PRINCIPLE:
Sludge volume index is the volume in milliliters occupied by 1 gm of a
suspension after 30
min settling. SVI Typically is used to monitor settling
characteristics of activated sludge and
other biological suspensions.
REQUIREMENT:
- Filtering apparatus:
0.40 – 0.60 mm
- Oven
PROCEDURE:
TOTAL
SUSPENDED SOLIDS:
Assemble filtering apparatus wet filter with a sample volume
of a reagent grade
water. Stir sample with a magnetic stirrer at a speed to shear larger
particles. Wash filter with 3 successive 10 ml volumes of reagent grade water
allowing
complete drainage between washings and continue suction for about 3
min after filtration
is compete. Samples with high dissolved solids may
required additional washing.
Carefully remove filter from filtration apparatus
and transfer to an aluminium weighing dish
and dry for at least one hour at 103
to 105 °C in oven cool in desiccator to
balance
temperature and weigh. Repeat the cycle of drying, cooling, desiccating
and weighing until
a constant weigh is obtained.
(A –B) X
1000
mg total suspended solids/L
= ------------------------------
Sample
volume in ml
A = Weight of filter + dried residue (mg)
B =
Weight of filter (mg)
SETTLED
SLUDGE VOLUME:
Place 1 ml sample in settling column and distribute solids
by covering the top
of inverting cylinder 3 times. Insert stirring rods activate stirring
mechanism. Starts the stop watch and let the suspension settle continue
stirring throughout
test. Maintain suspension temperature during test.
Determination volume occupied
by suspension at measured time intervals 30
minutes.
Report settled
sludge volume of the suspension in ml for an indicated time interval.
CALCULATION:
Settled sludge volume (mg/L) x 1000
SVI =
---------------------------------------------------
Suspended solids (mg/L)
REFERENCE: APHA - 2710 D.
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