Info

As with any subject, the study of the biochemical operations used in wastewater treatment systems requires an understanding of the terminology used. The purpose of Chapter 1 is to provide that understanding by defining the nature of biochemical operations in terms of the biochemical transformation being performed, the environment in which the transformation is occurring, and the reactor configuration employed. Engineering design is greatly facilitated by application of mathematical models to...

Abiotic Removal Mechanisms

Biod gradation may not be the only mechanism contributing to the loss of an XOC from a bioreactor. Because of the physicochemical properties of some XOCs, abiotic removal mechanisms such as volatilization to the atmosphere and sorption onto solids may contribute to their loss. Quantification of those losses is important for a variety of reasons. First, they represent ways in which the XOCs can enter the environment without alteration. Since XOCs may have negative environmental effects, such...

Sio 222

In which Qi.xoc's the gas phase concentration of the XOC (mg L) and H, Xoc is the dimensionless Henry's Law coefficient for the XOC. The Henry's Law coefficient in this context is the mass per volume based dimensionless coefficient mg of XOC in gas phase moles of XOC in gas phase L of gas phase L of gas phase mg of XOC in liquid phase moles of XOC in liquid phase L of liquid phase L of liquid phase It is related to the conventional Henry's Law coefficient, HXO(, which has units of (atmospheres...

Key Points

The models used to depict suspended growth biochemical operations are phenomenological mass transport models that contain a number of implicit assumptions. 2. The mass balance equation for any constituent in the control volume of a suspended growth reactor is Accumulation Input - Output + Generation 3. Reactors may be characterized by the distribution of residence times within them, with continuous stirred tank reactors (CSTRs) and plug-(low reactors (PFRs) representing the two extremes of...

J 73 FwsvxM

Thus, if wastage is from each bioreactor in proportion to its volume, the SRT will be controlled solely by the total bioreactor volume and the total wastage flow rate, regardless of the MLSS concentration in each bioreactor. Because of its simplicity, this technique will be used in all simulations in this chapter, even though the wastage streams will not be shown in the schematic diagrams to simplify them. 7.1.3 Importance of Process Loading Factor In Section 5.1.5...

Relative Importance Of Biotic And Abiotic Removal

The relative contributions of biotic and abiotic removal mechanisms toward the removal of an XOC from a bioreactor can be obtained by substitution of the rate expressions for biod gradation, volatilization, and sorption into the mass balance equations for the XOC in the particular bioreactor type and solving those equations as discussed elsewhere in this text. The resulting output will depend on the configuration of the bioreactor and the method of oxygen transfer employed, and will be specific...

Process Description

Lagoons represent one of the oldest forms of biological wastewater treatment, having been used in some form for more than 3,000 years.4' They have been used as the only means of treatment prior to discharge to surface waters and for pretreatment and or storage prior to treatment in a conventional system or a wetland. A wide range of industrial and municipal wastewaters has been treated in lagoon systems. Lagoons are mechanically simple, which often translates into low capital and operating...

Q O O

0 4 8 12 16 20 0 4 8 12 16 20 SRT, days SRT, days Figure 7.44 Effect of the effective SRT on the concentrations at the end of a cycle in an SBR operated in a manner to mimic the performance of the MLE system shown in Figure 7.28. For comparison, the dashed curves represent the concentrations in the aerobic (second) tank of that system. They are the same as the curves in Figure 7.29. With the exception of the SRT, the characteristics were the same as those listed in Figure 7.43. in Chapter 5 can...

Part V

APPLICATIONS ATTACHED GROWTH REACTORS 19.1 Process Description 843 19.2 Factors Affecting Performance 859 19.4 Process Operation 895 20. Rotating Biological Contactor 907 20.1 Process Description 907 20.2 Factors Affecting Performance 914 20.4 Process Operation 941 20.6 Study Questions 944 References 945 21. Submerged Attached Growth Bioreactors 949 21.1 Process Description 949 21.2 Factors Affecting Performance 963 21.4 Process Operation 981 21.6 Study Questions 983 References 984

Ueo

Strate concentrations are almost parallel. This suggests that data from one substrate concentration can be extrapolated with reasonable accuracy to another, provided that care is taken to ensure that the range over which the extrapolation is made is reasonable. The effects of hydraulic loading on the substrate concentration profile within a chain of RDRs is shown in Figure 17.10 where the hydraulic loading decreases as the number of discs, N, is increased. As would be anticipated from the...

References

Koopman, R. Jain, B. Holloway, G. Lyberatos. and S. A. Svoronos, Effect of temperature and pH on the effective maximum specific growth rate of nitrifying bacteria. Water Research 24 97- 101, 1990. 2. Berthouex, P. M. and D. R. Gan, Discussion of 'A comparison of estimates of kinetic-constants for a suspended growth treatment system from various linear transformations.' Research Journal, Water Pollution Control Federation 63 820-823, 1991. 3. Brown, S. C., C. P. L....

Use Of Batch Reactors To Determine Monod Kinetic Parameters For Single Substrates

The values of the Monod kinetic parameters XH and Ks determined by the techniques discussed in Section 8.2.5 are for general organic matter as measured by COD. Frequently, however, it is desirable to know the kinetic parameters associated with the biod gradation of a single organic compound in a wastewater. Because of the relatively low specific growth rates at which suspended growth bioreactors operate, it is permissible to use parameter values determined during metabolism of the compound as...

Volatilization

Volatilization is an interphase mass transfer process in which a constituent in the liquid phase is transferred to the gas phase and it may contribute to the loss of an XOC from an activated sludge bioreactor during the transfer of oxygen to the system. Models for interphase mass transfer are of the form rv.x.K- - .xo Sx,,,. - S5,x-)V (22.1) where r, X(H is the rate of loss by volatilization of the XOC from the control volume V (mg hr), K, XIK a is the overall liquid...

3

The equation for the active fraction, Eq. 5.61 is unchanged. As usual, the term F in Eqs. 5.64-6.68 (either directly or through the HRT, t) is the flow rate entering the bioreactor. It should be noted, however, that for this situation, the flow often arises from another bioreactor, e.g., as its waste solids stream. Furthermore, bioreactors receiving only biomass in their feed often do not employ a biomass separator, but discharge their entire effluent stream to...

Axd

Figure 7.17 Effect of the biomass recycle ratio (a) on the steady-state concentrations of various constituents in each reactor of the SFAS system described in Figure 7.11. SRT 10 days. Figure 7.18 Effect of the biomass recycle ratio (a) on the steady-state oxygen requirement in each reactor of the SFAS system described in Figure 7.11. SRT 10 days. Figure 7.18 Effect of the biomass recycle ratio (a) on the steady-state oxygen requirement in each reactor of the SFAS system described in Figure...

Sorption

Any XOC that is sorbed onto the biomass and other solids in a bioreactor will be removed from the system with the waste biomass. Since the sorbed XOC will not be chemically altered, the potential exists for it to desorb from the waste biomass during its handling, processing, and disposal, potentially leading to release of the XOC to the environment. Because of the potential of such releases, it is important to quantify them so that they may be controlled or eliminated if necessary. Mechanisms...

Future Challenges

Fate and Effects of Xenobiotic Organic Chemicals 969 22.2 Abiotic Removal Mechanisms 994 22.3 Relative Importance of Biotic and Abiotic Removal 999 22.4 Effects of Xenobiotic Organic Chemicals 1002 22.5 Experience with Xenobiotic Organic Chemicals 1005 22.7 Study Questions 1008 References 1009

O

Figure 7.45 Effect of the mixed liquor recirculation ratio ((3) on the concentrations at the end of a cycle in an SBR operated in a manner to mimic the performance of the MLE system shown in Figure 7.28. For comparison, the dashed curves represent the concentrations in the aerobic (second) tank of that system. They are the same as the curves in Figure 7.31. With the exception of the recirculation ratio, the characteristics were the same as those listed in Figure 7.43. 0.4 0.6 0 8 1.0 0.0 0.2 0...

Wm

Figure 15.2 A Iransmission electron micrograph of a Pseudomonas aeruginosa biofilm consisting almost entirely of a base film. (From P. A. Wilderer and W. G. Characklis, Structure and function of biofilms. In Structure and Function of Biofilms, W. G. Characklis and P. A. Wilderer, eds. Wiley, New York, pp. 5-17, 1989. Reprinted by permission of John Wiley & Sons, Inc.) between the bulk fluid and the biofilm, on the other hand, is dominated by advection and turbulent diffusion.Is These...

Tf iN7Ta

Figure 10.19 is a plot of Eq. 10.43 over the range of recycle ratios and number of equivalent tanks likely to be encountered in practice. To determine whether a proposed SFAS system will work, the fraction of MLSS in the last tank should be determined with Eq. 10.42 or Figure 10.19 for the smallest anticipated recycle ratio and that value should be used to determine if Eq. 10.41 is satisfied. As long as that fraction is greater than the right side of Eq. 10.41, the desired effluent quality will...

Atad Greenhouse Gases Digester Aerobic Autothermal

Aerobic Digester

Figure 12.7 Anoxic aerobic digestion a. intermittent feed b. continuous feed without thickening c. continuous feed with thickening. Figure 12.7 Anoxic aerobic digestion a. intermittent feed b. continuous feed without thickening c. continuous feed with thickening. with the exception of the addition of mixing equipment where necessary for anoxic operation. Because of the need to recirculate nitrified mixed liquor for denitrification, as shown in Figure 12.7, complete denitrification will not...

Study Questions

Prepare a table summarizing the advantages and disadvantages of anaerobic digestion compared to aerobic digestion for the stabilization of waste solids. 2. Prepare a table summarizing the advantages and disadvantages of low-rate and high-rate anaerobic wastewater treatment processes relative to aerobic processes. When is each typically used When might either be used 3. Discuss the roles of H, utilizing and aceticlastic methanogens in anaerobic processes. 4. Prepare a table summarizing the...

Srt

Constraints on. 354-355 effects of, 217-220 substrate composition. 511 trickling filter, 848 Denitnfiers. 22. 24, 29 Density bioparticles. FBBR. 812-813. 817-820 media. RBC. 908 choice of. 924-927. 929-930. 933. 938939 and Beggiatoa growth, 915-916 Depth of media, TF, 851-852 design. 876-887 effect of. 864-866 Depth of packed tower (L). 767-770. 773-774. 777-778. 780-782 Depth of trickling filter (see Depth of media) Design of biochemical operations see also design under individual named...

Converting Kinetic And Stoichiometric Parameter Values Between Chemical Oxygen Demand And Other Units

Be converted between the two units systems by using the coefficients i()xn.t and ioxis.v defined in Section 8.2.1 and quantified in Table 3.1. To assist in the interconversions for particulate constituents, the following conventions will be adopted throughout the remainder of this book. All symbols for particulate constituents defined in the simplified model of Chapter 5 and in ASM No. 1 will be assumed to be in COD units. When particulate constituents are expressed in TSS units, a subscripted...

XMTVb XMVssltm1056

Where XM ,, is the settled MLSS concentration. Thus, it can be seen that when the settled MLSS concentration is as large as possible, the retained volume, Vb will be as small as possible. Although experience with treatment of a particular wastewater is the best way to select the maximum achievable value of XM Ir, it can also be estimated from the definition of the sludge volume index (SVI). As discussed in Section 10.2.1, the SVI is defined as the volume in mL occupied by a gram of solids after...

Ar

RAS is recycled to the anoxic zone while a denitrified AR stream is directed from the end of the anoxic zone to the anaerobic zone. However, several differences exist between the VIP and UCT processes. In the VIP process, all zones are staged, i.e., they consist of at least two (and as many as six) completely mixed cells in series the process is designed as a high-rate, i.e., a short SRT, process to maximize phosphorus removal and the NR is mixed with the RAS for recycle to the anoxic zone....

International Association On Water Quality Activated Sludge Models

International Association on Water Quality ASM No. 1 is presented in matrix format in Table 6.1, where it can be seen to incorporate 8 processes and 13 components. Examination of the table reveals the utility of the matrix format, because application of the principles discussed in Section 5.1.2 allows immediate identification of the fate of each component and construction of the overall reaction rate term for it. It should be noted that components 1-8 are expressed in chemical oxygen demand...

Process Operation

The great variety of anaerobic processes results in a corresponding multiplicity of process monitoring and control techniques, as well as numerous operating problems. Nevertheless, because all of the processes employ similar microbial communities, a number of similarities exist between the monitoring and control techniques used and the operating problems encountered. These similarities are discussed below. 13.4.1 Process Monitoring and Control Control of anaerobic processes is accomplished...

Multispecies Biofilms

All of the models we have considered so far in this chapter have considered only a single type of bacteria growing on a single electron donor. Furthermore, they have considered only one type of electron acceptor. However, as we saw when we studied suspended growth systems, if both organic carbon and ammonia-N are available, then both heterotrophs and autotrophs will grow if the environmental conditions are appropriate. In addition, if an electron donor is present but environmental conditions...

Extant Kinetics

The requirements for determining extant values of the Monod (or Andrews) kinetic parameters are just the opposite of the requirements for the determination of intrinsic-values. This follows from the fact that extant parameter values reflect the conditions of the biomass in the bioreactor from which they were obtained. Consequently, the test conditions need to be such that few changes occur in the physiological state of the biomass or the composition of the microbial community during the test....

Modeling Complex Systems

Table 1.2 shows that several activated sludge types use CSTRs in series or plug flow reactors with dispersion. Actually, for purposes of modeling system response, the latter can be represented adequately as CSTRs in series,12 and only that configuration need be considered. Thus, this chapter will focus on the theoretical performance of a number of systems containing CSTRs linked in various ways. Conventional activated sludge (CAS) systems use long rectangular bioreactors with influent and...

D

Reactors Single sludge systems Aerobic digestion Conventional Anoxic aerobic Anaerobic contact Upflow anaerobic sludge blanket Anaerobic digestion Lagoon aerated Facultative aerated Anaerobic Anaerobic Anoxic Rotating biological contactor Trickling filter Packed bed Completely mixed batch X X CSTRs in series with internal X X AC CSTR with biomass recycle X UASB Upflow sludge blanket reactor X

Theory Modeling of Ideal Attached Growth Reactors

All of the biochemical operations considered in the preceding chapters have been suspended growth systems in which the biomass is suspended uniformly throughout the liquid phase. One assumption made in their modeling is that they behave as homogeneous systems that is, that all microorganisms experience the dissolved constituents at the concentration of the liquid phase surrounding them. Even though the biomass exists in floe particles in most of those operations, no consideration was given to...

Process Design

As we saw in Section 13.1, a wide range of anaerobic process options exists. Although the various processes operate according to a unified set of principles, they differ in many ways. In some, such as anaerobic digestion, the bioreactor functions as a CSTR without biomass recycle so that the SRT is equal to the HRT. In others, significant quantities of biomass are accumulated, allowing long SRTs to be maintained at relatively short HRTs. However, because of the mechanisms used to accumulate...

Nature Of Biofilms

Biofilms are very complex, both physically and microbiologically. In fact, they are so complex that it is impossible to fully explore all aspects of them in the space available here. Therefore, those interested in a more detailed explanation of their properties should consult the treatise edited by Characklis and Marshall and the reviews by Costerton et al.y and Lazarova and Manem. ' The basic conceptualization of a biofilm system is shown in Figure 15.1. The biofilm grows attached to a solid...

Treatability Studies

Treatability studies must be carefully designed. That is because biological reactors are subject to their own version of the Heisenberg uncertainty principle. Biological wastewater treatment systems all use mixed microbial communities, which involve complex interactions among their members. In other words, bioreactors contain their own ecosystems. As a consequence, the physical characteristics of the treatment system and the manner in which it is operated will influence the composition of the...

Attached Growth Bioreactors

Fluidized bed bioreactors (FBBRs) can be operated with any of the three biochemical environments, and the nature of that environment determines what the bioreactor accomplishes. Fluidized bed systems for denitrification were among the earliest developed because all materials to be reacted were present in a soluble state. However, through use of pure oxygen as a means of providing dissolved oxygen at high concentration, aerobic fluidized beds soon followed. Their chief...

Cl

Where C and n are empirical coefficients. Combining these two equations and combining k, C, and XH into a new coefficient K, called the treatability coefficient, gives When recirculation is not used, the applied soluble substrate concentration is just the concentration in the process influent wastewater. However, when recirculation is used, the influent is diluted by the recirculated effluent, making the applied substrate concentration less than the concentration in the untreated wastewater. In...

Cd

0 100 200 300 400 500 600 Cross Sectional Area, cm2 Figure 16.8 Effect of cross-sectional area and the associated total hydraulic loading at a fixed flow rate on the depth and volume of media in a packed tower without recirculation required to achieve a 90 reduction in substrate concentration. The values of the kinetic parameters, stoichiometric coefficients, and system variables are given in Table 16.1 unless otherwise specified. factors act to cause significant degrees of intermixing, the...

Recirculation Ratio a

Figure 16.7 Effect of recirculation ratio on the ability of a packed tower of fixed size to remove substrate. The recirculation of effluent is from a perfect clarifier. The values of the kinetic parameters, stoichiometric coefficients, and system variables are given in Table 16.1 unless otherwise specified. Although the model results discussed above show that recirculation of clarified effluent will decrease substrate removal, circumstances exist in which recirculation could increase it. For...

Fractional Distance from the Inlet xL

The reduced reaction rate due to dilution of the substrate, with the result that the output substrate concentration is higher from a tower with recirculation, as can be seen in Figure 16.6b. A more detailed examination of the effect of recirculation on the effluent substrate concentration is presented in Figure 16.7. At low recirculation rates the decrease in reaction rate associated with the lower applied substrate concentration offsets the positive effect of recirculation on the mass transfer...

Co

Figure 16.4 Effect of influent flow rate and the associated total hydraulic loading on the performance of a packed tower with fixed cross-sectional area without recirculation. The values of the kinetic parameters, stoichiometric coefficients, and system variables are given in Table 16.1 unless otherwise specified. erally require greater tower depths to achieve a fixed effluent concentration, as shown in Figure 16.5. Recirculation of clarified effluent has a complicated effect on tower...

Performance Of An Ideal Packed Tower

Predictions of ideal tower performance were obtained by Grady and Lim' by numerically integrating Eq. 16.6 with a fourth-order Runga-Kutta method using the parameter values in Table 16.1, unless noted otherwise. Equations of the form Table 16.1 Kinetic Parameters, Stoichiometric Coefficients, and System Variables Used to Generate Figures 16.2-l 6.8 Table 16.1 Kinetic Parameters, Stoichiometric Coefficients, and System Variables Used to Generate Figures 16.2-l 6.8 mg substrate COD (mg biomass...

Simple Soluble Substrate Model With Traditional Decay As Presented In Chapter

This model should be applied only to wastewaters without significant quantities of particulate organic matter for which the primary focus is on carbon oxidation. It can also be applied to situations in which nitrification is an objective. The focus here will be on carbon oxidation, but the reader can extend the principles presented to nitrification, in which case the substrate would be ammonia-N rather than soluble, biodegradable organic matter. Generally, particulate organic matter is...

B

Figure 13.8 Systems for degassifying anaerobic mixed liquor before sedimentation A cascade B. (low-through tank C. thin-film trickle-film. the range of HRTs associated with this range of SRTs is dependent on the strength of the wastewater and the concentration of active biosolids that can be attained in the bioreactor. Bioreactor suspended solids concentrations may range from 4 to 6 g L as VSS to as high as 25 to 30 g L as VSS, depending on the settleability of the solids that develop. The...

Fate and Effects of Xenobiotic Organic Chemicals

It is clear from the material presented in the preceding chapters that our ability to design bioreactors for oxidation of biogenic organic matter, nitrification, and deni-trification is well established. Furthermore, our understanding of biological phosphorus removal is advancing rapidly, leading to better models which will result in improved design procedures. Less well established, however, is our ability to design biological treatment systems for the biod gradation of xenobiotic organic...

Aerobic Growth of Heterotrophs in a Single Continuous Stirred Tank Reactor Receiving

5.1 Basic Model for a Continuous Stirred Tank Reactor 145 5.2 Extensions of Basic Model 160 5.3 Methods of Biomass Recycle and Wastage 172 5.4 Performance of a CSTR as Predicted by Model 175 5.6 Study Questions 188 References 190 6. Multiple Microbial Activities in a Single Continuous Stirred Tank Reactor 191 6.1 International Association on Water Quality Activated 6.2 Effect of Particulate Substrate 200 6.3 Nitrification and Its Impacts 208 6.4 Denitrification and Its Impacts 216 6.7 Study...

Techniques for Evaluating Kinetic and Stoichiometric Parameters

In the preceding chapters of Part II, we have examined models for characterizing the performance of ideal suspended growth bioreactors. Before those models can be used for design and evaluation of wastewater treatment systems, however, values must be available for the kinetic and stoichiometric parameters in them. Some of those values may be obtained from the literature or from experience with the particular wastewater to be treated. Generally, however, parameters must be evaluated...

Model For Substrate Removal In A Packed Tower

By making certain simplifying assumptions, the effectiveness factor approach may be used to investigate the theoretical performance of a packed tower, and this has been done by Grady and Lim.' Consequently, their approach will be presented here. The first assumption is that the electron acceptor is present in excess so that the electron donor acts as a single limiting nutrient. The second is that only one type of microorganism is present heterotrophs if the electron donor is organic matter and...

Phb

Figure 2.6 Schematic diagram depicting the Mino model for the uptake and release of inorganic phosphate by PAOs A. Anaerobic conditions B. aerobic conditions. (Adapted from Went el et al.v) Soluble and Particulate Substrates plus Debris Figure 2.7 Overview of fundamental events occurring in an aerobic bioreactor receiving a soluble substrate (Ssi). (Adapted from Mason et al.J) will also be soluble microbial product (SMP) formation associated with that substrate consumption and growth....

The Complexity of Microbial Communities Reality Versus Perception

It is apparent from the preceding that the microbial communities in biochemical operations are very complex, involving many trophic levels and many genera and species within a trophic level. Unfortunately, most studies on community structure have been descriptive and the exact roles of many organisms have not even been defined, much less quantified. As a consequence, wastewater treatment engineers have tended to view the communities in biochemical operations as if they were monocultures...

Anaerobic Operations

The microbial communities in anaerobic operations are primarily procaryotic. with members of both the Bacteria and the Archaea being involved. Although fungi and protozoa have been observed under some circumstances, the importance of eucary-otic organisms is questionable. N Thus, the emphasis here will be on the complex and important interactions between the Bacteria and the Archaea that are fundamental to the successful functioning of methanogenic communities. Because those intcrac- tions...

Aerobic Anoxic Operations

Activated sludge, aerated lagoons, and aerobic digesters have similar microbial ecosystems, although they differ somewhat in the relative importance of various groups. The microorganisms in those operations are all Bacteria and microscopic Eucarya, and generally may be divided into five major classes (1) Hoc-forming organisms, (2) saprophytes, (3) nitrifying bacteria, (4) predators, and (5) nuisance organisms.' With the exception of nitrifying bacteria, these are...

Microbial Ecosystems In Biochemical Operations

An ecosystem is the sum of interacting elements (both biological and environmental) in a limited universe. Consequently, each biochemical operation will develop a unique ecosystem governed by the physical design of the facility, the chemical nature of the wastewater going to it, and the biochemical changes wrought by the resident organisms. The microbial community which develops in that ecosystem will be unique from the viewpoint of species diversity, being the result of physiological, genetic,...

Theory Modeling of Ideal Suspended Growth Reactors

The primary function of a mathematical model is to reduce a complex system to the minimum terms essential for its description so that those terms may be manipulated, thereby helping us to understand how the system will respond under a variety of conditions. Generally, mathematical models do not describe a system completely, but if the terms are chosen with care, the model response will be qualitatively similar to the real system. In Part I we considered in detail the major events occurring in...

Important Processes In Biochemical Operations

Regardless of the nature and complexity of the microbial community involved, there are certain fundamental processes that occur universally in biochemical operations. The relative importance of these processes, and hence the outcome from a biochemical operation, depends on the physical configuration of the operation and the manner in which it is operated. Our ability to select and design the appropriate biochemical operation for a specific task depends on our recognition of the importance of...

Stepwise Growth Process Of Filamentous Organism

Activated Sludge Formation

Above, result in a reduction in the SRT required to achieve good bioflocculation. This reduction is reflected in the typical SRT operating ranges presented in Figure 9.3. Bioflocculation forms the microstructure of activated sludge floe.'1 The resulting floes are relatively weak, however, and can readily be broken into smaller particles by turbulence. Consequently, if bioflocculation is the only mechanism of floe formation, a variety of particle sizes will be present, ranging from large floes...

Influent

Figure 20.1 Schematic diagram of an RBC. Figure 20.1 Schematic diagram of an RBC. A description of the RBC process is provided in Chapter 17 and immediately above. As indicated in Figure 20.1, a cover (typically fiberglass) is provided over each individual RBC unit for physical protection and process enhancement. Alternatively, entire installations can be placed in buildings, but this can result in a humid, corrosive atmosphere, leading to accelerated corrosion. Covers provide protection...

K

Where Ks is the half-saturation coefficient. Ks determines how rapidly p. approaches i and is defined as the substrate concentration at which p. is equal to half of i, as shown in Figure 3.1. The smaller it is, the lower the substrate concentration at which X approaches (1. Because of his pioneering efforts in defining the kinetics of microbial growth, Eq. 3.36 is generally referred to as the Monod equation. Because of the similarity of Eq. 3.36 to the Michaelis-Menten equation in enzyme...

Classes of Biodgradation and their Models

Engineers need to quantify biod gradation rates in order to design a biological process capable of achieving a desired effluent concentration of a given XOC. This requires the use of models and the evaluation of the parameters in them. For modeling purposes, biod gradation has been divided into two broad categories, growth-linked and cometabolic. Growth-Linked Biod gradation. Most biod gradation occurs by growth-linked metabolism. By that we mean that the microorganisms performing the biod...

Factors Influencing Biodgradation

The primary factor determining the ability of microorganisms to degrade an XOC, as well as the kinetics of that biod gradation, is its molecular structure. The closer that structure is to the structure of a biogenic compound, the easier the XOC will be to biodegrade because the more readily it will fit into common metabolic pathways. Xenophores are substituents on organic molecules that are physiologically uncommon or entirely nonphysiological,1 and their presence is one factor that can make a...

Phosphorus Uptake And Release

Biological phosphorus removal is a complex process that is dependent on the growth of specialized phosphate accumulating organisms (PAOs), which store phosphorus as polyphosphate (poly-P), as discussed in Section 2.4.6. Because biological phosphorus removal is still the subject of active experimental investigation, there is little consensus concerning all of the rate expressions describing it. Furthermore, the microbial events involved are subject to complex control through the concentrations...

Common Names Of Biochemical Operations

In almost all fields, certain operations have gained common names through years of use and development. Although such names are not always logical, they are recognized and accepted because of their historical significance. Such is the case in environmental engineering. In fact, some of the names bear little resemblance to the process objectives and are even applied to more than one reactor configuration. For purposes of discussion, twelve common names have been chosen and are listed in Table...

Substrate Cone mgL

Figure 3.2 Typical plot ol the relationship between (he specific growth rate coefficient and the concentration of an inhibitory substrate. The parameter values given were used to construct the curve with the Andrews equation (3.39). Note that the values of jj. and Ks are the same as in Figure 3.1. growth of heterotrophic bacteria on biogenic organic matter. In those cases it is necessary for the kinetic expression to depict the effect of the concentration of the inhibitor (SJ on the...

[pH

Activated sludge, 395 aerobic digestion, 569, 570-570, 580581 anaerobic processes, 632-637 BNR processes, 512, 515-516 decay, biomass, 569-571 fermentation, solids, 655 HPOAS, 384 kinetic parameters, 91-92, 94 lagoons, 676-677, 689 methanogens, 632-633 nitrification, 76, 91-92, 212, 512, 515516 yield, 43 Phoredox process (see A oTM process) Phosphate accumulating organisms (PAOs) (see also Biological phosphorus emo-val BPRJ processes), 24. 29, 49-52, 489-490, 537-538 kinetic parameters, values,...

SRT hr

Figure 5.5 Effect of SRT on the active fraction of the biomass in a CSTR receiving a soluble substrate. Kinetic parameters and stoichiometric coefficients are listed in fable 5.2. to substrate removal. Nevertheless, the amount of active biomass continues to increase as the SRT is increased, as can be seen by multiplying the active fraction from Figure 5.5 times the mass of biomass from Figure 5.4. As a consequence, increases in SRT are generally worthwhile, although a point of diminishing...

Two Stage Phoredox

Reaktor Phoredox Schemat

Significant nitrogen removal can also occur in SBRAS systems.' ' '' The performance of SBRAS systems and their analogy to continuous flow activated sludge systems, particularly the MLE process, is discussed in Section 7.8. The design and operation of SBRAS systems is discussed in Chapter 10. Many operating SBRAS facilities use an anoxic till period or anoxic aerobic cycling as an anoxic selector to control the growth of filamentous bacteria, also resulting in a significant degree of nitrogen...

Biomass Growth And Substrate Utilization

3.2.1 Generalized Equation for Biomass Growth It will be recalled from Section 2.4.1 that biomass growth and substrate utilization are coupled. Furthermore, we see in Section 2.4.2 that environmental engineers account for maintenance energy needs through the decay reaction. This means that as long as the production of soluble microbial products is negligible, the only use of substrate is for biomass growth. Consequently, when a stoichiometric equation for biomass growth is written with the...

Effects Of Temperature

Temperature can exert an effect on biological reactions in two ways by influencing the rates of enzymatically catalyzed reactions and by affecting the rate of diffusion of substrate to the cells. The importance of both has not always been recognized and this has led to some confusion in the quantification of temperature effects. For example, temperature effects observed in the laboratory are often more pronounced than those observed in the field. This is due in part to the fact that full-scale...

Ph

Figure 3.4 Effect of pH on the maximal activity of Nitrosomonas. The listed references are cited in 98. (From A. V. Quinlan, Prediction of the optimum pH for ammonia-N oxidation by Nitrosomonas curopaea in well-aerated natural and domestic-waste waters. Water Research 18 561-566, 1984. Copyright Elsevier Science Ltd. reprinted with permission.) noted that this equation only predicts the decline in rate at low pH and does not predict the observed drop-off at pH above 8.5. This is not generally a...

Simple Soluble Substrate Model With Traditional Decay In The Absence Of Data On The Active Fraction

As discussed in Section 8.2.1, the active fraction of the biomass, fA, is difficult to assess and thus data will generally not be collected on it during routine treatability studies for wastewater treatment. As a result, it will generally be impossible to determine bH and YM by the techniques outlined in Section 8.2.2. Rather, an additional experiment must be conducted which will allow independent determination of bH. Once bH is known, the value of YM can be determined by using an assumed value...

Oxygen Requirement Index

Benefits, drawbacks, 502-503 BOD5 phosphorus removal ratio, 509-510 Abiotic removal mechanisms, XOCs, 994 sorption. 997-999 volatilization. 994-997 Acetate, removal from domestic wastewater, and SRT. 356-357. 537-538 uptake, specific rate, 105 Acidogenesis. 31 microbiology, 33-34 SRT, choice of, 356-357. 624 temperature effects, 630 Activated biofilter (ABF) (see also Trickling filter activated sludge TF AS ). 854855, 858-859, 870, 897 Activated sludge (see also Completely mixed activated...

Multiple Microbial Activities in Complex Systems

Chapters 5 and 6 introduce us to the response of microbial cultures in single continuous stirred tank reactors (CSTRs) and demonstrated the importance of solids retention time (SRT) in determining that response. Although such reactors have found extensive use in research and in the treatment of some industrial wastewaters, more complex reactor systems are commonly used in practice and it is important to consider them. Consequently, in this chapter we will use International Association on Water...

Bacteria

Sludge Good Settling

Bacteria can be classified in many ways however, the most important from an engineering perspective is operational. Consequently, we will focus on it. Like all organisms, members of the domain Bacteria derive energy and reducing power from oxidation reactions, which involve the removal of electrons. Thus, the nature of the electron donor is an important criterion for their classification. The two sources of electrons of most importance in biochemical operations are organic and inorganic...

Simplified Stoichiometry And Its

In Chapter 5, we use the concepts developed in Section 3.1.3 to construct mathematical models that incorporate the various events discussed in this chapter. There are many circumstances, however, in which the use of stoichiometric concepts would be very useful even without the development of rigorous equations. For example, examination of Eq. 3.13 expressing biomass growth and Eq. 3.52 expressing biomass decay by the traditional approach reveals that they could be combined into a single...

Ab F

Less information is available about net process yields in coupled TF AS systems than is available for activated sludge systems. However, because the retention of biomass in a trickling filter increases as the TOL is decreased, the value of Y typically is influenced more by the TOL on the trickling filter than by the SRT of the suspended growth bioreactor and decreases as the TOL is decreased. Furthermore, values are typically on the order of 0.7 to 0.9 mg TSS mg BODs. The following...

Maintenance Endogenous Metabolism Decay Lysis and Death

Screen Grid Resistor

The yield values in the preceding section are those that result when all energy obtained by the biomass is being channeled into synthesis. Energy for synthesis is not the only energy requirement for microorganisms, however. They must also have energy for maintenance.' Cellular processes, whether mechanical or chemical, require energy for their performance, and unless a supply is available these essential processes will cease and the cell will become disorganized and die. Mechanical processes...

Positive Draft Of Air Flow

The choice between the two alternative designs would have to be made on the basis of economics and other such factors since they should both give similar performance. This example illustrates the relationship between THL and media depth for a fixed media volume. Although it is recognized today that a minimum THL must be maintained to fully utilize the media and that recirculation can be used to achieve that THL, analysis of historical studies suggests that this requirement was not widely...

Factors Affecting Performance

Trickling Filter Loading Rates

Over its long history of use, a large data base has been assembled describing the factors affecting the performance of the trickling filter process. Unfortunately, in many cases the data are contradictory and incomplete. This arises largely because of the interrelation between trickling filter design and operational parameters. It also arises because our understanding of the trickling filter has evolved throughout its history and continues to evolve today. Our current understanding allows...

Multiple Events

The purpose for development of the model in Table 6.1 was to allow engineers to simulate biochemical reactors in which all of the listed processes are occurring. Thus, it would be instructive to use it to investigate such a situation in a single CSTR. It is apparent, by now, however, that the conditions required for anoxic growth of heterotrophs and aerobic growth of autotrophs are mutually exclusive, since both are controlled by the dissolved oxygen concentration, but in the opposite manner....

Extensions Of Basic Model

The simple model developed in Section 5.1 was for a system receiving only soluble substrate. However, most wastewaters contain soluble organic matter that is nonbiodegradable. Furthermore, all domestic and many industrial wastewaters contain suspended matter that escapes removal by sedimentation prior to entrance of the wastewater into the biochemical operation, and the impacts of those solids must be accounted for in any models depicting fully the operation of CSTRs. Suspended material may be...

Conventional And High Purity Oxygen Activated Sludge

Cstr Activated Sludge

Figure 7.1 presents a schematic diagram of the system used to simulate conventional and high purity oxygen activated sludge systems. All influent and all biomass recycle enters the first bioreactor and passes from bioreactor to bioreactor down the chain. For the purposes of this chapter, the bioreactors were considered to be of equal volume, but different residence time distributions can be attained by using bioreactors of different size.1* The influent flow rate used in simulations was 1000 m'...

Modeling Nonideal Reactors

Courbe Dissociation Hemoglobine

The use of RTDs for the prediction of reactor performance is a complex subject and the reader is encouraged to consult other sources for more complete coverage. v The techniques commonly used in environmental engineering are relatively straightforward, however, and thus we will look at them briefly. 4.4.1 Continuous Stirred Tank Reactors in Series Model The simplest way to model a reactor with a nonideal flow pattern is as a series of CSTRs and this technique will be used extensively in this...

Terminal Reynolds Number

Figure 18.5 Effect of terminal Reynolds number, Re on the drag coefficient, C, of bio-particles. (From K. S. Ro and J. B. Neethling, Terminal settling characteristics of bioparticles. Research Journal, Water Pollution Control Federation 62 901-906, 1990. Copyright < ' Water Environment Federation reprinted with permission.) Figure 18.5J shows three relationships and compares them to the relationship of Schiller et al. (referenced in 24) for clean spherical particles. The equations are given...

Aerobic Growth of Biomass in Packed Towers

Several types of attached growth bioreactors were listed in Table 1.2. Among those, the most widely used is the packed tower, which contains microorganisms growing on an immobile support over which wastewater flows in thin sheets. Most recently installed packed towers use plastic media as the immobile support. Two types are in current use, random packing, which is typically in the form of cylinders approximately 5 cm in diameter and 5 cm long, and bundle media, which consists of sheets formed...

Step Feed Activated Sludge

Phostrip Process

Figure 7.10 presents the schematic diagram for the configuration used to simulate an SFAS system. As in Figure 7.1, five equal sized CSTRs in series were used, with all biomass recycle to the first bioreactor, but in this case the feed was distributed evenly among the bioreactors. All other characteristics of the system, including the flow rates, feed concentrations, etc., were the same as those used to simulate the performance of the tanks-in-series system. 7.3.2 Effect of SRT on Steady-State...

Basic Model For A Continuous Stirred Tank Reactor

A schematic diagram of a single CSTR is shown in Figure 5.1. A bioreactor with volume V receives a flow at rate F containing only soluble, noninhibitory, biodegradable organic substrate at concentration Sso (in COD units) and sufficient inorganic nutrients to make the organic substrate the growth limiting material. The influent flow and concentrations are constant, as are pH, temperature, and other environmental conditions. Within the bioreactor the heterotrophic biomass uses the substrate as...

Requirements for Biodgradation

Becausc initiation of biod gradation of an XOC requires the presence of an enzyme that is able to perform a transformation reaction, it follows that biod gradation of the XOC requires the presence of a microorganism with the genetic capability to synthesize that enzyme. Furthermore, if mineralization of the XOC is to occur, the transformation product from the first reaction must serve as the substrate for another transforming enzyme, etc., until ultimately a biogenic product is formed that will...

Introduction And Background

Classification of Biochemical Operations 3 1.1 The Role of Biochemical Operations 4 1.2 Criteria for Classification 6 1.3 Common Names of Biochemical Operations 10 1.5 Study Questions 18 References 18 2. Fundamentals of Biochemical Operations 19 2.1 Overview of Biochemical Operations 19 2.2 Major Types of Microorganisms and Their Roles 21 2.3 Microbial Ecosystems in Biochemical Operations 25 2.4 Important Processes in Biochemical Operations 35 2.6 Study Questions 55 References 55 3....

Multiple Microbial Activities in a Single Continuous Stirred Tank Reactor

In Chapter 5, we investigated the growth of aerobic heterotrophic bacteria in a single continuous stirred tank reactor (CSTR) receiving a soluble substrate. Through development of a simple model we saw that the SRT is an important determinant of bioreactor performance because it is related to the specific growth rate of biomass at steady-state. We also saw that there is a minimum SRT below which biomass growth cannot occur, as well as a minimum substrate concentration that can be achieved no...

Applications Attached Growth Reactors

Part IV presents the fundamental principles of ideal attached growth reactors and their application to packed towers, rotating disk reactors, and fluidized bed reactors. In Part V, those principles are applied to the practical design and operation of a variety of attached growth reactors. Chapter 19 addresses the design of trickling filters, the principal packed tower used in practice. Chapter 20 addresses rotating biological contactors, the principal rotating disk reactor used in practice....

1

In that case, the required digester volume is given by In determining the degree of thickening that can be accomplished during digestion it is often desirable to know the suspended solids concentration on a TSS basis. The TSS is just the sum of the VSS and the FSS, XM F Although some FSS are solubilized during digestion, as discussed in Section 12.1.1, many designers assume that they remain unchanged, thereby giving a conservative estimate of the TSS concentration. In that case, the FSS act...

Estimation of Kinetic Parameters

Because of all of the terms in ASM No. 1 and the generation of soluble substrate from slowly biodegradable substrate, it is not possible to use the approach described in Section 8.2 to obtain iH and Ks. Conse quently, an alternative approach must be used. The batch techniques described in Section 8.4 may be applied using the soluble fraction of the wastewater, although as discussed in that section, it is currently unclear whether intrinsic or extant parameter...

Packed Bed Bioreactors

The design of packed bed bioreactors is based on selection of an appropriate TOL and bioreactor configuration consistent with constraints on the maximum THL that can be applied to the bioreactor to avoid excessive headloss and backwash recycle volumes. These principles are illustrated in the following example where the technology is applied for a carbon removal application. Size an UFPB bioreactor using fired clay media to treat a wastewater with a flow rate of 10,000 m' day. The wastewater has...

Sizing A Fluidized Bed Biological Reactor

The sizing of an FBBR proceeds in a logical and straight forward manner, utilizing the information presented earlier in this chapter. As with all other biological processes, the parameters in the model must be specified, as must the influent flow rate and concentration, and the desired substrate removal across the system. Shieh and Keenan1 have presented procedures for estimating the needed parameters. The sizing of the FBBR entails choosing a porosity, the carrier particle, the optimal biofilm...

Estimation of Monod Parameters and Ks

Once S, is known, Ss can be calculated with Eq. 8.4, thereby allowing i and Ks to be determined from Eq. 5.13 using the value of h> ,( determined previously As with YH and h,,, the best way to determine p.,, and Ks is through use of a nonlinear least squares analysis. Ss is treated as the dependent variable, with 1 0, + bh as the independent variable. If a nonlinear least squares routine is unavailable, or if the error structure is inappropriate for nonlinear techniques, Eq. 5.13 can be...

Using Traditional Measurements To Approximate Wastewater Characteristics For Modeling

As seen in the preceding section, characterization of a complex wastewater in a manner suitable for use with ASM No. 1 is quite involved and represents a significant investment of time and money. Consequently, such characterizations are not ordinarily done as part of the routine measurements made at wastewater treatment plants. Rather, in the United States, wastewaters are normally characterized in terms of the concentrations of TSS, VSS, five-day biochemical oxygen demand (BOD.), ammo-nia-N,...

Biomass Growth Substrate Utilization and Yield

When reduced to their barest essentials, biochemical operations are systems in which microorganisms are allowed to grow by using pollutants as their carbon and or energy source, thereby removing the pollutants from the wastewater and converting them to new biomass and carbon dioxide, or other innocuous forms. Because of the role of enzymes in microbial metabolism, the carbon and or energy source for microbial growth is often called the substrate, causing wastewater treatment engineers to...

Ao

-Ac cross sectional area available for flow where is the cross-sectional area of the reactor, x the distance from the reactor entrance, Ax the length of the infinitesimal volume, and F CA and F-C J A the mass flow rates of A evaluated at the distances x and x -I- Ax from the reactor entrance. In the limit as Ax 0, the first term on the right side in Eq. 4.8 becomes the partial derivative of FCA with respect to distance and Eq. 4.8 reduces to At constant flow rate, the reactor will achieve...

P 1000 Q

The necessity to indicate that the minimum feasible volume calculated with Eq. 10.4 comes from the floe shear criterion stems from the fact that there is a maximum volumetric rate at which oxygen can be transferred in activated sludge systems, and it also imposes a lower limit on the bioreactor volume. This maximum rate is device specific, and the manufacturer of the particular equipment of interest must be contacted to determine the appropriate maximum value for a given application. For...