Nitrogen Removal

The Influence of pH on the Denitrification Rate

Aquaponics Nitrification Lowers

Denitrification only partially offsets the alkalinity loss caused by nitrification, as the alkalinity gain per mg of nitrogen is only one-half of the loss caused by nitrification. This is because the alkalinity gain per mg of nitrogen is only one-half the loss caused by nitrification. A value for alkalinity production suitable for engineering calculations would be 3,0 mg alkalinity as CaC03 produced per mg nitrogen reduced. In the design of systems where alternating nitrification and...

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...

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.,...

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...

Application of Breakpoint Chlorination for Removal of Nitrogen

Breakpoint Chlorination Water

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...

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...

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

Dissolved Oxygen Removal

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...

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...

Principles of Ion Exchange

Break Seal Polymerization

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...

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...

Activated carbon is able to adsorb chloramines and so a

Breakpoint Chlorination For Ammonia

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...

Process Variables

In the removal of ammonia with a dose of chlorine followed by contact with activated carbon, pH determines the major chlorine species. The studies reported herein indicate that a pH value near 4.5 should be avoided, because NHCI2 predominates and thus 10 parts by weight of chlorine are required for each part of NH3-N oxidized to N2. At a slightly higher pH and using acclimated and activated carbon, the portion of mono-chloramine increases and the chlorine required per unit weight of NH3-N...

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...

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...

The Role of Nitrogen in The Environment

Role Env Flow Chart

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...

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...

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...

Cd Newton Reynolds Number

Drag Coefficient

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,...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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,...

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...

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...

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...

Suspendedculture Reactors

Ludzack Ettinger Reactor

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...

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...

Practical Experience

Ammonia Stripper Process

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...

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...

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...

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...

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...

Effect of Inhibitors on Nitrification

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...

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...

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...

Phase Diagram Of Concentrated Phosphoric Acid

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....

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...

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...

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...

Biochemical Pathways

Denitrification is a two-step process in which the first step is a conversion of nitrate into nitrite. The second step carries nitrite through two intermediates to nitrogen gas. This two-step process is normally termed dissimilation . Each step in the denitrification process is catalysed by a separate enzyme system. Denitrifiers are also capable of an assimilation process whereby nitrate (through nitrite) is converted into ammonia. Ammonia is then used for the nitrogen requirements of the...

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...

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...

The Influence of Temperature on the Denitrification Rate

Nitrification Temperature

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

Precipitation

Precipitation in a strictly chemical sense is the transition of a substance from the dissolved state to the non-dissolved state upon the addition of other (dissolved) reagents that lead to the formation of precipitates. However, if chemicals causing precipitation are added to water, other reactions may also take place such as for instance coagulation. Thus, in any practical application of the precipitation process it is often very difficult to distinguish between these reactions. Only on the...

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...

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)...

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...

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...

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,...

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...

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...

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...