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...

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...

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...

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...

Sulfuroxidizing Bacteria

Sulfur-oxidizing bacteria oxidize inorganic sulfur in low oxidation states by adding oxygen to the inorganic sulfur. Sulfur-oxidizing bacteria obtain energy from the oxidation of inorganic sulfur. Some sulfur-oxidizing bacteria are chemoautotrophs and use the energy that they obtain from the oxidation of inorganic sulfur for the synthesis of organic compounds from carbon dioxide (CO2). Sulfur-oxidizing chemoautotrophs include species in the genera Thiobacillus, Thiospirillopsis, and Thiovulum....

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...

Filamentous Sulfur Bacteria

There are three filamentous sulfur bacteria that are found in activated sludge processes (Table 13.3). These filamentous organisms are Beggiatoa, Thiothrix, and TABLE 13.3 Filamentous Sulfur Bacteria and Operational Conditions Associated with Their Rapid Growth type 021N. Beggiatoa is a white or colorless filamentous organism and is associated more commonly with fixed film processes such as trickling filters than suspended growth systems (activated sludge processes). In trickling filter...

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...

Zoogloeal Growth Viscous Floc

Zoogloeal growth or viscous floc is the rapid and undesired proliferation of floc-forming bacteria such as Zoogloea ramigera. Zoogloeal growth may appear in the dendritic or finger-like pattern Figure 20.7 or in the amorphous or globular pattern Figure 20.8 . Zoogloeal growth is associated with the production of large quantities of insoluble gelatinous material Figure 20.9 that entraps air and gas bubbles. The entrapment of air and gas bubbles results in the production of billowy white foam....

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....

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...

Nitrification

Nitrification is the biological oxidation of ionized ammonia to nitrite Equation 10.2 and or the biological oxidation of nitrite to nitrate Equation 10.3 . Nitro-somonas and Nitrosospira oxidize ionized ammonia to nitrite, while Nitrobacter and Nitrospira oxidize nitrite to nitrate. NH4 1.5O2 Nitrosomonas amp Nitrosospira , NO2- 2H energy 10.2 NO2- 0.502 Nitrobacter amp Nitrospira gt NO3- energy 10.3 Nitrifying bacteria oxidize ionized ammonia and nitrite in order to obtain energy for cellular...

Specific Oxygen Uptake Rate SOUR

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...