Iq - Degremont Formulae Digest

8 FORMULAE DIGEST

The Water Treatment Handbook was originally compiled to provide both water treatment engineers and technicians with basic data and practical information most frequently required on-site. Water treatment engineering calls for increasingly specialized and diversified knowledge, yet there is still a definite need for a digest of basic information and simple numeric or graphicdata most frequently used by technicians, particularly when working on rushed projects or during start-up operations. The Formulae Digest sets out to meet this need, although it is difficult to set clear limits to its contents, which should remain concise:

for example, the definition of elementary geometric volumes could be useful for determining the capacity of a reagent storage tank;reiterating certain essential regulatory provisions regarding wastewater discharge could be of use to the site manager who may not be familiar with certain regulations, etc. To some readers, this digest will no doubt seem incomplete, while others will feel it contains too many universally known basic facts. The Digest aims to be of help to the largest possible number of Handbook users. It is simply a "toolkit", for each to use according to their particular requirements.

Chap. 8: Formulae digest

1. UNITS OF MEASUREMENT
1.1. SYSTEMS OF UNITS
Systems of units derived from the metric system have gradually been replaced by a single system termed the International System of Units (SI), presented in the first part of this sub-chapter. The cgs (centimetre-gramme-second) system, in which most unitscorrespond to decimal multiples or sub-multiples of the International System, still has advantages in certain fields. As many countries still persist in using British or US systems of units, the second part of this chapter lists the equivalent values of the British/US and SI systems of units. poses, affect water treatment. The first of these tables are taken from documents published by the AFNOR(French Standards Committee) and particularly from the International System summary table in accordance with documentation item No. NF X 02-004.
Note: Extracts from the AFNOR standards included in this document have been reproduced with the authorization of the French Standards Committee AFNOR - Association Française de Normalisation (address: Tour Europe, Cedex 7, 92080 Paris La Defense, France)- which should be addressed if complete documents are required, as only original versions of standards in their most recent editions can be considered valid.

1.1.2. General principles 1.1.1. The International System of Units (SI) This system, gradually accepted and improved by the efforts of the General Conferences on Weights and Measures (GCWM) and the International Committee on Weights andMeasures (ICWM), comprises base units, derived units, and supplementary units. Its application involves decimal multiples and sub-multiples, with the corresponding prefixes. Besides the units listed below, it admits units called "common units defined in terms of SI units" and "temporarily accepted" units. In principle, it discourages the use of cgs and other units. The International System tablesbelow relate to units which, for various purUnit symbols: writing rules Unit symbols are only used after a number expressed in figures.. They are printed in straight characters, are invariable in the plural, written without final period and placed after complete numeric values, leaving a space between the numeric value and the symbol. They are written in small letters; however, the first letter isa capital when the name of the unit is derived from a proper noun. There should be no more than one fraction line on the same line to represent a composite unit that is the quotient of two units, unless parentheses are used to avoid any ambiguity.

1.

Units of measurement

. Base units
Quantity . length . mass . time .electric current intensity . absolute temperature . amount of...