Review Of Equipment Options

Although we have discussed the major hardware, it is still worthwhile reviewing these in relation to the major classes of clarifier processes. The major categories of this process are Conventional clarification is the simplest form of the process. It relies on the use of a large tank or horizontal basin for sedimentation of flocculated solids. Figure 21 provides a sketch of the basic configuration. The basin normally contains separate chambers for rapid mix and settling. The first two steps...

Algae Protozoa And Multicellular Animals

Algae are microscopic photosynthetic plants. They are among the simplest plant forms, having neither roots, stems, nor leaves. Algae typically range from single-cell entities (which impart a green color to surface waters) to branched forms that can be seen by the naked eye. The latter often appear as attached green slime on surface bodies of water. Diatoms refers to singlecelled algae which are housed in silica shells. The blue-green algae generally associated with water pollution are...

Evaluating The Merits Of Carbon Adsorption

Where activated carbon is a potential treatment technology, the first evaluation step is generally to run simple isotherms to determine feasibility. Isotherms are based on batch treatment where impurities reach equilibrium on available carbon surface. While such tests provide an indication of the maximum amount of impurity a GAC can adsorb, it cannot give definite scale up data for a GAC operation due to several factors In a GAC column, dynamic adsorption occurs along an adsorption wave front...

An Overview Of The Options

The solids that result from wastewater treatment may contain concentrated levels of contaminants that were originally contained in the wastewater. A great deal of concern must be directed to the proper disposal of these solids to protect environmental considerations. Failure to do this may result in a mere shifting of the original pollutants in the waste stream to the final disposal site where they may again become free to contaminate the environment and possibly place the public at risk. A...

Application To Subsurface Treatment

The application of adsorption to contaminated groundwater remediation is not only an important subject, but one we could expand upon into several volumes unto itself. At best, all we can do is try to provide a concise overview in this volume. When we discuss this subject, we cannot separate groundwater treatment from subsurface soil treatment, as the two often go hand in hand. Furthermore, carbon adsorption is not the only technology applicable to subsurface (soil and water) remediation, but it...

Applications

Applications of carbon adsorption go far beyond conventional water treatment applications which we will discuss in a general sense shortly. Table 8 provides a summary of the key applications of carbon adsorption systems for liquid phase applications. Table 8. Liquid Phase Applications of Carbon Adsorption. Table 8. Liquid Phase Applications of Carbon Adsorption. Granular activated carbons (GAC) installed in rapid gravity filters Removal of dissolved organic contaminants, control of taste and...

Biosolids Regulations

EPA has developed comprehensive federal biosolids use and disposal regulations , which are organized in five parts. These parts are general provisions, land application, surface disposal, pathogens and vector attraction reduction, and incineration. Parts of the regulations which address standards for land application, surface disposal, and incineration practices consist of general requirements, pollutant limits, operational requirements, management practices, frequency of monitoring,...

C

Cake The solids discharged from a dewatering apparatus. Calendering A process by which fabric or wire is passed through a pair of heavy rolls to reduce thickness, to flatten the intersections of the threads wires and to control air permeability. Rolls are heated when calendering synthetic materials. Carbonized threads Nylon or polyester therads that have been treated to include varrying degrees of carbon. Cation exchange capacity The ability of a soil or other solid to exchange cations...

Cake Filtration Equipment

There are three general categories of filters used. These are Clarifying Filters - Usually cartridge-type or bag filters designed to remove small amounts of particles from a solution. Laboratory personnel typically use these types of filters. These types of filters are also used for 0.2 micron terminal sterilization. Cross low Filters - These are usually membrane-type filters used for ultrafiltration. In the field of biotechnology these types of filters are used in ultrafiltration devices used...

Charcoal

Charcoal, whether animal or vegetable, when used as a filter medium, is required to perform the dual services of decoloring or adsorbing and filtering. The char filters used in the sugar industry are largely decoloring agents and the activated carbons used in water clarification are for deodorizing and removal of taste. There are many types of charcoal in use as filter media, ranging from ordinary wood char to specially prepared carbons. Activated carbon in particular is very versatile as a...

Chemistry Of Bromine Chloride

Various organic and inorganic species that act as reducing agents react with and destroy free halogen residuals during interaction with microorganisms (see Figure 2.13 for examples of competitive reactions). Competitive reactions depend on the reactivity of the chemical species, temperature, contact time, and pH. The quality of the effluent and the method of adding the disinfectant also help determine the specific reaction pathways. Bromine chloride is about 40 percent dissociated into bromine...

Chlorine Contact Tanks

The configuration of contact tanks can result in appreciable differences between actual and theoretical contact times. Contact times and germicidal efficiency depend on a number of parameters, the most important being the mixing characteristics of the basin. Proper designs must account for possible flow pattern elimination via short circuiting, acceptable dosage rates, optimumpH range, and upstream removal Rapid dispersement of chlorine at the addition point increases chlorine contact and...

Coal And Coke

Coal (hard) and coke are used in water filtration, primarily for the removal of coarse suspensions, care being taken to prevent them from scouring or washing away, because of their relative lightness and fine division. Coal is principally composed of carbon, and is inert to acids and alkalies. Its irregular shapes are advantageous at times over silica sand. Though inert to acids, sand is affected by alkalies, and its spherical particle shape allows deeper solids penetration and quicker clogging...

Combustible Offgases

RESIDUE (CAN BE I* TO XK COMBUSTIBLE ICI STARVID-AIR COMBUSTION (OXYGEN DEFICIENT) Figure 27. Basic elements of high temperature processes. The primary combustible elements in sludge and in most available supplemental fuels are fixed carbon, hydrogen, and sulfur. Because free sulfur is rarely present in sewage sludge to any significant extent and because sulfur is being limited in fuels, the contributions of sulfur to the combustion reaction can be neglected in calculations without compromising...

Comparing Mechanical Dewatering Technologies

As we see from the above descriptions there are a variety of technologies from which to select from for sludge dewatering operations. Each has its own set of advantages, disadvantages, and limitations in operating ranges. Selection greatly depends on the volumes and nature of the sludge. Table 3 provides a relative comparison between the principle mechanical dewatering techniques. Table 3. Comparison of the Advantages and Disadvantages of Mechanical Thickening Technologies. Table 3. Comparison...

Conditions That Impact On Performance

Adsorption usually increases as pH and temperature decrease. Chemical reactions and forms of chemicals are closely related to pH and temperature. When pH and temperature are lowered many organic chemicals are in a more adsorbable form. The adsorption process is also influenced by the length of time that the AC is in contact with the contaminant in the water. Increasing contact time allows greater amounts of contaminant to be removed from the water. Contact is improved by increasing the amount...

Cone Of Flowing Solids

Illustrates angle of internal friction. Figure 4. Illustrates angle of internal friction. The angle of repose is sensitive to the conditions of the supporting surface the smoother the surface, the smaller the angle. The angle may also be reduced by vibrating the supporting surface. When handling slow moving materials having large angles of repose, well-designed, bunkers and hoppers are provided with highly polished internal surfaces and low amplitude vibrators. The angle is also...

Constant Pressure Differential Filtration

When the space above the suspension is subjected to compressed gas or the space under the filter plate is under a vacuum, filtration proceeds under a constant pressure differential (the pressure in the receivers is constant). The rate of filtration decreases due to an increase in the cake thickness and, consequently, flow resistance. A similar filtration process results from a pressure difference due to the hydrostatic pressure of a suspension layer of constant thickness located over the filter...

Constantpressure Drop Filtration

Constant-pressure drop filtration can result in saturation or blockage of the filter medium. The network of pores within the filter medium can become blocked because of one or a combination of the following situations Pores may become blocked by the lodging of single particles in the pore passage. Gradual blockage can occur due to the accumulation of many particles in pore passages. Blockage may occur during intermediate-type filtration. Proper filter medium selection is based on understanding...

Constantrate Filtration

When sludge is fed to a filter by a positive-displacement pump, the rate of filtration is nearly constant (i.e., dV dx constant). During constant-rate filtration, the pressure increases with an increase in cake thickness. Therefore, the principal variables are pressure and filtrate volume, or pressure and filtration time. Equation 9 is the principal design relation, which may be integrated for a constant-rate process. The derivative, dV dt, may be replaced simply by V x The ratios in...

Contact Time pH And Temperature Effects

Hypochlorous acid and hypochlorite ion are known as free available chlorine. The chloramines are known as combined available chlorine and are slower than free chlorine in killing microorganisms. For identical conditions of contact time, temperature, and pH in the range of 6 to 8, it takes at least 25 times more combined available chlorine to produce the same germicidal efficiency. The difference in potency between chloramines and HOC1 can be explained by the difference in their oxidation...

Contaminant Properties

Organic contaminants in the subsurface can be present as a separate nonaqueous phase liquid, dissolved in the aqueous phase, in the vapor phase in the soil gas, partitioned into the soil organic matter, or adsorbed onto the solid mineral phase. The relative amount of the contaminant in each of these phases is determined largely by the properties of the contaminant. Generally, the most important property of the soil in determining the distribution of contaminants is the soil organic matter,...

Disinfection By Chlorination

Disinfection has received increased attention over the past several years from regulatory agencies through the establishment and enforcement of rigid bacteriological effluent standards. In upgrading existing wastewater treatment facilities, the need for improved disinfection as well as the elimination of odor problems are frequently encountered. Adequate and reliable disinfection is essential in ensuring that wastewater treatment plants are both environmentally safe and aesthetically acceptable...

Disinfection With Bromlne Chlorine

In chlorination, chlorine's reaction with ammonia forms chloramines, greatly reducing its bactericidal and virucidal effectiveness. The biocidal activity of monochloramine is only 0.02 - 0.01 times as great as that of free chlorine. Typical ammonia concentrations found in secondary sewage range from 5-20 ppm, which is about an order of magnitude greater than the amount needed to form monochloramine from normal chlorination dosages (which requires about 5-10 ppm). Therefore, monochloramine is...

Disinfection With Iodine Compounds

Two interhalogens having strong disinfecting properties are iodine monochloride (IC1) and iodine bromide (IBr). Iodine monochloride has found use as a topical antiseptic. It may be complexed with nonionic or anionic detergents to yield bactericides and fungicides that can be used in cleansing or sanitizing formulations. These generally have a polymer structure which establishes its great stability, increased solubility, and lower volatility. By reducing the free halogen concentration in...

Dynamics Of Cake Formation

Filtration operations are capable of handling suspensions of varying characteristics ranging from granular, incompressible, free-filtering materials to slime-like compositions, as well as finely divided colloidal suspensions in which the cakes are incompressible. These latter materials tend to contaminate or foul the filter medium. The interaction between the particles in suspension and the filter medium determines to a large extent the specific mechanisms responsible for filtration. In...

Effects Of Heterogeneity Nonuniforms And Anisotropy On Permeability

Heterogeneity, nonuniformity and anisotropy are terms which are defined in the volume-average sense. They may be defined at the level of Darcy's law in terms of permeability. Permeability, however, is more sensitive to conductance, mixing and capillary pressure than to porosity. Heterogeneity, nonuniformity and anisotropy are defined as follows. On a macroscopic basis, they imply averaging over elemental volumes of radius e about a point in the media, where e is sufficiently large that Darcy's...

Electron Beam

The idea of using ionizing radiation to disinfect water is not new. Ionizing radiations can be produced by various radioactive sources (radioisotopes), by X-ray and particle emissions from accelerators, and by high-energy electrons. The advances in reliable, relatively low-cost devices for producing high-energy electrons are more significant. Unlike X-rays and gamma rays, electrons are rapidly attenuated. The maximum range of a 1-million-volt electron is about 4 m in air and about 5 cm in...

Equipment And Operation

Ion exchange processing can be accomplished by either a batch method or a column method. In the first method, the resin and solution are mixed in a batch tank, the exchange is allowed to come to equilibrium, then the resin is separated from solution. The degree to which the exchange takes place is limited by the preference the resin exhibits for the ion in solution. Consequently, the use of the resins exchange capacity will be limited unless the selectivity for the ion in solution is far...

Equipment Selection Methodology

Equipment selection is seldom based on rigorous equations or elaborate mathematical models. Where equations are used, they function as a directional guide in evaluating data or process arrangements. Projected results are derived most reliably from actual plant operational data and experience where duplication is desired from standards set up where there are few variations from plant to plant, so that results can be anticipated with an acceptable degree of confidence (as in municipal water...

Filter Aids

Filter aids as well as flocculants are employed to improve the filtration characteristics of hard-to-filter suspensions. A filter aid is a finely divided solid material, consisting of hard, strong particles that are, en masse, incompressible. The most common filter aids are applied as an admix to the suspension. These include diatomaceous earth, expanded perlite, Solkafloc, fly ash, or carbon. Filter aids build up a porous, permeable, and rigid lattice structure that retains solid particles and...

Filter Media Selection Criteria

Due to the wide variety of filter media, filter designs, suspension properties, conditions for separation and cost, selection of the optimum filter medium is complex. Filter media selection should be guided by the following rule a filter medium must incorporate a maximum size of pores while at the same time providing a sufficiently pure filtrate. Fulfilment of this rule invokes difficulties because the increase or decrease in pore size acts in opposite ways on the filtration rate and solids...

Filtration Dynamics

When a suspension of solids passes through a porous media, the solid particles are collected on the feed side of the plate while the filtrate is forced through the media and carried away on the leeward side. A filter medium is, by nature, inhomogeneous, with pores nonuniform in size, irregular in geometry and unevenly distributed over the surface. Since flow through the medium takes place through the pores only, the micro-rate of liquid flow may result in large differences over the filter...

Final Comments And Evaluating Economics

A great deal of our discussions have focused on municipal treatment applications, particularly in this chapter. However, most if not all of the principles throughout the book are readily applicable to industrial water treatment applications. Try to approach each water treatment assignment from a first principles standpoint, and then develop design-specific cases with as much information on the chemistry, physical and thermodynamic properties of the wastewater stream and sludge to be handled. In...

Flocculation And Filtration Together

The sand filtration process is normally comprised of a clarification chain including other unit operations which precede filtration in the treatment sequence and can not be conceived of completely independent of the filtration stage. The conventional treatment scheme consists of coagulation-flocculation-settling followed by filtration. When the preceding process, in this case flocculation and or settling, becomes insufficient, subsequent rapid filtration can be used to ensure a high quality of...

Fouling Considerations

A critical consideration with UF technology is the problem of fouling._Foulants interfere with UF by reducing product rates- sometimes drastically-and altering membrane selectivity. The story of a successful UF application is in many respects the story of how fouling was successfully controlled. Fouling must be considered at every step of UF process development in order to achieve success. When we talk about this subject, the term foulant or foulant layer comes to the forefront. Foulant, or...

Fundamentals Of Fluid Filtration A Technical Primer

2nd edition 1998 ISBN 0-927188-01-5 By Peter R. Johnston Softcover, 136 pages . 29. This book is written as the book one wants to read when first starting the study of filtration. This book is intended for the person who has some technical background outside of filtration, and who now wants to get his feet wet in this subject This book is also for the old filtration hand who, while he has some experience in some special field of filtration, may now want to step back and see a larger view. And...

Fungi And Molds

Fungi are microscopic nonphotosynthetic plants which include in their classification yeast and molds. Yeasts have a commercial value as they are used for fermentation operations in distilling and brewing. When anaerobic conditions exist, yeasts metabolize sugar, manufacturing alcohol from the synthesis of new cells. Alcohol is not manufactured under aerobic conditions and the yield of new yeast cells is greater. Filamentous forms of fungi are molds. These best resemble higher orders of plant...

General Properties Of Loose And Granular Media

The physical properties of loose and granular media are important, both from the standpoint of the operation of the filtration device, but also from the standpoints of feeding and storing these materials in bins and silos. These considerations are equally important and quite pertinent to dry chemicals that are used as filtration aids (Chapter 3). In a general sense, loose solid matter is comprised of large numbers The ratio of pmaJpmin can be as high as 1.52 depending on the material....

Granular Media Filtration

Granular media filtration is used for treating aqueous waste streams. The filter media consists of a bed of granular particles (typically sand or sand with anthracite or coal). The anthracite has adsorptive characteristics and hence can be beneficial in removing some biological and chemical contaminants in the wastewater. This material may also be substituted for activated charcoal. The bed is contained within a basin and is supported by an underdrain system which allows the filtered liquid to...

Gravity Sedimentation Thickeners And Clarifiers

Sedimentation involves the removal of suspended solid particles from a liquid stream by gravitational settling. This unit operation is divided into thickening, i.e., Figure 4. Cross-sectional view of a thickener. Figure 4. Cross-sectional view of a thickener. Thickeners can be operated in a countercurrent fashion. Applications are aimed at the recovery of soluble material from settleable solids by means of continuous countercurrent d cantation (CCD). The basic scheme involves streams of liquid...

How Ion Exchange Works

Ion exchangers are materials that can exchange one ion for another, hold it temporarily, and then release it to a regenerant solution. In a typical demineralizer, this is accomplished in the following manner The influent water is passed through a hydrogen cation-exchange resin which converts the influent salt (e.g., sodium sulfate) to the corresponding acid (e.g., sulfuric acid) by exchanging an equivalent number of hydrogen (H +) ions for the metallic cations (Ca+ Mg+2, Na+). These acids are...

How Particles Settle

If a particle at rest (with mass 'm' and weight 'mg') begins to fall under the influence of gravity, its velocity is increased initially over a period of time. The particle is subjected to the resistance of the surrounding water through which it descends. This resistance increases with particle velocity until the accelerating and resisting forces are equal. From this point, the solid particle continues to fall at a constant maximum velocity, referred to as the terminal velocity, ut. You should...

How Water Becomes Contaminated

The circumstances under which water becomes contaminated are as varied as the ways water is taken internally. It is then conceivable that almost any virus could be transmitted through the water route. The increased use of water for recreational purposes increases the incidence of human contact with bodies of water and, consequently, with waterborne viruses and bacteria. The major waterborne viruses among pathogens, and the most likely candidates for water transmission, are the picornaviruses...

Hydraulic Performance

The hydraulic performances required of the sand with slow filters are inferior to those for rapid filters. In the case of slow filters, one can use fine sand, since the average filtration velocity that is usually necessary lies in the range 2 to 5 m day. In slow filtration, much of the effect is obtained by the formation of a filtration layer, including the substances that are extracted from the water. At the early stages of the operation, these substances contain microorganisms able to effect,...

1

Ftt t Si,> cct Ce.ll lAdiilh 7 5' 0 j -3jc tria ------ 1. J -kWU'TIJ Mfii Figure 6. Range of common particle sizes (diameter) over range of UF pore size. The retention efficiency of membranes is dependent on particle size and concentration, pore size and length, porosity, and flow rate. Large particles that are smaller than the pore size have sufficient inertial mass to be captured by inertial impaction. In liquids the same mechanisms are at work. Increased velocity, however, diminishes the...

Wpf

Operational schemes of ion exchange. To be suitable for industrial use, an ion-exchange resin must exhibit durable physical and chemical characteristics which are summarized by the following properties. Functional Groups - The molecular structure of the resin is such that it must contain a macroreticular tissue with acid or basic radicals. These radicals are the basis of classifying ion exchangers into two general groups (1) Cation exchangers, in which the molecule contains acid...

Importing Biosolids From New York Case Studyl

Y., have been imported into southeastern Colorado for application to dry land wheat, grassland, and reclamation sites. The Colorado Department of Health and the EPA have issued land application permits for about 7700 ha (19,000 ac). Annual precipitation in the area averages 36 cm. Biosolids from this project were used to reclaim a 104 ha (258 ac) sand blowout on private land near Granada, Colorado. The sandy dunes began as a 12 ha (30 ac) area subject to wind...

Incineration

In all types of incinerators, the gases from combustion must be brought to and kept at a temperature of 1250 F to 1400 F. until they are completely burned. This is essential to prevent odor nuisance from stack discharge. It is also necessary to maintain effective removal of dust, fly ash and soot from the stack discharge. This may be done by a settling chamber, by a centrifugal separator, or by a Cottrell electrical precipitator. The selection depends on the degree of removal efficiency...

Industrial Water And Wastewater Treatment

The markets for ozone in industrial water and wastewater treatment are quite small. Industrial applications for ozone could grow. The use of ozone for treating photoprocessing solutions is a novel application that has been limited, but might grow. In this process, silver is recovered electrolytically then the spent bleach baths of iron ferrocyanide complexes are ozonated. Iron cyanide complexes are stable to ozonation so that the ferrous iron is merely oxidized to ferric, which is its original...

Info

Clay - The use of clay based flocculating agent(s) in conjunction with a strong metal precipitator has proven successful in many wastewater treatment applications where the objectives are aimed at metals removal. Clay based flocculants cleans the wastewater and in some cases replaces multistage conventional treatment system and saves the traditional operational difficulties of treatment with several chemicals such as metal hydroxide precipitation, coagulant, flocculants and other methods....

Introducing The Physical Treatment Methods

The following technologies are among the most commonly used physical methods of purifying water Heat Treatment - Boiling is one way to purify water of all pathogens. Most experts feel that if the water reaches a rolling boil it is safe. A few still hold out for maintaining the boiling for some length of time, commonly 5 or 10 minutes, plus an extra minute for every 1000 feet of elevation. One reason for the long period of boiling is to inactivate bacterial spores (which can survive boiling),...

Introduction

This chapter provides a summary of the governing expressions describing conventional pressure-induced filtration and a description of major equipment. Standard filtration practices refers to the most common or classical method of filtration, sometimes referred to as cake filtration. This type of filtration relies on the use of a porous bed, or more accurately - a porous media which can be cloth. With high-solids-concentration suspensions, even relatively small particles (in comparison to the...

Ion Exchange And Carbon Adsorption

Ion exchange and carbon adsorption are unrelated technologies, and often have different objectives. They are however oftentimes used in compliment to achieve Ion exchange is a reversible chemical reaction wherein an ion (an atom or molecule that has lost or gained an electron and thus acquired an electrical charge) from solution is exchanged for a similarly charged ion attached to an immobile solid particle. These solid ion exchange particles are either naturally occurring inorganic zeolites or...

Key Words

The following are key words you will run across in reading over the next several chapters. air flotation - This treatment usually follows oil-water separation. Wastewater is pressurized to 3-5 times normal atmospheric pressure in the presence of air to produce a saturated air-water solution. When this solution is released to normal pressure in the flotation unit, tiny air bubbles form throughout the liquid the same effect is observed when a bottle of pop is opened. As the air bubbles form they...

L

Frictional drag on particles in compressible cakes. The terra ps is a fictitious pressure, because the cross-sectional area A is not equal to either the surface area of the particles nor the actual contact areas In actual cakes, there is a small area of contact Ac whereby the pressure exerted on the solids may be defined as Fs Ac. Taking differentials with respect to x, in the interior of the cake, we obtain This expression implies that drag pressure increases and hydraulic pressure...

Lets Look At How A Single Particle Behaves In A

During the motion of viscous flow over a stationary body or particle, certain resistances arise. To overcome these resistances or drag and to provide more uniform fluid motion, a certain amount of energy must be expended. The developed drag force and, consequently, the energy required to overcome it, depend largely on the flow regime and the geometry of the solid body. Laminar flow conditions prevail when the fluid medium flows at low velocities over small bodies or when the fluid has a...

Lets Take A Closer Look At Sand Filters

A typical sand filter system consists of two or three chambers or basins. The first is the sedimentation chamber, which removes floatables and heavy sediments. The second is the filtration chamber, which removes additional pollutants by filtering the runoff through a sand bed. The third is the discharge chamber. The treated filtrate normally is then discharged through an underdrain system either to a storm drainage system or directly to surface waters. Sand filters are able to achieve high...

Loose Rigid Media

Filter media may also be composed of particles that are rigid in structure, but are applied in bulk loose form. That is, individual particles merely contact each other. This form has the advantage of being cheap and easy to keep clean by rearrangement of the particles. When the proper size and shape of particles are selected, the section of passage may be regulated over extremely wide limits. The disadvantages of a rigid medium in simple contact are that it can be used conveniently only in a...

Lowther Plate Generator Unit

Contactor design is important in order to maximize the ozone-transfer efficiency and to minimize the net cost for treatment. The three major obstacles to efficient ozone utilization are ozone's relatively low solubility in water, the low concentrations and amounts of ozone produced from ozone generators, and the instability of ozone. Several contacting devices are currently in use including positive-pressure injectors, diffusers, and venturi units. Specific...

Municipal Drinking Water

In the United States, Whiting, Indiana and Strasburg, Pennsylvania have used ozone in their drinking water treatment process. Other cities have run pilot studies. Ozone is used as a bleaching agent for miscellaneous items petroleum, clays, wood products, and chemical baths. It has been proposed as a bleaching agent for hair and as a disinfectant for oils and emulsions. Ozone is used to modify tryptophan and indigo plant juice. It is an important factor in colorfastness. The desulfurization of...

N

NPDES Permit National Pollutant Discharge Elimination System permit is the regulatory agency document issued by either a federal or state agency which is designated to control all discharges of pollutants from point sources into U.S. waterways. NPDES permits regulate discharges into navigable waters from all point sources of pollution, including industries, municipal wastewater treatment plants, sanitary landfills, large agricultural feed lots and return irrigation flows. Nitrification An...

National Secondary Drinking Water Regulations

National Secondary Drinking Water Regulations (NSDWRs or secondary standards) are non-enforceable guidelines regulating contaminants that may cause cosmetic effects (such as skin or tooth discoloration) or aesthetic effects (such as taste, odor, or color) in drinking water. EPA recommends secondary standards to water systems but does not require systems to comply. However, states may choose to adopt them as enforceable standards. The following table summarizes the secondary standards. Table 6....

Nonwoven Media

Nonwoven media are fabricated in the form of belts or sheets from cotton, wool, synthetic and asbestos fibers or their mixtures, as well as from paper mass. They may be used in filters of different designs, for example, in filter presses, filters with horizontal discs and rotary drum vacuum filters for liquid clarification. Most of these applications handle low suspension concentrations examples are milk, beverages, lacquers and lubricating oils. Individual fibers in nonwoven media are usually...

Operational Sequencing Considerations

The mode of operation for ion-exchange units can vary greatly from one system to the next, depending on the user's requirements. Service and regeneration cycles can be fully manual to totally automatic, with the method of regeneration being cocurrent, countercurrent, or external. The exhaustion phase is called the service run. This is followed by the regeneration phase which is necessary to bring the bed back to initial conditions to cycle. The regeneration phase includes four steps backwashing...

P Fl in

Where P is present worth or present value, F is future value, i is the interest or discount rate, and n is the number of periods. As a simple example, if we have or hold 1,000, in one year at 6 percent interest compounded annually, the 1,000 would have a computed present value of Because our money can work at 6 interest, there is no difference between 943.40 now and 1,000 in one year because they both have the same value now. Economically, there is an additional factor at work in present value,...

Sludge Conditioning By Thermal Methods

There are two basic processes for thermal treatment of sludge. One, wet air oxidation, is the flameless oxidation of sludge at temperatures of 450 to 550 F and pressures of about 1,200 psig. The other type, heat treatment, is similar but carried out at temperatures of 350 to 400 F and pressures of 150 to 300 psig. Wet air oxidation (WAO) reduces the sludge to an ash and heat treatment improves the dewaterability of the sludge. The lower temperature and pressure heat treatment is more widely...

Pcv

Process scheme for Wet Air Oxidation (WAO). Note that RCOOH denotes short chain organic acids such as acetic acid which make up the major fraction of residual oxidation intermediates in a typical wet oxidation effluent. Properties of wet oxidation liquid effluent include negligible NOx and S02, negligible particulate matter, and some VOCs, depending on the waste. Wet oxidation is a mature technology with a long history of development and commercialization. Wet oxidation is applicable...

Preface

This volume covers the technologies that are applied to the treatment and purification of water. Those who are generally familiar with this field will immediately embrace the subject as a treatise on solid-liquid separations. However, the subject is much broader, in that the technologies discussed are not just restricted to pollution control hardware that rely only upon physical methods of treating and purifying wastewaters. The book attempts to provide as wide a coverage as possible those...

Pressure Filtration

Pressure filtration is a process similar to vacuum filtration where sludge solids are separated from the liquid. Leaf filters probably are the most common type of unit. Refer back to Chapter 5 for a detailed discussion. Like vacuum filtration, a porous media is used in leaf filters to separate solids from the liquid. The solids are captured in the media pores they build up on the media surface and they reinforce the media in its solid-liquid separation action. Sludge pumps provide the energy to...

Principles Of Ozone Effluent Treatment

Ozone was first discovered by the Dutch philosopher Van Marun in 1785. In 1840, Schonbein reported and named ozone from the Greek word ozein, meaning to smell. The earliest use of ozone as a germicide occurred in France in 1886, when de Meritens demonstrated that diluted ozonized air could sterilize polluted water. In 1893, the first drinking water treatment plant to use ozone was constructed in Oudshorrn, Holland. Other plants quickly followed at Wiesbaden (1901) and Paderborn (1902) in...

Properties Of Bromine And Bromides

Bromine (from the Greek word bromos, meaning stench) has an atomic weight 79.909, atomic number 35, melting point - 7.2 C, and boiling point 58.78 C. As a gas it has a density of 7.59 g 1 and as a liquid 3.12 g 1 (20 C). The element was discovered by Balard in 1826 but not prepared in quantity until 1860. It is a member of the halogen group of elements. Bromine is found mainly in the bromide form, widely distributed and in relatively small proportions. Extractable bromides occur in the ocean...

Properties Of Iodine

Iodine (from the Greek, iodines, meaning violet) has an atomic weight of 126.9044, atomic number 53, melting point 113.5 C, and boiling point 184.35 C. As a gas, its density is 11.27 g 1 and as a solid its specific gravity is 4.93 (20 C). This halogen was discovered by Courtois in 1811. It occurs sparingly in the form of iodides in sea water from which it is assimilated by seaweeds, in Chilean saltpeter and nitrate-bearing soil, in brines from ancient sea deposits, and in brackish waters...

Properties Of Ozone

Ozone is an unstable gas, having a boiling point of -112 C at atmospheric conditions. Its molecular weight is 48. Ozone is partially soluble in water (approximately 20 times more soluble than oxygen), and has a characteristic penetrating odor which is readily detectable at concentrations as low as 0.01 - 0.05 ppm. Ozone is the most powerful oxidant currently available for use for wastewater treatment. Commercial generation equipment generates ozone at concentrations of 1 percent to 3 percent in...

Pump

Components of a gaseous sodium chlorite-chlorine dioxide generation system. A major disadvantage of this system is the limitation of the single-pass gas-chlorination phase. Unless increased pressure is used, this equipment is unable to achieve higher concentrations of chlorine as an aid to a more complete and controllable reaction with the chlorite ion. The French have developed a variation of this process using a multiple-pass enrichment loop on the chlorinator to achieve a much...

Questions For Thinking And Discussing

It is recognized that pore blockage in a filter medium occurs because (1) Pores become blocked by the lodging of a single particle in the pore passage, (2) Gradual blockage can occur due to the accumulation of many particles in pore passages and (3) Blockage may occur during intermittent filtration practices. Consider aim2 surface of filter medium containing Np number of pores. The average pore radius and length are rp and 0p, respectively. Assuming laminar flow, develop an expression to...

R

Rack Evenly spaced parallel metal bars or rods located in the influent channel to remove rags, rocks, and cans from wastewater. Radio frequency interference (RFI) EMI in electronic equipment caused by radio frequencies, ranging typically from 10 kHz (104 Hz) to 1000 MHz (109 Hz or 1 GHz). RAS Return activated sludge - settled activated sludge that is collected in the secondary clarifier and returned to the aeration basin to mix with incoming raw settled wastewater. RASVSS Return Activated...

Rapid Sand Filtration

Rapid filtration is performed either in open gravitational flow filters or in closed pressure filters. Rapid pressure filters have the advantage of being able to be inserted in the pumping system, thus allowing use of a higher effective loading. Note that pressure filters are not subject to development of negative pressure in a lower layer of the filter. These filters generally support higher speeds, as the available pressure allows a more rapid flow through the porous medium made up by the...

Reactions for Hydrogen Cation Exchanger Resins Regeneration Reactions

Calcium, Magnesium and or Sodium-Cation Exchanger (Insoluble) + Sulfuric Acid (Soluble) Hydrogen Cation Exchanger (Insoluble) + Calcium, Magnesium and or Sodium Sulfates (Soluble). Reactions for Hydrogen Cation-Exchanger Resins -Reactions with Sulfates or Chlorides Ca, Mg, Na2 S04, Cl2 + H2Z Ca, Mg, Na2 Z + H2S04 or HCl Calcium, Magnesium and or Sodium as Sulfates and or Chlorides (Soluble) + Hydrogen Cation Exchanger (Insoluble) Calcium, Magnesium and or Sodium-Cation Exchanger (Insoluble) +...

Recommended Resources For The Reader

Vigneswaran, S. and Ben Aim, R., Water, Wastewater and Sludge Filtration, CRC Press, Boca Raton, FL, pp 139-224, (1989). 2. Paulson, David J. Wilson, Richard L. and Spatz, D. Dean, Crossflow Membrane Technology and Its Applications, Food Technology 38 (12) 77-87,& 111(1984). 3. Mohr, C.M. Leeper, S.A. Engelgau, D.E. and Charboneau, B.L., Membrane Applications and Research in Food Processing, (Noyes Data Corporation, Park Ridge, NJ) p. 305 (1989). 4. Morr, C.V., Current Status of Soy Protein...

Rectangular Sedimentation Tanks

The process concept for sedimentation tanks has hardly changed over the past 80 years. Dimensioning these vessels according to existing guidelines guarantees safe operation. With ever tightening legislation, however, the question of expansion or upgrading of existing sewage treatment plants arises. Expansion is an expensive solution and impossible if the available space is scarce so that a new construction has to be built. The basis of upgrading consists in changed process concepts which are...

Region Of Light Phase Liquid

Separation is achieved by use of stack discs. The position of the separating zone is controlled by adjusting the back pressure of the discharged liquids or by means of exchangeable ring dams. Figure 16 illustrates the main features of a disk-bowl centrifuge, which includes a seal ring (1), a bowl (2) with a bottom (13) a central tube (18), the lower part of which has a fixture (16) for disks a stack of truncated cone disks (17), frequently flanged at the inside and outer diameters to...

Resin Performance

Variances in resin performance and capacities can be expected from normal annual attrition rates of ion-exchange resins. Typical attrition losses that can be expected include (1) Strong cation resin 3 percent per year for three years or 1,000,000 gals cu.ft (2) Strong anion resin 25 percent per year for two years or 1,000,000 gals cu.ft (3) Weak cation anion 10 percent per year for two years or 750,000 gals cu. ft. A steady falloff of resin-exchange capacity is a matter of concern to the...

Rigid Filter Media Fixed Rigid Media

Fixed rigid media are available in the forms of disks, pads and cartridges. They are composed of firm, rigid particles set in permanent contact with one another. The media formed have excellent void uniformity, resistance to wear and ease in handling as piece units. Depending on the particle size forming the filter media, temperature, pressure and time for caking, it is possible to manufacture media with different porosities. The higher the pore uniformity, the more uniform the shape of the...

Sand And Gravel

Sand and gravel are the most widely used of the rigid media simple contact. Most of the sand used this way is for the clarification of water for drinking or industrial uses. Washed, screened silica sand is sold in standard grades for this work and is used in depths ranging from a few inches to several feet, depending on the type of filter and clarification requirements. Heavy, irregular grains, such as magnetite, give high rates of flow and low penetration by the solid particles, and are easily...

Slow Sand Filtration

Slow sand filtration involves removing material in suspension and or dissolved in water by percolation at slow speed. In principle, a slow filter comprises a certain volume of areal surface, with or without construction of artificial containment, in which filtration sand is placed at a sufficient depth to allow free flow of water through the bed. When the available head loss reaches a limit of approximately 1 m, the filter must be pulled out of service, drained, and cleaned. The thickness of...

Sludge Conditioning Using Chemicals

Sludge conditioning is a process whereby sludge solids are treated with chemicals or various other means to prepare the sludge for dewatering processes. Chemical conditioning (sludge conditioning) prepares the sludge for better and more economical treatment with vacuum filters or centrifuges. Many chemicals have been used such as sulfuric acid, alum, chlorinated copperas, ferrous sulfate, and ferric chloride with or without lime, and others (refer back to discussions in Chapter 8). The local...

Sludge Lagoons

This is a technique that relies both on the settling characteristics of sludge and solar evaporation. The considerable labor involved in sludge drying bed operation may be avoided by the use of sludge lagoons. These lagoons are nothing but excavated areas in which digested sludge is allowed to drain and dry over a period of months or even a year or more (refer to Figure 22 for an example). They are usually dug out by bulldozers, or other dirt-moving equipment, with the excavated material used...

Some Case Studies For You To Ponder

Studies have shown that the biosolids application reduce runoff from treated rangeland. Results were attributed to increase increased ground surface roughness and water adsorption by the dry biosolids. Over time, the biosolids should decompose and have a less direct effect on surface runoff. However, the increase in vegetative cover in response to the fertilizer effect of the biosolids should further improve the surface hydrology of the treated rangeland. Potential surface water contamination...

Some Final Comments On Incineration

High-temperature processes have been used for the incineration or combustion of municipal wastewater solids since the early 1900s. Popularity of these processes has fluctuated greatly since their adoption from industrial combustion. Thirty years ago, combustion of wastewater solids was both practical and inexpensive. Solids were easily dewatered and the fuel required for combustion was cheap and plentiful. In addition, air-emission standards were virtually nonexistent. Today, wastewater solids...

Some General Comments

So there we have it - a broad overview of a complex subject that spans both technical and legal arenas. Much of the discussions have focused on drinking water, but from this point forward we will depart from the subject and only address this in passing. Recognize that there are a large number of technologies that are applied to treating water. The combination of technologies needed for a water treatment application depend on what we are ultimately trying to achieve in terms of final water...

Some Important Definitions

Maximum Contaminant Level (MCL) - The highest level of a contaminant that is allowed in drinking water. MCLs are set as close to MCLGs as feasible using the best available treatment technology and taking cost into consideration. MCLs are enforceable standards. Maximum Contaminant Level Goal (MCLG) - The level of a contaminant in drinking water below which there is no known or expected risk to health. MCLGs allow for a margin of safety and are non-enforceable public health goals. Maximum...

Source Type

Heavy Metals - Heavy metals represent problems in terms of groundwater pollution. The best way to identify their presence is by a lab test of the water or by contacting county health departments. There are concerns of chronic exposure to low levels of heavy metals in drinking water. Turbidity - Turbidity refers to suspended solids, i.e. muddy water, is very turbid. Turbidity is undesirable for three reasons solids may contain heavy metals, pathogens or other contaminants, turbidity decreases...

Stabilization Via Anaerobic Digestion

The purpose of digestion is to attain both of the objectives of sludge treatment a reduction in volume and the decomposition of highly putrescible organic matter to relatively stable or inert organic and inorganic compounds. Additionally, anaerobic sludge digestion produces a valuable by-product in the form of methane gas (the primary constituent of natural gas, which we can burn for heat or convert to electricity). Sludge digestion is carried out in the absence of free oxygen by anaerobic...

Sterilization Using Ozone

Ozone (03) is a powerful oxidant, and application to effluent treatment has developed slowly because of relatively high capital and energy costs compared to chlorine. Energy requirements for ozone are in the range of 10 to 13 kWh lb generated from air, 4 kWh lb from oxygen, and 5.5 kWh lb from oxygen-recycling systems. Operating costs for air systems are essentially the electric power costs for oxygen systems the cost of oxygen (2 to 30 lb) must be added to the electrical cost. Capital costs of...

Strongly Acidic Cation Resins

Strongly acidic cation resins derive their exchange activity from sulfonic functional groups (HSO). The major cations in water are calcium, magnesium, sodium, and potassium and they are exchanged for hydrogen in the strong acid cation exchanger when operated in the hydrogen cycle. The following stoichiometric equation represents the exhaustion phase, and is written in the molecular form (as if the salts present were undissociated). It shows the cations in combination with the major anions, the...

Summarizing Solidliquid Separations Technology

As a resource that can be recycled or reused. That concept embodies the spirit of pollution prevention. As already noted, all the sludge produced at a treatment plant (whether it be sewage or industrial in origin) must be disposed of ultimately. Treatment processes such as have been described may reduce its volume or so change its character as to facilitate its disposal, but still leave a residue which in most cases must be removed from the plant site. Like the liquid effluent from the...

Terminology And Governing Equations

There are essentially four important physical parameters that characterize a filter media and are used as a basis for relating the characteristics of the material to the system flow dynamics. These are porosity, permeability, tortuosity and connectivity. We may begin by describing any porous medium as a solid matter containing many holes or pores, which collectively constitute an array of tortuous passages. Refer to Figure 1 for an example. The number of holes or pores is sufficiently great...

The Clean Water

Drinking water standards are not the only regulations we need to comply with in the U.S. Today's Clean Water Act has its origins from the late 1940s. The original 1948 statute (Chapter 758 PL 845), the Water Pollution Control Act, authorized the Surgeon General of the Public Health Service, in cooperation with other federal, state, and local entities, to prepare comprehensive programs for eliminating or reducing the pollution of interstate waters and tributaries and improving the sanitary...

The Disc Filter

The Disc Filters belong to the side feed group of filtering machines. They are generally used in heavy duty applications such as the dewatering of iron ore, hematite, coal, aluminum hydrate, copper concentrate, pyrite flotation concentrates and other beneficiation processes. The filter consists of several discs, up to 15 in the larger machines, each made up from sectors which are clamped together to form the disc. The sectors are ribbed towards the neck and designed for a high capacity drainage...