Question Answer
The quality of water that has a hardness (calcium carbonate) of more than 200 mg/L is considered as? poor
The quality of water that has a hardness (calcium carbonate) of less than 80 mg/L is considered as? Very good
A water treatment plant operates best under _______? constant flow
To control algae, which method is preferred: chemical treatment or removal by coagulation, flocculation, sedimentation, and filtration (conventional treatment)? Conventional treatment
Which chemical is commonly used to control algae? Copper sulfate
The purpose of these two steps is to precondition the raw water so that the efficiency of the next process, clarification, is greatly improved? Coagulation and flocculation
The operation of these three processes are so interdependent that they are often considered as a single process? Coagulation, flocculation, and clarification
What are the two broad categories for the coagulation, flocculation, and clarification process? Conventional system and solids contact process
This category of the coagulation, flocculation, and clarification process uses separate tanks for each three processes? Conventional system
This category of the coagulation, flocculation, and clarification process uses a single tank for all three processes? Solids contact
List three causes of colour in the raw water supply? Dissolved organic matter, colloidal organic matter, and mineral substances
What is the most effective way for removing colour from a water supply? Coagulation and flocculation
In which process are dissolved colour-causing substances converted into an insoluble form? Coagulation
What are the two main types of chemicals used in the coagulation process? Primary coagulants and coagulant aids
This coagulation chemical is responsible for the main coagulation reaction? Primary coagulant
This coagulation chemical is used to increase the density of slow-settling floc particles, or to strengthen them so that they do not break up during settling and filtration? Coagulant aid
The mixing of the coagulant chemical and the raw water is commonly referred to as? Rapid mixing or flash mixing
This step of the treatment process is intended to distribute the coagulant chemical quickly and evenly throughout the water? Rapid/flash mixing
The coagulation reaction during rapid/flash mixing occurs in how much time? Fraction of a second
Coagulation is immediately followed by this step, where the water is agitated very gently for a fairly long period of time? Flocculation
Flocculation in a conventional system usually lasts about? 30 minutes
This treatment step is the separation of suspended solids from water by gravity? Sedimentation
A sedimentation tank is also known as a____ or a ____? settling tank or clarifier
In this treatment process a bed of previously formed sludge is maintained in the unit which improves the efficiency of solids removal? Solids contact system
What is the most common type of filtration unit? Rapid gravity filter
This type of intake structure consists of a small concrete structure containing a slide gate, which when opened, water spills into a canal, ditch, or pipeline that carries the water to the treatment plant? Surface diversion intake
This type of intake structure is used where the water level may vary greatly, or where other conditions prevent construction of a permanent intake? Movable intake
This type of intake collects seepage water, and is located near the edge of the water source, or sometimes on the sides of hills or mountains where groundwater is intercepted? Infiltration gallery
This type of intake structure is typically below ground and not usually subject to freezing? Infiltration gallery
In the coagulation process, the coagulant and the water react to form ____ that are described as ____? precipitates/insoluble reaction products
This step of the treatment process involves several chemical and physical reactions involving dissolved and suspended matter in the raw water? Coagulation
During this treatment process, floc particles grow and are brought into contact with (entrap) more particles of suspended matter? Flocculation
These two treatment processes, combined, precondition the raw water so that the efficiency of the next process (clarification) is greatly improved? Coagulation and flocculation
The diameters of many non-settleable particles such as clay, colour, and viruses are less than? 0.001 mm
This type of particle cannot be removed by most direct sedimentation or filtration processes? Non-settleable particle
Because molecules in water are always moving randomly, and these molecules collide with suspended particles affecting their motion and behavior to the extent that they will never settle, even in completely still water. What is this? Brownian movement
The particles suspended in water are subject to several different forces acting on them simultaneously. These forces are? Brownian movement; turbulence; and electrical repulsion
Almost all suspended particles in water have ____ ? Negative electrical charges
It is a physical force which causes suspended particles to repel each other, preventing these particles from forming larger floc? Electrical repulsion
This treatment process cancels the negative electrical charges that cause particles to repel each other? Coagulation
The neutralization of negatively charged particles occurs in this step of the treatment process? Coagulation
It is the component of alum, by the third reaction, that is an insoluble molecule in water and precipitates out in the form of floc? Aluminum hydroxide
Alum tends to ___ the pH and alkalinity of water? Lower
In this treatment step, there is an increase in hydrogen ion concentration which consequently lowers the pH? Coagulation
What is the ideal pH range for effective coagulation? 5 to 7
Which two chemical characteristics of water are typically adjusted to achieve effective coagulation? PH and alkalinity
It is the most commonly used coagulant aid, and also known as a polyelectrolyte? Polymer
What is the only way to determine the best polymer to use? Jar testing
As an alternative to a polymer, this coagulant aid is supplied in liquid form and needs to be “activated” by one of several methods before it is added to the raw water? Sodium silicate
This coagulant aid is used to add weight to floc which will not settle adequately (such as those formed from very low turbidity raw water). List the coagulant aid and one example? Weighing agent/bentonite clay
This type of coagulation equipment makes use of turbulence created by baffles, weirs, throttling valves, and similar devices to mix and distribute chemical in the water? Hydraulic mixers
This type of coagulation equipment requires effective flow velocity for turbulence, but they are not very efficient, they have limited operating flexibility, and they are not commonly used? Hydraulic mixers
This commonly used, versatile, and reliable type of coagulation equipment consists of paddles, turbines, and propellers? Mechanical mixers
This type of coagulation equipment is known as flash mixers, and is available in many different styles? Mechanical blenders
This type of coagulation equipment consists of a motor-driven paddle or propeller assembly installed directly in a pipeline, and the coagulant is injected at one or more injection points into the line near the coagulation equipment? Mechanical blender/flash mixer
This type of coagulation equipment does not require the use of a tank, and it provides very high turbulence with very short detention times? Mechanical blender/flash mixer
The purpose of this treatment step is the creation of a floc particle having the proper size, density, and toughness for effective removal by sedimentation and filtration? Flocculation
This treatment step depends on the rate at which collisions between particles occur, and on the degree to which the particle stick together after collision? Flocculation
List the four factors that combine in order to provide an efficient flocculation process? Coagulant dosage; detention (mixing) time; mixing intensity; and flocculation tank design
Detention times shorter than about ____ minutes can lead to incomplete floc formation? 20 minutes
This condition can lead to incomplete floc formation because flocculation reaction is slowed down? Cold conditions
What is one manner in which collisions between the floc and turbidity particles can increase in order to create larger floc particles? Increase mixing intensity
This type of flocculation system makes use of the turbulence created when water flows through pipes, channels and other devices, but is not commonly used? Non-mechanical system
What are the two basic types of mechanical flocculation in common use? Vertical and horizontal
With this flocculation tank system, the tank is divided into more than one compartment (usually three), and the intensity of mixing in the first compartment is relatively high and decreases in each of the subsequent compartments? Tapered flocculation system
For flocculation tanks, it is a measure of the mixing intensity expressed in terms of the power input per unit of flow. And how is it expressed? Velocity gradient/G-factor
For flocculation tanks, it is considered as one of the most important factors in tank design? Type of baffle used to divide the tank into compartments
This feature of a flocculation tank must prevent short-circuiting and uneven flow distribution as much as possible, while at the same time reducing the danger of floc breakup? The baffles
List three of the most common tank baffles used in flocculation tank systems? “Over and under”, “around the end”, and perforated plate types
The two main variables controlled by the operator in the flocculation process are? Mixing intensity and chemical dosage
These two variables are the most important factor in the efficient overall operation of a water treatment plant? Mixing intensity and chemical dosage for flocculation
In the event of raw water low turbidity, coagulation/flocculation/clarification turbidity will often actually increase. Why? Because of the floc particles added in the coagulation process
The most common response to problems encountered in a coagulation/flocculation/clarification system is? Coagulant chemical dosage
Sudden changes in the condition of the raw, settled, or filtered water quality are signals that the operator should immediately? Review the performance of the plant processes
The coagulation and flocculation processes are most often affected by changes in the? Raw water quality
If a problem encountered in a coagulation/flocculation/clarification system is not remedied by a coagulant chemical dosage change, then what is the next parameter to adjust? Mixing intensity
If a problem encountered in a coagulation/flocculation/clarification system is not remedied by a coagulant chemical dosage change or mixing intensity adjustment, then what is the next parameter to adjust? Add or adjust coagulant or filter aid
If a problem encountered in a coagulation/flocculation/clarification system is not remedied by a coagulant chemical dosage change, mixing intensity adjustment, or coagulant/filter aid addition or adjustment, then what is the next parameter to adjust? pH and Alkalinity
The main purpose for this process step in water treatment is to reduce the solids loading on filters so that longer runs can be achieved? Sedimentation
This water treatment step is achieved by decreasing the velocity of the water being treated to below the point where it can transport settleable suspended material, which settles to the bottom of a tank and is drawn off in the form of sludge? Sedimentation
Which is the most important factor that influences the sedimentation process? Settling characteristics of suspended particles in water
List the three factors that affect the settling characteristics of a suspended particle? Specific gravity of a particle; the size and shape of the particle; water temperature
It is defined as a particle’s weight compared to an equal volume of water? Specific gravity
Particles having a ____ specific gravity will settle quickly? High
Particles will settle faster in ____ water? Warm
A compact particle (sphere shaped) will settle ___then one with a less “streamlined” shape? Faster
What are the two properties of water important to settling rate and affected by water temperature? Density and viscosity
This term is defined as a measure of how easily a liquid flows? Viscosity

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