where:

A weight of dried residue  dish, mg,

B weight of dish,

C weight of wet sample  dish, mg, and

D weight of residue  dish after ignition, mg.

5. Precision and Bias

Precision and bias data are not now available.

6. Bibliography

GOODMAN, B.L. 1964. Processing thickened sludge with chemical conditioners. Pages 78 et seq. in Sludge Concentration, Filtration and

Incineration. Univ. Michigan Continued Education Ser. No. 113,

Ann Arbor.

GRATTEAU, J.C. & R.I. DICK. 1968. Activated sludge suspended solids

determinations. Water Sewage Works 115:468.

2550 TEMPERATURE*

2550 A. Introduction

Temperature readings are used in the calculation of various

forms of alkalinity, in studies of saturation and stability with

respect to calcium carbonate, in the calculation of salinity, and in

general laboratory operations. In limnological studies, water

temperatures as a function of depth often are required. Elevated

temperatures resulting from discharges of heated water may have

significant ecological impact. Identification of source of water

supply, such as deep wells, often is possible by temperature

measurements alone. Industrial plants often require data on water

temperature for process use or heat-transmission calculations.

2550 B. Laboratory and Field Methods

1. Laboratory and Other Non-Depth Temperature

Measurements

Normally, temperature measurements may be made with any

good mercury-filled Celsius thermometer. As a minimum, the thermometer should have a scale marked for every 0.1°C, with markings etched on the capillary glass. The thermometer should have a

minimal thermal capacity to permit rapid equilibration. Periodically

check the thermometer against a precision thermometer certified by

the National Institute of Standards and Technology (NIST, formerly

National Bureau of Standards)* that is used with its certificate and

correction chart. For field operations use a thermometer having a

metal case to prevent breakage.

A total immersion thermometer is designed to indicate temperatures correctly when the bulb and the entire liquid column

are exposed to the temperature being measured, except for a

minimal emergent length. A partial-immersion thermometer has

a line around it at the immersion distance from the bottom. It

indicates correctly when the bulb and the liquid column to that

line are exposed to the temperature being measured and the

emergent stem is at ambient temperature.

2. Depth Temperature Measurements

Depth temperature required for limnological studies may be

measured with a reversing thermometer, thermophone, or thermistor. The thermistor is most convenient and accurate; however, higher cost may preclude its use. Calibrate any temperature

measurement devices with a NIST-certified thermometer before

field use. Make readings with the thermometer or device immersed in water long enough to permit complete equilibration.

Report results to the nearest 0.1 or 1.0°C, depending on need.

The thermometer commonly used for depth measurements is

of the reversing type. It often is mounted on the sample collection apparatus so that a water sample may be obtained simultaneously. Correct readings of reversing thermometers for changes

due to differences between temperature at reversal and temperature at time of reading. Calculate as follows:

T 

(T1  t) (T1  V0)

K 

  1 

T1  t) (T1  V0)

K   L

where:

T correction to be added algebraically to uncorrected reading,

T1 uncorrected reading at reversal,

* Approved by Standard Methods Committee, 2000.

* Some commercial thermometers may be as much as 3°C in error.

TEMPERATURE (2550)/Laboratory & Field Methods 2-61
t temperature at which thermometer is read,

V0 volume of small bulb end of capillary up to 0°C

graduation,

K constant depending on relative thermal expansion of

mercury and glass (usual value of K 6100), and

L calibration correction of thermometer depending on T1

.

If series observations are made it is convenient to prepare graphs

for a thermometer to obtain T from any values of T1 and t.

3. Bibliography

WARREN, H.F. & G.C. WHIPPLE. 1895. The thermophone—A new instrument for determining temperatures. Mass. Inst. Technol. Quart.

8:125.

SVERDRUP, H.V., M.W. JOHNSON & R.H. FLEMING. 1942. The Oceans.

Prentice-Hall, Inc., Englewood Cliffs, N.J.

AMERICAN SOCIETY FOR TESTING AND MATERIALS. 1949. Standard Specifications for ASTM Thermometers. No. E1-58, ASTM, Philadelphia, Pa.

REE, W.R. 1953. Thermistors for depth thermometry. J. Amer. Water

Works Assoc. 45:259.

2560 PARTICLE COUNTING AND SIZE DISTRIBUTION*

2560 A. Introduction

1. General Discussion

Particles are ubiquitous in natural waters and in water and wastewater treatment streams. Particle counting and size distribution

analysis can help to determine the makeup of natural waters, treatment plant influent, process water, and finished water. Similarly, it

can aid in designing treatment processes, making decisions about

changes in operations, and/or determining process efficiency. Methods for measuring particle size distribution included herein depend

on electronic measurement devices because manual methods are

likely to be too slow for routine analysis. However, when particle

size analysis is to include size distribution of large (500-m)

aggregates, use direct microscopic counting and sizing. Principles

of various types of instruments capable of producing both size and

number concentration information on particulate dispersions are

included. Unless explicitly stated otherwise, the term “size distribution” means an absolute size distribution, i.e., one that includes

the number concentration or count.

In most particle-counting instruments, particles pass though a

sensing zone where they are measured individually; the only

exception included is the static type of light-scattering instrument. Instruments create an electronic pulse (voltage, current, or

resistance) that is proportional to a characteristic size of the

particle. The instrument responses (pulse height, width, or area)

are classified by magnitude and counted in each class to yield the

particle size distribution.

2. Selection of Method

Three instrument types are included: electrical sensing zone

instruments, light-blockage instruments, and light-scattering instruments.

Select instrument consistent with expected use of the particle size

analysis. Instruments vary in the particle characteristic being sensed,

lower and upper size limits of detection, degree of resolution of the

size distribution, particle number concentration range that can be

measured accurately, amount of shear to which a sample is subjected before measurement, amount of sample preparation, operator

skill required, and the ease with which data can be obtained and

manipulated into the desired forms. See Sections 2560B.1, C.1, and

D.1, and manufacturers’ literature for information on characteristics

of each type of instrumentation.

Some instruments can be set up for either continuous-flow or

batch sampling. Others can be used only for batch analysis. For

instruments usable in both modes, check that no systematic

differences in particle size distributions occur between continuous-flow measurements and batch samples taken at or near the

intake point for continuous-flow samples.

3. Sample Collection and Handling

a. Batch samples: Use extreme care in obtaining, handling,

and preparing batch samples to avoid changing total particle

count and size distribution.

Choose representative times and locations for sampling. Ensure

that particles are not subjected to greater physical forces during

collection than in their natural setting. Collect samples from a body

of water with submerged vessels to minimize turbulence and bubble

entrainment. If sampling from particular depths, use standard samplers designed for that purpose. For flowing systems, make sure that

the velocity into the opening of the sampling device is the same as

that of the flowing stream (isokinetic sampling) and that the opening

* Approved by Standard Methods Committee, 2000.

Joint Task Group: 20th Edition—Desmond F. Lawler (chair), Erika E. Hargesheimer, Carrie M. Lewis, Nancy E. McTigue, Theodore S. Tanaka, John E. Tobiason,

Mark R. Wiesner.

2-62 PHYSICAL & AGGREGATE PROPERTIES (2000)