inorganic compounds, chlorine reacts with _____ compounds to form _____ compounds in the treated water? Organic/Chloro-organic compounds
Once chlorine reacts with inorganic compounds, then forms chloro-organic compounds, chlorine reacts with which two compounds to form_____ (3 answers)? Ammonia or Nitrogen compounds/Chloramines
When chlorine demand is satisfied, additional chlorine will form which two substances (ions)? Hypochlorous and hypochlorite ions
Once hypochlorous and hypochlorite is formed in water during chlorination, this stage of the disinfection process is called? Free chlorine
The disinfection process by which the free chlorine level is reached is called? Breakpoint chlorination
Hypochlorous and hypochlorite ions partly destroy which two compounds? Chloro-organics and chloramines
This disinfectant is sometimes referred to as High Test Hypochlorite (HTH)? Calcium hypochlorite
This category of disinfectants are white in colour and have toxic and pungent odors? Hypochlorites
This category of disinfectants produce heat, oxygen and chlorine in the presence of organic compounds? Hypochlorites
What is the ratio of liquid to gas when chlorine gas vaporizes from the liquid form to the gas form? 450 volumes of gas per volume of liquid
At what temperature is chlorine gas at atmospheric pressure? -35°C
This disinfectant is non-explosive and non-flammable, but supports combustion at high temperatures? Chlorine gas
It is only considered as slightly soluble in water and becomes highly corrosive when water and this type of disinfectant are combined? Chlorine gas
This disinfectant is typically used to treat difficult taste and odour waters, and for oxidizing iron and manganese in difficult to treat water? Chlorine dioxide
This disinfectant is explosive in concentrations over 10% in air, and may be ignited by heat or sunlight? Chlorine dioxide
This disinfectant is flammable in the presence of organic materials if ignited? Chlorine dioxide
This type of chlorination is practiced where extended chlorination is needed to control algae and bacterial growths after filtration? Combined residual chlorination
This type of chlorination is practiced to reduce dead-end red water problems in distribution systems? Combined residual chlorination
This type of chlorination is practiced to provide a stable residual throughout the distribution system? Combined residual chlorination
XXXWhich type of chlorination precedes the other: combined residual or free residual? Free residual
What determines the process to create a combined Available Chlorine Residual in a water supply? Water characteristics and the presence of naturally occurring ammonia in the water supply (chloramines)
This type of chlorine residual should contain little or no free available chlorine? Combined Available Chlorine Residual
This type of chlorination is practiced as a “pre” and “post” disinfection? Free Residual Chlorination
This type of chlorination is practiced when water quality is poor? Free Residual Chlorination
This type of chlorination is practiced if contact time is insufficient to accomplish disinfection by combined available chlorination techniques? Free Residual Chlorination
This type of chlorination is practiced when high concentrations of iron, manganese, and colour are present? Free Residual Chlorination
XXXThis type of chlorination is practiced to minimize biological growths in filters and to eliminate chlorine resistant bacteria, slimes, and biological growths in distribution systems? Free Residual Chlorination
This is practiced in lengthy distribution systems where the plant residual is insufficient to control bacterial and algae growth, or if there are red water problems (dead-end)? Re-chlorination
It is a practice where chlorine is applied to the end of lengthy mains and at points where the main supplies a reservoir, stands pipe, or pumping station? Re-chlorination
Combined residual chlorine treatment may be used as plain chlorination, pre-chlorination, post chlorination, or re-chlorination under what ideal circumstance? When long contact periods are possible
When the addition of chlorine and ammonia as a form of disinfection is practiced, which substance should allow for thorough mixing before both chemicals are combined? Ammonia, prior to the injection of chlorine
Under what circumstance is free residual chlorination pre-chlorination followed by combined chlorination to stabilize the chlorine in the distribution system? For short contact periods
What are the two substances used in the practice of de-chlorination? Sulfur dioxide (or chemical derivative) and activated carbon
What are two essential factors for effective disinfection using chlorine? Chlorine residual and contact time
What is the minimum requirement for free chlorine residual and contact period? 0.5 mg/L free chlorine residual and 20 minute period
What is the minimum requirement for combined chlorine residual and contact period? 2.0 mg/L and a 2+ hour period
These two physical factors, which can be controlled with equipment and process design, are critical factors affecting disinfection by chlorination? Injection point/method of mixing (thorough diffusion of the chlorine)
List the 6 critical factors required for effective disinfection by chlorination? Thorough diffusion of the chlorine, regular monitoring, correct dosage, efficiency of upstream process, ideal water temperature, ideal pH
An increase in turbidity will have what impact on chlorine disinfection dosages? Increased dosages are required
An increase in water temperature will have what impact on chlorine disinfection efficiency: increased or decreased? Increased efficiency
What are the two basic chlorination process calculations? Chlorine dosage and chlorine demand
This type of chlorination system is mainly used in smaller water systems? Hypo-chlorinators
A smaller water system that requires lower chlorine requirements and has simplicity in operation will use what type of chlorination system? Hypo-chlorinators
This type of chlorination system consists of a chemical solution tank, a diaphragm pump, a pressurized water supply, and a mixing tank? Hypo-chlorination
The diaphragm pump used in a hypo-chlorination system is normally what type of pump? Positive displacement type
On a typical gas chlorination installation, this component controls the downstream gas pressure? Inlet regulating valves
On a typical gas chlorination installation, this component allows gas to pass only when a vacuum exists on the downstream side of the valve? Pressure relief valve
On a typical gas chlorination installation, this component is comprised of a floating disk or ball contained within a tapered glass tube. What is this component called, and what does it do? Flow rate indicator (rotameter); measures the chlorine flow rate
On a typical gas chlorination installation, this component consists of an orifice that is adjusted to control the chlorine gas flow? Rate setter
On a typical gas chlorination installation, this component ensures that the vacuum upstream remains steady in order to maintain a constant flow rate through the orifice? Regulating valves
On a typical gas chlorination installation, it is the principal component that creates the vacuum. And what causes the vacuum? Injector/process water flowing through a tapered opening in the injector
This type of gas chlorination installation is directly mounted on chlorine gas cylinders or containers? Advanced gas chlorinators
This specific gas chlorinator includes a heater which is used to heat incoming chlorine at the inlet to completely evaporate the chlorine? Fisher and Porter chlorinator
This specific gas chlorinator has an injector which consists of a tapered tube or venturi tube and a diaphragm check valve, and water flowing through the injector creates a vacuum? Wallace and Tiernan V-Notch Chlorinator
What is considered as a moderate concentration of fluoride? 1 mg/L
What are the three principal chemicals used for fluoridating water supplies? Sodium fluoride; sodium silicofluoride; hydrofluosilicic acid
This method of fluoridating water relies on the trickling of water through a bed containing sodium fluoride? Saturator
This term is defined as the result of chemical reactions whereby metals in contact with water are oxidized by substances in the water? Corrosion (of metals)
This chemical parameter of water governs the electro potential of metal transfer exposed to water, and it controls the solubility of precipitates that may form on the metal surface? pH
This chemical compound in water affects the formation of calcium carbonate deposits? Carbon dioxide
This common mineral deposit in a distribution system form a protective film on metal surfaces which helps prevent corrosion? Calcium carbonate deposits
Which dissolved minerals (ions) tend to interfere with the formation of protective films in pipes (list two)? Chlorides and sulfates
List three types of films (mineral based) which coat the interior of pipes and prevent corrosion (corrosion inhibitors)? Calcium carbonate, phosphate, and silicate films
This property of water (as it increases) promotes the rate of corrosion by increasing the relative solubility of corrosive products and gases in the water? Temperature
This term is generally defined as the deposition (and growth) of matter on the surface of the container? Scaling
List three typical compounds that are constituents of scale? Calcium carbonate, rust (iron oxide), iron and manganese
This term is often used to describe deposits, though it’s exact term defines rust growths over pits on the surfaces of iron metals? Tuberculations
The deposition of scale can be categorized as (list three processes)? Chemical; suspended matter; biological
It is a form of chemical deposition that is influenced by the relative hardness of the water and its pH? Calcium carbonate
A common deposit that consists of oxidized substances which may include these two minerals? Iron and manganese
List two types of common process wastes generated during the production of potable water? Alum sludges; filter backwash water
This method of handling and disposing of process water is used for both storing and drying? Ponds
The application of a sludge onto land is only allowed when the sludge is suitable for use as? A soil conditioner
Belt filter press; centrifuge; filter press; and vacuum filters are which type of methods for handling and disposing of process water waste? Mechanical dewatering processes
This method for handling and disposing of process water waste consists of a layer of sand, a support gravel bed, and a underdrain system? Sand drying beds
This method for handling and disposing of process water waste consists of small volume storage ponds in which the process waste is stored to allow for sedimentation, decanting and evaporation? Solar drying ponds
These type of samples are taken when the water flow is not continuous; water quality is fairly uniform; or to analyze changes in a water quality parameters that varies? Grab sample
The name given to the process of chemical mixing, coagulation, flocculation, and sedimentation when carried on in a single tank in such a manner that the mixed chemicals are introduced into a zone of already precipitated floc which serves as the nuclei for further floc formation? Contact process

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