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Solids, Colour, Turbidity
& Conductivity
Presented by:
M S Bhatti
Guru Nanak Dev University, Amritsar
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Physical characteristics:
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Solids: floating, settable, colloidal, dissolved
Odour
Temperature Density or specific gravity
Colour
Turbidity
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How they are relatedHow they are related
y TDS with conductivity
y Suspended solids with turbidity in settledsecondary effluent.
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Solids Total solids at 103 to 105 C
Total dissolved solids at 180 C for clean water
Volatile solid analysis at 550 C to measure the
biological activity (MLSS & MLVSS) in municipal
sludge.
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1. Total Solids dried at 103 to 105 degree C
2. Total dissolved solids dried at 180 C
3. Total Suspended Solids at 103-105 C
4. Fixed & Volatile Solids Ignited at 550 C
5. Settleable solids for semisolids & sludge
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Significance of Solids
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Water with high dissolved solids are of inferior quality A limit of 500 mg/l is desirable in drinking water
Highly mineralized water is also unsuitable for many industrialapplications
Water with high suspended solids may be aesthetically
unsatisfactory (for bathing!) Solids analysis is important
in the control of biological and physical wastewater treatmentprocesses
for assessing compliance with regulatory requirements
Fixed and volatile solids are used to represent active biomassin the mixed liquor in activated sludge process Volatile and fixed solids do not precisely distinguish organic and
inorganic matter many mineral salts also volatilize
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Solidsy Total solids (TS): Material residue left behind after evaporationof a sample and its subsequent drying in a oven at a definedtemperature to constant weight
y Total suspended solids (TDS): Portion of the material residue of
a sample retained by a filter
y Total dissolved solids (TDS): Portion of the material residue of asample that passes through a filter
y Fixed solids: Residue of TS or TSS or TDS left after ignition for aspecified time at a specified temperature
y Volatile solids: weight loss on ignition
y Settleable solids: Material settling out of suspension within adefined period
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Temperature and duration of drying
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Temperature at which the residue is dried and duration ofdrying are very important - influences
Weight loss due to volatilization of organic matter
Weight loss from loss of mechanically occluded water andwater of crystallization
Weight loss from loss of gases (heating convertsbicarbonates into carbonates and release CO2, anddecomposes carbonate to release CO2)
Weight loss from chemical decomposition and weight gainfrom oxidation
Usually duration of drying is adjusted to obtain constantweight of the residue
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Temperatureand duration of drying
Drying temperatures in practice
103-105rC
1802rC
For estimating fixed solids the residue is
usually ignited at 55050rC to constant
weight in a muffle furnace
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Sample handling, preservation and preparation
If acceptable, avoid large floating particles or submergedagglomerates of non-homogenous materials while sampling
Resistant glass or plastic bottles, provided the material insuspension of the sample does not adhere to walls, are used forholding the samples
Analysis of samples is started as soon as possible (impractical topreserve sample)
To minimize microbiological decomposition refrigerate sample at 4 C
Before taking sample disperse floating oil and grease with a blender
Choose sample size/volume to give 2.5 to 200 mg of residue
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Sample handling, preservation and preparation
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Evaporation dishes of 100 mL capacity of one ofthe following material are used:
Porcelain (9 cm dia.)
Platinum
High silica glass
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Sample handling & preparation
Preparation of the evaporation dish
Heat clean dish to 103-105C/1802C/55050C for 1 hourdepending on the temperature of drying and on the need forignition of the residue
Storing the heated dish in desiccator until needed
Weighing the dish immediately before use for initial weight -balance capable of weighing to 0.1 mg is required
Transfer measured volume of well mixed sample into pre-weighed dish
and evaporate to dryness on a steam bath or drying oven For evaporation in a oven, use temperature 2C below boiling
point to prevent splattering
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Sample evaporation, and drying to constantweight and ignition of residue
Once evaporated to dryness, dry the sample at least for 1hour in a oven at 103-105C or 1802C as required andcool the dish in a desiccator to balance temperature and
weight
Use repeat cycles of drying, cooling in desiccator andweighing until constant weight.
Weight loss
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Fixed & Volatile Solids ignited at 550 C
Ignite the dried residue of the dish to constant weight in a
muffle furnace at 55050C
Raise the furnace temperature to desired level prior toinserting the sample and ignite for 15-20 minutes
Air cool the dish partially and then transfer into
desiccator for final cooling in dry atmosphere, then
weight the dish
Use repeat cycles of drying, cooling in desiccator and
weighing until constant weight is obtained
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Total solids
Well mixed sample is evaporated in a weighed dish and dried toconstant weight in a oven at 103-105rC
Increase in weight of dish represents total solids
)(
1000)/(
mLvolumeSample
BALmgsolidsTotal
v
!B is weight of empty dish
A is weight of dish with residue
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Total dissolved solids
Filter well mixed sample through a fiber filter and evaporate filtrate in
weighed dish and dry to constant weight at 1802rC Filtrate from TSS determination can also be used
Increase in dish weight represents TDS
Highly mineralized samples may require prolonged drying, properdesiccation and rapid weighing
Significant concentrations of calcium, magnesium, chloride and/orsulfate can be hygroscopic and cause problem
Samples high in bicarbonate may require careful and prolongeddrying to ensure complete conversion to carbonate
Glass fiber filter disks, filtration apparatus with membrane filterfunnel or Gooch crucible, and suction flask may be needed
)(
1000)/(
mLvolumeSample
BALmgTDS
v
!B is weight of empty dish
A is weight of dish with residue
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Total suspended solids
Filter well mixed sample through a weighed standard glass fiberfilter and dry the residue retained on the filter to constant weight at103-105rC
In case of filter clogging and prolonged duration of filtration take
difference of TS and TDS as TSS
Increase in dish weight is represented by
In case of samples with high dissolved solids, thoroughly wash thefilter to ensure removal of dissolved material
Clogging and prolonged filtration can produce high results dueexcessive solids capture
)(
1000)/(
mLvolumeSampleLmgSS
v
!B is weight of empty dish
A is weight of dish with residue
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Fixed and volatile solids
Dried residue left in the dish during TS, TDS and TSS is ignited toconstant weight at 55050rC in a muffle furnace
Solids left after ignition represent fixed solids (total fixed solids
from TS, total dissolved fixed solids from TDS and total suspendedfixed solids from TSS)
Fixed solids can be calculated by
)(
1000)/(
mLvolumeSample
CLmgsolidsFixed
v
!
B is weight of dish after ignition
C is weight of the empty dish
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Fixed and volatile solids
Weight lost on ignition represent volatile solids (totalvolatile solids from TS, total dissolved volatile solids fromTDS and total suspended volatile solids from TSS)
)(
1000)/(
mLvolumeSample
BALmgsolidsVolatile
v
!
B is weight of dish after ignition
A is weight of dish after drying
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Settleable solidsDetermined & reported on either volume (mL/L) or weight (mg/L)
basis
Measurement on volume basis requires an Imhoff cone
Fill Imhoff coneto 1-L mark with sampleand settle for 45 min.
Gently stir sides ofthe cone witharod by spinningand settle for
another 15 minutes Record volume ofthe settled solids inthe Imhoff cone
Measurement on weight basis (indirectmethod)
Determine total suspended solids of well mixed sample
Pour >1-L of sample into a glass vessel of >9 cm dia. to depth >20cm
Let it stand quiescent for one hour
Without disturbing settled or floating material siphon out 250 ml fromvessel center and determine its TSS as non-Settleable TSS
Settleable solids = TSS non-Settleable TSS
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Sludge volume index (SVI)
)/(
1000)/(
Lmgionconcentratsolidssuspended
LmLvolumesludgesettledS I
v
!
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Volume in mL occupied by 1 g of a suspension after 30 min. settling
Applications:
1. Used to monitor settling characteristics of activated sludge and otherbiological suspensions
2. Determined for the mixed liquor of the aeration tank of the ASP
3. Determine SS concentration of a well mixed sample of suspension
4. Determine the 30 min. settled sludge volume
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Applications of solids data in
Environmental Engineering:
Suitability of potential supplies
Need for water softening Corrosion control through pH adjustment
which depends on solids
Design of Primary sedimentation tank
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measures the light transmittingproperties of water
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Turbidity
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Turbidity
Water quality standard: < 5 NTU
Indicates clarity of water
Optical property due to the presence of colloidal matterlike
Clay, silt, finely divided organic and inorganic matter, planktonand other microscopic organisms etc.
Causes light to be scattered and absorbed
Clarity of water is important for Producing products destined for human consumption
Potability Water bodies condition and productivity
Coagulation, settling and filtration are needed for theremoval of turbidity and clarity of water
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Significance of Turbidity
Aesthetic
Filterability: Slow and rapid sand filter
Hindrance in Disinfection
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Principle of Nephlometric Turbidity:
For measurement intensity of light scattered in one
particular direction (at right angles to the light path)
by the sample under defined conditions is compared
with that by a standard reference suspension under
the same conditions
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Turbidity measurement
Should be measured on the same day of sampling If unavoidable sample can be stored in dark up to 24 hours
Storage for longer periods can cause irreversible changes inturbidity
Sample free of debris and rapidly settling coarse sediments,after vigorous shaking, should be transferred into sampletube
Dirty glassware, presence of air bubbles and vibrations canaffect the results
Water colour due to dissolved substances that absorbcolour can lower the turbidity measurement ??
Higher the intensity of the scattered light higher is theturbidity
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Standard unit of turbidity:
Initially 1 mg SiO2/l = 1 unit of turbidity
Now Formazin polymer suspension is used
Preparation of standard stock suspension Dissolve 1.000 g of hydrazine sulfate, (NH2)2.H2SO4 (carcinogenic), in
turbidity free water and dilute to 100 ml
Dissolve 10.000 g hexamethylene tetramine, (CH4)6NH4, in turbidityfree water and dilute to 100 ml
Mix 5 ml of hydrazine sulfate solution and 5 ml of hexamethylenetetramine solution in a 100 ml volumetric flask and allow it to standfor 24 hours at 253rC
Dilute the mixer with turbidity free water to 100 ml to obtainstandard stock suspension of 400 NTU turbidity
Can stand for one month
Can be used for daily preparation of standard reference suspensions ofother turbidities (dilute with turbidity free water)
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Turbidity measurement
Calibration of the turbidity meter:
Follow manufacturers instructions
Run at least one standard reference suspension in each of the ranges
Turbidity measurement
When turbidity expected is 40 NTU dilute the sample to get 30-40
NTU range of turbidity and then measure
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C
CN U
)( v!
A is NTU measured of diluted sample
B is volume of the diluted sample
C is volume of the sample diluted
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Application of turbidity data: