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...

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,...

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...

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...

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...

Establishing Baseline Costs

To properly determine the cost of any engineering project, we first need to establish a baseline for comparative purposes. If nothing else, a baseline defines for management the option of maintaining the status quo. If we are faced with meeting a legal discharge limit, then obviously we need to do something other than status quo to remain in business. But here is where we can develop some interesting and very detailed justifications for one water treatment technology or piece of equipment over...

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...

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...

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....

Germicidal Destruction

Chlorine's ability to destroy bacteria and various microorganisms results from chemical interference in the functioning of the organism. Specifically, it is the chemical reaction between HOC1 and the bacterial or viral cell structure which inactivates the required life processes. The high germicidal efficiency of HOC1 is attributed to the ease by which it is able to penetrate cell walls. This penetration is comparable to that of water and is due both to its low molecular weight (that is, it's a...

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...

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...

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,...

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...

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

In the United States, chlorine was first used as a disinfectant for municipal wastewater treatment in the Jersey City, New Jersey, Boonton reservoir in 1908. This also marked the first legal recognition of chlorine as a disinfectant for public health protection. Chlorine is a strong oxidizing agent and can be used to modify the chemical character of water. For example, it is used to control bacteria, algae, and macroscopic biological-fouling organisms in condenser cooling towers. It is also...

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 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...

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...

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,...

Pac

Diffused Aeration Oxidation Processes RO For inactivation of microorganisms disinfection. Typical disinfectants are chlorine, chlorine dioxide, chloramines, and ozone. For organic contaminant removal from surface water packed-tower aeration, granular activated carbon (GAC), powdered activated carbon (PAC), diffused aeration, advanced oxidation processes, and reverse osmosis (RO). For inorganic contaminants removal, membranes, ion exchange, activated alumina, and GAC. For corrosion control...

Permeability And Darcys

The term reservoir description is applied to characterizing a homogeneous system as opposed to a heterogeneous one. A reservoir description defines the reservoir at a level where a property changes sufficiently so that more than a single average must be used to model the flow. In this sense, a reservoir composed of a section of coarse gravel and a section of fine sand, where these two materials are separated and have significantly different permeabilities, is heterogeneous in nature. Defining...

Pore Structure

A microscopic description characterizes the structure of the pores. The objective of a pore-structure analysis is to provide a description that relates to the macroscopic or bulk flow properties. The major bulk properties that need to be correlated with pore description or characterization are the four basic parameters porosity, permeability, tortuosity and connectivity. In studying different samples of the same medium, it becomes apparent that the number of pore sizes, shapes, orientations and...

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 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...

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...

Questions For Thinking And Discussing

Go to the Web and develop a list of suppliers along with unit costs for some of the various types of flocculants described in this chapter. Also obtain the MSDS (Material Safety Data Sheets) for these chemicals. Once you have collected the information, develop a relative ranking of unit cost and health risk associated with each. For question 2 you will need information of recommended doses. 2. For a 50,000 GPD filtration operation with an average loading 50 mg L TSS (Total Suspended Solids)...

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

Check out these references on Pretreatment. They can all be found on the EPA Website (www.epa.gov). 1. Application and Use of the Regulatory Definition of Significant Noncompliance for Industrial Users, September 9, 1991 (Memorandum) ERIC W986 NTIS PB95-201786. 2. CERCLA Site Discharges to POTWs Treatability Manual, August 1990 540 2-90-007 ERIC W570 NTIS PB91-921269 Disk PB91-507236. 3. CERCLA Site Discharges to POTWs CERCLA Site Sampling Program -Detailed Data Report, May 1990 540 2-90-008...

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...

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...

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...

Selectivity And General Considerations

As noted, ion exchange reactions are stoichiometric and reversible, and in that way they are similar to other solution phase reactions. For example In this reaction, the nickel ions of the nickel sulfate (NiS04) are exchanged for the calcium ions of the calcium hydroxide Ca(OH)2 molecule. Similarly, a resin with hydrogen ions available for exchange will exchange those ions for nickel ions from solution. The reaction can be written as follows 2(R-S03H) + NiS04 (R-S03)2Ni+ H2S04 R indicates the...

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...

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 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...

Some More Important Comments On Thickening

Gravity Thickening - This process involves the concentration of thin sludges to more dense sludge in special circular tanks designed for this purpose. Its use is largely restricted to the watery excess sludge from the activated sludge process, and in large plants of this type where the sludge is sent direct to digesters instead of to the primary tanks. It may also be used to concentrate sludge to primary tanks or a mixture of primary and excess activated sludge prior to high rate digestion. The...

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...

Synthetic Fiber Cloths

Cloths from synthetic fibers are superior to many of the natural cloths thus far considered. They do not swell as do natural fibers, are inert in many acid, alkaline and solvent solutions and are resistant to various fungus and bacterial growths (the degree depending on the particular fiber and use). Several synthetic fibers resist relatively high temperatures, and have a smooth surface for easy cleaning and good solids discharge. Some of the most widely used synthetic filter media are nylon,...

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 Drinking Water Standards

When the objective of water treatment is to provide drinking water, then we need to select technologies that are not only the best available, but those that will meet local and national quality standards. The primary goals of a water treatment plant for over a century have remained practically the same namely to produce water that is biologically and chemically safe, is appealing to the consumer, and is noncorrosive and nonscaling. Today, plant design has become very complex from discovery of...

The Final Touches To Water

< > Disinfection - water completely free of suspended sediment, is treated with a powerful oxidizing agent usually chlorine, chlorine and ammonia (chloramine), or ozone. A residual disinfectant is left in the water to prevent reinfection. Chlorine can form harmful byproducts and has suspected links to stomach cancer and miscarriages. < > pH adjustment - so that treated water leaves the plant in the desired range of 6.5 to 8.5pH units. conditioner, as well as a some fertilizer value....

The Horizontal Belt Filter

This devise consists of a continuous traveling horizontal belt that looks like a conveyor belt. Slurry is loaded at one end and vacuum is pulled on the underside of the belt. The filtrate passes through the belt and the solid cake remains on top. As the belt moves the cake is washed and dried and is then discharged off the end of the belt as is wraps around under the machine. This equipment is usually used for slurries that have solids that are not easily suspendible in solution. Although there...

The Lamella Clarifier

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....

The Plateandframe Filter Press

This type of filter allows pressurized filtration of a slurry mixture to remove solids. A set of filter plates is sandwiched together in series with a configuration similar to the plates on a plate-and-frame heat exchanger. After the plates are compressed together hydraulically, a channel throughout all the plates allows the slurry to be pumped into one side of each of the plates. The filtrate goes through the filter media on the plate leaving the solid cake on the media. Filtrate on the other...

The Tilting Pan Filter

The Tilting Pan Filter is predominantly employed in the phosphoric acid industry and, to some extent, in the washing of phosphate rock. There was a traditional rivalry over the years between the Pan and Belt Filter which now, owing to the substantial progress in rubber technology, swings in the favor of the later. The operation of Tilting Pan Filters is based on a series of horizontal independent trapezoidal pans mounted on a circular supporting structure that rotates under vacuum during the...

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...

Toxicity Of Aquatic Life

Bromamines are considerably less stable than chloramines in receiving waters. Bromamines tend to break down into relatively harmless constituents typically in under 60 minutes. Consequently, BrCl is less damaging to marine life than chlorine. Chloramines at concentrations below 0.1 ppm have resulted in fish kills. There are also indirect effects from chloramine contamination. For example, fish populations tend to avoid toxic regions, even at very low levels of concentrations. Consequently,...

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...

Wash Water

I NO. 2 NO. 3 Figure 5. Flow scheme for three-stage CDD. THICKENER THICKENER THICKENER NO. I NO. 2 NO. 3 Figure 5. Flow scheme for three-stage CDD. The diameters on these machines are over 400ft., with operating torques to 2,400,000ft.-Lbs. The stationary center pier supports the drive and rake mechanisms. The truss extends from the center pier to the tank periphery supports walkway, power lines and feed asunder. (,Diameters are up to 600ft with operating...

Washing And Dewatering

When contaminated, polluted, or valuable suspension liquors are present, it becomes necessary to wash the filter cake to effect clean separation of solids from the mother liquor or to recover the mother liquor from the solids. The operation known as dewatering involves forcing a clean fluid through the cake to recover residual liquid retained in the pores, directly after filtering or washing. Dewatering is a complex process on a microscale, because it involves the hydrodynamics of two-phase...

Wastewater Treatment Plant Operations

Before getting into the subject of sand filtration, we should first attempt to put the technologies of municipal wastewater treatment into some perspective. Wastewater treatment plants can be divided into two major types biological and physical chemical. Biological plants are more commonly used to treat domestic or combined domestic and industrial wastewater from a municipality. They use basically the same processes that would occur naturally in the receiving water, but give them a place to...

Water And Wastewater Treatment Technologies Measurement And Control

Favorable operational economics and good management practices require high levels of control of the ozonation system. Depending on the specific process of ozone applications, plant size, and design philosophy, the control system may be simple or complex. The trend in Europe is toward highly sophisticated and Several parameters should be measured to provide a fully operable ozonation system. There should be a means of providing full temperature and pressure profiles of the ozone generator...

Water And Wastewater Treatment Technologies Precipitates And Salts

Precipitates or salts are used when corrosive liquor must be filtered, and where there is no available medium of sufficient fineness that is corrosion-resistant and will not contaminate the cake. In these cases, precipitates or salts are used on porous supports. In the filtration of caustic liquors, ordinary salt (sodium chloride) is used as the filter medium in the form of a precoat over metallic cloth. This procedure has the advantage that the salt medium will not be detrimental to either the...

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...

Water Treatment In General

Water must have eye appeal and taste appeal before we will drink it with much relish. Instinctively we draw back from the idea of drinking dirty, smelly water. Actually far more important to our well-being is whether or not a water is safe to drink. If it holds disease bacteria, regardless of its clarity and sparkle, we should avoid it. Let's consider these two highly important aspects of water potability and palatability. Regardless of any other factors, water piped into the home must be...

Wet Air Oxidation

When the organic sludge is heated, heat causes water to escape from the sludge. Thermal treatment systems release water that is bound within the cell structure of the sludge and thereby improves the dewatering and thickening characteristics of the sludge. The oxidation process further reduces the sludge to ash by wet incineration (oxidation). Sludge is ground to a controlled particle size and pumped to a pressure of about 300 psi. Compressed air is added to the sludge (wet air oxidation only),...

What Eletcrodialysis Is

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...

What Filtration Is

Filtration is a fundamental unit operation that, within the context of this volume, separates suspended particle matter from water. Although industrial applications of this operation vary significantly, all filtration equipment operate by passing the solution or suspension through a porous membrane or medium, upon which the solid particles are retained on the medium's surface or within the pores of the medium, while the fluid, referred to as the filtrate, passes through. In a very general...

What Microfiltration And Nanofiltration

In the case of microfiltration, a more porous membrane is used than in the other membrane separation technologies, thus yielding a relatively higher flux. It is mainly useful in removing turbid causing materials and can replace conventional granular filtration processes. The most significant design parameters are Size and geometry of modules The clean water flux across a membrane without any material being deposited follows Darcy's Law The net pressure differential across a membrane, taking...

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...

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...

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...

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....

What The Current Drinking Water Standards

The following matrices provide you with a summary of the NPDWRs or primary standards. You should visit the EPA Web site (www.epa.gov) and become familiar with the various documents that are publically available. You will not only find these regulations there, but detailed information that explains the reasoning behind each MCLG. You will also find the entire legislation on this site and can become familiar with all of the subtleties of this piece of complex environmental legislation. Tables 1...

What Viruses

Viruses are ultramicroscopic organisms. They are parasites they need to infest a host in order to duplicate themselves. Viruses excreted with human and animal feces are called enteric viruses, and more than 100 such organisms have been identified. As many as one million viruses can be found in one gram of excrement. The concentration in raw sewage varies over a wide range as many as 463,500 infectious particles per liter of raw sewage have been detected. Viruses found in surface waters are...

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...

Why They Survive

A variety of factors is responsible for the survival of viruses in water bodies. Some of the more significant ones are listed for you in Figure 1. The survival of enteric viruses under laboratory conditions and in estuaries varies from a few hours to up to 200 days. Survival in winter is superior to that at summer temperatures. It is not known exactly what happens to these multitudes of viruses introduced in water bodies. The inability of rhinoviruses to withstand pH changes, temperature...

The Rotary Drum Filter

This continuous filter is used when the solids in the slurry can be easily suspended in solution and remain there. In this filter a cylindrical drum sets horizontally half submerged in a trough holding the filtration slurry. The drum is coated with a filter media and a vacuum is pulled on the inside of it. The filtrate passes through the filter media leaving the solids on the outside of the drum. The drum is rotated continuously allowing the solids to be washed and dried before they are removed...

Gunnison Colo Case Study

This southern Colorado town uses about 32.5 ha (80 ac) of grass on a private ranch for application of biosolids slurry from its oxidation ditch. Application is approximately 56 dry Mg yr (62 dry tons yr) through a sprinkler gun. Other dry land parcels on ranches have also been used. Average annual precipitation in Gunnison is 28 cm (11 in.) the typical yearly application rate is 5 dry Mg ha (2.3 dry ton ac). Grazing on the biosolids-treated land has increased from once to twice per year....

Carbon Adsorption In Water Treatment How Adsorption Works

Activated carbon is a crude form of graphite, the substance used for pencil leads. It differs from graphite by having a random imperfect structure which is highly porous over a broad range of pore sizes from visible cracks and crevices to molecular dimensions. The graphite structure gives the carbon it's very large surface area which allows the carbon to adsorb a wide range of compounds. Activated carbon can have a surface of greater than 1000 m2 g. This means 5g of activated carbon can have...

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

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...

Sample pointSample point

Configuration of column scale-up tests. It is also preferred where suspended solids create a high pressure drop, or dissolved gases create bubbles in the carbon bed. For a downflow or percolation system, an influent line should be installed at the top of the column, with an effluent at the bottom. To prevent the column from draining during operation, the effluent line from the last column should extend from the bottom of the column to above the top of the column. This will keep the...

Wvh

Ecology The study of all aspects of how organisms interact with each other and or their environment. Ecosystem Groupings of various organisms interacting with each other and their environment. E-coli Escherichia coli - one of the non-pathogenic coliform organisms used to indicate the presence of pathogenic bacteria in water. Effective area The total area of the porous medium exposed to flow in a filter element. Efficiency The ability, expressed as a percent, of a filter to remove specified...

The Sludge Pasteurization Process

Filter Press Sludge Treatment

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...

The Pressure Leaf Filter

Diagram Agitated Nutsche Filter Dryer

This device is similar to a plate-and-frame filter press but the whole plate assembly is also housed in a tank or pressure vessel. This design allows higher pressures to be used, and also allows the filtration operation to be done more efficiently in many applications. There are two basic configurations, namely a horizontal plate and a vertical pressure leaf filter. Horizontal plate pressure filters were commonly applied to the fine chemical process industries such as antibiotics , pesticides...