II. DOs and DON’Ts in the Laboratory
The normality of basic solution to measure mineral acidity as CaCO3 is:
Acidity — 1/eq. wt. = 1/50 = N/50 = 0.020N
The normality of silver nitrate to measure chloride and sodium chloride is:
Chloride — 1/eq. wt. = 1/35.45 = N/35.45 = 0.0282N
Sodium chloride — 1/eq. wt. = 1/58.44 = N/58.44 = 0.071N
Thus the substance measured is calculated as follows:
Most materials subjected to the analysis of water and wastewater fall in the realm of dilute solutions i.e., a few mg in a litre. So the results are normally expressed in mg/L or ppm. Parts per million (ppm) is a weight ratio; but mg/L is a weight by volume ratio. The relationship is given as follows:
If concentrations are less than 0.1 mg /L, express them in µg/L (micrograms per litre). If concentrations are more than 10,000 mg/L, they are expressed in percentages.
Plotting of Graphs
Rules listed by Worthing and Geffner are to be followed while plotting graphs. They are:
Classification of Procedures
Laboratory analytical procedures are classified to quantify the chemical substances as follows:
Standards of Water Quality
Standards of water quality are presented as follows:
Chemical and Physical Quality
Significance and Determination of Chemical Parameters
Chemical parameters and their significance are presented as follows. The methods of the analysis adopted are also presented. However, only simple methods will be dealt within this manual.
Chemical parameters commonly determined in natural waters and water supplies
Humanity and Environment
A characteristic, which has set Homo sapiens apart from other species, has been their ability to control many aspects of their environment. Throughout recorded history people have continually struggled to manage their natural environment in order to improve their health and well-being. In recent years environmental sanitation in many parts of the world has led to large reduction or virtual elimination of diseases spread via the environment. Continuous environmental vigilance is necessary to keep away these weeds from the garden of humanity from increasing out of proportion among a large part of the earth's population.
People's success in the control of environmental borne diseases has not reduced the need for ever-increased efforts of effective management of the total environment. The population explosion, an affluent society with desires for a vast array of products, increased radiations, greater energy use, increased food production needs, and other developments have created strains on parts of the ecological systems. Perhaps never in history have people demonstrated such great concern for their total environment as is now being witnessed in many parts of the earth, particularly in those areas which have benefited most from people's environmental control efforts toward effective use of human, material and natural resources. Over the years, intensification of old problems and the introduction of new ones have led to basic changes in the philosophy of environmental engineering practice.
Water is one of the materials required to sustain life and has long been suspected of being the source of many of the illnesses of man. It was not until a little over 100 years ago that definite proof of disease transmission through water was established. Originally the major objectives were to produce hygienically safe water supplies and to dispose off wastes in a manner that would prevent the development of nuisance conditions. Many other factors concerned with aesthetics, economics, recreation and other elements of better living are important considerations and have become part of the responsibilities of the modern environmental engineer.
The public has been more exacting in their demands as time has passed, and today water engineers are expected to produce finished waters that are free of colour, turbidity, taste, odour and harmful metal ions. In addition, the public desires water, which is low in hardness and total solids, non-corrosive, and non-scale forming. To meet with such stringent standards, chemists, biologists and engineers must combine their efforts and talents together and hence the need for analytical testing of water and waste becomes necessary.
Importance of Quantitative Analysis
Quantitative analysis serves as the keystone of engineering practice. Environmental engineering is perhaps most demanding in this respect, for it requires the use of not only the conventional measuring devices employed by engineers but, in addition many of the techniques and methods of measurement used by chemists, physicists and some of those used by biologists.
Every problem in environmental engineering must be approached initially in a manner that will define the problem. This approach necessitates the use of analytical methods and procedures in the field and laboratory, which have proved to yield reliable results. Once the problem has been defined quantitatively, the engineer is usually in a position to design facilities that will provide a satisfactory solution.
After construction of the facilities has been completed and they have been placed in operation, usually constant supervision employing quantitative procedure is required to maintain economical and satisfactory performance. The increase in population density and new developments in industrial technology are constantly intensifying old problems and creating new ones. In addition, engineers are forever seeking more economical methods of solving old problems. Research is continuously under way to find answers to the new problems and better answers to old ones. Quantitative analysis will continue to serve as the basis for such studies.
Character of Problems
Most problems in environmental engineering practice involve relationships between living organisms and their environment. Because of this, the analytical procedures needed to obtain quantitative information are in often a strange mixture of chemical and biochemical methods, and interpretation of the data is usually related to the effect on microorganisms or human beings. Also, many of the determination used fall into the realm of microanalysis because of the small amounts of contaminants present in the samples. Ordinarily, the amounts determined are a few milligrams per litre and often they are found only in few micrograms.
Standard Methods of Analysis
Concurrent with the evaluation of environmental engineering practice, analytical methods have been developed to obtain the factual information required for the resolution and solution of problems. In many cases different methods have been proposed for the same determination, and many of them were modified in some manner. As a result, analytical data obtained by analysis were often in disagreement.
In an attempt to bring order out of chaos, the American Public Health Association appointed a committee to study the various analytical methods available and published the recommendation of the committee as "Standard Methods of Water Analysis" in 1905.
"Standard Methods" as published today is the product of the untiring effort of hundreds of individuals who serve on committees, testing and improving analytical procedures for the purpose of selecting those best suited for inclusion in "Standard Methods", which is now available as "Standard methods for the examination of water and waste water".
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