External Structures

There are several external structures. These structures are the axial filament, capsule, flagella, glycocalyx, and pili. All external structures perform specific functions, but these structures are not found on bacteria. Spirochetes possess axial filaments or endoflagella (Figure 3.5).The axial filament runs the length of the spirochete and extends beyond the cell wall. The filament assists provides motility and allows the rigid spirochete to rotate like a corkscrew. The capsule is a protective...

Atmospheric Inversion

An atmospheric inversion is an adverse weather condition that can intensify malodors and malodor-related problems. Atmospheric inversions most commonly occur during warm and often humid summer months. During a cloudless summer day, the ground is warmed directly by the sun and more quickly than the atmosphere. The atmosphere is then warmed indirectly by the upward movement of heat or thermals from the ground. With the upward movement of thermals, malodors that are produced at a wastewater...

Capture Of Air And Gas Bubbles But No Foam

Some bacteria in the activated sludge process are capable of capturing air and gas bubbles, but they do not produce foam. For example, aerobic Acetobacter synthe- FIGURE 20.8 Globular or amorphous Zoogloeal growth. FIGURE 20.8 Globular or amorphous Zoogloeal growth. sizes cellulose. When strands of cellulose build on the cellular surface, they form a mat that captures air and gas bubbles and keeps the Acetobacter afloat near the surface of the wastewater where oxygen is most concentrated.

Wastewater Microorganisms

Although most organisms in biological wastewater treatment plants are microscopic in size, there are some organisms such as bristleworms and insect larvae that are macroscopic in size. Macroscopic organisms can be observed with the naked eye that is, without the use of a light microscope. Microscopic organisms can only be observed with the use of a light microscope. Of the microscopic organisms the bacteria (singular bacterium) are the most important in wastewater treatment plants and can be...

Polymers

Cationic polyacrylamide polymers are used at many wastewater treatment plants for sludge dewatering and sludge thickening. These polymers contain numerous amino groups that are released as the polymer degrades in the anaerobic digester. The released amino groups form ionized ammonia that increase the alkalinity of the digester sludge resulting in foam production. Therefore, periodic testing of polymers to ensure their compatibility for dewatering and thickening sludges should be performed....

Chemical Oxygen Demandto Biochemical Oxygen Demand Ratio

Chemical oxygen demand (COD) is not affected by bacterial activity. Therefore, COD is not affected by toxicity. Biochemical oxygen demand (BOD) is affected by bacterial activity. However, BOD may or may not be affected by toxicity. If a sample of wastewater that contains a toxic waste is placed into a BOD bottle, the BOD of the wastewater may be affected. The BOD as affected by the toxic waste may be within, less than, or greater than the normal or expected range of values for the wastewater....

Classification Of Bacteria According To The Roles They Perform

Bacteria at wastewater treatment plants can be classified according to the roles that they perform (Table 4.3). Some bacteria perform positive roles in the treatment of wastewater, while other bacteria perform negative roles that contribute to inefficient treatment of wastewater, increased operational costs, and permit violations. Many bacteria perform positive and negative roles depending upon the operational conditions. TABLE 4.3 Significant Groups of Wastewater Bacteria Acetongenic bacteria...

Controlling Toxicity

There are several operational measures that can be used to minimize or prevent toxicity in a biological treatment process. These measures include the following Identify potential toxic dischargers. Identify potential toxic wastes. Monitor and regulate the discharge of potential toxic wastes. Develop simplistic and reliable indicators of toxicity in the treatment process. Regulate solids inventory in reaction tanks. Use granular activated carbon (GAC). Use coagulants and polymers. Potential...

Septage

Septage is the liquid and solid (scum and sludge) waste produced in individual on-site wastewater disposal systems such as septic tanks and cesspools and is approximately 90-98 water. Septage periodically is removed from septic tanks and cesspools during cleaning operations and is often discharged to wastewater treatment plants for disposal and treatment. Periodic removal or pumping of septage is essential to the long-term operation of septic tanks (Figure 18.l) and septic systems. Once...

Atmospheric Inversions

A major problem associated with the operation of wastewater treatment plants is the microbial (bacterial) production and release of malodors. Even the most efficiently operated plants experience malodor problems, and they are a concern to wastewater personnel and people who live near the treatment plants. These problems involve economic, legal, technical, and public relations issues. The intensity of the malodorous condition may be greatly enhanced, if a wastewater treatment plant experiences...

Sulfatereducing Bacteria

During dissimilatory sulfate reduction relatively large quantities of sulfate are removed from the bulk solution by sulfate-reducing bacteria (SRB). The principal SRB belong in the genera Desulfovibrio and Desulfotomaculum. Sulfate is removed FIGURE 13.3 Assimilatory sulfate reduction. During aerobic conditions, aerobic bacteria remove sulfate from the bulk solution and use sulfate as the sulfur nutrient. Here, sulfate is reduced intracel-lularly to sulfide (-SH), and the sulfide is...

Bacteria

The most important organisms in biological, wastewater treatment plants are the bacteria eubacteria and archaebacteria. Recognition of the distinction between these two groups of organisms or domains (Bacteria and Archaea) is relatively recent, and it is common for species of both groups to be referred to as bacteria. Bacteria enter wastewater treatment plants through fecal waste and I I as soil and water organisms. The archaebacteria consist of the halophiles, thermacidophiles, and...

Feedback Inhibition

During the anaerobic degradation of organic substrates, several compounds are produced that can cause inhibition of methane-forming bacteria if these compounds accumulate to relatively high concentrations. These compounds include hydrogen (H2) and volatile fatty acids. The accumulation of hydrogen results in an increase in hydrogen pressure. This pressure inhibits acetate production. Acetate is the primary substrate for methane-producing bacteria in an anaerobic digester. The accumulation of...

Activated Sludge Process Significant Abiotic And Biotic Factors

Significant abiotic factors in the activated sludge process include alkalinity, ionized ammonia (NH4+), dissolved oxygen, hydraulic retention time (HRT), nutrients, pH, quantity and types of substrates, return activated sludge (RAS) rate, temperature, toxic wastes, and turbulence. Significant biotic factors include denitrifying bacteria, filamentous organisms, floc-forming bacteria, mean cell residence time (MCRT) or sludge age, mixed liquor volatile suspended solids (MLVSS) concentration,...

Wastewater Bacteria

Water Pollution Biology Williamsport, Pennsylvania A JOHN WILEY & SONS, INC., PUBLICATION Nitrification and Denitrification in the Activated Sludge Process Michael H. Gerardi Settleability Problems and Loss of Solids in the Activated Sludge Process The Microbiology of Anaerobic Digesters Michael H. Gerardi and Mel C. Zimmerman

Long Chain Fatty Acids

Long-chain fatty acids can exert toxicity individually or collectively. Significant sources of long-chain fatty acids include wastewaters from homes, edible oil refinery processes, palm oil processing, slaughterhouses, and wool scouring processes. Methane-forming bacteria have unique cell wall structure. A significant component of the cell wall, especially in acetoclastic (acetate-degrading) methane-forming bacteria, is the lipid portion. Lipids in the cell wall are structurally similar to many...

Forms Of Toxicity

There are some toxic wastes (heavy metals) that harm most or all organisms in biological treatment processes. Also, there are some toxic wastes that are unique and TABLE 19.7 Examples of Minimum Concentrations of Heavy Metals that Inhibit cBOD Removal and nBOD Removal TABLE 19.7 Examples of Minimum Concentrations of Heavy Metals that Inhibit cBOD Removal and nBOD Removal Toxic Wastes Unique to Nitrifying Bacteria Recognizable, soluble cBOD Substrate toxicity Toxic Wastes Unique to...

Floc Forming Bacteria

Floc formation does not occur in an anaerobic digester. Septicity in the digester destroys floc formation. Floc formation does occur in the activated sludge process and is essential for its success. Floc formation permits the packaging of a large and diverse population of bacteria in numerous floc particles that (1) can be separated from the waste stream in the secondary clarifier and (2) can be recycled (Figure 14.1) as needed to achieve the following treatment objectives Remove fine solids...

Interactions Between Wastes

Within biological treatment units, bacteria are exposed to many wastes simultaneously. Interactions between these wastes can either increase (synergistic effect and potentiation) or decrease (antagonistic effect) the toxicity of the wastes. The mode of interaction between different wastes can be due to the molecular structure of the wastes or changes in the metabolic processes in the organisms. A synergistic effect or response occurs when the combined effect of two wastes is greater than the...

Nitrifying Bacteria

Nitrogen (N) is an essential nutrient of all living organisms. In the amino group ( NH2) nitrogen is in the -3 oxidation state or valence and is incorporated into amino acids such as glycine (CH2NH2COQH) (Figure 10.1). Amino acids are used by organisms to build proteins. Proteins then are used to build structural materials, enzymes, and genetic materials. Amino acids, proteins, and compounds built with proteins are organic nitrogen compounds.These compounds are found in fecal waste and food...

Bacterial Groups

In order to reproduce all bacteria require (1) a source of carbon for the synthesis of new cellular materials, (2) a source of energy for cellular activity, and (3) inorganic nutrients. Growth factors such as amino acids and vitamins also may be required for reproduction. Bacteria can be classified according to their similarities. Most often bacteria are placed largely into groups according to their carbon and energy sources. However, bacteria also are classified according to their structure...

Sheath Bacteria Example Sphaerotilus

Sheath bacteria consist of a chain of Gram-negative cells that are surrounded by a transparent tube or sheath (Figure 4.3). When the cells leave the sheath, they become motile by means of flagella and are referred to as swamer cells. The swamer cells quickly produce sheaths and form filamentous chains. There are two sheathed, filamentous bacteria in the activated sludge process Haliscomenobacter hydrossis and Sphaerotilus natans. FIGURE 4.3 Sheath filamentous organism. Some filamentous...

Tannins

TABLE 19.14 Indicators of an Unstable Biomass in the Activated Sludge Process TABLE 19.14 Indicators of an Unstable Biomass in the Activated Sludge Process Effluent ionized ammonia concentration Effluent orthophosphate concentration Favorable, dominant protozoan groups X Mixed liquor dissolved oxygen concentration Specific oxygen uptake rate (SOUR) X TABLE 19.15 Indicators of an Unstable Biomass in the Anaerobic Digester

Cytoplasm and Its Contents

The cytoplasm is inside the cell membrane and is mostly water by composition. However, it has a semifluid nature due to a suspension of carbohydrates, enzymes, inorganic ions, lipids, and proteins. Within this suspension can be found the nuclear region, ribosomes, storage products, and endospores. Instead of a nucleus, bacterial cells have a nuclear region or nucleoid. The nuclear region consists mostly of genetic material in one large and circular chromosome. In addition to the chromosome,...

Heavy Metals

Metals that have a significant detrimental impact upon biological treatment units are referred to as heavy metals. These metals cause the following undesired consequences when present in excessive quantities Toxicity to organotrophic bacteria in aerobic treatment reactors Toxicity to organotrophic bacteria in anaerobic treatment reactors Toxicity to nitrifying bacteria in aerobic treatment reactors Interruption of floc formation Accumulation of metals in sludges Increased operational costs...

Glossary

Abiotic The nonliving components or factors in an environment that affect an organism absorb Penetration of a substance into the body of an organism acclimate The process by which bacteria spend time and energy to repair damage to enzyme systems caused by toxic wastes acetoclastic The splitting of acetate by methane-forming bacteria to produce methane acetongenic Acid-forming or fermentative bacteria that produce large quantities of acetate acid-forming bacteria Organisms that produce a mixture...

Nitrification

Degradation of nBOD occurs through two biologically mediated reactions. First, Nitrosomonas and Nitrosospira oxidize ionized ammonia to nitrite (Equation 19.4). Second, Nitrobacter and Nitrospira oxidizes nitrite ions to nitrate ions (Equation 19.5). Because Nitrobacter and Nitrospira are not as tolerant of toxicity as Nitro-somonas and Nitrosospira, the nitrite produced by Nitrosomonas and Nitrosospira accumulates due to the inability of Nitrobacter and Nitrospira to oxidize nitrite as rapidly...

Chemical Treatment

Several chemicals may be added to the sewer system to control the biological production of malodorous compounds. Chemicals commonly used include sodium hydroxide (NaOH), calcium hydroxide (Ca(OH)2), chlorine as sodium hypochlorite (NaOCl) or calcium hypochlorite (Ca(OCl)2), hydrogen peroxide (H2O2), ozone (O3), and metal salts. By increasing the pH of the sewer system to > 12 with sodium hydroxide or calcium hydroxide, the biofilm within the sewer system degrades. With the degradation of the...

Nutrient Deficiency

Nutrient deficiencies commonly are experienced in activated sludge processes and usually are due to the presence of nutrient-deficient industrial wastewater. Nutrients that are most often deficient are nitrogen and phosphorus. During a nutrient deficiency, soluble substrate that is absorbed by bacterial cells in floc particles but cannot be degraded. The nondegraded substrate is converted by bacterial cells to insoluble polysaccharides and stored outside the bacterial cells. Often, the...

Cell Membrane Cell Wall and Outer Membrane

The cell membrane or plasma membrane is a flexible semipermeable membrane that surrounds the cytoplasm. The cell membrane contains two different layers (bilayer) that regulate the movement of substances in and out of the cell. The outer layer is hydrophilic (water-loving), while the inner layer is hydrophobic (water-fearing). Together these layers form a protective and regulating barrier between the cytoplasm and the environment. TABLE 3.1 Significant Differences Between Gram-Negative and...

Microbial Ecology

Microbial ecology as applied to the activated sludge process and the anaerobic digester is the review of the significant groups of wastewater organisms and the operational conditions in each biological treatment unit. This review includes the effects of abiotic and biotic factors upon the organism including their activity and growth that is, wastewater treatment efficiency. Biological treatment units are simply biological amplifiers that is, the removal or degradation of waste results in an...

Ammonia

Ionized ammonia (NH ) is not toxic and is produced in the anaerobic digester through the degradation of amino acids, proteins, polymers, and surfactants. Ammonia (NH3) is toxic and is produced in the anaerobic digester with increasing pH (Equation 19.3). Ammonia is toxic to methane-forming bacteria at concentrations of 1500-3000mg liter. Ammonia toxicity in an anaerobic digester can be controlled by decreasing pH and diluting the digester feed sludge. Ammonia toxicity also can be controlled by...

Use Of An Anoxic Period Or Zone

An anoxic period or zone may be used to improve treatment plant performance. The use of an anoxic period or zone of 1-2 hours on an as-needed basis or as part of the standard operating procedures of the treatment process can provide the following benefits for an activated sludge process Control of undesired filamentous organism growth Improvement in floc formation Decrease in sludge production Some filamentous organisms such as Haliscomenobacter hydrossis, Nocardio-forms, Sphaerotilus natans,...

Sulfur Bacteria

There are five major groups of sulfur bacteria (Table 13.5). These groups include the sulfate-reducing bacteria (SRB), sulfur-oxidizing bacteria, colorless sulfur bacteria, sulfur-oxidizing photosynthetic green bacteria, and sulfur-oxidizing photosyn-thetic purple bacteria. Growth media and identification of sulfur bacteria are provided in the latest edition of Standard Methods for the Examination of Water and Wastewater. Sulfur bacteria, especially SRB, often grow with other bacteria, and...

Protozoa

Most protozoa are free-living and solitary, but some do form colonies. Most protozoa are strict aerobes, but some including amoebae and flagellates can survive anaerobic conditions. In the activated sludge process, protozoa are placed commonly in five groups according to their means of locomotion. These groups are amoebae (Figure 1.3), FIGURE 1.4 Flagellate. The flagellate is a single-celled organism that moves by the beating action of one (flagellum) or more...

Recognizable Soluble cBOD

It is generally accepted that nitrification can occur when the cBOD in the biological process is < 40mg liter. When the cBOD has been reduced to this relatively low Examples of Recognizable, Soluble cBOD concentration, nitrification occurs for two reasons. First, nitrifying bacteria are able to compete successfully for dissolved oxygen as the cBOD concentration decreases and organotrophic bacteria require less dissolved oxygen. Second, those forms of cBOD that inhibit enzymatic activity in...

Toxicity And Methaneforming Bacteria

Methane-forming bacteria are the most susceptible bacteria to toxicity in the anaerobic digester. When strict anaerobic, methane-forming bacteria are compared to TABLE 19.11 Forms of Toxicity to Methanogens Alkali alkaline metals Ca2+, K+ Feedback inhibition H2, volatile fatty acids Long-chain fatty acids Carprylic acid, lauric acid Sulfate nitrate (alternate electron acceptors) SO42-, NO3- TABLE 19.12 Long-Chain Fatty Acids that Are Toxic to Methanogens Fatty Acid Number of Carbon Units...

Denitrifying Bacteria

Facultative anaerobic bacteria or denitrifying bacteria are capable of using either free molecular oxygen, nitrate, or nitrite to degrade soluble cBOD in order to obtain carbon and energy for cellular growth and activity. Although denitrifying bacteria TABLE 11.1 Industrial Wastewaters that Contain Nitrate or Nitrite Industrial Wastewater Nitrate (NO3-) Nitrite (NO2-) Floc particle diameter _ > 100 um Floc particle diameter _ > 100 um Dissolved oxygen concentration at the core of the floc...

Toxicity And Nitrifying Bacteria

Because the nitrifying bacteria, Nitrosomonas, Nitrosospira, Nitrobacter, and Nitro-spira, obtain very little energy from the oxidation of ionized ammonia (NH ) and nitrite (NO2-), these organisms have little energy available to reproduce or repair cellular damage as compared to organotrophic bacteria. Nitrifying bacteria reproduce every 2-3 days and make up only 3-10 of the bacterial population as compared to organotrophic bacteria that reproduce every 30 minutes and make up over 90 of the...

Bioaugmentation

Bioaugmentation or biomass enhancement is the addition of commercially prepared bacterial cultures to a wastewater treatment system to (1) increase the density of desired bacteria and their enzymes and (2) achieve a specific operational goal for example, decrease sludge production or control malodor production. The addition of bacterial cultures increases the density of desired bacteria without significantly increasing the solids inventories and solids residence times of an activated sludge...

Fermentative Bacteria

Organotrophic bacteria degrade organic compounds in order to obtain carbon and energy for cellular synthesis and activity. The degradation of organic compounds occurs intracellularly and results in the release of electrons from the hydrogen atoms in the organic compounds (Figure 16.1). The electrons provide the cell with energy and are removed from the cell by an electron transport molecule. The electron transport molecule may be free molecular oxygen (O2), nitrate (NO3-), sulfate (SO42-),...

Pathogenic Bacteria

A large number and diversity of pathogenic (disease-causing) bacteria enter sanitary sewer systems and wastewater treatment plants on a daily basis. Pathogenic bacteria enter sewer systems from (1) domestic wastewater, (2) industrial wastewaters such as slaughterhouses, (3) cat and dog excrement through inflow and infiltration (I I), and (4) rats that inhabit the sewer system. Pathogenic bacteria can be found in the sewer system in the wastewater, sediment, and biofilm and at waste-water...

Species of Dominant Bacteria

Some bacteria are more tolerant (or less susceptible) to heavy metal toxicity than other bacteria. There are two basic metal resistance mechanisms or safe metal accumulation (bioaccumulation) mechanisms used by metal resistant bacteria (Figure 19.14). Bacterial reactions with heavy metals can occur extracellularly, pericellularly (surrounding the cell), and intracellularly. Metals may accumulate extracellularly through chelation by extracellular polysaccharides that are secreted by bacteria...

Cellular Composition

Bacteria are perhaps the most versatile and diversified organisms with regard to their nutritional requirements. Some represent the entire spectrum of nutritional types, while others require complex organic compounds or a few inorganic compounds. Although there is considerable variation in the specific requirements for growth, the chemical composition of bacteria is similar (Table 3.2). Bacteria are approximately 80 water and 20 dry material. Of the dry material, approximately 90 is organic and...

PolyP Bacteria

Phosphorus (P) is a major nutrient that is necessary to all living cells. It is an essential element in the production of adenosine triphosphate or ATP (Figure 12.1), the nucleic acids DNA and RNA, phospholipids, teichoic acids, and teichuronic acids. ATP serves as a high-energy molecule and is used in the transfer of energy within the cell. Phospholipids are key components in the structure of cell membranes, while teichoic acids and teichuronic acids are key components in the structure of cell...

Methane Forming Bacteria

Methane-forming bacteria or methanogens are a specialized group of Archaea that utilize a limited number of substrates (Table 17.1), principally acetate (CH3COOH), carbon dioxide, and hydrogen for methane production or methanogenesis. These substrates are the end products of more complex substrates that were degraded by fermentative bacteria. Methane-forming bacteria are some of the oldest bacteria and are grouped in the domain Archaebacteria. The term arachae means ancient. Methane-forming...

Enzymes

Enzymes are a special group of complex proteins found in all living organisms. Most cells contain hundreds of enzymes and are continuously synthesizing enzymes. Enzymes act as catalysts of biochemical reactions. Enzymes accelerate the rate reactions as much as 1,000,000 times the rate of uncatalyzed reactions and permit the occurrence of biochemical reactions at temperatures that living cells can tolerate. Some enzymes contain nonprotein groups or cofactors. Cofactors include coenzymes or...

Hydrolytic Bacteria

A large and diverse population of bacteria and their enzymes are necessary to degrade the large quantity and variety of substrates that enter a biological treatment unit. Because different groups of bacteria reproduce at different rates, the mean cell residence time (MCRT) or solids retention time (SRT) of a treatment unit must be adjusted to grow the required bacterial population and their appropriate enzymes for appropriate biological activities. These activities include (1) the degradation...

Biological Malodors

The biological (bacterial) production and release of offensive or malodorous compounds in sanitary sewers, lift stations, and wastewater treatment plants are a nuisance to wastewater personnel and people who live near wastewater collection, conveyance, and treatment facilities. Although malodors are not typically addressed by federal and state air quality regulations, they often are regulated by local authorities. Biological malodor production occurs when wastewater or sludge becomes septic....

Forms Of Nitrification

Nitrification may be complete or incomplete (Table 10.11). Because there are two groups of nitrifying bacteria and two biochemical reactions that are involved in nitrification, there are four possible forms of incomplete nitrification. The identification of the form of nitrification that occurs in the activated sludge process is of value to an operator to (1) ensure proper nitrification, (2) provide for cost-effective operation, (3) maintain permit compliance, and (4) initiate prompt correct...

Enhanced Biological Phosphorus Removal

Enhanced biological phosphorus removal (EBPR) or luxury uptake of phosphorus occurs when phosphorus uptake by bacteria is in excess of cellular requirements. Typically, activated sludge phosphorus content is approximately 1-3 , while the activated sludge phosphorus content is approximately 6-7 when EBPR is used. EBPR is relatively inexpensive and is capable of removing phosphorus to low effluent concentrations. EBPR also reduces chemical costs and sludge disposal costs that are associated with...

Anabolism Versus Catabolism

Substrate that is absorbed by bacterial cells is degraded to provide carbon and energy for cellular growth and cellular activity. When substrate is used for cellular synthesis, small molecules are joined together to form large molecules and cellular growth occurs. This is referred to anabolism, and sludge production increases. When FIGURE 9.4 Bacterial growth curve, occurrence of anabolism and catabolism. Anabolic reactions favor increased sludge production, while catabolic reactions favor...

Biological Reduction Of Nitrate

Denitrification Tanks

Denitrification is one of two forms of nitrate reduction. When nitrate is reduced through bacterial activity, oxygen is removed from nitrate. Facultative anaerobic bacteria reduce nitrate to degrade soluble cBOD when free molecular oxygen is not available. This is referred to as denitrification or dissimilatory nitrate reduction, because the nitrogen in nitrate is not incorporated into cellular material that is, nitrogen leaves the bacterial cell in molecular nitrogen (N2) and nitrous oxide...

Anaerobic Digester Significant Abiotic And Biotic Factors

Anaerobic Sludge Digester

Significant abiotic factors in the anaerobic digester include ionized ammonia (NH4+), alkalinity, carbon dioxide, hydrogen, nitrate (NO3-), nutrients, pH, quantity and types of substrates, sulfate (SO42-), temperature, toxic wastes, and volatile acids. Significant biotic factors include acetogenic bacteria, fermentative (acid-forming) bacteria, hydrolytic bacteria, methane-forming bacteria, solids retention time (SRT), sulfur-reducing bacteria, and volatile suspended solids (VSS). Within each...

Slow Specific Control Measures

Slow, specific control measures for undesired filamentous growth consists of the following steps Identify the undesired filamentous bacteria. Identify the operational conditions responsible for undesired filamentous growth. Adjust the operational condition to control the undesired filamentous growth. SELECTORS There are three selectors that commonly are used to control undesired filamentous growth. These selectors are anoxic, anaerobic, and F M (Figure 15.5). The selectors have operational...

Sources Of Sulfur

Sulfur is found in many different compounds of natural and pollutant origin and is very common in wastewater. Domestic wastewater contains approximately 3-6 mg liter of organic sulfur as proteinaceous wastes and approximately 4mg liter of organic sulfur as sulfonates derived from detergents. Domestic wastewater also con- Operational Condition Associated with Rapid Growth Low F M, organic acids, readily degradable cBOD, septicity sulfides Low F M, organic acids, readily degradable cBOD,...

Toxicity

Municipal wastewater treatment plants often treat a combination of industrial, commercial, and domestic wastewaters. Some municipal wastewater treatment plants also treat septage. These wastewaters and septage contain several significant components that are of concern to operators of municipal wastewater treatment plants (Table 19.1). Several of these components represent a risk of toxicity to aerobic, biological treatment units such as the activated sludge process and anaerobic, biological...

Bacterial Growth

Biological, wastewater treatment plants are simply biological amplifiers. The plants permit organisms (biomass or sludge), primarily bacteria, to increase in number by using the pollutants (substrates and nutrients) in the wastewater and converting them to new organisms (biomass or sludge) and nonpolluting wastes and less polluting wastes (Table 9.1). Nonpolluting wastes do not contribute to operational or environmental problems. Less polluting wastes are not as harmful as the original...

Fungi In Activated Sludge

Activated Sludge Problems

Fungi usually are saprophytic organisms and are classified by their mode of reproduction. As saprophytes they obtain their nourishment from the degradation of dead organic matter. Most fungi are free-living and include yeast, molds, and mushrooms. FIGURE 1.2 Filamentous fungi. Filamentous fungi occasionally bloom in activated sludge processes due to low pH or nutrient deficiency. Filamentous fungi are relatively large in size and display true branching. FIGURE 1.2 Filamentous fungi. Filamentous...

Phosphorus Removal By Chemical Addition

Chemical precipitation of orthophosphate is commonly practiced at wastewater treatment plants. Although polyphosphates and organic phosphorus compounds are not removed by chemical precipitation, they are hydrolyzed and mineralized (degraded) to release orthophosphate, which is then chemically precipitated. Metals that are commonly used to precipitate orthophosphate are Al3+, Ca2+, Fe3+, and Mg2+ (Table 12.7). Chemical precipitation of orthophosphate is controlled by pH for example, pH > 8.5...

Rotifers And Nematodes

Wastewater Microorganisms

Rotifers Figure 1.9 and nematodes Figure 1.10 are multicellular microscopic animals metazoa that also provide numerous benefits to the activated sludge process. In addition to these benefits provided by the ciliated protozoa, the metazoa burrow into floc particles.The burrowing action promotes acceptable bacterial activ- FIGURE 1.9 Rotifer in free-swimming mode. FIGURE 1.9 Rotifer in free-swimming mode. ity for the degradation of substrates in the core of the floc particle by permitting the...

Soluble cBOD

The quantity of substrate or soluble cBOD is the most important factor that influences denitrification. The greater the quantity of soluble cBOD, the greater the demand is for electron acceptors such as free molecular oxygen and nitrate. As soluble cBOD is degraded inside the bacterial cell, electrons are released from the degraded substrate. The released electrons are removed from the bacterial cell by electron acceptors. Therefore, the greater the quantity of soluble cBOD that is degraded,...

Filamentous Bacteria Example Haliscomenobacter

There are approximately 30 filamentous organisms that contribute to settleability problems in activated sludge processes due to their rapid and undesired growth. Of these filamentous organisms, 10 bacteria are responsible for most bulking episodes. Although better known for operational problems, filamentous bacteria due contribute to the degradation of soluble cBOD and floc formation.The most commonly occurring filamentous bacteria are Haliscomenobacter hydrossis, Microthrix parvi-cella,...

Death Or Decline Phase Of Growth

During the death or decline phase of growth, the death rate for bacteria exceeds the growth rate for bacteria. In batch cultures Figure 9.2 the negative slope of the death phase or decline phase of growth is more dramatic or steep than the negative slope in continuous cultures Figure 9.3 . Batch cultures are limited with respect to the quantity of substrates received, while continuous cultures receive some substrates at all times. Therefore, the death rate of bacteria in the continuous cultures...

Log Phase Of Growth

Log phase of growth also is known as exponential or logarithmic phase, because the bacterial population grows at a logarithmic rate. There are three significant portions to the log phase of growth. These portions are 1 substrate uptake, 2 synthesis of cells and rapid growth, and 3 synthesis of cells and declining growth. During substrate uptake, bacterial cells simple become fat due to the uptake adsorption and absorption of substrates. Because the muffle furnace cannot distinguish between fat...

Endogenous Phase Of Growth

At endogenous stationary or equilibrium phase of growth, the bacterial population has reached the carrying capacity of the biological treatment unit. The bacteria cannot grow indefinitely due to 1 the lack of an ever-increasing quantity of substrates, 2 the lack of electron acceptors such as free molecular oxygen or nitrate, and 3 production and accumulation of toxic metabolic wastes. There is no net increase in bacterial growth. Cellular growth is balanced by cellular death during endogenous...

Acetogenic Bacteria Example Acetobactei

Members of the Acetobacteracae family produce acetate CH3COOH and are important in the degradation of soluble cBOD to methane in anaerobic digesters. They are a special group of fermentative bacteria and convert organic acids, alcohols, and ketones to acetate, carbon dioxide, and hydrogen Figure 4.1 . Acetate is Hydrolytic bacteria Methane-forming bacteria Nitrifying bacteria Nocardioforms Pathogenic bacteria Poly-P bacteria Saprophytic bacteria Sheathed bacteria Spirochetes Sulfur-oxidizing...

Microscopic Indicators

Protozoa and metazoa are two significant groups of higher life forms in the activated sludge process. They enter the process through inflow and infiltration I I as soil and water organisms and make up approximately 5 of the weight of the MLVSS. Ciliated protozoa may be present as high as 50,000 per milliliter. Metazoa usually are present in highly variable numbers. Unless the MCRT of the activated sludge process is gt 28 days, most metazoa are not provided with sufficient time to reproduce and...

Accidental Anoxic Condition

An accidental anoxic condition or undesired anoxic condition is most often associated with poor settling solids and loss of solids in the secondary clarifier. This condition is commonly referred to as clumping, denitrification, rising sludge, or dark sludge rising. Within the sludge blanket of the secondary clarifier, facultative anaerobic bacteria use nitrate to degrade soluble cBOD. Many of the gases produced through the anoxic condition collect in floc particles and produce buoyant solids....

Movement Of Sulfur Through An Anaerobic Digester

Sulfur compounds that are transferred to an anaerobic digester also undergo numerous biological and chemical events Figure 13.7 . Sulfides that enter the digester or released in the digester through anaerobic degradation of sulfur-containing compounds or dissimilatory sulfate reduction may be Removed from solution by anaerobic bacteria as their sulfur nutrient, Bonded and precipitated from solution by soluble metals such as cadmium, iron, and zinc, Sequestered chelated and held in solution by...

Cyanobacteria Example Oscillatoria

Members of cyanobacteria are photosynthetic bacteria. Before their procaryotic cell structure was recognized, they were considered to be blue-green algae. Cyanobacteria may be found as individual cells Chlorella or a chain of cells or filament Oscillatoria that are approximately 100-500 im in length. Some filamentous forms of cyanobacteria do occasionally occur in the activated sludge process and may contribute to settleability problems. Cyanobacteria commonly are found on the surface of...

Specific Oxygen Uptake Rate SOUR

Oxygen Uptake Rate Activated Sludge

Because toxicity affects cellular structure and cellular activity, a decrease in the number of active bacteria in the activated sludge process occurs. With a smaller number of active bacteria, less oxygen is consumed as less BOD is degraded. Therefore, a higher dissolved concentration is maintained in the activated sludge process and a decreased specific oxygen uptake rate SOUR occurs Tables 19.19 and 19.20 . SOUR mg hr g VSS is determined by the following calculation DO uptake rate mg liter...

Sulfur Oxidizing and Sulfur Reducing Bacteria

Although sulfur S accounts for lt 1 of the dry weight of most organisms, sulfur is an essential element for all organisms. Basic compounds that are necessary for all organisms are proteins, and sulfur is found in most proteins. Sulfur also is needed for the production of enzymes and enzyme cofactors such as thiamin and biotin. The sulfur requirement for organisms can be noted in their carbon-to-sulfur ratio. For most bacteria in wastewater treatment processes, the carbon-to-sulfur ratio is 100...