Drinking Water

Unit operations and unit processes

Drinking Distilled Water Unit Operation

Figure 1 shows the schematic of a conventional wastewater treatment plant using primary treatment. Raw wastewater is introduced either to the screen or to the comminutor. The grit channel removes the larger particles from the screened sewage, and the primary clarifier removes the larger particles of organic matter as well as inorganic matter that escapes removal by the grit channel. Primary treated sewage is then introduced to a secondary treatment process train downstream (not shown) where the...

Removal of Iron and Manganese by Chemical Precipitation

Iron Reducing Bacteria

Iron concentrations as low as 0.3 mg L and manganese concentrations as low as 0.05 mg L can cause dirty water complaints. At these concentrations, the water may appear clear but imparts brownish colors to laundered goods. Iron also affects the taste of beverages such as tea and coffee. Manganese flavors tea and coffee with medicinal tastes. Some types of bacteria derive their energy by utilizing soluble forms of iron and manganese. These organisms are usually found in waters that have high...

Alkalinity And Acidity Expressed As CaCO3

To find the equivalent concentration of alkalinity in terms of CaCO3 proceed as follows CaCO3 + 2H+ H2CO3 + Ca2+ (12.85) Note We have reacted the alkalinity species (CaCO3) with the hydrogen ion, since it is the property of alkalinity to react with an acid. From this reaction, the equivalent mass of CaCO3 is 50. Therefore, a mass equivalent of alkalinity is equal to 50 mass units expressed as CaCO3. For example, 1 gram equivalent of alkalinity is equal to 50 grams of alkalinity expressed as...

Ion Exchange Reactions

Ion exchange is the displacement of one ion by another. The displaced ion is originally a part of an insoluble material, and the displacing ion is originally in solution. At the completion of the process, the two ions are in reversed places the displaced ion moves into solution and the displacing ion becomes a part of the insoluble material. Two types of ion exchange materials are used the cation exchange material and the anion exchange material. The cation exchange material exchanges cations,...

Mass Transfer Units

The major purpose of dissolving air is to provide oxygen to be used by microorganism in the process of wastewater treatment. This is exemplified by the aeration employed in the activated sludge process. Aeration may also be employed for the removal of iron and manganese from groundwaters. In the removal of hardness, the presence of high concentrations of carbon dioxide may result in high cost for lime, as CO2 reacts with lime. Thus, excess concentrations of this gas may be removed from the...

Sludge Production

Phosphorus is normally removed from wastewaters and, as such, the solids produced would include the original suspended solids or turbidity. Therefore, two sources contribute to the production of solids in phosphorus removal the original suspended solids and the solids produced from chemical reaction. If V is the cubic meters of water treated and spss are the solids removed at a fractional efficiency of fss, the kilograms of solids produced from the suspended solids is (fss spss mg 1000) V,...

Colloid Destabilization

Destabilization Colloids

Colloid stability may further be investigated by the use Figure 12.1b. This figure portrays the competition between two forces at the surface of the colloid particle the van der Waal's force of attraction, represented by the lower dashed curve, and the force of repulsion, represented by the upper dashed curve. The solid curve represents the resultant of these two forces. As shown, this resultant becomes zero at a - a' and becomes fully an attractive force to the left of the line. When the...

Water Turbine Impeller Homemade

Centrifugal Pumps Impeller Types

FIGURE 4.1 Plan and section of a pumping station showing parallel connections. FIGURE 4.2 Pumps connected in series. unit through the eye of the impeller. This is indicated in Figure 4.2 where the Q in line meets the eye. In positive-displacement pumps, no eye exists. The left-hand side of Figure 4.3 shows an example of a positive-displacement pump. Note that the screw pump literally pushes the wastewater in order to move it. The right-hand side shows a cutaway view of a deep-well pump. This...

And Flocculation

Vaned Disc Turbine

Mixing is a unit operation that distributes the components of two or more materials among the materials producing in the end a single blend of the components. This mixing is accomplished by agitating the materials. For example, ethyl alcohol and water can be mixed by agitating these materials using some form of an impeller. Sand, gravel, and cement used in the pouring of concrete can be mixed by putting them in a concrete batch mixer, the rotation of the mixer providing the agitation....

Residual Chlorine Vs Applied Chlorine

Chlorine Residual Breakthrough Curve

In all pH ranges up to less than 7.5. At exactly pH 7.5, the concentrations of HOCl and OCl- are equal and above this pH, OCl- predominates over all chlorine disinfectant species. This reality is more than just a theoretical interest, because HOCl is 80 to 100 more effective than OCl- as a disinfectant (Snoeyink and Jenkins, 1980). We now conclude that the optimum pH range for chlorination is up to 7.0. Beyond this range, OCl- predominates and the disinfection becomes less effective. The three...

Chlorine Dosing

Les Organes Tour

Diaphragm type gage protector (typical) Diaphragm type gage protector (typical) FIGURE 17.7 Schematic of chlorine feeder system using chlorine cylinders. Following the schematic, tonne containers containing liquid chlorine are put on top of a scale in order to measure usage. Through a suitable piping, liquid chlorine under pressure flows into the evaporator. The chlorine is then evaporated into its gaseous state and conveyed into the chlorinator. The driving mechanism that abstracts the...

Chemical Reactions Using Activated Carbon

Carbon is a reducing agent thus, it follows that when in contact with chlorine it will reduce it to the chloride state. Carbon, itself, will be oxidized to carbon dioxide. The chemical reactions follow C + 2H2O CO2 + 4H+ + 4e- (17.57) 2HOCl + 2H+ + 4e- 2Cl- + 2H2O (17.58) C + 2HOCl CO2 + 2Cl- + 2H+ (17.59) The unit operation of carbon adsorption is discussed in Part II of this book. The use of activated carbon in dechlorination will use the same unit operation, except that in the present case,...

Effect of Dechlorinated Effluents on Dissolved Oxygen of Receiving Streams

Although precise control may be achieved in dosing the sulfur dechlorinating agents, some residual will exist. This residual should be minimized not only because of waste of chemicals but also because of its effect on the dissolved oxygen of receiving streams. The reactions of these residuals on oxygen are as follows 2HSO- + 2H2O 2S 2- + 6H+ + 4e- (17.60) 2HSO- + 2 2S 2- + 2H+ (17.62) 2Na2S 3 + 2H2O 2S 2- + 4Na+ + 4H+ + 4e- (17.63) 2Na2S 3 + O2 2S 2- + 4Na+ (17.65) Na2S2 5 + 3H2 2S 2- + 2Na+ +...

Glossary

Available chlorine The ratio of the mass of chlorine to the mass of the disinfectant that has the same unit of oxidizing power as chlorine. Breakpoint The endpoint of the breakpoint reactions. Breakpoint reactions Decomposition reactions before the breakpoint. Chloramines Reaction products of chlorine with ammonia and organic amines. Chlorination Application of chlorination for disinfection and for other purposes. Combined chlorine Chloramines composed of monochloramines and dichloramines....

Problems

17.1 It is desired to design a bromide chloride contact tank to be used to disinfect a secondary-treated sewage discharge. To determine the contact time, an experiment was conducted producing the following results Contact Time (min) Residual Fecal Coliforms (No. 100 mL) BrCl Dosage (mg L) 15 30 60 Determine the contact time to be used in design, if it is desired to have a log 3 removal efficiency for fecal coliforms. The original concentration of fecal coliforms is 40,000 per 100 mL. 17.2 It is...

Bibliography

Comparison of various membrane types and module configurations in the treatment of natural water by means of low-pressure membrane methods. Separation Purification Technol., 14, 1-3, 69-78. Bryan, E. H. (1990). The National Science Foundation's support of research on uses of ionizing radiation in treatment of water and wastes. Environ. Eng., Proc. 1990 Specialty Conf., ASCE. Arlington, VA, 47-54. Buisson, H., et al. (1997). Use of immersed membranes for...

Plant Types For Hardness Removal

Suez Solids Contact Clarifier

In practice, two types of plants are generally used for chemical precipitation hardness removal One type uses a sludge blanket contact mechanism to facilitate the precipitation reaction. The second type consists of a flash mix, a flocculation basin, and a sedimentation basin. The former is called a solids-contact clarifier. The latter arrangement of flash mix, flocculation, and sedimentation were discussed in previous chapters on unit operations. A solids-contact clarifier is shown in Figure...

Active Or Exchange Zone

Exchange Zone

Figure 16.2 is the same figure illustrated in a previous chapter under carbon adsorption. The length of the active zone was derived in that chapter and is reproduced next. total volume of water or wastewater treated at complete exhaustion of bed influent concentration to 8 total volume treated at time tn+1 total volume treated at time tn concentration of solute at effluent of 8 at time tn+1 concentration of solute at effluent of 8 at time tn surficial area of exchanger bed FIGURE 16.2 Active...

Quantity of Water and Wastewater

Related to and integral with the discussion on quantity are the important knowledge and background on the types of wastewater, sources of water and wastewater, and methods of population projection. The various categories of quantities in the form of design flow rates are also very important. These topics are discussed in this chapter. Because of various factors that have influenced the rate of wastewater generation in recent times, including water conservation and the expanded use of onsite...

Types Of Filters

Figures 7.1 to 7.8 show examples of the various types of filters used in practice. Filters may be classified as gravity, pressure, or vacuum filters. Gravity filters are filters that rely on the pull of gravity to create a pressure differential to force the water through the filter. On the other hand, pressure and vacuum filters are filters that rely on applying some mechanical means to create the pressure differential necessary to force the water through the filter. The filtration medium may...

Unit Processes of Water and Wastewater Treatment

10.3 Plant Types for Hardness Removal 10.4 The Equivalent CaCO3 Concentration 10.5 Softening of Calcium Hardness 10.6 Softening of Magnesium Hardness 10.7.1 Calculation of Stoichiometric Lime Required in the Lime-Soda Process 10.7.2 Key to Understanding Subscripts 10.7.3 Calculation of Stoichiometric Soda Ash Required 10.7.4 Calculation of Solids Produced 10.10 Excess Lime Treatment and Optimum Operational pH 10.11 Summary of Chemical Requirements and Solids Produced 10.13 Chemical Species in...

How Much Kla Of Tap Water

9.1 The value of (KLa)20 for a certain industrial waste is 2.46 per hour and the value of (KLa)w at 25 C 2.77 per hour. What is the value of the temperature correction factor 9.2 The value of (KLa)w at 25 C 2.77 per hour. If the value of the temperature correction factor is 1.024, what is the value of (KLa)20 9.3 The value of (KLa)w 2.77 per hour. If the value of the temperature correction factor is 1.024 and the value of (KLa)20 2.46 per hour, at what temperature is the value of (KLa)w for 9.4...

Pressure Membranes

Pressure membranes are membranes that are used to separate materials from a fluid by the application of high pressure on the membrane. Thus, pressure membrane filtration is a high pressure filtration. This contrasts with electrodialysis membranes in which the separation is effected by the impression of electricity across electrodes. Filtration is carried out by impressing electricity, therefore, electrodialysis membrane filtration may be called electrical filtration. According to Jacangelo...

Coagulation Process

The destabilization of colloids through the addition of counterions should be done in conjunction with the application of the complete coagulation process. Four methods are used to bring about this process double-layer compression, charge neutralization, entrapment in a precipitate, and intraparticle bridging. When the concentration of counterions in the dispersion medium is smaller, the thickness of the electric double layer is larger. Two approaching colloid particles cannot come close to...

Chemical Reactions In Nitrogen Removal

In biochemical nitrogen removal, BNR, two steps are required oxidation of nitrogen to nitrate and subsequent reduction of the nitrate to gaseous nitrogen, N2. The oxidation steps are mediated by Nitrosomonas and by Nitrobacter, as mentioned previously. The reduction step is mediated by the normal heterotrophic bacteria. We will now discuss the chemical reactions involved in these oxidations and reduction. 15.6.1 Nitrification Nitrosomonas Stage From Table 15.2, the generalized donor reaction,...

Bibilography Of Drinking Water Supply

Prospects for utilization of activated anthracites in technology for cleaning the waste waters. Koks i Khimiya Coke Chem, 8, 30-32. American Water Works Association (1990). Alternative Oxidants for the Removal of Soluble Iron and Manganese. Am. Water Works Assoc., Denver. American Water Works Association (1984). Softening, Iron Removal, and Manganese Removal. Am. Water Works Assoc., Denver. AWI MARKETING. Anglian House, Ambury Road, Huntingdon, Cambs PE18 6NZ,...

Criteria For Effective Mixing

As the impeller pushes a parcel of fluid, this fluid is propelled forward. Because of the inherent force of attraction between molecules, this parcel drags neighboring parcels along. This is the reason why fluids away from the impeller flows even if they were not actually hit by the impeller. This force of attraction gives rise to the property of fluids called viscosity. Visualize the filament of fluid on the left of Figure 6.6 composed of several parcels strung together end to end. The motion...

Microbial Thermodynamics

The study of the relationships between heat and other forms of energy is called thermodynamics. All living things utilize heat, therefore, the science of thermodynamics may be used to evaluate life processes. An example of a life process is the growth of bacteria when wastewater is fed to them to treat the waste. Knowledge of microbial thermodynamics is therefore important to professionals involved in cleaning up wastewaters. Variables involved in the study of the relationship of heat and...

Reaction Kinetics

The discussion so far has simply dealt with material balances. For example, they predict the concentration of nitrogen in the effluent, alkalinity requirement and production, and carbon requirement. None, however, would be able to compute the size of the reactor and how fast or how long the sewage should be treated and, although the concentrations of the nitrogen in the effluent have been predicted, the actual resulting value would depend on how long the reaction was allowed to take place. The...

Unit Operations of Water and Wastewater Treatment

Chapter 3 Flow Measurements and Flow and Quality Equalizations 3.4 Flow and Quality Equalizations Glossary 4.1 Pumping Stations and Types of Pumps 4.2.2 Inlet and Outlet Manometric Heads Inlet and Outlet Dynamic Heads 4.3 Pump Characteristics and Best Operating Efficiency 4.6 Net Positive Suction Head and Deep-Well Pumps 4.7 Pumping Station Head Analysis Glossary Chapter 5 Screening, Settling, and Flotation 5.1.1 Head Losses in Screens and Bar Racks 5.1.2 Head Loss in Microstrainers 5.2.1...

Design Of Ion Exchangers

Generally, designs of ion exchangers should include the following quantity of exchange materials and regenerants dimension of the bed (volume of bed) interval of bed regeneration, backwash, and rinse water requirements. The amount of exchange materials determines the dimension of the bed. The interval of regeneration may be arbitrarily set from which the quantity of exchange bed material may be calculated. Regeneration, backwash, and rinse waters may pose pollution problems. 16.6.1 Quantity of...

XiTqilC DQtmt r1000

Also, assume that all of the cations are removed. q. C+. i 8meq L 0.004 geq L 1 1412.8 gea 1412.8 000 1.96 M ) uit m3 720( 1000) g g (Ti n1qi C+sq' )(Q)(tint)(1 + swell) 10001 CatTBedVol (1 + 0.8) 0.13 m3 Ans 16.6.2 Quantity of Regenerant Let CatRegenerant in kilogram equivalents be the quantity of regenerant required and R be the regenerant requirement in equivalents per equivalent of solute removed. The concentration of removable cations in gram equivalents per liter is CatT eq X Ilqi Cs.'...

Pressure At Pool Datum

It is instructive to derive Equation (4.44) by applying the energy equation between the wet well pool surface (point 1 of the lower tank) and the inlet to the pump (a or g). The equation is where V1 velocity at the wet pool level, z1 elevation of the pool level with reference to a datum (the pool level, itself, in this case), P1 pressure at pool level, hfs friction loss from pool level to inlet of pump (the suction side friction loss), Va velocity at inlet to the pump, za elevation of the inlet...

Criteria For Water Stability At Normal Conditions

In the preceding discussions, a criterion for stability was established using the equilibrium constant called Ksp. At normal conditions, as especially used in the water works industry, specialized forms of water stability criteria have been developed. These are saturation pH, Langelier index, and the precipitation potential of a given water. 11.2.1 Saturation pH and the Langelier Index Because pH is easily determined by simply dipping a probe into a sample, determination of the saturation pH is...

General chemistry

Chemistry is a very wide field however, only a very small portion, indeed, of this seemingly complex subject is used in this book. These include equivalents and equivalent mass, methods of expressing concentrations, activity and active concentration, equilibrium and solubility product constants, and acids and bases. This knowledge of chemistry will be used under the unit processes part of this book. The literature shows confused definitions of equivalents and equivalent masses and no universal...

Chemical Reactions Of The Ferrous

The ferrous salt used as coagulant in water and wastewater treatment is copperas, FeS04 7H20. For brevity, this will simply be written without the water of hydration as FeS04. When copperas dissolves in water, it dissociates according to the following equation As in the case of alum, the ions must be rapidly dispersed throughout the tank in order to effect the complete coagulation process. The solid precipitate Fe(OH)2(s) and complexes are formed and expressing in terms of equilibrium with the...

Chemical Reactions Of The Ferric

The ferric salts used as coagulant in water and wastewater treatment are FeCl3 and Fe2(SO4)3. They have essentially the same chemical reactions in that both form the Fe(OH)3(s) solid. When these coagulants are dissolved in water, they dissociate according to the following equations Fe2(SO4)3 2Fe3+ + 3SO4- (12.32) As in any coagulation process, these ions must be rapidly dispersed throughout the tank in order to effect the complete coagulation process. The solid precipitate Fe(OH)3(s) and...

Sodium Silicate

Activated silica Sodium silicate that has been treated with sulfuric acid, aluminum sulfate, carbon dioxide, or chlorine. Acidity The capacity of a solution to absorb the effect of the addition of a base. Alkalinity The capacity of a solution to absorb the effect of the addition of an acid. Anionic polyelectrolytes Polyelectrolytes possessing a net negative charge in the molecules. Cationic polyelectrolytes Polyelectrolytes possessing a net positive charge in the molecules. Charge...

Types Of Hardness

Two basic types of hardness are associated with the ions causing hardness carbonate and noncarbonate hardness. When the hardness ions are associated with the HCO- ions in water, the type of hardness is called carbonate hardness otherwise, the type of hardness is called noncarbonate hardness. An example of carbonate hardness is Ca(HCO3)2, and an example of noncarbonate hardness is MgCl2. In practice, when one addresses hardness removal, it means the removal of the calcium and magnesium ions...

Softening Of Magnesium Hardness

As in the case of calcium hardness, magnesium can also be present in the form of carbonate and noncarbonate hardness. The Ksp of Mg(OH)2 is a low value of 9(10 ). Thus, the hardness is removed in the form of Mg(OH)2. To remove the carbonate hardness of magnesium, a source of the OH ion is therefore added to precipitate the Mg(OH)2 as shown in the following softening chemical reaction Mg (HCO3 )2 + 4OH Mg (OH )2i + 2CO2 + 2HOH (10.10) The carbonate ions in the product side will pair with...

Limesoda Process

As shown by the various chemical reactions above, the chemicals soda ash and lime may be used for the removal of hardness caused by calcium and magnesium. Thus, the lime-soda process is used. This process, as mentioned, uses lime (CaO) and soda ash (Na2CO3). As the name of the process implies, two possible sets of chemical reactions are involved the reactions of lime and the reactions of soda ash. To understand more fully what really is happening in the process, it is important to discuss these...

Summary Of Chemical Requirements And Solids Produced

To summarize, let MCaO be the total lime requirement MsodAsh be the total soda ash requirement and Msolids be the total solids produced. MCaO is equal to the amount of lime used for the removals of the carbonate hardness of calcium (M CaOCaHCO3), the carbonate hardness of magnesium (MCaOMgHCO ), the noncarbonate hardness of magnesium (MCaOMgCa), the requirement to neutralize the dissolved carbon dioxide (MCaOCO), and the requirement to raise the pH to 10.4 for the precipitation of Mg(OH)2,....

Chemical Species In The Treated Water

In addition to the H+ and OH- species, a great majority of ions present in the treated water are the cations Ca2+, Mg2+, and Na+ and the anions SO4- and HCO-. Occasionally, the anions Cl- and NO- may also be present when the hardness cations in natural waters are associated with these anions. The effluent water from the hardness removal reactor is basic and tends to deposit scales in distribution pipes. For this reason, this water should be stabilized. Stabilization is normally done using...

Use Of Alkalinity In Water Softening Calculations

It will be noted that we have avoided the use of alkalinity in any of the softening equations, yet, in the literature, this parameter is used in softening calculations. The reason is that the use of this parameter in softening is often misleading. It will be recalled that the carbonate ion and the bicarbonate ion play very different roles in the unit process reactions. They are on the opposite sides, the carbonate being produced from the bicarbonate. How then is the literature able to use...

Coagulation

Colloids are agglomerates of atoms or molecules whose sizes are so small that gravity has no effect on settling them but, instead, they stay in suspension. Because they stay in suspension, they are said to be stable. The reason for this stability is the mutual repulsion between colloid particles. They may, however, be destabilized by application of chemicals. Coagulation is the unit process of applying these chemicals for the purpose of destabilizing the mutual repulsion of the particles, thus...

Low pH Range

Under this category, iron is removed as Fe(OH)3 and manganese is removed as MnO2, which involves oxidation of the metal ions to their higher oxidation states. The unit operations under the previous category are applicable under the present category, only that under the present scheme, oxidation of the metals is involved. The unit process involves one of Eqs. (13.23) through (13.25) for the case of manganese and similar equations for iron. The equation designed into the unit operations depends...

Chemical Requirements

The chemical requirements are those for the hydroxide source, chlorine, permanganate, ozone, and oxygen. The discussion will be subdivided into requirements in the ferrous reactions and into requirements in the manganous reactions. The treatment on chemical requirements, in effect, is reduced to the determination of the equivalent masses of the pertinent chemicals. 13.7.1 Requirements in the Ferrous Reactions Under these requirements are the reactions at the high and low pH ranges. At the high...

Removal of by Nitrification Denitrification

We define a biological reaction as a reaction mediated by organisms. It encompasses both the organisms and the underlying chemical reactions. To fully apply the knowledge of biological reactions to the treatment of water and wastewater, the chemical nature of these reactions must be given center stage. In other words, to control the process of removing nitrogen by nitrification-denitrification, the intrinsic chemical reactions must be unraveled and fully understood. The organisms only serve as...

[Sno 1 f rs1

dnmiK.NO- + NO, JiK + SjJ where 6cdn MCRT for the denitrifiers, kddn kd for denitrifiers, and SNO lim limiting value of SNO . Values for kddn range from 0.04-0.08 per day, typical 0.04 d. As mentioned, three types of kinetics are involved in the removal of nitrogen nitrification kinetics, denitrification kinetics, and carbon kinetics. Carbon kinetics refer to the kinetics of the heterotrophic aerobic reactions. By analogy with the nitrification or denitrification kinetics, where c specific...

Recarbonation Of Softened Water

After the softening process, the pH is so high that reduction is necessary to prevent deposition of scales in distribution pipes. This can be accomplished inexpensively using carbon dioxide. We will therefore develop the method for determining the carbonic acid necessary to set the water to the equilibrium pH. In recarbonation, the available calcium ion in solution is prevented from precipitation. Therefore, it remains to determine at what pH will the equilibrium condition be, given this...

Order Of Removal

Suppose that there are four gram-equivalents of Ca2+, one gram-equivalent of Mg2+, and 2.5 gram-equivalents of HCO . Suppose further that the decision has been made to use lime. The question is which reaction takes precedence, Equation (10.15) or Equation (10.16) Assuming the former takes precedence, the bicarbonate species present will be composed of 2.5 gram-equivalent of Ca(HCO3)2 and none of the Mg(HCO3)2. The amount of lime needed to remove this bicarbonate is 2.5(CaO 2) 70 g. Assuming the...

J[Xfi 1 [Xf[x [xf I Vmx T

ZT is the tower height and the expressions with overbars are average values between elevations 1 and 2, respectively. If the ZT's of the previous equations are solved, they will be expressed in terms of the product of the reciprocal of the overbarred factors by the respective integrals. Thus, the tower height may be expressed as the product of two factors. Consider the first as the height of a mass transfer unit, H, and the second as the number of mass transfer units, N. Therefore, H based on...

Notes On Equivalent Masses

If all the softening reactions were reviewed, it would be observed that the equivalent masses of the hardness molecules and their associated ionic species are obtained by dividing the molecular masses by the respective total number of valences of the positive or negative ions of the associated species, irrespective of the coefficients in the reaction. For example, in Equation (10.17), the equivalent mass of the molecule MgSO4 is obtained by dividing the molecular mass MgSO4 by 2, the valence of...

Disinfection Using Ozone

Ozone is a very strong oxidizer and has been found to be superior to chlorine in inactivating resistant strains of bacteria and viruses. It is very unstable, however, having a half-life of only 20 to 30 min in distilled water at 20 C. It is therefore generated on site before use. Ozone may be produced by first refrigerating air to below the dew point to remove atmospheric humidity. The dehumidified air is then passed through desiccants such as silica gel and activated silica to dry to -40 to...

T fica v fRm8T

Where f is the absolute viscosity of filtrate c, the mass of cake per unit volume of filtrate collected a, the specific cake resistance -AP, the pressure drop across the cake and filter So, the filter area and Rm, the filter resistance. In RO, c is the solute collected on the membrane (in the concentration boundary layer) per unit volume of permeate and Rm, the resistance of the membrane. All the other parameters have similar meanings as explained earlier in Chapter 7. The volume flux F is V...

Jar Tests For Optimum pH Determination

We may summarize the optimum pH's of the coagulants obtained in the previous examples alum _ 5.32, ferrous _ 11.95, and ferric _ 8.2. The problem with these values is that they only apply at a temperature of 25 C. If the formulas for the determination of these pH's are reviewed, they will be found to be functions of equilibrium constants. By the use of the Van't Hoff equation, values at other temperatures for the equilibrium constants can be found. These, however, as mentioned before, also need...

Background Prerequisites

Physical-Chemical Treatment of Water and Wastewater Unit Operations and Unit Processes Coverage Clean Water Act Regulatory Requirements Federal Financial Assistance Permits and Enforcement Federal and State Relationships Safe Drinking Water Act Highlights of the Safe Drinking Water Act Development of MCLs and MCLGs Drinking Water Regulations under the Act Federal Financial Assistance Federal and State Relationships Relationship of This Book to the Acts Glossary Background Chemistry and Fluid...

Introduction

This book is titled Physical-Chemical Treatment of Water and Wastewater. This chapter begins by defining wastewater and physical-chemical treatment of water and wastewater and treats briefly the coverage. It also addresses the unit operations and unit processes. In addition, in the environmental engineering field, construction of water and wastewater treatment plants and the requirements of their levels of performance are mostly driven by government laws and regulations. For example, the Clean...

R Screening Settling and Flotation

Colubris Redox Drum Sceen

Screening is a unit operation that separates materials into different sizes. The unit involved is called a screen. As far as water and wastewater treatment is concerned, only two sizes of objects are involved in screening the water or wastewater and the objects to be separated out. Settling is a unit operation in which solids are drawn toward a source of attraction. In gravitational settling, solids are drawn toward gravity in centrifugal settling, solids are drawn toward the sides of cyclones...

Softening Of Calcium Hardness

Calcium hardness may either be carbonate or noncarbonate. The solubility product constant of CaCO3 is Ksp Ca2+ CO3_ 5(10_9) at 25 C. A low value of the Ksp means that the substance has a low solubility a value of 5(10_9) is very low. Because of this very low solubility, calcium hardness is removed through precipitation of CaCO3. Because there are two types of calcium hardness, there corresponds two general methods of removing it. When calcium is associated with the bicarbonate ion, the hardness...

Mathematics Of Mass Transfer

Between liquid and gas phases, the transfer of mass from one phase to the other must pass through the interfacial boundary surface. Call the concentration of the solute at this surface as yj referred to the gas phase. The corresponding concentration referred to the liquid phase is xj . xi and yi are the same concentration of the solute only that they are referred to different basis in effect, they are equal. Because they are equal and because the thickness of the interface is zero, xi and yi...

Electrodialysis Membranes

Figure 8.1a shows a cut section of an electrodialysis filtering membrane. The filtering membranes are sheet-like barriers made out of high-capacity, highly cross-linked ion exchange resins that allow passage of ions but not of water. Two types are used cation membranes, which allow only cations to pass, and anion membranes, which allow only anions to pass. The cut section in the figure is a cation membrane composed of an insoluble matrix with water in the pore spaces. Negative charges are fixed...

Chemical Requirements For pH Adjustments

As we have seen, the pH needs to be adjusted to the optimum for optimal coagulation. In general, there are two directions in which this can happen. If the pH is high, then it needs to be adjusted in the downward direction and if it is low, it needs to be adjusted in the upward direction. To adjust in the downward direction, an acid is needed. The cheapest way to do this is to use carbon dioxide. To adjust in the upward direction, a base is needed and the cheapest way to do this is to use lime....

Symbols

Aadd Alkalinity to be added to water Aadd geq Gram equivalents per liter of alkalinity to be added to water Acadd Acidity to be added to water Acadd geq Gram equivalents per liter of acidity to be added to water Acur Current alkalinity of water Acur geq Gram equivalents per liter of current alkalinity of water A Fe mg mg L of ferrous to be removed FeOH+ Monohydroxo Fe(II) complex ion FeOH2+ Monohydroxo Fe(III) complex ion Fe (OH)+ Dihydroxo Fe(III) complex ion Fe (OH)- Trihydroxo Fe(II) complex...

Fluid Mechanics

Of the fluid mechanics applications used in this book, the Reynolds transport theorem is a bit sophisticated. Hence, a review of this topic is warranted. This theorem will be used in the derivation of the amount of solids deposited onto a filter and in the derivation of the activated sludge process. These topics are discussed somewhere in the textbook. Except for these two topics, the theorem is used nowhere else. The general knowledge of fluid mechanics will be used under the unit operations...

Mechanics Of Aeration

In suspended-growth processes, such as the activated sludge process, air must be literally forced into the liquid. The air, thus, dissolved provides the necessary oxygen nutrient for the microorganism stabilizing the wastewater. The basic process for oxygen mass transfer from air to water is absorption. Call the equilibrium concentration of oxygen in water at a particular temperature and pressure as Cos . This equilibrium concentration is also called the...

Chemical Reactions Of The Ferrous And The Ferric Ions

The chemical reactions of the ferrous and the ferric ions were already discussed in a previous chapter. From the topic in the preceding section, iron is more efficiently removed as ferric hydroxide. The natural iron is in the form of Fe(II), so this ferrous must therefore oxidize to the ferric form in order to precipitate as the ferric hydroxide, if, in fact, the iron is to be removed in the ferric form. In Chapter 12, this was done using the dissolved oxygen that is relatively abundant in...

Hydraulic Mixers

Hydraulic mixers are mixers that use the energy of a flowing fluid to create the power dissipation required for mixing. This fluid must have already been given the energy before reaching the point in which the mixing is occurring. What needs to be done at the point of mixing is simply to dissipate this energy in such a way that the correct value of G for effective mixing is attained. The hydraulic mixers to be discussed in this chapter are the hydraulic-jump mixer and the weir mixer. Figure 6.9...

Physical And Chemical Characteristics

The constituent physical and chemical characterizations to be discussed include the following turbidity (physical), color (physical), taste (physical) temperature (physical), chlorides (chemical), fluorides (chemical), iron and manganese (chemical), lead and copper (chemical), nitrate (chemical), sodium (chemical), sulfate (chemical), zinc (chemical), biochemical oxygen demand (chemical), solids (physical), pH (chemical), chemical oxygen demand (chemical), total organic carbon (chemical),...

Miscellaneous Flow Meters

According to Faraday's law, when a conductor passes through an electromagnetic field, an electromotive force is induced in the conductor that is proportional to the velocity of the conductor. In the actual application of this law in the measurement of the flow of water or wastewater, the salts contained in the stream flow serve as the conductor. The meter is inserted into the pipe containing the flow just as any coupling would be inserted. This meter contains a coil of wire placed around and...

Q Aeration Absorption and Stripping

Aeration, absorption, and stripping are unit operations that rely on flow of masses between phases. When a difference in concentration exists between two points in a body of mass, a flow of mass occurs between the points. When the flow occurs between two phases of masses, a transfer of mass between the phases is said to occur. This transfer of mass between phases is called mass transfer. Examples of unit operations that embody the concept of mass transfer are distillation, absorption,...

Absorption And Stripping

As mentioned before, aeration is absorption. Thus, the discussions that follow apply equally to aeration (and air stripping). More specifically, the following discussions address the sizing of absorption and stripping towers. 9.6.1 Sizing of Absorption and Stripping Towers Absorption and stripping are reverse processes to each. Thus, discussing one is the same as discussing the other. Two design parameters required for the design of absorption towers are the cross section and the height. The...

Two Form Of Giardia Found In Stool

Image Organism Found Stool

FIGURE 2.7 Life-reproductive cycle of a virus as illustrated by a T-even bacteriophage infecting a bacterial cell (a) dormancy, (b) adsorption, (c) penetration, (d) replication of new proteins and nucleic acids, (e) maturation, and (f) release and bursting of hold cell. Protozoa move through the use of the pseudopod or the use of the cilia and flagella. In pseudopodic movement, the ectoplasm flows inside the cell toward the direction of motion. As the mass of ectoplasm moves, the rear of the...

Colloid Behavior

Much of the suspended matter in natural waters is composed of silica, or similar materials, with specific gravity of 2.65. In sizes of 0.1 to 2 mm, they settle rapidly however, in the range of the order of 10-5 mm, it takes them a year, in the overall, to settle a distance of only 1 mm. And, yet, it is the particle of this size range that causes the turbidity and color of water, making the water objectionable. The removal of particles by settling is practical only if they settle rapidly in the...

Re 0075702997 597 105 88 104

Tema Type Bem Heat Exchanger

From c of Figure 3.5, at d D 75 150 0.5, K 1.02 therefore, 2(9.81)(26000) nmo 3. nmi 3, 0.032 m s 0.031 m s Therefore, design values approach diameter 150 mm, throat diameter 75 mm, Figure 3.6 shows the plan and elevation of a Parshall flume. As indicated, the flow enters the flume through a converging zone, then passes through the throat, and out into the diverging zone. For the flume to be a measuring flume, the depth somewhere at the throat must be critical. The converging and the subsequent...

Effect of Temperature

We have learned from previous chapters that equilibrium and reaction constants are affected by temperature. The length of time that a disinfection process proceeds is a function of the constants of the underlying reaction between the microorganism and the disinfectant thus, it must also be a function of temperature. The variation of the contact time to effect a given percentage kill with respect to temperature can therefore be modeled by means of the Van't Hoff equation. This equation was...

Acknowledgments

Eckenrode, former Publisher, Environmental Science & Technology, Technomic Publishing Company, Inc. Dr. Eckenrode was very thorough in determining the quality, timeliness, and necessity of the manuscript. It was only when he was completely satisfied through the strict peer review process that he decided to negotiate for a contract to publish the book. Additionally, I acknowledge Brian Kenet and Sara Seltzer Kreisman at CRC Press. This book was written...

Design of Chlorination Unit Operations Facilities

Important parameters to be considered in the design of chlorination unit operations facilities should include chlorine feeders, dosage control, chlorine injection and initial mixing, contact time and chlorine dosage, and maintenance of self-cleaning velocities through the chlorine contact tank. Each of these will be discussed in succession. Chlorine feeders. Chlorine feeders may be categorized as feeders for chlorine gas and feeders for hypochlorite solutions. Schematics of chlorine gas feeder...

Unit Operations in Ozonation

In its simplest form, the unit operations of ozonation involve the production of ozone and the mechanics of dissolving and mixing the ozone in the water or wastewater. The unit operations of dissolving and mixing have already been discussed in Part II of this book. The design of the contact tank is similar to that of chlorination, the contact time and dosage being best determined by a pilot plant study. As mentioned before, a contact time of 20 min is not unreasonable, and a residual of 0.4 mg...

Safe drinking water act

The codification of the Safe Drinking Water Act is found in Title 42, The Public Health and Welfare. The chapters of this title range from Chapter 1 to Chapter 139. Chapter 139, the last chapter, is Volunteer Protection. Chapter 1, The Public Health Service, was repealed and renamed as Chapter 6A, but The Public Health Service was retained as the chapter title. Subchapter XII of Chapter 6A is Safety of Public Water Systems this is the Safe Drinking Water Act, which, as passed...

Appendices and Index

Appendix 1 Density and Viscosity of Water Appendix 2 Atomic Masses of the Elements Based on C-12 Appendix 3 Saturation Values of Dissolved Oxygen Exposed to Saturated Atmosphere at One Atmosphere Pressure at Given Temperatures Appendix 5 Sample Drinking Water VOCs Appendix 6 Sample Drinking Water SOCs and IOCs Appendix 7 Secondary MCLs for a Number of Substances Appendix 8 Some Primary Drinking-Water Criteria Appendix 9 Some Secondary Drinking-Water Criteria The background prerequisites for...

Other Disinfection Formulas

The literature reveals other disinfection formulas. These include Chick's law for contact time, modifications of Chick's law, and relationship between concentration of disinfectant and concentration of microorganisms reduced in a given percentage kill. Chick's law and its modification called the Chick-Watson model, however, are not useful formulas, because they do not incorporate either the concentration of the disinfectant that is needed to kill the microorganisms or the incorporation of the...

Disinfection Using Ultraviolet Light

Water, air, and foodstuff can be disinfected using ultraviolet light, UV. This radiation destroys bacteria, bacterial spores, molds, mold spores, viruses, and other microorganisms. Radiation at a wavelength of around 254 nm penetrates the cell wall and is absorbed by the cell materials including DNA and RNA stopping cell replication or causing death. The use of UV radiation for disinfection dates back to the 1900s when it was used to a limited extent in disinfecting water supplies. The...

Cake Filtration

Sludges may be reduced in volume by using the unit operation of dewatering to remove excess water. In dewatering using a vacuum (such as using a vacuum filter) or the plate-and-frame press, a cake is formed on the surface of the filter cloth. Thus, these processes of dewatering may be called cake filtration. In cake filtration, the flow of the filtrate in its most elementary form, may be considered as through a tightly packed bank of small crooked tubes across the cake. The rightmost drawing of...

Water Stabilization

As mentioned in Chapter 10 on water softening, as long as the concentrations of CaCO3 and Mg(OH)2 exceed their solubilities, the solids may continue to precipitate. This condition can cause scale to form, a solid that deposits due to precipitation of ions in solution. To prevent scale formation, the water must be stabilized. A water is said to be stable when it neither dissolves nor deposits precipitates. If the pH is high, stabilization may be accomplished using one of several acids or using...

Flow Meters

Rectangular Weir Figure

Flow meters are devices that are used to measure the rate of flow of fluids. In wastewater treatment, the choice of flow meters is especially critical because of the solids that are transported by the wastewater flow. In all cases, the possibility of solids being lodged onto the metering device should be investigated. If the flow has enough energy to be self-cleaning or if solids have been removed from the waste-water, weirs may be employed. Venturi meters and critical-flow flumes are well...

Pneumatic Mixers

Bubble Dissipation

Diffused aerators may also be used to provide mixing. The difference in density between the air bubbles and water causes the bubbles to rise and to quickly attain terminal rising velocities. As they rise, these bubbles push the surrounding water just as the impeller in rotational mixers push the surrounding water creating a pushing force. This force along with the rising velocity creates the power of mixing. It is evident that pneumatic mixing power is a function of the number of bubbles...

Natural Occurrences Of Iron And Manganese

Iron and manganese have the electronic configurations of Ar 3d 64s2 and Ar 3d 54s2, and are located in Groups VIIIB and VIIB of the Periodic Table, respectively. They are both located in the fourth period. Ar means that these elements have the electronic configuration of the noble gas argon. The letters d and s refer to the d and s orbitals the superscripts indicate the number of electrons that the orbitals contain. Thus, the d orbital of iron contains 6 electrons and that of manganese contains...

Physicalchemical treatment of water and wastewater

What is physical-chemical treatment of water and wastewater The dictionary defines physical as having material existence and subject to the laws of nature. Chemical, on the other hand, is defined as used in, or produced by chemistry. Being used in and produced by chemistry implies a material existence and is subject to the laws of nature. Thus, from these definitions, chemical is physical. The fact that chemical is physical has not, however, answered the question posed. To explore the question...

Backwashing Head Loss In Granular Filters

In the early development of filters, units that had been clogged were renewed by scraping the topmost layers of sand. The scraped sands were then cleaned by sand washers. In the nineteenth century, studies to clean the sand in place, rather than taking out of the unit, led to the development of the rapid-sand filter. The method of cleaning is called backwashing. In backwashing, clean water is introduced at the filter underdrains at such a velocity as to expand the bed. The expansion frees the...

Carbon Adsorption

Solids are formed because of the attraction of the component atoms within the solid toward each other. In the interior of a solid, attractive forces are balanced among the various atoms making up the lattice. At the surface, however, the atoms are subjected to unbalanced forces the ones toward the interior are attracted, but the ones at the FIGURE 8.7 Raw carbon material on the left transforms to the carbon on the right after activation. FIGURE 8.7 Raw carbon material on the left transforms to...

Chlorine Disinfectants

The first use of chlorine as a disinfectant in America was in New Jersey in the year 1908 (Leal, 1909). At that time George A. Johnson and John L. Leal chlorinated the water supply of Jersey City, NJ. The principal compounds of chlorine that are used in water and wastewater treatment are the molecular chlorine (Cl2), calcium hypochlorite Ca(OCL)2 , and sodium hypochlorite NaOCl . Sodium hypochlorite is ordinary bleach. Chlorine is a pale-green gas, which turns into a yellow-green liquid when...

A Removal of Phosphorus by Chemical Precipitation

Phosphorus is a very important element that has attracted much attention because of its ability to cause eutrophication in bodies of water. For example, tributaries from as far away as the farmlands of New York feed the Chesapeake Bay in Maryland and Virginia. Because of the use of phosphorus in fertilizers for these farms, the bay receives an extraordinarily large amount of phosphorus input that has triggered excessive growths of algae in the water body. Presently, large portions of the bay...

Free Energy

Will a certain food provide energy when utilized by microorganisms If the answer is yes, then the food will be eaten and if it is in a wastewater, the wastewater will be cleaned up. The answer to this question can now be quantified by the combination of the concept of enthalpy and entropy. This combination is summed up in a term called free energy. Free energy G is defined as Because H is an energy content and S is a wasted energy, G represents the useful energy (or, alternatively, the maximum...

Time of Contact and Intensity of Disinfectant

In the context of how we use the term, intensity refers to the intensive property of the disinfectant. Intensive properties, in turn, are those properties that are independent of the total mass or volume of the disinfectant. For example, concentrations are expressed as mass per unit volume the phrase per unit volume makes concentration independent of the total volume. Hence, concentration is an intensive property and it expresses the intensity of the disinfectant. Another intensive property is...

Oxidationreduction Reactions Of Nitrogen Foods

Life processes involve electron transport. Specifically, the mitochondrion and the chloroplast are the sites of this electron movement in the eucaryotes. In the procary-otes, this function is embedded in the sites of the cytoplasmic membrane. As far as electron movement is concerned, life processes have similarity to a battery cell. In this cell, electrons move because of electrical pressure, the voltage difference. By the same token, electrons move in an organism because of the same electrical...

To Remove Or Not To Remove Nitrogen

The formula of algae is (CH2O)106(NH3)16H3PO3 (Sincero and Sincero, 1996). Gleaning from this formula, to curtail its production in any water body such as the Chesapeake Bay, it is necessary to control only any one of the elements of nitrogen, phosphorus, oxygen, hydrogen, or carbon. It must be stressed that only one needs to be controlled, because absence of any element needed for the construction of the algal body prevents the construction of the body. This is analogous to a car. To disable...

Effect Of The Ksps On The Precipitation Of Phosphorus

The worst of the precipitants are the ferric salts. Compare Ksp,Fe( OH)3 . 1.1(10-3D) and Kjp,FepO 10-219. These two Ksp's produce comparable concentrations of the ferric ion to precipitate either Fe(OH)3 or FePO4. Thus, at high pH conditions, the phosphate ion would have a big competitor in the form of the hydroxide ion. An Fe3+ available in solution is grabbed by the OH- ion to form the ferric hydroxide, leaving less amount of Fe3+ to precipitate ferric phosphate. The ferric salts are,...

Comments On The Optimum pH Ranges

When the ferric salts are used to precipitate FePO4, the PO - ion must compete with the OH- ion. When the pH is high, there will be a large concentration of the OH-and the phosphate ion can lose the competition and fail to precipitate Fe(OH)3 may precipitate instead of FePO4. Thus, to precipitate the phosphate ion, the concentration of OH- must be suppressed. This is done by adding more H +, which reacts with the OH-. If the OH- is busy satisfying the hydrogen ion, the Fe3+ ion is now available...

Chemical Reaction Of The Phosphate Ion With The Ferric Salts

The chemical reaction to precipitate the phosphate ion as ferric phosphate is shown next FePO41 Fe3+ + P 4- Ksp po4 10-219 As in the case of precipitation using alum and precipitation using lime, the phosphate ion produces the set of reactions given by Eqs. (14.2) through (14.4). Let spPO Feiii be the species in solution containing the PO4 species of the orthophosphates using the ferric salts FeCl3 and Fe2(SO4)3 as the precipitants. Again, spPO FeIII will be the same as given by Equation (14.5)...