Info

Matsuo, M. C. Wentzel. and G. v. R. Marais. Activated sludge model No. 2. IAWQ Scientific and Technical Reports, No 3, 1995. 20. Inomae, K., H. Araki, K. Koga, Y. Awaya, T. Kusuda, and Y. Matsuo, Nitrogen removal in an oxidation ditch with intermittent aeration. Water Science and Technology 19(1 2) 209-218, 1987. 21. Joel, A. R. and C. P. L. Grady Jr., Inhibition of nitrification Effects of aniline following biod gradation. Journal, Water Pollution Control...

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...

Study Questions

Draw a sketch of the nitrogen cycle, labeling all reactions. Then explain the following terms and their importance in biochemical operations am-monification, assimilation, nitrification, denitrification, and assimilative reduction. 2. Define or explain the following terms and their use in classifying the microorganisms in biochemical operations electron donor, electron acceptor, heterotroph, autotroph, nitrifier, denitrifier, methanogen, obligate aerobe, obligate anaerobe, facultative anaerobe,...

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...

References

E., A pilot plant study of a rotating biological surface for secondary treatment of unbleached kraft mill waste. Technical Association of the Pulp and Paper Industry 57(9) 106-1U, 1974. 2. Antonie, R. L., Response of the Bio-Disc process to fluctuating wastewater flow. Proceedings of the 25th Industrial Waste Conference, Purdue University Engineering Extension Series No. 137, pp. 427-435, 1970. 3. Antonie, R. L., Fixed Biological Surfaces-Wastewater Treatment The Rotating Biological...

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

Oxygen Transfer Diagram

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...

Key Points

Five guiding principles provide the basis for the design and evaluation of all suspended growth bioreactors The biochemical environment imposed upon a bioreactor determines the nature of the microbial community that develops and the character of the biological reactions that they perform. The solids retention time (SRT) is the most important design and control parameter available to the engineer. A chemical oxygen demand (COD) balance across a bioreactor provides valuable information about the...

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

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

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

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

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

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...

Q O O

Figure 7.36 Effect of SRT on the steady-state concentration of various constituents in the last reactor of the Bardenpho system depicted in Figure 7.35. For comparison, the dashed curves represent the performance of the MLE system described in Figure 7.29. Influent flow 1000 m' day. Influent concentrations are given in Table 6.6. Biomass recycle flow 500 m' day mixed liquor recirculation flow 2000 m' day, reactor volumes V, 50 m' V, 100 m' V, 75 m' V4 25 m Parameters are listed in Table 6.3....

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

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...

Methods Of Biomass Recycle And Wastage

In developing the models in the preceding sections a portion of the flow from the bioreactor passed through a biomass separator, as shown in Figure 5.1. However, the characteristics of that separator were not specified. On a laboratory scale, reactors have been used which mimic closely the situation depicted in Figure 5.1. In one design, the biomass is contained in a vessel with porous walls through which clear liquid flows, leaving the biomass inside. The wastage flow is taken directly from...

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...

Q

02468 10 02468 10 SRT, days SRT, days Figure 7.39 Effect of SRT on the steady-state concentrations of various constituents in the aerobic (last) reactor of the Phoredox system depicted in Figure 7.38. For comparison, the dashed curves represent the performance of a single CSTR with a volume of 250 m'. Influent tlow 1000 m' day. Influent concentrations are given in Table 7.1. Biomass recycle How 500 m day volume of the anaerobic (first) reactor 50 m', volume of the aerobic (second) reactor - 200...

Model For Substrate Removal In A Single Rotating Disc Reactor

Because of the complex nature of an RDR, certain simplifying assumptions must be made to model it. The first is that steady-state conditions prevail so that microorganisms are sheared from the surface of the biofilm at a rate equal to their growth. Thus, the biofilm behaves as a steady-state biofilm of known thickness. That thickness is an input parameter and is not computed in the model. The second assumption is that the turbulence in the bioreactor fiuid is sufficient to keep the detached...

Process Description

Oxygen Transfer Cocurrent Bioreactors

Since its inception by Arden and Lockett in 1914,4 the activated sludge process has grown in popularity until today it is the most widely used biological wastewater treatment process. Much experimentation has occurred since its initial development, and many variations are known. Most of the variations can be grouped into the eight named operations listed under activated sludge in Table 1.2. Theoretical simulations of the performance of many of those variations are presented in Chapters 5, 6,...

Suspended Growth Srt Srtmin for Nitrification

Figure 19.10 Effect of the SRT in a suspended growth bioreactor and the nitrification efficiency in an upstream trickling filter on the effluent ammonia-N concentration from a coupled TF AS system. (From G. T. Daigger, L. E. Norton, R. S. Watson, D. Crawford, and R. B. Sieger, Process and kinetic analysis of nitrification in coupled trickling filter activated sludge processes. Water Environment Research 65 750- 758, f993. Copyright Water Environment Federation reprinted with permission.) ling...

Biological Nutrient Removal

Biological nutrient removal (BNR) processes are modifications of the activated sludge process that incorporate anoxic and or anaerobic zones to provide nitrogen and or phosphorus removal. Many BNR variants have been developed, representing a wide range of nutrient removal capabilities. This chapter presents the basic design and operational principles for several of them. It builds upon the theoretical concepts presented in Chapters 2, 3, 6, and 7. 11.1 PROCESS DESCRIPTION 11.1.1 Historical...

Process Design

This section describes procedures and presents illustrative examples for the design of BNR systems. The design of these systems builds upon and utilizes all of the procedures and principles presented in Chapters 9 and 10. The major difference, however, lies in the fact that more interrelated processes arc at work in BNR systems, making it impossible to derive accurate analytical expressions for them. As a consequence, the only way to accurately predict the performance of any proposed BNR system...

Other Packed Tower Models

It is apparent by now that a packed tower is a very involved biochemical operation that is difficult to model theoretically. Consequently, empirical and semiempirical approaches have been used to model it and a number of design equations have been developed. The NRC' and Gollar-Gotaas1 equations are strictly empirical because they are based only on the application of regression analysis techniques to experimental observations. Consequently, they are valid only in the limited region over which...

Stoichiometry and Kinetics of Biochemical Operations

Stoichiometry is concerned with the relationships between the quantities of reactants and products in chemical reactions. Kinetics is concerned with the rates at which reactions take place. Because stoichiometry quantitatively relates a change in one reactant (product) to the change in another, when the reaction rate of one reactant (product) becomes known, stoichiometry may be used to determine the reaction rate of another in the reaction. In this chapter we will first examine these...

Rotating Biological Contactor

The term rotating biological contactor (RBC) refers to a class of aerobic attached growth bioreactors containing circular shaped corrugated plastic media that are mounted on a horizontal shaft, partially submerged (typically 40 ) in the wastewater, and rotated at a speed of one to two revolutions per minute to alternately expose them to the wastewater and to the atmosphere. Figure 20.1 provides a schematic diagram. A number of manufacturers produce RBC equipment, but they are all similar and...

Bioreactor Configuration

The importance of classifying biochemical operations according to bioreactor type follows from the fact that the completeness of a given biochemical transformation will be strongly influenced by the physical configuration of the bioreactor in which it is being carried out. Therefore, it is important to get a clear picture of the many bioreactor types available. Wastewater treatment bioreactors fall into two major categories, depending on the way in which microorganisms grow in them suspended in...

Performance Of A Cstr As Predicted By Model

The major value of the models in this chapter is as an aid to understanding how CSTRs behave under a variety of conditions. We saw during derivation of the equations that the most important operational variable is the SRT. Consequently, we will first use graphs generated with the parameter values in Table 5.2 to see how SRT influences bioreactor performance. Next, we will investigate the impact of adding inert and microbial solids to the influent to a CSTR. Finally, we will consider the impact...

Aerobic Growth of Heterotrophs in Rotating Disc Reactors

As shown in Table 1.2, one type of attached growth bioreactor is the rotating disc reactor (RDR). In it, closely spaced discs are mounted on a common horizontal shaft placed very near to or touching the liquid surface in a long narrow tank. The shaft is rotated at constant speed, thereby allowing any point on a disc to be alternately submerged and exposed to the atmosphere. When water containing organic matter, nitrogen, and other nutrients flows through the bioreactor, microorganisms consume...

Basic Decisions During Design And Evaluation

Design of a biochemical operation requires that decisions be made that are consistent with the guiding principles summarized in Section 9.1. Some of those decisions establish the nature of the facility, whereas others determine its size. Since the biochemical environment has a profound effect, its choice is one of the earliest decisions that must be made. Then the SRT is chosen, determining the various factors that follow from it, such as the mass of biomass, electron acceptor requirement, etc....

Hawkes H 1963 Ecology Of Wastewater References

E., Slow down that trickling filter. Operations Forum 6(1) 15 20. 1989. 2. Albertson, O. E., Slow-motion trickling filters gain momentum. Operations Forum 6(8) 28-29, 1989. 3. Anderson. B H. Aspegren, D. S. Parker, and M. P. Lutz, High rate nitrifying trickling tillers. Water Science and Technology 29( 10 11 ) 47-60, 1994. 4 Barker, t S G. T. Daigger, and R. C. Naef, A comparative evaluation of trickling filter media performance a preliminary comparison of rock and plastic media....

Denitrification And Its Impacts

In the context of biochemical operations, anoxic growth of heterotrophic bacteria is simply an alternative mode of growth in response to the absence of oxygen and the presence of nitrate-N as the terminal electron acceptor. Because the resulting reduction of nitrate-N to N, removes nitrogen from the wastewater undergoing treatment, the process is also referred to as denitrification. Generally, it occurs when the appropriate conditions are purposely established in bioreactors, but as the rate...

Key Points For Nitrification

International Association on Water Quality activated sludge model No. 1 incorporates eight processes acting on thirteen components. The processes are aerobic and anoxic growth of heterotrophic biomass, aerobic growth of autotrophic bacteria, decay of both heterotrophic and autotrophic biomass, ammonification of soluble organic nitrogen, and hydrolysis of both particulate organic substrate and particulate organic nitrogen. 2. The thirteen components incorporated into ASM No. 1 include six...

Ammonification And Ammonia Utilization

Ammonification is the conversion of soluble organic nitrogen into ammonia-N that occurs as bacteria consume soluble organic matter containing nitrogen. Actually, the true rate of ammonification is difficult to measure because ammonia-N is being consumed by the bacteria as they grow, and the only measurable event is the net accumulation or loss of ammonia in the medium. If the amount of nitrogen available in the organic substrate is just sufficient to meet the biosynthetic needs of the new...

Nitrification And Its Impacts

We see in Section 3.2.7 that the kinetics of growth of autotrophic nitrifying bacteria can be represented in the same manner as that of heterotrophic bacteria. Consequently, the general conclusions derived in Chapter 5 about biomass growth in CSTRs are equally applicable to them. We also see in Section 3.2.10 that the values of their kinetic coefficients are quite different from those for heterotrophs. This means that the specifics of their behavior in a given reactor environment will differ...

An

' 0.98F(SN. , SM1 SNS) (1L7) Furthermore, for the flow diagram depicted in Figure 11.4, the fraction of the nitrateN produced in the aerobic zone that is recirculated to the anoxic zone (fM).K ) can be calculated by simple mass balance. The result is where p is the MLR flow rate expressed as a ratio of the process influent flow rate and a is the RAS flow rate, also expressed as a ratio of the process influent flow rate. The minimum allowable MLR recirculation rate results when the fraction of...