Environmental Engineering

Environmental Significance Of Nitrogen Species

Mandalas Ciles

While nitrogen is seen to be an essential component of all living things, excessive concentrations of certain nitrogen species in some compartments of the environment can lead to significant environmental problems. This is true of some nitrogen species in the atmosphere as well as in terrestrial and aquatic environments. Atmospheric Concerns with Nitrogen Species The three major environmental problems associated with nitrogen species in the atmosphere are photochemical smog, global warming, and...

Significance Of Chloride

Chloride in reasonable concentrations is not harmful to humans. At concentrations above 250 mg L it gives a salty taste to water, which is objectionable to many people. For this reason a secondary standard of 250 mg L for chloride in drinking water has been set by the U.S. EPA, the same value contained in the WHO guidelines. In many areas of the world where water supplies are scarce, sources containing as much as 2000 mg L are used for domestic purposes without the development of adverse...

Types Of Hardness

In addition to total hardness, it is desirable and sometimes necessary to know the types of hardness present. Hardness is classified in two ways (1) with respect to the metallic ion and (2) with respect to the anions associated with the metallic ions. Calcium and magnesium cause by far the greatest portion of the hardness occurring in natural waters. In some considerations it is important to know the amounts of calcium and magnesium hardness in water. For example, it is necessary to know the...

Methods Of Determining Volatile Acids

Two methods of deteimining volatile acids are currently described in Standard Methods. One uses column-partition chromatography, and the other involves distillation. Several laboratories today also use gas chromatography or ion chromatography (Sec. 12.4) for the measurement of the concentration of individual volatile acids, although these procedures are not yet considered as standard. They may be in the future as we leam more about the significance of individual volatile acids in the control of...

Solubility Of Salts

Basic concepts of salt solubility and the concept of solubility product were discussed in Sec. 2.13. Consideration of solubility relationships can aid in understanding the natural forces that dissolve rocks and other minerals, bringing minerals into aqueous solution. Variations in mineral characteristics of water can also be understood to some degree by considering the factors affecting solubility of minerals. Knowledge of solubility relationships can also help to devise methods for treating...

Ch3ch2ch2ch2 coohi

The carbon atom next to the carboxyl group is alpha, the next beta, then gamma, . delta, and so on. The terminal carbon atom is also referred to as being in the omega position. The -amino acids are particularly important compounds and are dis- f cussed in The principal unsaturated monocarboxylic acids are as follows Acrylic Acid (CH2 CHCOOH) Acrylic acid is used extensively because of its ability to polymerize, a characteristic of many compounds with unsaturated link- Table 5.8 I Physical...

Water and Wastewater Analysis 399

9.1 Importance of Quantitative Measurements 401 9.2 Character of Environmental Engineering and Science Problems 402 9.3 Standard Methods of Analysis 402 9.4 Scope of a Course in Analysis of Environmental Samples 402 9.6 Other Items 408 Problems 408 Statistical Analysis of Analytical Data 410 10.2 Rounding Numerical Data 411 10.4 Distribution of Experimental Data 416 10.8 Lognormal Distribution 433 10.10 Quality Assurance and Quality Control 446 11.2 The Analytical Balance 455 11.6 Physical...

Methods Of Chlorine Residual Determination

It was not until about 1940 that the difference in disinfecting power of chloramine and free chlorine residuals was demonstrated. Prior to that time no attempt had been made to develop analytical procedures for differentiation. Therefore, methods for measuring chlorine residuals may be classed into old methods that measure total chlorine and new methods that allow measurement of free and combined forms. CHAPTER 20 Residual Chlorine and Chlorine Demand AH common methods of measuring chlorine...

Methods Of Expressing Alkalinity

Pressure Temperature Relationship

Alkalinity measurements are made on a wide variety of materials. These range from relatively pure waters through polluted waters, such as municipal and industrial wastewaters, to digesting sludges. The methods of expressing alkalinity values vary considerably therefore, it is necessary to explain the methods in some detail and to indicate the areas where the various methods are employed. Phenolphthalein and Total Alkalinity Inspection of the titration curves for a strong base (hydroxide...

Other Considerations

A number of situations are encountered in practice that involve carbon dioxide-alkalinity-pH relationships and deserve some explanation. It is common practice to aerate water to remove carbon dioxide, ammonia, and volatile organic chemicals. Since carbon dioxide is an acidic gas, its removal tends to decrease H+ and thus raise the pH of the water in accordance with Eq. (18.17). Normai air contains about 0.035 percent by volume of carbon dioxide, which is equivalent to lO3 46 atm at sea level....

Drinking Water Standards

EPA drinking water standards and WHO guidelines for trace organic contaminants are listed in Table 34.1 and for trace inorganic contaminants in Table 34.2. Values of EPA secondary standards or WHO guidelines for substances causing consumer complaints are listed in Table 34.3. For some contaminants, such as epichlorohydrine, acrylamide, copper, and lead, the MCL specifies that best available treatment technology be used rather than providing a numerical...

[HgClM [Hg2I[cr4

Here the subscript, on the equilibrium constant has the same meaning as in Eqs. (2.38) to (241). It can easily be shown that 3, Kh Kfa, fa KXK2KZ, and KyKtK-iK . Sometimes the reciprocal of the overall formation constant of the highest complex is given as the instability constant for that reaction. Thus, 1 Th chloride concentration in a typical freshwater stream is IO 3 M. If the HgGl2(a

Computer Methods For Solving Equilibrium Problems

The chemical equilibrium problems presented in this chapter are relatively simple ones involving only a few species and equilibrium expressions. They have been solved using equilibrium constants, mass balances, charge balances, and sometimes proton conditions, and spreadsheets or by making simplifying assumptions and generating quadratic equations or by drawing log concentration diagrams. However, for more complex problems where many species are involved (say more than 15 to 20), where several...

Method Of Determining Alkalinity

Alkalinity Titration Curve

Alkalinity is measured volumetrically by titration with N 50 or 0.020 N H2S04 and is reported in terms of equivalent CaC03. For samples whose initial pH is above 8.3, the titration is made in two steps. In the first step the titration is conducted until the pH is lowered to 8.3, the point at which phenolphthalein indicator turns from pink to colorless. The second phase of the titration is conducted until the pH is lowered to about 4.5, corresponding to the bromcresol green end point. When the...

Colloidal Dispersions In Liquids

Colloidal dispersions of solids, liquids, and gases in liquids are commonly encountered in environmental engineering and science. The nomenclature and behavior of each type differ somewhat consequently, discussions of each will be given. Colloidal dispersion's of solids in liquids are generally of two types, those that bind j strongly with the liquid and those that do not. Dispersions binding strongly with the I liquid are generally more stable and difficult to separate from the liquid than...

Oxidationreduction Reactions

Oxidation-reduction reactions are among the most important with which environmental engineers and scientists deal. Many reactions of interest in wastewater treatment such as organic oxidation and methane fermentation, nitrification, and denitri-fication are of this type and are mediated by bacteria. Oxidation-reduction reactions are important in the solubilization and precipitation of iron and manganese. Oxidants such as chlorine and ozone are added to water and wastewater to bring about...

Darrin Lee Environmental Health

23.1 What use is made of the BOD test in water pollution control 23.2 List five requirements that must be complied with in order to obtain reliable BOD data. 23.3 List five requirements of a satisfactory dilution water for BOD work. 23.4 What purpose or purposes are served by each of the following in BOD dilution water (a) FeClj, (b) MgSO*. (c) K2HP04, (d) NH4C1, and (e) CaCl, 23.5 Explain how a sample of river water having a temperature below 20 C should be pretreated in preparation for BOD...

Preparation Of 100 N AND 0020 N NaOh Solutions

Standard solutions of sodium hydroxide are used to measure carbon dioxide and acidity. The equivalent weight of carbon dioxide when reacting with sodium hy- I droxide, to pH 8.3 or the phenolphthalein end point, is 44, as may be calculated from the equation COa + Na+ + OH -> Na+ + HCOj (15.1) Therefore, N 44 or 0.0227 N solutions of NaOH are best suited for determination of carbon dioxide. Mineral acidity is always expressed in terms of calcium carbonate, which has an equivalent weight of 50,...

Method Of Measuring

The BOD test is based upon determinations of dissolved oxygen consequently, the accuracy of the results is influenced greatly by the care given to its measurement. BOD may be measured directly in a few samples, but in general, a dilution procedure is required. For samples with 5-day BOD less than 7 mg L, it is not necessary to dilute them, provided that they are aerated to bring the dissolved-oxygen level nearly to saturation at the start of the test. Many river waters fall into this category....

K um K kb[ ORT

Care must be taken to ensure that the units used in these rate expressions are The concept of half-life is often used to describe the persistence of an organic in the environment. Half-life (i1 2) was defined in Sec. 3.10 as 0.693Ik, where k is a grst-orderrate coefficient. With hydrolysis, k is represented by kh or kh N , Hydrolysis reactions may be quite slow (half-lives of years) or quite rapid (half-lives of seconds) depending on the organic and the environmental conditions. The following...

Adsorption

Sorption processes are very important to the fate and transport of contaminants in the environment and for the removal of contaminants in engineered reactors. Sorption is most often defined as the concentration or movement of contaminants from one phase to another. Absorption involves the partitioning of a contaminant from one phase into another phase. Examples include the dissolution (absorption) of oxygen gas into water and the absorption of the pesticide DDT into the organic solvent hexane....

Logarithmic Diagram Of Concentration Of Weak Acid

Acid Base Logarithmic Diagram

Note that in mass balance, charge balance, and proton condition relationships, molar concentrations and not activities are required. - V- . The ionic strength must now be calculated so that activity corrections can be made. Since HAc is a weak acid, its ionization can be ignored ( Ac- - 0) and we can assume that the ionic strength is due entirely to the added NaCl. ,V P- Sc.z 0.5 0.01(1)2 + O.Ol(-l)2 0.01 M Using the Guntelberg approximation Eq. (4.2) . log 7 -0.5Z2 V5 L -0.0455Z2 ' 1 + VOOl...

Methods Of Determining Dissolved Oxygen

Originally, measurement of dissolved oxygen was made by heating samples to drive out the dissolved gases and analyzing the collected gases for oxygen by methods applied in gas analysis. Such methods require large samples and are very cumbersome and time-consuming. The Winkler or iodometric method and its modifications are the standard volumetric procedures for determining dissolved oxygen at the present time. The test depends upon the fact that oxygen oxidizes Mn2* to a higher state of valence...

Rate Of Biochemical Oxidations

For a great many years the BOD reaction was considered to have a rate constant k' equal to 0.23 per day at 20 C, This value was established by extensive studies on polluted river waters and domestic wastes in the United States and England. As application of the BOD test spread to the analysis of industrial wastes, and the use of synthetic chapter 23 Biochemical Oxygen Demand Table 23.2 I Significance of reaction rate constant k' upon BOD dilution waters became established, it was soon noted...

Public Health Significance Of Disinfection Residuals

Breakpoint Chlorination Graph

Disinfection is a process designed to kill harmful organisms, and it does not ordinarily produce a sterile water. These generalizations hold for disinfection with chlorine, chlorine dioxide, ultraviolet radiation, and ozone. Two factors are extremely important in disinfection time of contact and concentration of the disinfecting agent. Where other factors are constant, the disinfecting action may be represented by Kill o C X (n > 0) (20.12) The important point is that with long contact times...

Quantitative Chemistry

Quantitative chemistry may be considered a keystone in the training of environmental engineers and scientists. It serves as. the basis for most research work and many field investigations. Unfortunately, most college courses in quantitative analysis, although they furnish excellent fundamental information, do not provide laboratory instruction and practice that are particularly valuable to environmental engineers. For this reason, specialized courses in quantitative analysis, often described as...

Cause And Source Of Hardness

Hardness is caused by multivalent metallic cations. Such ions are capable of reacting with soap to form precipitates and with certain anions present in the water to form scale. The principal hardness-causing cations are the divalent calcium, magnesium, strontium, ferrous iron, and manganous ions. These cations, plus the most important anions with which they are associated, are shown in Table 19.1 in the order of their relative abundance in natural waters. Aluminum and ferric ions are sometimes...

General Considerations

The subject of trace organic and inorganic contaminants in foods has been under investigation for over a century1 and, since 1960, has become an item of increasing concern in the field of water supply.2 In the context used here, the term trace means low concentration, perhaps 1 mg L or less. Although the primary interest here is in water, air, and their impurities, the effects of chemical impurities in water on human populations ordinarily cannot be easily isolated for epidemiological or...

Oxidationreduction Equations

Concepts of oxidation and reduction are based upon the idea of atomic structure and electron transfer as described in Sec. 2.4. An atom, molecule, or ion is said to undergo oxidation when it loses an electron, and to undergo reduction when it gains an electron. With reference to Fig. 2,1, when sodium reacts with chlorine to form sodium chloride, the sodium atom loses an electron and becomes oxidized to the sodium ion, Na+. Chloride gains an electron and is reduced to the anion, CI . When...

Effect Of Radiation On Humans

Radiation effects on humans are classified as somatic or genetic. Somatic effects are those that cause damage to the individual and include anemia, fatigue, loss of hair, cataracts, skin rash, and cancer. Genetic effects include inheritable changes ) resulting from mutations in reproductive cells. It is widely held that even small dosages of radiation can have some adverse effects, genetic effects being of most concern. Humans are exposed to varying levels of natural radiation, especially from...

Significance Of Carbon Dioxide And Mineral Acidity

Acidity is of little concern from a sanitary or public health viewpoint. Carbon dioxide is present in malt and carbonated beverages in concentrations greatly in excess of any concentrations known in natural waters, and no deleterious effects due to the carbon dioxide have been recognized. Waters that contain mineral acidity are so unpalatable that problems related to human consumption are nonexistent. Acid waters are of concern because of their corrosive characteristics and the expense involved...

Binary Mixtures

Binary mixtures of miscible liquids such as Water and ethanol are of interest because of the differences in vapor pressure that they exhibit and the influence that vapor pressure has upon their separation by distillation. All mixtures fall into one of three classes, and their properties are considerably different. Class 1 includes all mixtures with total vapor pressure, regardless of the composition of the mixture, that is always less than that of the most volatile component and always more...

Why Is Turbitiy And Color Imporatn To Environmental Engineers

Nvironmental engineers and scientists have evolved as professionals over the past century to address human health and environmental problems resulting from industrial expansion, resource utilization, and the concentration of growing populations in cities. Such trends over the past two centuries have resulted in the biological and chemical contamination of water supplies, pollution of rivers, and severe fouling of air and land. To address these problems, environmental engineers have worked...

Application Of Turbidity Data

Turbidity measurements are of particular importance in the field of water supply. They have limited use in the field of domestic and industrial waste treatment. Knowledge of the turbidity variation in raw-water supplies is of prime importance to water treatment plant operation. Such measurements are used in conjunction with other information to determine whether a supply requires special treatment by chemical coagulation and filtration before it may be used for a public water supply. Many large...

Wastewater And Water Pollution Control

The disposal of human wastes has always constituted a serious problem. With the development of urban areas, it became necessary, from public health and aesthetic considerations, to provide drainage or sewer systems to carry such wastes away from the area. The normal repository was usually the nearest watercourse. It soon became apparent that rivers and other receiving bodies of water have a limited ability to handle waste materials without creating nuisance conditions. This led to the...

Air Pollution And Global Environmental Change

Although the problems of water supply and liquid-waste disposal are of major importance to urban populations, their solution alone does not ensure a completely satisfactory environment. Pollution of the atmosphere increases in almost direct ratio to the population density and is largely related to the products of combustion from heating plants, incinerators, and automobiles, plus gases, fumes, and smokes arising from industrial processes. The intensity of most air pollution problems is usually...

Sources And Nature Of Acidity

Carbon dioxide is a normal component of all natural waters. It may enter surface waters by absorption from the atmosphere, but only when its concentration in water is less than that in equilibrium with carbon dioxide in the atmosphere, in accordance with Henry's law. Carbon dioxide may also be produced in waters through biological oxidation of organic matter, particularly in polluted water, In such cases, if photosynthetic activity is limited, the concentration of carbon dioxide in the water...

The Safe Drinking Water

The critical nature of the water supply problem brought congressional action resulting in Public Law 93-523, known as the Safe Drinking Water Act (SDWA), which was signed into law in 1974, It then became incumbent upon the newly formed Environmental Protection Agency (EPA) to interpret the law and establish Drinking Water Standards that apply to all public water systems in the United States, not just those that supply common carriers, as did the U.S. Public Health Standards. The SDWA was...

Problems

25.1 In what forms does nitrogen normally occur in natural waters 25.2 Discuss the significance of nitrogen analysis in water pollution control. 25.3 Analyses for various forms of nitrogen were made at three points in a stream as follows On the basts of your knowledge of the nitrogen cycle, explain the processes involved in the relative changes in each nitrogen form, as well as the decrease in total nitrogen in moving downstream from point 1 to point 3. 25.4 Would you expect to find the highest...

Basic Concepts from Equilibrium Chemistry

A knowledge of equilibrium chemistry has become increasingly important for determining quantitatively the relationships between the various constituents in natural and contaminated waters, and for understanding the effect of alterations in the water on the various chemical species present. This is a matter of growing importance because of the use of physical-chemical methods for treating wastewaters and sanitary-landfill leachates and the need to understand the fate and transport of both...

Methods Of Determining Fluoride

There are four standard methods for determination of fluoride at the present time the electrode method, two colorimetric procedures, and ion chromatography. The electrode method is the simplest but does require use of an expanded-scale pH meter and a special electrode. The principles behind and limitations of the electrode method are described under Crystalline Membrane Electrode in Sec. 12.3. The ion chromatographic technique, described in Sec. 12.4, permits analysis for fluoride and several...

Disinfection With Chlorine Dioxide

A discussion of chlorination should also include chlorine dioxide, as it has certain advantages over free chlorine and hypochlorite. It is about as effective an oxidizing agent as hypochlorous acid and is a particularly good disinfectant at high pH values. A new application in late 2001 by the U.S. EPA was the use of about 800 ppm chlorine dioxide in air in the Hart Senate Office Building in Washington, DC, to decontaminate rooms of anthrax spores contained in a letter sent by an unknown...

Methods Of Analysis

All the standard methods of determining oil and grease depend upon a preferential solution of the greasy materials using extractions with organic solvents and are subject in some degree to the limitations already discussed. The methods employed for water samples and sludges differ somewhat, and separate discussions are needed. The oil or grease content of relatively clean waters is not a routine determination and is seldom performed except in special cases in which accidental contamination has...

Preparation Of 100 N And 0020 N H2s04 Solutions

Standard solutions of sulfuric acid are used for the determination of alkalinity which is normally expressed in terms of CaC03, with an equivalent weight of 50 'Beginners should add slightly less water to avoid overdilution. therefore, N 50 or 0.020 N solutions are required. Because large amounts of this reagent are used, it is most convenient to prepare a stock solution of LOO N acid and prepare the 0.020 N solution from it by simple dilution. The purity of sulfuric acid as purchased usually...

Instrumental Methods of Analysis

A variety of sensitive instruments have been developed in recent years that have increased considerably the analyst's ability to measure and to cope with pollutional materials of increasing complexity. Instrumental methods of analysis are finding wide usage for routine monitoring of air quality, groundwater and surface water quality, and soil contamination, as well as during the course of water or waste treatment. Such methods have allowed analytical measurements to be made immediately at the...

Chemical Kinetics

Chemical kinetics is concerned with the speed or velocity of reactions. Many reactions have rates that at a given temperature are proportional to the concentration of one, two, or more of the reactants raised to a small integral power. For example, if a reaction is considered in which A, B, and C are possible reactants, then the rate equations that express the concentration dependence of the reaction rate may take one of the following forms, among others Rate kC2a or kCaCb second order Rate kC...

Thermodynamics

Thermodynamics is the study of energy changes accompanying physical and chemical processes. The energy changes associated with chemical reactions are of considerable importance and will be briefly discussed to indicate the relationships of most interest in environmental engineering and science. First, it is necessary to review the relationship between heat and work. Heat and work are related forms of energy. Heat energy can be converted into work,-and work can be converted into heat energy....