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FIGURE 7.10 Free-body diagram of a cylinder (pipe) of fluid and bed material. element in the downward z direction p is the fluid mass density v is the component fluid element velocity in the z direction and t is the time. Since the fluid is in the interstitial spaces, dV needs to be multiplied by the porosity to get the fluid volume. The law of inertia states that a body at rest will remain at rest and a body in uniform motion will remain in this uniform motion unless acted upon by an...

Chemical Reactions Using Sulfur Dechlorinating Agents

Irrespective of the type of residual chlorine present, all the species can be represented by a single species by means of the equivalence of chemical reactions. It is convenient to use HOCl to represent all these species. Thus, the chemical reactions using sulfur dioxide as the dechlorinating agent with HOCl representing the residual chlorine species are as follows Sodium sulfite is Na2SO3. Thus, the chemical reactions using sodium sulfite as the dechlorination agent are as follows Na2SO3 + H2O...

Carbonate Equilibria

The carbonate equilibria is a function of the ionic strength of water, activity coefficient, and the effective concentrations of the ionic species. The equilibrium coefficients that are calculated from the species concentrations are a function of the temperature. This functionality of the coefficients can, in turn, be calculated using the Van't Hoff equation, to be addressed later. One of the major cations that can form scales as a result of the instability of water is calcium. Calcium plays an...

Pumping

Pumping is a unit operation that is used to move fluid from one point to another. This chapter discusses various topics of this important unit operation relevant to the physical treatment of water and wastewater. These topics include pumping stations and various types of pumps total developed head pump scaling laws pump characteristics best operating efficiency pump specific speed pumping station heads net positive suction head and deep-well pumps and pumping station head analysis. 4.1 pumping...

Problems

10.1 Write the balanced chemical reaction in the softening of calcium bicarbonate using lime. 10.2 Write the balanced chemical reaction in the softening of calcium sulfate using soda ash. 10.3 The total mass of calcium carbonate solids produced from softening a bicarbonate of calcium using lime is 500 g. Calculate the original number of equivalents of the bicarbonate. Calculate the original number of moles of the bicarbonate. 10.4 The total mass of calcium carbonate solids produced from...

Bibliography

Pretreatment of the municipal wastewater feed for reverse osmosis plants, Desalination. 109, 2, 211-223. Abuzaid, N. S. and G. Nakhla (1997). Predictability of the homogeneous surface diffusion model for activated carbon adsorption kinetics formulation of a new mathematical model, J. Environment. Science Health, Part A Environment. Eng. Toxic Hazardous Substance Control. 32, 7, 1945-1961. Alawadhi, A. A. (1997). Pretreatment plant design Key to a successful...

[ sp po ai 3 3

Ypo4YaiI Al + Yhpo4-hpo4Yai Al + Yh2po4-h2po4-hpo4Yai Al + YP , YAl, YH, Yhp , and yh2p 4 are, respectively, the activity coefficients of the phosphate, aluminum, hydrogen, hydrogen phosphate, and dihydrogen phosphate ions. Khp , Khp , and are, respectively, the equilibrium constants of the hydro gen phosphate and dihydrogen phosphate ions and phosphoric acid. Al3+ needs to be eliminated for the equation to be expressed solely in terms of H+ . When alum is added to water, it will unavoidably...

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...

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...

Table

Solubility Product Constants of Respective Solids at 25 C Ca3 ( PO4 )2( s) 3Ca2a(q) + 2PO2a(q) Coagulation, iron removal, corrosion Coagulation, iron removal, corrosion From A. P. Sincero and G. A. Sincero (1996). Enviromental Engineering A Design Approach. Prentice Hall, Upper Saddle River, NJ, 42. Another important application of the equilibrium constant K in general, Equation (11) , is in the coagulation treatment of water using alum, Al2(SO4)3-14 H2O. (The 14 actually varies from 13 to 18.)...

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...

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...

Methods Of Disinfection And Disinfectant Agents Used

Generally, two methods of disinfection are used chemical and physical. The chemical methods, of course, use chemical agents, and the physical methods use physical agents. Historically, the most widely used chemical agent is chlorine. Other chemical agents that have been used include ozone, ClO2, the halogens bromine and iodine and bromine chloride, the metals copper and silver, KMnO4, phenol and phenolic compounds, alcohols, soaps and detergents, quaternary ammonium salts, hydrogen peroxide,...

Age of the Microorganism

The effectiveness of a disinfectant also depends upon the age of the microorganism. For example, young bacteria can easily be killed, while old bacteria are resistant. As the bacterium ages, a polysaccharide sheath is developed around the cell wall this contributes to the resistance against disinfectants. For example, when using 2.0 mg L of applied chlorine dosage, for bacterial cultures of about 10 days old, it takes 30 min of contact time to produce the same reduction as for young cultures of...

Plant Types For Hardness Removal

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...

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...

J1

FIGURE 3.9 Long-term extreme sewage flow and BOD pattern in a sewage treatment plant. difficulty imposed by these extreme variations, an equalization basin should be provided. Equalization is a unit operation applied to a flow for the purpose of smoothing out extreme variations in the values of the parameters. In order to produce an accurate analysis of equalization, a long-term extreme flow pattern for the wastewater flow over the duration of a day or over the duration of a suitable cycle...

R Screening Settling and Flotation

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...

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...

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...

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...

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),...

Po4 H hpo2

HPO2- PO3-+ H+ Khpo4 10-12 3 (14.2) H2PO- HPO4- + H+ Kh2po4 10-7 2 (14.3) H3PO4 H2PO- + H+ Kh3po4 10-21 (14.4) Let sp p Al represent the species in solution containing the PO4 species of the orthophosphates, using alum as the precipitant. Therefore, spPOAl PO3- + HPO2- + H2PO- + H3PO4 (14.5) Express Equation (14.5) in terms of PO33- using Eqs. (14.2) through (14.4). This will enable spP Al to be expressed in terms of Al3+ using Equation (14.1) and Kjp,AlPO . Proceed as follows HPO4- HOT W Q 1...

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...

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...

Derivation of design flows of wastewaters

The accurate determination of wastewater flows is the first fundamental step in the design of wastewater facilities. To ensure proper design, accurate and reliable data must be available. This entails proper selection of design period, accurate population projection, and the determination of the various flow rates. Again, the discussion that follows addresses the particulars of the community however, parallel concerns should also be directed to the determination of industrial wastewaters and...

Pneumatic Mixers

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...

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,...

Cap

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...

Unit operations and unit processes

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...

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...

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...