Info

Table 3.2 Factors influencing the Nitrification Process and the section considering the this influence Bacterial Population Dynamics 3.12 3.4 The Energy and Synthesis Relationship The overall stoichiometric reactions in the oxidation of ammonia into nitrate can be summed upas follows NH4+ + 1,5 02 > 2H+ + H20 + N02 (3.1) N02 + 0,5 02 > N03 (3.2) Equations (3.1) and (3.2) serve as energy-yielding reactions for Nitrosomonas and Nitrobacter, respectively. Equation (3.1) has been estimated by...

Kinetic Constants in the Denitrification Process

The value of the saturation constant KD is very low. Davies (1973), found the Kd value for suspended growth systems to be 0,08 mg l nitrate nitrogen without solids recycling. For attached growth systems the value of KD was found to be 0,06 mg l nitrate nitrogen at 25 C. Using these small KD values in equation (4.29), that is Sdenjt is above 1-2 mg nitrate nitrogen, the denitrification will approach a zero order rate. Several investigators (Christensen and Harremoes 1972 Stensel etal. 1973...

Equilibrium curve

Operating line and equilibrium curve for a single-stage operation. If sufficient time of contact is allowed, so that equilibrium is almost reached, the final liquid and solid concentration will correspond to a point (see Q, Fig. 9.10), which is quite close to the equilibrium curve. The mass balance assumes that the amount of liquid mechanically retained with the solid after filtration or settling is negligible. This is usually the case. If Freundlich's isotherm can be used, we can,...

Log size pm

Membrane processes and particle size. The relation between the process and the removable particle size see Figure 10.1, indicates the possibilities of using membrane processes for nitrogen removal. Proteins can accordingly be removed from waste water and waste products such as whey by application of ultrafiltration. This has found a wide use particularly in the dairy industry. Ammonium and nitrate can be removed at least to a certain extent by use of reverse osmosis. This...

Solution

Plot the term 1 < > versus (S0 - S) < > X. 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 Figure B1.2 1 < > versus (S0 - S) 0 X. The y intercept on Figure B1.2 equals (- Kd) 0,05 d1. The value of the slope of the curve on Figure B1.2 equals the yield factor Yobs. Yobs 0,35 d1 0,70 d'1 0,5 Determine the value of the coefficient using the following equation Using this equation is found to be 1,5 d1. A Stripping Column An Ion Exchange Column A Reverse Osmosis Unit A Sedimentation Tank

Energy and Synthesis Relationship

The use of oxygen as the final electron acceptor is more energtically favored than the use of nitrate. By oxygen respiration the energy yield per mole of glucose is 686 kcal mole and by nitrate dissimilation the energy yield per mole glucose is only 570 kcal mole. The greater free energy released for oxygen favors its use whenever it is available. Therefore, denitrification must be conducted in an anoxic environment to ensure that nitate, rather than oxygen, serves as the final electron...

Parameter Untreated Treated

Two large municipal waste water installations in California and in Virginia utilize a regenerant with a pH near neutral. The active portion of the regenerant is a 2 percent sodium chloride solution. A typical elution curve for ammonium with this type of regenerant is shown Fig. 9.8. It is seen that approximately 25-30 bed volumes are required before the ammonium concentration reaches equilibrium, while 10-20 bed volumes are sufficient at high pH regeneration. If the r g n rant is recovered, see...

C

Figure 5.13 The relative concentrations of oxygen and substrate for the loading condition and RBC rotational speed as a function of location of the media. The arrangement of multiple RBC units. Staging of RBC media is recommended to maximize the removal of ammonium. In secondary treatment applications, three or four stages are generally provided for each stream. For small installations, four stages can be provided on a single shaft by installing three inter-stage baffles within the tank, and...

Nmax7 522

The value of E depends on the media used, see Table 5.8 j02 max(T) maximum surface oxygen rate for specific media design The factor 4.3 in equation (5.22) reflects the unit mass of oxygen consumption per unit mass of ammonia nitrogen oxidized. Where recirculation is used, a repetitive solution of the above equation is necessary because recycle effects are included in both the Sn, and Vn terms. The effect of the media on the nitrification rate is not considered in...

Ultrafiltration

Both ultrafiltration and reverse osmosis depend on pressure as the driving force and require a membrane that is permeable to some components and impermeable to others. The difference between the two processes is that, while ultrafiltration is usually used to separate solutes above a molecular weight of 500-2000, which implies a relatively small osmotic pressure, reverse osmosis is used to remove material of low molecular weight, which causes a high osmotic pressure. The polarization is,...

Kinetic Expression for the Denitrification Process

Environmental factors also have a significant effect on the kinetic rates of denitrifier growth and nitrate removal. Temperature, pH, carbon concentration and substrate concentration are considered below. A combined kinetic expression considering factors that affect denitrification is proposed. As in the case of nitrification the Monod Kinetic, equation (4.28), has also been proposed to explain the rate of conversion of nitrate to nitrogen gas, by several investigators, for example Henze and...

Ion Exchange

Ion exchange is a process in which ions on the surface of a solid are exchanged for ions of a similar charge in a solution with which the solid is in contact (Chapter 9). When all the exchange sites have been replaced, the resin must be regenerated. Both natural solids, such as the natural clay mineral clinoptilolite, and synthetic ion exchange, can be used in the removal of ammonium ions. pH control is crucial in the ion exchange process, as the form of the ion exchanger is dependent on the...

Precipitation

Precipitation, in a strictly chemical sense, is the transition of a substance from the dissolved state to the non-dissolved state by the addition of other reagents that lead to the formation of precipitates. Most nitrogen compounds are, unfortunately, readily dissolved in water, which implies that precipitation cannot be used as an easy solution to the problem of nitrogen removal. Nitrogen removal by the use of precipitation may, however, be carried out by the two processes shown as equations...

The Influence of Oxygen on the Denitrification Rate

Investigators have reported various results for the influence of oxygen on the biochemistry of the denitrification process. Dissimilatory nitrate reduction (denitrification) is inhibited by oxygen, whereas assimilatory nitrate reduction is unaffected. Payne (1973) explains that oxygen either represses the formation of the enzyme nitrate reductase or acts just as an electron acceptor, thereby preventing the reduction of nitrate. Beneficial effects of oxygen in the denitrification process have...

Kinetics of the Nitrification Process

The aim of this section and the following sections is to consider the number of environmental factors affecting the rate of growth and nitrification of a nitrifying biomass. A combined kinetic expression is proposed which accounts for the effect of ammonia concentration, temperature, pH, organic content, and dissolved oxygen concentration. At several points, references are made to data obtained from various types of nitrification processes. One distinction that needs to be clearly understood in...

V

Figure 11.4 Destabilization by flocculation. Lawler et al. (1983) has presented a mathematical model describing changes in the particle size (PSD) immediately below the solid liquid interface in gravity thickening based upon Brownian motion, fluid shear, and differential sedimentation. Although the model predicted trends for the coagulation and differential sedimentation for changes in time, solids concentration, particle stability, and the subsidence velocity at the interface, the model was...

Conclusions

The following conclusions can be made on the basis of a comparison between the nitrifying attached and suspended growth processes. 1. The nitrification rate for the attached-growth processes is higher than for the suspended-growth processes. 2. The attached-growth processes are generally used in small sewage works (less than 20 000 Person Equivalent (P.E.)), while the suspended-growth processes are used in large treatment works. Today much effort is being put into the development of large...

Introduction

This chapter aims to give a broad overview of the biological nitrification and denitrification systems and to compare the different unit processes explained in detail in later chapters. This should facilitate the understanding of the following chapters 3-6, dealing with the biological unit processes. The contents of this chapter may be summarized as follows 1) Classification of the different nitrification and denitrification unit processes (section 2.2). 2) The terminology used in the basic...

Some Useful Definitions

To understand the concept of biological treatment processes, it will be helpful to know the following definitions. Aerobic processes are biological treatment processes that occur in the presence of oxygen. Anaerobic processes are biological treatment processes that occur in the absence of oxygen. Anoxic denitrification is the process by which nitrate-nitrogen is converted biologically into nitrogen gas in the absence of oxygen. This process is also known as anaerobic denitrification. Biological...

Dy

For all ordinary purposes the arithmetic mean is entirely satisfactory, and equation (7.28) is changed to The calculation of the number of transfer units for dilute mixtures can be simplified. When the gas mixture is dilute, the second term of equation (7.29) becomes negligible and the equation may be simplified as follows If the equilibrium curve and the operating line in terms of mole fraction are considered as straight lines, it is possible to rewrite equation (7.32) as

The Biofilm

Nitrifier, denitrifier, oxidizer or a combination of these types of bacteria can attach themselves to different types of medium and grow into dense films of a viscous, gelatinous matrix called the biofilm. Waste water passes over this film in thin sheets, with dissolved organics, NH4+ or N03 passing into the biofilm due to diffusion gradients within the film. Suspended particles and colloids cannot penetrate the surface of the biofilm, but will be decomposed on the surface of the biofilm into...

The Sequential and Continuous Ion Exchange Operation

The sequential adsorption or ion exchange operation is limited to treatment of solutions where the solute to be removed is adsorbed relatively strongly when compared with the remainder of the solution. This is often the case when colloidal substances are removed from aqueous solutions using carbon, as in the production of process water. The method for dealing with the spent adsorbent or ion exchanger depends upon the system under consideration. If the material taken up is valuable (e.g.,...

W wc lw Ie

Figure 9.15 Idealized break-through curve. Correspondingly we call the time required for the ion exchange zone to establish itself and move out the bed, Te, which can then be calculated from If we call the height of the entire ion exchange bed, Z(m), and, Tf, the time required for formation of the ion exchange zone, we get The quantity of solid removed from the water in the ion exchange zone from the break-point to exhaustion is U kg solid m2. This area is areas 1 and 2 in Fig. 9.15. If all the...

AmmoniumN concentration

The concentration of ammonium-N in the ion exchanger is shown as a function of the depth at ammonium breakthrough. The ion exchanger is saturated up to the transition zone, where the capacity is not used entirely. The depth of the transition zone is dependent on the flow rate (m h), but not on the total depth of the column. Figure 9.5. The concentration of ammonium-N in the ion exchanger is shown as a function of the depth at ammonium breakthrough. The ion exchanger is saturated up...

The Role of Nitrogen in The Environment

Nitrogen compounds are becoming increasingly important in waste water management, because of the many effects that nitrogenous material can have on the environment. Nitrogen, in its various forms can deplete oxygen due to nitrification, fertilize aquatic plant growth, exhibit toxicity toward aquatic life, affect chlorine disinfection efficiency and present a public health hazard. These effects will be reviewed further in Section 1.4. This volume is about the nitrogen removal processes applied...

Alternative Electron Donors and the CN Relationship

Carbon Sources For Denitrification

As shown in section 4.3, (equations 4.1 and 4.2), the denitrification process needs an electron donor to be accomplished. A variety of compounds that can substitute for methanol as a carbon source have been evaluated experimentally and described in the literature. Table (4.5) shows the wide variety of carbon sources which have been used experimentally other than methanol and internal carbon. The selection of an electron donor depends upon three factors which will be discussed in this section...

Process Variables

It is possible to play on two variables to optimize the application of precipitation by nitrogen removal the stoichiometric coefficient and pH. The composition of the waste water determines the possibilities of finding a good solution to a particular waste water problem by the use of these two variables. The optimum pH for precipitation of magnesium-ammonium-phosphate may be found by use of double logarithmic diagrams, as presented in Section 11.1. The method is best illustrated by presentation...

Design of Breakpoint Chlorination Units

The design of breakpoint-chlorination follows the stoichiometric relations already presented in Sections 8.1 and 8.2. The amounts of chlorine, and other chemicals including acids and bases for pH-adjustment and sulfur dioxide for dechlorination, can be calculated from these relations. The design of the adsorption unit is mainly based on empirical relations - A hydraulic application rate of s 0.1 ml m2 is recommended. - 50 000 - 100 000 m3 waste water can be dechlorinated per m3 of activated...

B

Figure 2.4 Oxidation pond and aerated lagoon with simultaneous primary and secondary treatment Several experiments have been made to combine the suspended and attached growth systems as listed in Table 2.2. The main reasons for the combined cultivation are as follows - increase in the biomass content in the system without an additional loading of the unit - achievement of better and more stable nitrification. Table 2.3 shows a comparison of the amount of suspended solids produced and the yield...

SE Jorgensen

Environmental Chemistry Section Universitetsparken 2,2100 Copenhagen 0, Denmark Amsterdam - London - New York - Tokyo 1993 ELSEVIER SCIENCE PUBLISHERS B.V Molenwerf 1 P.O. Box 211,1000AE Amsterdam, The Netherlands 1993 Elsevier Science Publishers B.V. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system ortransmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without the prior written permission of the...

Nitrification

The two principal genera of bacteria of importance in biological nitrification processes are Nitrosomonas and Nitrobacter. But Nitrosospira, Nitrosolobus and Nitrosovibrio are also nitrifying bacteria. These groups are classified as autotrophic organisms. They are distinguished from heterotrophic bacteria in deriving energy from oxidation of inorganic nitrogen compounds, rather than from the oxidation of organic compounds. These organisms are also special because carbon dioxide is used for the...

Design of the Reverse Osmosis Unit

A reverse osmosis plant consists of a series of modules arranged in parallel. The design data include recovery, pressure, brine, flow rates, product water quality and flux maintenance procedure. To be able to design a reverse osmosis unit one must know the feed water composition, its temperature and osmotic pressure. The capacity requirements of a plant are usually based on a certain reject flow rate at a given temperature or, in the case of waste water treatment, on the feed flow rate. Based...

Carbon monoxide 2 N03 5 CO H20 N2 2 OH 5 C02

Denitrification can also be accomplished by autotrophic bacteria, which can use hydrogen or various reduced-sulphur compounds as energy sources. Under autotrophic growth conditions, no organic carbon sources are required, rather carbon dioxide or bicarbonate is used as a carbon source for cell synthesis. Paracocus denitrificans and Thiobacillus denitrificans can denitrify using hydrogen and reduced-sulphur compounds, respectively. Both of these bacilli can also grow heterotrophically, if an...

C6h1206 N03 05 N2 125 C02 075 H20 Oh

Gaseous organic substrates, such as methane and carbon monoxide, can also be used as substrates in denitrification. Among gaseous substrates, methane is one of the most studied but some contradictions remain in the literature regarding methane metabolism. There is evidence that methane can be used as a terminal electron acceptor by some denitrifiers (Davies 1973). Other investigators have suggested that methane oxidation requires aerobic or microaerophilic conditions, and that subsequent...

Problem Formulation

Figure C2.1 illustrates the equilibrium data for protein uptake by a cellulose ion exchanger. Waste water with a protein concentration of 200 mg 1 is considered. The break-point will be considered as the time at which the effluent has a protein concentration of 20 mg 1 and the bed will be considered exhausted when the effluent has a protein concentration of 180 mg l. The depth of the ion exchange bed is 0.5 m. Find Za and the saturation in percentage.

H2c03 0056 Hc03

Equation (4.12) is shown since if any oxygen is present, it will be used preferentially before the denitrification. The theoretical methanol requirement for nitrate reduction, neglecting synthesis is 1,9 mg methanol per mg nitrate-N (4.1). Including synthesis (equation 4.10) the requirement is increased to 2,47 mg. Similarly, calculation of methanol requirements for nitrite reduction and deoxygenation allows a combined expression to be formulated for the methanol requirement.

Conclusion

Chapters 3 and 4 summarize the results from many scientists concerning different factors affecting nitrification and denitrification. It is often difficult in practice to evaluate the relevance of the different results, and thus it is also difficult to select the appropriate results for the planning of a particular biological nitrogen removal unit. The authors therefore recommend considering as many as possible of the different results mentioned, for the case study at the planning stage of a...

Cd A pe v

Where Cd Newton's dimensionless drag coefficient and A the projected particle area in the direction of the flow. Cd varies with the Reynolds number. By substituting the equations (11.24), (11.25) and (11.26) in equation (11.23), an expression for the dynamic behavior of the particles is obtained After an initial transient period the acceleration becomes zero and the velocity is constant. This velocity can be obtained from equation (11.27) vs If the particles are spherical and the diameter is d,...

Flow rate In m hr

Figure 9.6 Z-nu, the layer not used is plotted versus the flow rate. Z-nu is independent of the height of the column, but as shown on the figure dependent upon the flow rate. Clinoptilolite is available in different purities, dependent on the geological formation of this clay mineral. The clinoptilolite from California has a purity of 8595 , while a Hungarian type from Tokaj has a purity of only 60-70 . The capacity is roughly proportional to the purity. Investigations of the latter type of...

Membrane Processes

Membrane separation, electrodialysis, reverse osmosis, ultrafiltration and other such processes play an increasingly important role in the treatment of waste water (Chapter 10). A membrane is defined as a phase that can act as a barrier between other phases. It can be a solid, a solvent-swollen gel, or even a liquid. Osmosis is defined as the spontaneous transport of a solvent from a diluted solution to a concentrated solution across a semi-permeable membrane. At a certain pressure, the...

Kg h m2 gl m2 settl glgl

1.Sulfuric acid 0.06 1.1 18.2 4.Sulfite liquor 0.83 1.4 1.7 5.Lignin sulfonic acid 0.83 1.4 1.7 6. 3+10 The results show that precipitant number 6 is far the best due to the fast settling. The example shows furthermore, the importance of the use of polyflocculants. The more rapid settling implies that the need for settling area is reduced significantly. Figure C4.1. Settling is plotted versus time for precipitation with six different pr cipitants. The number used are explained in Table C4.1....

Y y yeq

Equation (7.27) may be integrated to obtain, Z, in terms of KG*a, but for many situations the first term on the left-hand side is very close to unity. Since the number of transferred units Ntog is defined as Ntog can, as shown, be related to the height of the packing and the height per transfer unit, termed Htog. The height per transfer unit is an experimental quantity, but it is more convenient to use it than KG*a and other mass-transfer coefficients in the design of towers. Htog has the...

Mg precipitant added pr liter of waste water

COD (mg l) of effluent versus dosage of three different pr cipitants used on waste water from a brewery are shown. 1. corresponds to the use of iron III chloride at pH 4.2, 2 the use of glucose-tri-sulfate at the same pH and 3 the use of lignosulphpnic acid at pH 4.5. Note that the initial COD is 3300 mg l. Figure 11.10. The figure gives the quality of the effluent obtained by precipitation with lignosulphonic acid (lower curve) and glucose-tri-sulfate (upper curve) on brewery...

CH3OH 56 H20 56 C02 5 H 5 e45

It is clear from equations (4.4) and (4.5) that nitrate gains electrons and is reduced to nitrogen gas, which is the electron acceptor. The carbon source, in this example methanol, loses electrons and is oxidized to carbon dioxide, therefore it is the electron donor. As mentioned in Section 3.4, these reactions take place in the context of the carbonic acid system. Equations (4.4) and (4.5) can be modified to reflect the fact that the hydroxide (OH) produced reacts with carbonic acid (carbon...

Yi yz

Absorption Factor Mass Transfer

Equation (7.33) demonstrates that one overall gas-transfer unit is obtained when the change in gas composition equals the average of the overall driving forces causing the change. Let us consider the diagram shown in Fig. 7.13. The line (3) is vertically half-way between the operating line (2) and the equilibrium curve (1). The step CFD, which corresponds to one transfer unit, has been constructed by drawing the horizontal line CEF, so that CE is equal to EF, and continuing vertically to D. HtL...

Comparison of the Biofilm and Activated Sludge Unit Processes

Biofilm techniques are generally used in small sewage works, serving populations of less than 20 000. They tend to be higher in capital costs but lower in running costs than activated sludge plants. Biofilms oxidize generally more nitrogen than activated sludge per unit of bed volume, but the final effluent carries more suspended solids. Activated sludge processes usually require more skilled operators and more frequent maintenance than biofilms, and activated sludge processes are often...

Xd 053 N03 N 032 N02 N 019 Do414

For instance, for a N03 value of 25 mg l of nitrate-N, 0,5 mg l nitrite-N and 3,0 mg l dissolved oxygen, the methanol requirement can be calculated to be 64,1 mg l from equation (4.13). The M N ratio, which is the mg of methanol per mg of initial nitrate nitrogen concentration, is therefore 2,57 (64,1 25), which Is only 4 percent greater then the requirement for nitrate alone. Most experimental data is expressed in terms of the C N ratio, which is the mg of carbon per mg of C per mg of initial...

Air stripping

The stripping process (Chapter 7) is used to remove volatile gases such as hydrogen sulfide, hydrogen cyanide and ammonia by blowing air through the waste water. The process is, therefore, to be considered as a transfer of a compound from a liquid phase to a gas phase. The basic principle of this process of nitrogen removal is illustrated in Figure 7.1. The rate at which ammonia can be removed by air stripping is highly dependent on pH, because the exchange between the two forms, ammonium which...

Characteristic packing data

Dimensions (inch) Poro- dh hydrau- Gas flow Packing Thick- Number Surface sity lie. diam. entry tower Diam. Height ness perm3 m2 m3 (-) (m) 103dh3 2 packings of Raschig rings Stoneware Partly after G.A. Morris and J. Jackson, Absorption Towers, 1953. Partly after G.A. Morris and J. Jackson, Absorption Towers, 1953.

Table Of Contents

NITROGEN COMPOUNDS AS POLLUTANTS 3 S.E. Jorgensen and B. Halling-Sorensen 1.1 The Role of Nitrogen in the Environment 3 1.3 Sources of Nitrogen Pollution 9 1.4 The Effect of Nitrogen Discharge 12 1.5 Treatment Processes for the Removal of Nitrogen 21 1.6 The Major Processes in the Removal of Nitrogen 22 1.8 Some Useful Definitions 39 BIOLOGICAL UNIT PROCESSES FOR THE REMOVAL OF NITROGEN 41 BIOLOGICAL NITRIFICATION AND DENITRIFICATION 43 B. Halling-S0rensen 2.2 Classification of Unit Processes...

Principles of Membrane Processes

Membrane separation, electrodialysis, reverse osmosis, ultrafiltration and other such processes are playing an increasingly important role in waste water treatment. A membrane is defined as a phase that acts as a barrier between other phases. It can be a solid, a solvent-swollen gel or even a liquid. The applicability of a membrane for separation depends on differences in its permeability to different compounds. Table 10.1 gives a survey of membrane separation processes and their principal...

N03 188 H2c03 310

The conversion of 100 mg l of ammonia nitrogen to nitrate-nitrogen according to equation (3.10) therefore yields about 17 mg l of total nitrifying biomass. This relatively low yield has some far reaching consequences in the design of nitrification treatment plants, as will be seen in later sections. The oxygen consumption ratios in equation (3.10) are 3.22 mg 02 per mg NH4+ -N oxidized and 1.11 mg 02 per mg N02 -N oxidized, respectively. This gives a total oxygen need of 4,32 mg 02 per mg NH4+...

Comparison of the Nitrification Rate for Different Unit Processes

In Table 2.4 a comparison is made between the different nitrification rates as a function of the temperature, from data found in the literature. The results shown are presented either with the surface rate in g N m2 * day or the media volume rate in kg N m3 * day. Results show that the submerged filters generally has high nitrification rates in particular the submerged filter named biocarbone, developed by OTV in France, is among the unit processes with the highest nitrification rate. Generally...

Source Henze Christensen and Harremoes 1977

The fact that common sewage bacteria are denitrifiers makes it simple to create an appropriate environment for the denitrification process. All that is needed is the presence of nitrate, an electron donor (carbon source) and an anaerobic environment. A more specialized knowledge of species of bacteria is hardly necessary in most cases. Exceptions are where a special carbon source, such as methane, is used, as only very few bacteria can metabolize methane under anaerobic conditions. Denitrifying...

Bacterial Population Dynamics Applied in the Nitrification Process

The kinetics of the growth of nitrifiers have been discussed in the previous sections. In all practical applications in waste water treatment, nitrifier growth takes place in waste treatment processes, where other types of biological growth occur. In no case are there opportunities for pure cultures to develop. This fact has significant implications in process design for nitrification. In combined carbon oxidation-nitrification systems as well as in separate stage nitrification systems, there...

Biological nitrification and denitrification

The principal effect of the nitrification process is to transform ammonia-nitrogen into nitrate by the use of nitrifying bacteria under aerobic conditions. Denitrification converts nitrate to nitrogen gas by use of denitrifying bacteria, under anoxic conditions. The efficiency of the nitrification process depends on the extent to which organic nitrogen is transformed into ammonia-nitrogen. Chapters 3 and 4 present, in detail, the different factors governing the nitrification and denitrification...

Bacterial Population Dynamics for the Denitrification Bacteria

The population dynamics of the denitrifying bacteria resemble the dynamics proposed for the nitrification bacteria, but the growth rate for the denitrifying bacteria is larger than for the nitrifying bacteria. It is, therefore not difficult for the denitrifying bacteria to compete with oxidizing bacteria in a combined organic and nitrogen removal, as is the case for the nitrifying bacteria. The safety factor SF concept used in Section 3.12 can also be applied to denitrification. It can be...

The Influence of Temperature on the Denitrification Rate

Denitrification can be performed in the temperature range 5 C - 35 C. Many of the denitrifying species are adaptive to temperature changes. It is, therefore, important to realize that there is a difference between long-term and short-term temperature influences on the denitrification process. The growth rate of the organism and removal rate of nitrate are both affected by temperature. To show the effect of temperature on growth and denitrification rates, the results at 20 C from the literature...

Application of Nitrogen Removal by Precipitation

Nitrogen removal by precipitation of magnesium-ammonium-phospate has not yet found a full scale application, but it cannot be excluded that the process will be used in the nearest future for industrial waste water of the right composition to allow an economical removal of phosphorus and nitrogen at the same time. Schulze-Rettmer (1991) has examined the process in details and finds that it is an attractive method to use for nitrogen removal, from a technical as well as from an economic's point...

Q1 Qo 01 02 Ql3 Oa 05 06 07 Q8 Q9 1x5 11

Fig 3.12 The Lineweaver-Burke plot for identifying the type of inhibition of sodium ion concentration for nitrite oxidizing bacteria (Krittiya 1984). Hassan et al. (1988) evaluated the performance of a packed-bed biological reactor in the presence of inhibitors, following either complete or partial modes of competitive, non-competitive, mixed or uncompetitive inhibition. For all types of inhibition, it was found that an increase in the inlet substrate concentration reduces the steady-state...

Break Point Chlorination

Breakpoint chlorination is accomplished by addition of chlorine to the waste stream in an amount sufficient to oxidize ammonia-nitrogen into nitrogen gas (see Chapter 8). In practice, approximately 9-10 mg l of chlorine is required for every 1 mg l of ammonia-nitrogen. In addition, the acidity produced by the process (equation 8.2) must be neutralized. The chemicals add greatly to the total dissolved solids and result in substantial operating expenses. The method has, however, two advantages 1)...

Types of Bacteria Accomplishing Denitrification

As distinct from nitrification, a relatively broad range of bacteria can accomplish denitrification. Genera of bacteria that are known to contain denitrifying bacteria include Pseudomonas, Micrococus, Archromobacter, Thiobacillus, and Bacillus (see Table 4.1). These bacteria are biochemically and taxonomically very diverse. Most are he-terotrophs and some utilize one-carbon compounds, whereas others grow auto-trophically on H2 and C02, or on reduced sulphur compounds. Most of the mentioned...

Sulphide Barrenstein et al 1986 S2 8 N03 8 H 5 S042 4 N2 4 H20 427

The C N relationship decribes the quantity of organic matter, which is needed per unit of nitrate-nitrogen that is converted to nitrogen gas by denitrification. Organic matter of many kinds (as shown in Table 4.5) can be used for the following three purposes in a denitrification plant. 1) Reduction of nitrate or nitrite into nitrogen gas. 2) Sludge production, i.e. biomass production. Knowing the values of the three parameters described, it is possible to quantify the C N relationship for a...

Reverse osmosis system

In constructing a system for reverse osmosis many problems have to be solved 1. The system must be designed to give a high liquid flux reducing the concentration potential. 2. The packaging density must be high to reduce pressure vessel cost. 3. Membrane replacement costs must be minimized. 4. The usually fragile membranes must be supported as they have to sustain a pressure of 20-100 atm. Comparison of the various techniques Comparison of the various techniques Four different system designs...

The Development of a Bacterial Biofilm

The successive steps of the development of an aerobic biofilm can be described as follows (Elmaleh and Grasmick 1985) step 1 - The biofilm is composed of a few aerobic bacteria included in a gelatinous matrix, i.e the density is low. step 2 - Aerobic micro-organisms grow rapidly, and the density is an increasing function of the thickness. step 3 - As oxygen depletion begins to occur in the biofilm, an anaerobic zone appears near the solid material. step 4 - Anaerobic and facultative bacteria...

Influence of Toxic Substances on the Denitrification Process

The inhibition equation of the denitrification process resembles the equation proposed for the nitrification process in Section 3.13. As for nitrification, the following overall expression takes both toxic substances and oxygen inhibition into account where f l is a term taking the inhibition of toxic substances into account, and f 02 the oxygen inhibition, during the denitrification. The major influence of toxic substances on denitrification is the short-term influence on the growth rate. It...

Application of Reverse Osmosis and Ultrafiltration

EPA has for several years performed experiments to determine the feasibility of membrane techniques in treatment of municipal waste water. The results can be summarized in the following 5 points (EPA, 1969, Feige and Smith, 1974 and Bilstad, 1989) 1. The flux decreased over a period of 20 days and was then stabilized. 2. The quality of the influent was important for the flux. Chemical precipitation seems to be an appropriate pretreatment to use in this context. 3. It is technically feasible to...

Percentage water recovery

Break Even Chart

Figure 10.3 Water flux related to water recovery for two concentrations of inorganic components (salts). The rejection ratio is also expressed by the following equation where, Cwp, is the water concentration in the permeate. Notice that Kp Cwp and Wp (AP - n) must be expressed in the same units. As Wp(AP - n) F is often expressed as g or kg cm2 or m2 sec. Cwp must be expressed as g cm3 or kg m3. The equations given so far are idealized because a good mixing on the brine side has been assumed,...

Classification of Nitrification and Denitrification Unit Processes

The nitrification and denitrification unit processes can be divided into two broad classes, the attached growth systems, and the suspended growth systems. In the attached-growth (biofilm) process (Chapter 5), the bulk of the blomass is retained on a medium and it does, therefore, not require a solids separation step for returning the solids to the nitrification reactor. The media that carry the nitrifying biofilm can be anything from plastic media to Nitrogen ion-selective zeolites. Trickling...

Operating line 1 2 operating line 2 3 equilibrium curve

Figure 9.12 Operating diagram for two stages adsorption. The minimum total adsorbent is found by setting Equation (9.16) can be solved for Yi, and the adsorbed quantity can be found by equations (9.13) and (9.14). Even greater economy in the use of adsorbent ion exchanger can be achieved by a countercurrent operation. Figure 9.13 shows a diagram of this operation and Fig. 9.14 shows the operation line and equilibrium curve for this case. The operating line can be set up as follows and if...

Discrete settling

The settling of a discrete non-flocculating particle in a dilute suspension can be described by means of classical mechanics. Such a particle is not affected by the presence of other particles, and settling is therefore a function only of the properties of the fluid and the characteristics of the particles. As shown in Fig. 11.5 the particle is affected by three forces (1) Gravity, Fg (2) the buoyant force, Fb and (3) the frictional force, Ff. In accordance with Newton's second law of motion,...

Application of Breakpoint Chlorination for Removal of Nitrogen

Complete removal of the 25-40 mg per liter ammonium-N is far too costly by this method. Chlorine costs about 38-45 US cents per kg, which means that the chlorine consumption alone will cost about 14 US cents per m3 waste. When the capital cost and the other operational costs are added the total treatment cost will be as high as 30-45 US cents per m3, which is considerably more expensive than other nitrogen removal methods. It is possible to use chlorine to oxidize ammonium compounds to free...

A

Figure 5.7 Ammonium removal efficiency for rock and plastic filters at various sites in the USA, applying different amounts of organic loading per unit of surface in kg BOD 1000 m2 * day. After Parker and Richards (1986). The EPA (1975) manual showed the removal rate for the NTF to be between 0.83 and 1.50 g N m2 * d. A conventional design practice has been to follow the NTF with either effluent filtration or clarification. Recognizing the costs advantages of operation and maintenance of NTF...

Number of bed volumes

An ammonium break through curve is shown. The ammonium-N concentration in the effluent is plotted versus the number of bed volumes treated. Furthermore, it is recommended to use two or more columns in series, because this makes it possible to utilize the entire capacity of the first column and let the second column provide the required concentration of ammonium-N in the final effluent. After regeneration of the first column at saturation, the second column becomes the first and the...

The Nitrogen Cycle

Layers The Earth Lithosphere

Figure 1.2 illustrates the global nitrogen cycle. The amount of nitrogen in the various pools and the transfer flows are mainly based upon the figures from Bolin and Cook (1983). As seen from Fig. 1.2 many of the numbers are indicated as ranges due to uncertainty in the estimation. The figures have steadily been adjusted due to new measurements and new knowledge gained during the last two decades. Further changes of our knowledge about the nitrogen cycle can be expected in the coming years. The...

Suspendedculture Reactors

Bardenpho Process

The activated-sludge process is based upon a suspended-culture system that has been In use since the beginning of the century. The most common arrangements for nitrogen removal are the single-stage carbon oxidation and nitrification systems and the separate stage nitrification system. The activated-sludge process can be designed with or without recycling of sludge, and may involve either a completely mixed or a plug-flow process (fig. 6.1). Other possibilities are the aerated lagoons, contact...

Sources of Nitrogen Pollution

The abatement of nitrogen pollution must be based upon a knowledge of the quantities of nitrogen from the various sources. Mass balances must be set up for ecosystems and for entire regions. Table 1.1 gives an example. The estimated nitrogen loadings for the San Francisco Bay Basin (from California , 1974) are shown. The mass balance shows clearly that major problems are rooted in the discharge of waste water and nitrogen from dairies and feedlots. The abatement should therefore concentrate...

Attached Growth Reactors

In attached growth systems the waste water is in contact with a microbial film, attached to the surface of a solid material medium. The surface area for growth of the biofilm is increased by the use of a porous medium in the reactor. The biological reactions take place in the biofilm, while suspended bacteria are washed out of the systems. When randomly packed reactors, are used and the waste water flows by gravity as a free surface stream, the reactor is called a trickling filter. The use of...

Nitrogen Removal From

Rate Photosynthesis

As seen from equation (7.8) the ratio ammonia ammonium is disfavored by increased ionic strength, implying that a higher pH is need to obtain the same stripping effect at higher ionic strength. Table 7.1 gives the activity coefficients for different ionic charges, calculated from the equation (7.5). Activity coefficient f at different ionic strengths Activity coefficient f at different ionic strengths I ionic strength, Z charge, f activity coefficient I ionic strength, Z charge, f activity...

Combined Kinetic Expression for the Denitrification Process

As for the nitrification process, a combined expression for the denitrifer growth jid and nitrate removal, taking some of the environmental factors into account, can be formulated. Removal rates can be related to growth rates through equation (4.34). Timmermanns and Van Hauten (1983) proposed an equation similar to (4.34), that also takes the influence of pH and temperature into account Figure 4.5 Determination of the growth rate i at different pH values in a batch reactor at 25 C. The biomass,...

Kinetic Expression Combining Several Limiting Factors of the Nitrification Process

In previous sections, the effects of ammonia level, temperature, pH, and dissolved oxygen on the nitrification rate have been presented. In all practical systems, these parameters influence the nitrification rate simultaneously. Chen (1970) showed that the combined effect of several limiting factors on biological growth can be introduced as a product of a Monod-type expression. Taking this approach for nitrification, the combined kinetic expression for nitrifier growth would take the following...

Principles of Ion Exchange

Ion Exchange Whey

Ion exchange is a process in which ions on the surface of a solid are exchanged for ions of a similar charge in a solution with which the solid is in contact. Ion exchange can be used to remove undesirable ions from waste water. Cations (positive ions) are exchanged for hydrogen or sodium, and anions (negative ions) for hydroxide or chloride ions. The cation exchange on a hydrogen cycle can be illustrated by the following reaction, using, in this example, the removal of calcium ions, which are...

PHlog [HA log [A

Pka Phosphoric

pKa log C 2 log C-0.3 log C 2 log C-0.3 Figure 11.2. pH - log C diagram for phosphoric acid. where H30+ A , log (_) log ( 2 H30+ ) -pH + 0.3 log (2 A' ). At still higher pH, but with values of pH< pKa, log A dominates. At pH> pKa, A C and log HA contributes the most to _ At very high pH, log 0H- will dominate. These considerations are used in the construction of Fig. 11.3 At pH pKa log_ log_ log_ log C - 0.6 Figure 11.3. Buffering capacity of sea water as function of pH. Figure 11.3....

Summary

Table 1.6 summarizes the effect, advantages and disadvantages of the various processes presented in this volume for the removal of nitrogen from waste water. The effect that each process has on each of the three major forms of nitrogen, organic nitrogen, ammonium and nitrate are shown. Average removal percentages which can be expected from the different processes are also indicated. Table 1.7 shows an estimation of costs for the different processes compared with the efficiency. The processes...

Hzhzhzhd1 4hhh

Multiple parallel flow streams, four or more units per flow stream, single-stage units Figure 5.14 Various schemes of staging RBC units. If an RBC is supplied with secondary influent, the unit will be divided into four sections. The first section will not be able to accomplish nitrification, because of a high content of organic matter and, therefore, no nitrifying population will be able to develop. Both nitrification and organic oxidation will be carried out in the second section. The waste...

Membrane separation processes

Electrodialysis Electrical poten- < 0.1 tial gradient Selective transport of water and small ions Selective to molecular size and shape However, one important difference is that the osmotic pressure, which is very small in ordinary filtration, plays an important role in reverse osmosis. Second, a filter cake with low moisture content cannot be obtained in reverse osmosis, because the osmotic pressure of the solution increases with the removal of solvents. Third, the filter separates a mixture...

Effect of Inhibitors on Nitrification

Nitrifiers are slow-growing organisms and they are accordingly particularly susceptible to toxicants. Certain heavy metals and organic compounds are toxic to nitrifiers. The presence of toxic compounds causes a change in the environmental conditions for the nitrifying population, and they are therefore, a threat to any nitrification plant. Tomlinson etal. (1966), however showed that nitrifiers are capable of adapting to almost any toxic substances, when the toxic compound is consistently...

The Influence of Dissolved Oxygen on the Nitrification Rate

Dissolved Oxygen Nitrification

In engineering calculations, an aeration requirement of 4,6 mg 02 per mg NH4+ -N is just sufficient to be used for the nitrification process. In almost all treatment systems, oxygen is also required to oxidize other materials than ammonia present in the waste water. This, therefore, often raises the total oxygen demand in a nitrifying plant. Results from a number of studies on the effect of dissolved oxygen concentrations on the nitrification efficiency are summarized in Table 3.12. Most...

Practical Experience

Ammonia Stripping Chart

The best results in practice are achieved by use of countercurrent packed towers see 0degaard (1988). The water is distributed on the top of the packing with distribution trays or spray nozzles. For a high air to water ratio, a mist eliminator is necessary at the air outlet. Random packing of Raschig rings or saddles or grids, made of metal, ceramic, plastic or even impregnated wood, can be used. Stripping ponds, see Fig. 7.15, might be used to remove 30-50 ammonia, but higher efficiencies can...

The Effect of Nitrogen Discharge

The effects of nitrogen discharge will be mentioned briefly in this section to be able to relate the methods of nitrogen removal with the expected effects of their application. 1. Fertilization (eutrophication) of aquatic ecosystems 2. Oxygen depletion in aquatic ecosystems. 4. Contamination of ground water by nitrate and its effect on the public The word eutrophic generally means nutrient rich. Naumann introduced in 1919 the concepts of oligotrophy and eutrophy. He distinguished between...

The Biochemical Pathway in the Nitrification Process

At the biochemical level the nitrification process is more complex than simply the sequential oxidation by Nitrosomonas of ammonia into nitrite, and the subsequent oxidation by Nitrobacter, of nitrite to nitrate. Various reaction intermediates and enzymes are involved in this processes. In soils, streams and treatment plants, conditions permitting the oxidation of ammonia and nitrite can be created by a variety of micro-organisms. Table 3.2 show some of the factors influencing the...

The Influence of pH on the Nitrification Rate

Nitrification Free Ammonia Inhibition

In the literature, the optimum pH value forthe nitrification process varies between 8 and 9. Figure 3.7 summarizes investigations of pH effects on the nitrification rate. Usually the nitrification rate decreases, as the pH decreases. By measuring the nitrification rates Meyerhof (1916) found the pH optimum for Nitrosomonas to be between 8,5 and 8,8, and for Nitrobacter to be 8,3 to 9,3. Hofman et al. (1973) made similar investigations, and found for both organisms an optimum pH of 8.3, and that...

Activated carbon is able to adsorb chloramines and so a

Combination of chlorination and adsorption on activated carbon can be applied for removal of ammonia. The most likely reaction for chloramine on activated carbon is a surface oxidation C + 2NHCI2 + H20 < > N2 + 4H+ + 4CI + CO (8.2) Furthermore, it is important to know that the CI2 NH3-N oxidized mole ratio is 2 1, for oxidation by this pathway. The mono-chloramine reaction with carbon appears more complex. On fresh carbon the reaction is most probably NH2CI + H20 + C NH3 + H+ + cr + CO...

The Influence of Temperature on the Nitrification Rate

Nitrification And Temperature

The optimum temperature for the growth of nitrifying bacteria, according to the literature, is between 28 C and 36 C, although an optimum temperature of up to 42 C has been reported for Nitrobacter by Painter (1970). Growth constants of nitrifying bacteria are greatly affected by temperature (Table 3.9). Figure 3.2 shows that the nitrification rate is a function of temperatures between 5 and 35 C. The maximum growth rate occurs at approximately 30 C. Curve A, which was produced by Borchardt...

Design of Plants for Precipitation of Nitrogen Compounds

Settling Curves Secondary Settler

As mentioned in Section 11.1, the application of precipitation requires a three-step plant. Addition of chemicals is the first step. It requires some sort of automatic dosage equipment, where the amount of chemicals added to the waste water is determined by either pH, the flow or another parameter, that is feasible to measure and relates to the quality of the influent. The design of the flocculation tank can be based on a first order process. The number of particles volume, N, is transformed...

Terminology Used in Waste Water Treatment

Typicalsewage Treatment Process

The terminology used in the treatment of waste water is often confusing. Terms such as primary, secondary and tertiary treatment, in the treatment of municipal waste water, frequently appear in the literature, and their usage is not always consistent. The meanings of these terms, as used in Chapters 5 and 6 are therefore outlined in this section. Figure 2.1 shows a flow diagram of a typical sewage treatment plant, and indicates the different nitrogen removal steps. The latter part of this...

Modelling the Transport and Reactions within a Biofilm

In spite of the heterogeneity of the biofilm, it is assumed in most of the models that the substrate is transported by molecular diffusion and, therefore, that an effective diffusivity is a characteristic constant of the system. (Atkinson and Fowler 1974 Harremoes and Riemer 1975 Harremoes, 1975, 1976, 1978, Arvin and Harremoes 1990 La Motta 1976 Williamson and McCarty 1976 Grasmick et al., 1979, 1981 Rittman and McCarty 1981). The rate of reaction in a biofilm is based on the concept of the...

Application of Ion Exchange

Aplication Ion Exchange

Mercer et al. (1970) has reported a successful application of the specific ion exchanger clinoptilolite for removal of ammonium from municipal waste water. Jorgensen (1979) reported the possibilities of recovering ammonium (ammonia) from industrial waste water. It is clear from these examinations that recovery of the regenerant by air stripping seems important, because even the neutral regenerant will cause discharge problems. An economic analysis shows, moreover, that the recovery of the...

Relationship Between Growth Rate and Oxidation Rate

The ammonia oxidation rate can be related to the Nitrosomonas growth rate, as follows or in the differantiated form of Michaelis-Menten Table 3.5 Effect of ammonia concentration on nitrification and nitrifying bacteria. Concentration of Ammonia-nitrogen mg l Condition of observation method of study Ammonia oxidation, a zero order reation Ammonia oxidation, a zero order reaction. No inhibition. Rate of ammonia oxida- Submerged filter Haug and McCarty (1972) tlon a function of receiving...

Tapered Aeration Figures

Activated Sludge Process Points

Overview of common applications of the activated-sludge process, (a) step aeration influent addition influent addition at intermidate points provides more uniform removal throughout the tank, (b) Tapered aeration air added in proportion to nutrient exerted, (c) Contact stabilization biomass adsorbs organlcs in contact basin and settles out in secondary clarifier the thickened sludge is aerated before being returned to the contact basin, (d) Pure-oxygen activated sludge oxygen added...