Recommended Resources For The Reader

There may be some golden oldies among these references, but the key word is golden. Check out references 13 through 15 in particular. 1. Anon., Water Sewage Works, 6, 266 (1968). 2. Maeckelburg, D., G.W.F.,119,23 (1978). 3. O'Mella, Ch. R., and D.K. Crapps, J. AWWA, 56,1326 (1964). 4. Drapeau, A.J., and R.A. Laurence, Eau Quebec, 10, 314 (1977). 5. Burman, N.P., H20, 11, 348, (1978). 6. Cleasby, J.L., J. Arboleda, D.E. Burns, P.W. Prendiville, andE.S. Savage, J. AWWA, 69,115 (1977). 7....

Separation Using Coalescers

A coalescer achieves separation of an oily phase from water on the basis of density differences between the two fluids. These systems obviously work best with non-emulsified oils. Applications historically have been in the oil and gas industry, and hence the most famous oil water separator is the API separator (API being the abbreviation for the American Petroleum Institute). Modern-day designs are more sophisticated than the early, simple separators of a few decades ago that were introduced by...

What Eletcrodialysis Is

Electrodialysis Cell

The principle behind electrodialysis is that electrical potential gradients will make charged molecules diffuse in a given medium at rates far greater than attainable by chemical potentials between two liquids as in conventional dialysis. When a DC electric current is transmitted through a saline solution, the cations migrate toward the negative terminal, or cathode, and the anions toward the positive terminal, the anode. By adjusting the potential between the terminals or plates, the electric...

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...

Info

Electrodialysis process diagram. In addition to the membrane stacks in electrodialysis units, various supporting equipment is essential. This includes pumps for circulation of concentrating and diluting flows flushing streams for cathode and anode plates injection systems for pH control pressure concentration, pH alarms, and control systems and backflushing controls feed strainers and filters and grounding systems. Because of the high pH of the cathode stream, substances, such as...

Revenues Expenses Profits

The most important aspect of this is that profits can be increased by either an increase in revenues or a decrease in expenses. Water treatment operations are by and large end-of-pipe treatment technologies, and hence from the standpoint industry applications that must treat water, the investments required increase expenditures and decrease profit. Municipal facilities view their roles differently, because their end-product is clean water which is saleable, plus they may have addon revenues...

What Stabilization And Conditioning Mean Prestage Basics

Before sludge undergoes treatment such as dewatering or thickening, it must be stored and pretreated. Sludge storage is an important, integral part of every wastewater sludge treatment and disposal system. Sludge storage provides many benefits including equalization of sludge flow to downstream processes, allowing sludge accumulation during times of non-operation of sludge-processing facilities, and allowing a uniform feed rate that enhances thickening, conditioning, and dewatering operations....

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...

Energy Intensive Treatment Technologies

Ozone is used extensively in Europe to purify water. Ozone, a molecule composed of 3 atoms of oxygen rather than two, is formed by exposing air or oxygen to a high voltage electric arc. Ozone is much more effective as a disinfectant than chlorine, but no residual levels of disinfectant exist after ozone turns back into 02. (One source quotes a half life of only 120 minutes in distilled water at 20 C). Ozone is expected to see increased use in the U.S. as a way to avoid the production and...

What We Mean By Water Purification

When we refer to water purification, it makes little sense to discuss the subject without first identifying the contaminants that we wish to remove from water. Also, the source of the water is of importance. Our discussion at this point focuses on drinking water. Groundwater sources are of a particular concern, because there are many communities throughout the U.S. that rely on this form. The following are some of the major contaminants that are of concern in water purification applications, as...

Practical Principles Of Ionexchange Water Treatment

Second Edition 1995, ISBN 0-927188-00-7 By Dean L. Owens 210 pages, hard cover, 55 The Practical Principles of Ion Exchange Water Treatment develops the fundamentals of understanding the ion exchange water treatment process for those people who work with or are concerned with the operation of systems employing this technology. Included are the basics of the mechanics and equipment of ionexchange water treatment, and the effect of these on the operation of the systems. Operation cycles of...

What Payback Period Is

The payback period of an investment is essentially a measure of how long it takes to break even on the cost of that investment. In other words, how many weeks, months, or years does it take to earn the investment capital that was laid out for a project or a piece of equipment Obviously, those projects with the fastest returns are highly attractive. The technique for determining payback period again lies within present value however, instead of solving the present-value equation for the present...

Foreword

This volume constitutes the beginning of what Butterworth-Heinemann Publishers and I hope to provide to environmental and pollution control engineers managers, namely an authoritative and extensive reference series covering control equipment and technologies. As a chemical engineer and a consultant, I not only had the great fortune of having a father, who was famous in the field of pollution control, but the opportunity to work in consulting practice with him on a broad spectrum of...

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...

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...

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...

Cost Considerations And Comparisons To Ro

The cost of resins is a major consideration. Heavy-metal-selective chelating resins are the most expensive. Table 4 provides some cost ranges for commercially Table 4. Cost Ranges of Commercial Resins Table 4. Cost Ranges of Commercial Resins The technology that competes with ion exchange in wastewater application is reverse osmosis (RO), therefor it is appropriate to make some comparisons. Direct cost comparisons are not straightforward, and requires comparison of some of the hidden cost...

Diatomaceous Earth

Diatomaceous earths may resemble the forms of the charcoals. The earths are primarily filter aids, precoats or adsorbents, the function of the filter medium being secondary. Fuller's earth and clays are used for decoloring applications diatomaceous earths are used for clarification. The adsorbtivity of diatomaceous earth works in the same fashion as activated carbon, but isotherms (affinity) for many chemical species like the hydrocarbons is weaker. For this reason, activated charcoal or carbon...

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...

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),...

What Waterborne Diseases

Untreated waters contain a number of harmful pollutants which give the water color, taste, and odor. These pollutants include viruses, bacteria, organic materials, and soluble inorganic compounds, and these must be removed or rendered harmless before the water can be used again. A breakdown of the documented outbreaks identifies acute gastroenteritis, hepatitis shigellosis, ciardiasis, chemical poisoning, typhoid fever, and salmonellosis. Sources of contaminated water can be traced to...

Method Of Purification Of Water 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...

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...

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...

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...

Solids Contacting

Solids contact processes combine chemical mixing, flocculation and clarification in a single unit designed so that a large volume of previously formed floe is retained in the system. The floe volume may be as much as 100 times that in a flow-through system. This greatly increases the rate of agglomeration from particle contacts and may also speed up chemical destabilization reactions. Solids contact units are of two general types slurry-recirculation and sludge-blanket. In the former, the high...

Chemical Mixing

Horizontal Flocculation Basin

Chemical mixing facilities should be designed to provide a thorough and complete dispersal of chemical throughout the wastewater being treated to insure uniform exposure to pollutants which are to be removed. The intensity and duration of mixing of coagulants with wastewater must be controlled to avoid overmixing or undermixing. Overmixing excessively disperses newly-formed floe and may rupture existing wastewater solids. Excessive floe dispersal retards effective flocculation and may...

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...

Bed Regeneration

In addition to washing the bed, a degradated mass containing agglomerates or fermentation zones (referred to as mud balls) can be regenerated by specific treatment techniques. Among the regeneration techniques that are usually used are sodium chloride, regeneration through application of chlorine, and treatment with potassium permanganate, hydrogen peroxide, or caustic soda. Cleaning methods based on the use of caustic soda are aimed at eliminating thin clay, hydrocarbons, and gelatinous...

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...

Chemical Stabilization

Chemical stabilization is a process whereby the sludge matrix is treated with chemicals in different ways to stabilize the sludge solids. Two common methods employed are lime stabilization, and the use of chlorine. The lime stabilization process can be used to treat raw primary, waste activated, septage and anaerobically digested sludge. The process involves mixing a large enough quantity of lime with the sludge to increase the pH of the mixture to 12 or more. This normally reduces bacterial...

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...

Types Of Filter Media To Choose From

There are many filter media from which to choose from however, the optimum type depends on the properties of the suspension and specific process conditions. Filter media may be classified into several groups, however the two most common classes are the surface-type and depth-media-type. Surface-type filter media are distinguished by the fact that the solid particles of suspension on separation are mostly retained on the medium's surface. That is, particles do not penetrate into the pores....

Questions For Thinking And Discussing

A suspension of aluminum hydroxide in water is to be filtered under constant pressure in a batch Nutsch filter having a filtering area of 1 m2. Each filter cycle is estimated to separate out 0.5 m3 of suspension. The operating temperature is 25 C. The following expression for the cake resistance was r0', S' constants determined to be 0.5 x 109 and 0.93, respectively The volume ratio of the cake to filtrate (xj is 0.01. Assuming that the resistance of the filter plate is negligible, determine...

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...

B

Bacillus- Bacterium with an elongated, rod shape. Bacteria Living organisms, microscopic in size, which usually consist of a single cell. Most bacteria use organic matter for their food and produce waste products as a result of their life processes. Bacteriochlorophyll- Light-absorbing pigment found in green sulfur and purple sulfur bacteria. Bacteriocin- Agent produced by certain bacteria that inhibits or kills closely related isolates and species. Bacteriophage- Virus that infects bacteria,...

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...

A

Abiotic factors Non living moisture, soil, nutrients, fire, wind, temperature, climate. Absolute filtration rating (largest particle passed) The diameter of the largest hard spherical particle that will pass through a filter under specified test conditions. This is an indication of the largest opening in the filter cloth. Absorption The taking in or soaking up of one substance into the body of another by molecular or chemical action (as tree roots absorb dissolved nutrients in the Absorption...

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...

Volume Fraction Of Liquid In Slurry

Settling factor for hindered settling. Figure 17. Plot of concentration versus height in a continuous sedimentation device. Curve (1) - low feedrate Curve (2) - high feed rate. Sedimentation equipment is designed to perform two operations to clarify the liquid overflow by removal of suspended solids and to thicken sludge or underflow by removal of liquid. It is the cross section of the apparatus that controls the time needed for settling a preselected size range of particles out of...

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...

Granular Media Filtration

Gravity Sand Filters

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...

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...

Waterborne Diseases

There are a number of infectious, enteric (that is, intestinal) diseases of man which are transmitted through fecal wastes. Pathogens (disease-producing agents) include bacteria, viruses, protozoa, and parasitic worms. Widespread diseases generally occur in regions where sanitary disposal of human feces is not practiced. The most common waterborne bacterial diseases are typhoid fever (Salmonella typhosa), Asiatic cholera (vibrio comma), and bacillary dysentery (Shigella dysenteriae). The first...

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...

The Contaminants Activated Carbon Can And Cannot Remove

Activated carbon (AC) filtration is most effective in removing organic contaminants from water. Organic substances are composed of two basic elements, carbon and hydrogen. Because organic chemicals are often responsible for taste, odor, and color problems, AC filtration can generally be used to improve aesthetically objectional water. AC filtration will also remove chlorine. AC filtration is recognized by the Water Quality Association as an acceptable method to maintain certain drinking water...

Rapid Sand Filtration

Water Cycle And Siphon System

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...

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...

Treatment Options Available To Us

Primary treatment of municipal waste involving settling and retention removes very few viruses. Sedimentation effects some removal. Virus removal of up to 90 percent (which is a minimal removal efficiency) has been observed after the activated sludge step. Further physical-chemical treatment can result in large reductions of virus titer, coagulation being one of the most effective treatments achieving as much as 99.99 percent removal of virus suspended in water. If high pH (above 11) is...

The Lamella Clarifier

Batch Settling Test

Cross-flow lamellar clarification is a technology used in industrial environments to remove oils and solids from residual water. It takes advantage of the natural tendency of oils to float, and the decantation principle for suspended solids that are denser than water. The originality of this process is the combination of natural flotation and clarification techniques in one system. The strip decanter performs as well as conventional clarifiers, but is more compact and occupies a smaller area....

Constant Pressure Differential Filtration

Normalized Permeate Flow

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...

Drying Beds

Incinerator Spent Caustic

This is one of two common methods of dewatering based upon thermaal energy. Drying beds are generally used for dewatering of well digested sludges. Attempts to air dry raw sludge usually result in odor problems. Sludge drying beds consist of perforated or open joint drainage pipe laid within a gravel base. The gravel is covered with a layer of sand. Partitions around and between the drying beds are generally open to the weather but may be covered with ventilated green-house type enclosures...

An Alternative Analysis The Forgotten Method Of Dimensional Analysis

I often refer to dimensional analysis as lost art - because it is usually not heavily emphasized in engineering education today. However, for well over 100 years its has provided simply a wealth of practical design correlations that are still relied upon in virtually all aspects of chemical engineering, ranging from classes of problems dealing with heat and mass transfer, reaction kinetics, momentum exchanges in flow dynamics. Much of sedimentation theory, and indeed the basis for more...

Potassium Permanganate

Potassium permanganate is no longer commonly used in the developed world to kill pathogens. It is much weaker than the other alternatives cited, more expensive, and leaves a objectionable pink or brown color. Still, some underdeveloped countries rely on it, especially in home-use applications. If it must be used, 1 gram per liter would probably be sufficient against bacteria and viruses (no data is available on it effectiveness against protozoan cysts). Hydrogen Peroxide can be used to purify...

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...

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...

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...

What Reverse Osmosis Is

When pure water and a salt solution are introduced on opposite sides of a semipermeable membrane in a vented container, the pure water diffuses through the membrane and dilutes the salt solution, At equilibrium, the liquid level on the saline water side of the membrane will be above that on the freshwater side this process is known as osmosis and is depicted in Figure 9. The view on the left illustrates the commencement of osmosis and the center view presents conditions at equilibrium. The...

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...

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...

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...

What Sludge Is

When we think of sludge, what automatically comes to mind is sewerage. Water carriage systems of sewerage provide a simple and economical means for removing offensive and potentially dangerous wastes from household and industry. The solution and suspension of solids in the transporting of water produces sewage. Thus, the role of solids and sludge removal at Sewage Treatment Plants is apparent. Sludge removal is complicated by the fact that some of the waste matters go into solution while others...

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...

Filtermedium Filtration Formulas

In the case of single-particle blockage, we first consider aim surface of filter medium containing Np number of pores. The average pore radius and length are rp and , respectively. For laminar flow, the Hagen-Poiseuille equation may be applied to calculate the volume of filtrate V' passing through a pore in a unit of time Consequently, the initial filtration rate per unit area of filtration is Consider 1 m of suspension containing n number of suspended particles. If the suspension concentration...

Cake Filtration Equipment

Plate And Frame Filter Equipment Process

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...

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...

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) +...

How Ion Exchange Works

Operation With Mixed Number

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+2, Mg+2, Na+). These acids are...

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...

Ironbased Compounds

Iron compounds have pH coagulation ranges and floe characteristics similar to aluminum sulfate. The cost of iron compounds may often be less than the cost of alum. However, the iron compounds are generally corrosive and often present difficulties in dissolving, and their use may result in high soluble iron concentrations in process effluents. Among the most commonly used iron compounds used in wastewater treatment applications are ferric chloride, ferrous Liquid ferric chloride is a corrosive,...

Water Quality Test Methods

Determination of the bacteriological quality of water is not a straightforward analysis. The testing for a specific pathogenic bacteria can often lead to erroneous conclusions. Analyses for pathogenic bacteria are difficult to perform. In general, data are not quantitatively reproducible. As an example, if Salmonella was found to be absent from a water sample, this does not exclude the possible presence of Shigella, Vibrio, or disease-producing viruses. The bacteriological quality of water is...

Properties Of Chlorine And Its Chemistry

Chlorine (Cl2) is a greenish-yellow-colored gas having a specific gravity of 2.48 as compared to air under standard conditions of temperature and pressure. It was discovered in 1774 from the chemical reaction of manganese dioxide (MnN02) and hydrochloric acid (HC1) by the Swedish chemist, Scheele, who believed it to be a compound containing oxygen. In 1810, it was named by Sir Humphrey Davy, who ins isted it was an element (from the Greek work chloros, meaning greenish-yellow). In nature, it is...

Vacuum Filtration

Process Control For Rotary Drum Filters

We have already discussed this important technology in Chapter 5, but a review may be helpful in placing its importance to sludge processing into perspective. The vacuum filter for dewatering sludge is a drum over which is laid the filtering medium consisting of a cloth of cotton, wool, nylon, dynel, fiber glass or plastic, or a stainless steel mesh, or a double layer of stainless steel coil springs. The drum with horizontal axis is set in a tank with about one quarter of the drum submerged in...

Gravity Sedimentation Thickeners And Clarifiers

Countercurrent Sedimentation

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...

The Kozeny Equation

Porous media is typically characterized as an ensemble of channels of various cross sections of the same length. The Navier-Stokes equations for all channels passing a cross section normal to the flow can be solved to give Where parameter c is known as the Kozeny constant, which is interpreted as a shape factor that is assigned different values depending on the configuration of the capillary (as a point of reference, c 0.5 for a circular capillary). S is the specific surface area of the...

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...

Lime

Lime is among a family of chemicals which are alkaline in nature and contain principally calcium, oxygen and, in some cases, magnesium. In this grouping are included quicklime, dolomitic lime, hydrated lime, dolomitic hydrated lime, limestone, and dolomite. The most commonly used additives are quicklime and hydrated lime, but the dolomitic counterparts of these chemicals (i.e., the high-magnesium forms) are also widely used in wastewater treatment and are generally similar in physical...

Stabilization Via Aerobic Digestion

Aerobic digestion is an extension of the activated sludge aeration process whereby waste primary and secondary sludge are continually aerated for long periods of time. In aerobic digestion the microorganisms extend into the endogenous respiration phase. This is a phase where materials previously stored by the cell are oxidized, with a reduction in the biologically degradable organic matter. This organic matter, from the sludge cells is oxidized to carbon dioxide, water and ammonia. The ammonia...

Closer Look At The Mechanical Clarification Process And The Chemistry Of Clarification

Homemade Laboratory Filter Paper

So by now it should be clear that what the process of clarification is all about is removing suspended solids from water. Important concepts that we have eluded to, but maybe not spelled out so clearly up to now are 1. Stable solids suspensions in water- The mechanisms involved in keeping solids suspended in water, 2. Chemical treatments -How organic polymers and inorganic coagulants work to counteract solids stabilization mechanisms and enhance removal of solids from water, and 3. The function...

Water Disinfection One More Time

Treatment of a water supply is a safety factor, not a corrective measure. There are a number of ways of purifying water. In evaluating the methods of treatment available, the following points regarding water disinfectants should be considered a. A disinfectant should be able to destroy all types of pathogens and in whatever number present in water. b. A disinfectant should destroy the pathogens within the time available for disinfection. c. A disinfectant should function properly regardless of...

Interhalogen Compounds And Their Properties

Interhalogen Compound

Interhalogen compounds are formed from two different halogens. These compounds resemble the halogens themselves in both their physical and chemical properties. Principal differences show up in their electronegativities. This is clearly shown by the polar compound IC1, which has a boiling point almost 40 C above that of bromine, although both have the same molecular weights. Interhalogens have bond energies that are lower than halogens and therefore in most cases they are more reactive. These...

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....

Theory And Practice Of Ion Exchange

Water can contain varying concentrations of dissolved salts which dissociate to form charged particles called ions. These ions are the positively charged cations and negatively charged anions that permit the water or solution to conduct electrical currents and are therefore called electrolytes. Electrical conductivity is thus a measure of water purity, with low conductivity corresponding to a state of high purity. The process of ion exchange is uniquely suited to the removal of ionic species...

Centrifuge Dewatering

Cone Disk Conical Disc Centrifuge

Centrifuges are machines that separate solids from the liquid through sedimentation and centrifugal force. In a typical unit sludge is fed through a stationary feed tube along the centerline of the bowl through a hub of the screw conveyor. The screw conveyor is mounted inside the rotating conical bowl. It rotates at a slightly lower speed than the bowl. Sludge leaves the end of the feed tube, is accelerated, passes through the ports in the conveyor shaft, and is distributed to the periphery of...

Aluminum Based Chemical Additive Compounds

Aluminum based chemicals have been used for many years in wastewater treatment applications for suspended solids removal. These include dry and liquid alum, with sodium aluminate used in activated sludge plants for phosphorus removal. The commercial dry alum most often used in wastewater treatment is known as filter alum, and has the approximate chemical formula A12(S04)3 -14H20 and a molecular weight of about 600. Alum is white to cream in color and a 1 percent solution has a pH of about 3.5....

Some Final Comments On Both Technologies

Both technologies are extremely important to achieving high quality water characteristics, and both are complex - each posing a different set of challenges in scaling up to commercial size operations. You will find that most equipment suppliers have the expertise to tailor their equipment and processes to specific applications, but that in many situations, pilot scale testing will be required. The overview of these technologies presented in this chapter should give you a flavor for the...

Chlorine Dioxide

Chlorine dioxide, discovered in 1811 by Davy, was prepared from the reaction of potassium chlorate with hydrochloric acid. Early experimentation showed that chlorine dioxide exhibited strong oxidizing and bleaching properties. In the 1930s, the Mathieson Alkali Works developed the first commercial process for preparing chlorine dioxide from sodium chlorate. By 1939, sodium chlorite was established as a commercial product for the generation of chlorine dioxide. Chlorine dioxide uses expanded...

Air Flotation Systems

Floatation Tank Daf Scheme

Air flotation is one of the oldest methods for the removal of solids, oil amp grease and fibrous materials from wastewater. Suspended solids and oil amp grease removals as high as 99 can be attained with these processes. Air flotation is simply the production of microscopic air bubbles, which enhance the natural tendency of some materials to float by carrying wastewater contaminants to the surface of the tank for removal by mechanical skimming. Many commercially available units are packaged...

The Sludge Pasteurization Process

This process is really sludge disinfection. Its aim is the destruction or inactivation of pathogenic organisms in the sludge. Destruction is defined as the physical disruption or disintegration of a pathogenic organism, while Inactivation is defined as the removal of a pathogen's ability to infect. In the United States procedures to reduce the number of pathogenic organisms are a requirement before sale of sludge or sludge-containing products to the public as a soil conditioner, or before...