Colloidal particles in the water are small or charged and stable in the water and difficult to settle, can be added to the coagulant in the water, destroying the stability of each other cohesion into a large floc, while stirring is conducive to the settlement.

Operation method

coagulation

Principle

Colloidal particles in the water are small or charged and stable in the water and difficult to settle, can be added to the coagulant in the water, destroying the stability of each other cohesion into a large floc, while stirring is conducive to the settlement.

Materials and Instruments

Water Sample
Sleeping Coagulant
Turbidity meter Acidity meter Thermometer Six stirrers Pipettes Beakers Glass rods Syringes Measuring cylinders

Move

I. Instrumentation
Turbidimeter, acidimeter, thermometer, six stirrer, 1 mL and 5 mL pipettes, beakers, glass rods, syringe, 500 mL measuring cylinder.
II. Reagents
10 g/l Aluminum Sulfate Solution: Weigh 10 g of Aluminum Sulfate ( _Al2SO4-18H2O ), dissolve it with water and condense it to 1 L.
III. Experimental steps
1. Measure and record turbidity, pH, and temperature of raw water samples.
2. Determine the minimum dosage of coagulant used to form alum flowers. Stir 500 mL of raw water slowly with a glass rod and add coagulant slowly until alum blooms appear, i.e., the minimum dosage A for alum bloom formation.
3. Determine the amount of dosage to be used in the experiment. Add 2/4A mL, 3/4A mL, 4/4A mL, 5/4A mL, 6/4A mL, 7/4A mL of dosage to beaker No. 1-6 containing 500 mL of raw water, and then put it on a six stirrer to stir rapidly for 1 min at 300 r/min; stir moderately for 10 min at 100 r/min; stir slowly for 10 min at 50 r/min. The speed is 50 r/min.
4. Turn off the stirrer, after 10 min of static precipitation, use a syringe to extract the supernatant immediately measured turbidity, each cup of water samples measured three times.
IV. Organization of experimental results
Take the turbidity of precipitation water as the vertical coordinate and the amount of coagulant dosing as the horizontal coordinate, plot the relationship curve between turbidity and the amount of agent dosing, and find out the optimal amount of coagulant dosing from the graph.

Caveat

1. Do not stir the bottom sediment when withdrawing the supernatant.

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