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43 Cards in this Set
- Front
- Back
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Alkalinity definition |
The capacity of water to neutralize acids. This is caused by carbonate, bicarbonate, hydroxide, borate, silicate and phosphate |
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Alum : alkalinity = |
1mg/L : 0.5 mg/L as CaCO3 |
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Coagulation definition |
The clumping together of very fine particles into larger particles (floc) caused by the use of chemicals |
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Cryptosporidium definition |
A waterborne intestinal parasite found in most surface waters and some groundwater that causes the disease cryptospoidiosis |
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Giardia definition |
A waterborne intestinal parasite found in most surface water and some ground water that causes the disease giardiasis |
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Disinfection by products definition |
A contaminant formed by the reaction of disinfection chemicals with other substances in the being disinfected |
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Representative sample- |
A sample of water that is nearly identical in content and consistency as possible to that in the larger body of water being sampled |
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Floc definition |
Clumps of bacteria and particulate impurities that have come together to form a cluster |
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Flocculation definition |
That gathering together of fine particles after coagulation to form larger particles by a process of gentle mixing |
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Jar test definition |
A lab procedure that simulates a water treatment plants coag/floc units with differing chemical doses to determine the optimum coagulant dose |
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What should you do if you are having filter problems |
Jar test |
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Specific gravity definition |
The weight of a particle, substance or solution in relation to the weight of an equal volume of water. Water has a specific gravity of 1.000 at 4C |
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Turbidity definition |
A cloudy appearance of water due to the presence of suspended or colloidal matter |
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Conventional/ complete treatment includes |
Coag Floc Sed Filtration |
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Coagulation chemistry basics |
Colloids in surface water are negative charge Colloids can’t floc unless charge is neutralized Pod. Ions (alum-coagulant) are added to neutralize the negative charge Once neutralized colloids begin to agglomerate and floc size increases Doesn’t work well when Alk is less than 40 mg/L |
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Most treatment plants use _________ coagulants |
Trivalent |
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Trivalent coagulants are __to __ time more effective than bivalent coagulants |
50-60 times |
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2 trivalent coagulants are |
Aluminum Iron |
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Aluminum sulfate is most common coagulant and often used with |
Cationic polymers |
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Ferrous sulfate is _____ pH dependent than alum |
Less |
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Maximum zeta potential is |
0 to +3 |
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Excellent zeta potential is |
-4 to -1 |
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Fair zeta potential is |
-10 to -5 |
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Poor zeta potential is |
-20 to -11 |
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Coagulant aides are chemical added in conjunction with primary coagulant for wht reasons |
Improves coag Strengthens floc Overcome cool water temp Reduce primary coag dose Reduce sludge production |
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Common coag aids include |
Activated silica Weighting agents Polyelectrolytes |
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Activated silica is prepared onsite by operator. It is a combination of |
Sodium silicate + hypochlorous acid (Na2Si03)+HOCl |
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Weighting agents such as bentonite are added to help |
Treat waters that are low in turbidity and high in color |
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Weighting agents include |
Bentonite Powdered limestone Powdered silica |
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Pilyelectrolytes (polymer) are |
Long carbon chain molecules that can produce highly charged ions when dissolved in water |
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Flash mixing takes less than ____ seconds |
60 |
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4 types of flash mixers |
Mechanical Static Pumps and conduit Baffled chambers |
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Mechanical mixers are placed in a small chamber where coag is added to the TAW water or installed directly ….. |
Into a pipeline ( in-line mixer) |
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Static mixers mixing energy depends on ….. |
Flow |
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Pumps and conduit mixer may have premature failure due to |
Coagulant may corrode the pump internals |
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Baffled chamber mixers work by |
Redirecting flow |
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Streaming current meter measure…. |
Electrical charge of water Most particles in water are anionic |
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Zeta potential is the difference between |
A particles charge and the water surrounding it. Measured in mV |
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Enhanced coagulation is accomplished by |
Reducing pH to optimum range Aluminum sulfate - 5.5-7.0 Ferric sulfate- 4.0-6.2 |
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Why jar test |
Optimize coag dose Determine optimum pH Determine how much acid to add Determine if Alk addition is necessary |
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Alum is impacted most by |
pH |
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Flocculation smaller particles called….. |
Microfloc collide with one another and agglomerate into larger floc |
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Why slow down mixing in floc process |
As floc gets larger you can shear the floc |
