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CEL212 Environmental EngineeringSecond Semester 2010-2011

Laboratory Experiment 7: Solids (Total Solids Dried at 103-105C)

Reference Material:

AWWA, WEF, APHA, 1998, Standard Methods for the Examination of Water andWastewater

Sawyer, C. N., McCarty, P. L., and Parkin, G. F. 2000. Chemistry forEnvironmental Engineering. Fourth Edition, McGraw-Hill, Inc., New York.

Methods: 2540 B. Total Solids Dried at 103-105C

Objective: Calculate total solids in a water sample.

Background:

Solids measurement is used in different water samples (industrial, domestic and drinking

water) and it is defined as residue upon evaporation and drying at 103-105C (here all mattersthat exert significant vapour pressure at such temperatures are evaporated and lost, resulting in

only those materials which have negligible vapour pressure at 105C) (gives total solids: TS).

This parameter is used to determine potential use of water for different purposes. It indicateseffectiveness of sedimentation process and it affects effectiveness of disinfection process in

killing microorganisms.

Dissolved and Undissolved (i.e., suspended) Solids: Water may have both dissolved andundissolved (i.e., suspended) solids, depending on water quality type. In drinking water, all

solids are generally in a dissolved form and it consists of inorganic salts, small amounts of

organic matter, and gases. For total dissolved analysis, evaporation is conducted at 180C as at

higher temperature, occulted water inside particles can also be evaporated (gives total dissolved

solids: TDS). After filtration, solids retained on filter paper are called suspended solids and theyare quantified by drying at 103-105C (gives total suspended solids=TSS).

Total solids= Total dissolved solids +Total suspended solids (1)

Volatile and Fixed Solids: This measurement is required to get an estimate of quantity oforganic matter in wastewater and volatile solids indicate these characteristics. This is achieved

by combusting sample at high temperature where organic matter is converted to carbon dioxide

and water and thus volatilized, while temperature is controlled in such a manner to prevent

decomposition and volatilization of inorganic substances as much as is consistent with completeoxidation of organic matter. The loss in weight during high temperature treatment oxidation andvolatilization is interpreted in terms of organic matter (i.e., volatile solids: VS). The remaining

amount is termed as fixed solids (FS). The standard temperature used for this process is 550C asat this temperature all organic matter, generally carbon residue resulting from pyrolysis of

carbohydrates and other organic matter can be oxidized at reasonable rate.

Lab Procedure:A well mixed sample is evaporated in a weighed dish and dried to constant weight in an

oven at 103-105C. The increase in weight over that of the empty dish represents the total solids.

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High mineralized water with significant calcium, magnesium chloride may be hygroscopic and

require prolonged drying and proper desiccation and rapid weighing.

Apparatus:

Evaporating dish, desiccator (with a descant containing color indicator of moisture

concentration), drying oven for operation at 103-105C, and analytical balance.

Steps:1. Heat clean the dish to 103 to 105C for 1 h. Store and cool dish in desiccators until

needed. Weight immediately before dish (Weight =WA, in mg).Item(Take three observations) Value

Weight of empty dish

Weight of sample + dish

Weight of sample+dish after drying

2. Pipet 50 mL well-mixed sample (Vsample, in mL) and put it in a dish. Measure weight ofthe dish (Weight = WB, in mg). Measure two sub-samples of the given sample (i.e.,

duplicate analysis; Sample 1A and Sample 1B).3. Put sample in an oven at 105 and wait till dryness. Come back after 10-12 hours of

drying (i.e., when all water is evaporated and sample is dried).

4. For measuring weight of residue + dish, first cool the dish in desiccator to balancetemperature (say for 10 minutes) and weigh it (Weight = WC , in mg).

5. Calculate concentration of total solids using following equation:Total solids (mg/L) = 1000 (WC-WA)/ (Vsample) (2)

6. Report total solids as average and standard deviation of duplicate samples.Answer these questions also (for Submission with Lab report):

Q1. Compare significance of solids in drinking water and wastewater.

++++++++Additional Question (Not for Submission)+++++++

QA1. Determine the concentration of total solids and total volatile solids in a raw wastewater

sample (sample volume analyzed = 100 mL), collected from the WWTP1 plant using the

following information. Express solids concentration in terms of g/L.

mass of evaporating dish (blank) 50.1111g

mass of evaporating dish + residue after evaporation at 105C 50.9321 g

mass of evaporating dish + residue after ignition at 550C 50.7611 g

QA2. Say my student wants to use volatile suspended solids measurement to indicate microbialconcentration in a raw wastewater. Would you recommend using this estimate for indicating

microbial concentration? How about in effluent coming out of the wastewater plant? (Hint:

Microorganisms are also made of organic matter and suspended organic matter in wastewater

effluent is generally very small.)