Question Answer
Finer filter media have _____filter runs, while coarser materials produce_____runs? shorter/longer
The choice of filter media not only determines the effluent _______, but also the backwashing _______? filter (effluent) quality/(backwashing) efficiency
Filter media are classified according to these two physical characteristics? Effective size; uniformity coefficient
The term which describes a physical characteristic of filter media is defined as the size of sieve opening which permits the passage of 10% by weight of the sand particles? Effective size
This physical characteristic of filter media determines the filtering time and the time for maximum allowable head loss to occur? Particle size
Scenario: if short filter runs are a problem because of head loss rather than breakthrough of the suspended solids, what remedy should be considered? A filter medium with a larger effective size
Scenario: in the event of turbidity breakthrough and limited head loss problems, what is a viable filter medium consideration to remedy the problem? Filter medium with a smaller effective size should be considered
Scenario: in the event that head loss and turbidity breakthrough occur during filtration, what is a viable filter medium consideration to remedy the problem? A deeper bed with a larger filter medium size on top overlying a smaller sized filter medium
The term which describes a physical characteristic of filter media is defined as the ratio of the particle sizes comprising 60% and 10% of the medium weight? Uniformity coefficient
Media with this uniformity coefficient provide more uniform filtering and are desired because backwashing is easier and more effective? A low uniformity coefficient
Media with this uniformity coefficient have a greater variance in grain size and have less effective filtering and backwashing properties? A high uniformity coefficient
What is the range of the uniformity coefficient scale? 1.3-1.5; below 1.3 is ideal
What properties should be similar (or somewhat similar) between an underlying layer of filtering media and the bottom of the overlying layer of filtering media? Flow rate for fluidizing during backwashing (ensures that the entire bed fluidizes at the selected backwash rate)
The efficiency of a filter depends on the quality of the____and the operating characteristics of the___? Influent water/filter
This type of media is typically used in pressure filter applications because of the head required? Mixed media filters
This type of filter is limited to waters with turbidities of 10 to 30 NTU, and reduce colour by about 40%? Slow sand filters
This type of filter typically consists of 12 to 18 inches of graded gravel as tile underdrain, followed by approximately 1 m of sand? Slow sand filter
The filtering rate of this type of filter is normally kept constant and is regulated by influent and effluent control devices? Slow sand filter
This gravity filter flow control method modulates the effluent valve to maintain a constant water level in the filter basin. As head loss increases across the filter, the effluent valve opens to compensate for the head loss by decreasing the resistance to flow. When the effluent valve is fully open the filter must be backwashed? Constant Rate-Constant Water Level
This gravity filter flow control method is used in multiple gravity filter applications, and a weir divides the influent flow equally to each gravity filter? Flow Splitting
During a backwash cycle, by how much does the flow rate differ from the the flow rate during filtration? It is approximately 4 times greater
This type of filter is normally operated at a constant rate and is backwashed when the head loss across the filter reaches a predetermined level? Pressure filter
This type of filter, when used, should follow other filter processes as an additional treatment? Activated Carbon Filters (remove taste and odour components)
This type of filter functions primarily as an absorption filter and has a lower capability to actually filter water? Activated Carbon Filters
The rate of filtration, for this type of filter, is based on the total volume of the medium used rather than the filtering area of the medium? Activated Carbon Filters
For this type of filter, the backwash rate is normally lower because the medium is of a lower specific gravity, requiring lower up flow velocity to fluidizes the bed? Activated Carbon Filters
When must activated carbon medium be changed? When it’s absorptive capacity has been reached
Why should chlorine be added after a carbon filter? Activated carbon absorbs chlorine (reducing effectiveness of chlorine treatment)
When filter effluent turbidity increases, the filtration rates should be_____, or the filter run_____? decreased/shortened
What are two ways in which filter efficiency can be monitored (be specific)? Sampling (turbidity) of filter influent and effluent/comparing pressure losses
Describe a manner in which the filtration process can be improved by making adjustments upstream? Chemical feed rates to improve floc formation
List five things an operator looks for when inspecting a filtration unit? Medium condition; loss of medium; mud balls; cracking; physical components
List four things an operator looks for when inspecting filtration medium? Depth; condition of medium; cracks; and shrinkage
What can happen during filtration if the hydraulic loading is too great? Breakthrough
What should happen to filter effluent (for 10 minutes) from a filtration unit immediately following a backwash cycle? Filter to waste (before sent to clear well)
What is a warning to the operator that there is a possible filtration problem? Sudden changes in water quality
This term describes a problem when air enters the filter media? Air binding
This problem during filtration is harmful to both the filtration and backwash cycles? Air binding
Its presence can prevent the passage of water during the filtration process, and cause loss of filter media during backwash process? Air
This problem during filtration is caused by excessive head loss across the filter? Negative pressure
This problem during filtration causes dissolved air in water to come out of solution and create pockets of air in the filter medium? Negative pressure
This forms when filter beds are not backwashed properly? Mud ball
It is filtered particles that stick together during backwashing? Mud balls
This progressively grows in size, eventually progressing downwards through the media and clogging the underdrain system? Mud balls
When an operator drains the filter to at least 30 cm below the surface of the medium following a backwash cycle, and takes a sample of media from a depth of 15 cm below the top of the medium surface, the operator is checking for? Mud balls
This part of a gravity filtration unit consists of a structural (non-corrosive) support floor and filter nozzles? Underdrain system
This is sometimes added above an underdrain system to separate the filter medium from the underdrain system? Gravel bed
What are two ways in which underdrain system can be damaged? Over pressurizing the underdrain system during backwashing; A backwash rate that is too high
This occurrence can damage the filter by lifting the components of the underdrain system out of place? A backwash rate that is too high
The presence of these minerals increase turbidity and colour in raw water sources? Iron and manganese
What is the food source for this filamentous slimy bacterial growth on the inside walls of distribution mains and household plumbing? Iron (iron bacteria)
Red or rust colored growths are caused by this end product? Iron reduction
Black slimes result from (answer is the mineral and the chemical process)? Manganese reduction
These minerals cause growths which can reduce the flow capacity of pipes? Iron and manganese growths
These minerals can decrease the flow area in pipes and increase internal pipe roughness (reducing flow)? Iron and manganese growths
The reaction between chlorine and manganese forms this jet black compound that sometimes break off the interior of pipes and are carried to consumers? Manganese dioxide
Under what conditions will iron and manganese change from an insoluble state to a soluble state? Low oxygen
Why are iron and manganese common constituents in groundwater sources? Low oxygen in underground environments
List three conventional ways in which insoluble iron and manganese can be removed from water sources? Coagulation, sedimentation, and filtration
What is the process used to convert soluble iron into an insoluble state? Aeration
What is the chemical compound for insoluble iron (oxidized iron) called? Iron hydroxide
Iron or manganese: which is more easily oxidized by aeration? Iron
This mineral can be partially reduced by increasing the pH to 8.5, followed by green sand filtration? Manganese
How can the time required for the oxidization process of iron be shortened? Increasing the pH above 7
List two factors that also increase the time required to oxidize iron from water? Organic substances/temperatures lower than 25°C
Forced Draft Aerators; Cascade (aeration); Spray Aerators are typical aeration methods for? The removal of iron
With this method, forced air flows in the opposite direction of the water flow for what reason? What is this called (not for flocculation)? Iron removal/Forced Draft Aeration
What is the greatest deterrence for using aerators in the removal of iron and manganese? Growths of slimes and coatings over aerator's contact surface
When is chlorine treatment in the oxidation of iron and manganese less effective? When the minerals are organically bound
Chlorine oxidizes manganese into this insoluble compound? Manganese dioxide
Chlorine oxidizes iron into this insoluble compound? Ferric hydroxide
List three common chemicals used in the dechlorination process (dechlorination agents)? Sodium sulfide (Na2S); Sodium bisulfite (NaHSO3); and sodium sulfite (Na2SO3)
What is the most popular type of oxidizing agent used to oxidize iron and manganese? Potassium permanganate (KMnO4)
This method of removing iron and manganese can be achieved using a sodium resin or a hydrogen cation? Ion exchange
This method of removing iron and manganese has a prohibitive cost and requires increased skill to operate such a system? Chlorine dioxide
Manganese or iron: Which is more so commonly removed with chlorine dioxide? Manganese
A chemical reaction in which certain chemicals tie up other chemicals, particularly metal ions, so that chemicals no longer react? Sequestration
These agents are used to prevent the formation of precipitates or other compounds (two terms)? Sequestering or chelating agents
Taste and odour problems are usually accompanied by this other water quality issue? Coloured water problems
Organic decomposition; microorganisms (algae); municipal wastewater; industrial wastes; urban runoff; agricultural runoff; and, dissolved gases. These are common sources for this water quality problem? Taste and odour problem
Which source contributes the greater portion of taste and odour problems, and why? Organisms/decomposition releasing metabolic by-products
What is one method (common practice) used to control organism growth before a population increase? The application of copper sulfate
Which of these two organisms is considered to be more troublesome with taste and odour problems: green algae or blue-green algae? Blue-green algae
Which industrial chemicals are the most troublesome with taste and odour problems (list two)? Phenols and cresols
List the two dissolved gases that cause taste and odour problems? Hydrogen sulfide and methane
Odour tests are recorded according to the______? Threshold number
This term refers to the number of times that the odour producing sample has to be diluted with odour free water so that the odour is slightly detectable, the result of which is calculated using an equation? Threshold number
List four factors that influence the effectiveness of copper sulfate as an algae control? Alkalinity; pH; turbidity; and temperature
Potassium permanganate can also be used as ______ to control taste and odour problems? Algaecide
This method of controlling algae is called “_______” which decreases the light penetration and reduces the sunlight in the upper levels of the water surface. What product is used to achieve this? blackout/Activated carbon
Accumulated sludges, especially alum, in a water treatment plant can cause this persistent problem if they are not removed through proper house-keeping and maintenance practices? Taste and odour problems
This common water treatment process is also effective in removing taste and odour from water when used in conjunction with chemical additions? Conventional sedimentation, preceded by coagulation and flocculation
This taste and odour removal method is partially effective, but only removes organic compounds and gases which are relatively volatile? Aeration (a.k.a Degasification)
This group of gases normally exist at low concentrations and tend to leave the water when in the presence of atmospheric pressure? Volatile gases

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