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Figure 5.19 Application, during the first 6 days, of waste water containing 30 mg l NH4+ - N, with a reactor of previously unused clinoptilolite. In the first three days, a breakthrough of nitrate was observed. The removal efficiency of the simultaneous nitrification and denitrification (SND) and the effluent concentration of ammonium-N and nitrate-N were measured throughout this run. Table 5.14 summarizes the results of RUN 1 where an organic carbon source was applied to the system in...

The Influence of Carbon Concentration on the Denitrification Rate

The effect of carbon concentration on the rate of denitrification has been explained with a Monod type of expression by, Stensel etal. (1973). Using methanol as the carbon source, the following expression was employed Km saturation constant for methanol, mg l. The kinetic value of KM is normally very low, normally in the order of 0,1 mg l methanol. Table 4.8 The influence of temperature on denitrification rate. Suspended Methanol 0,05 1,12 Suspended combined Raw sewage 0,06 1,15 Suspended...

Air Stripping

7.1 Physico-chemical Principles of Air Stripping The stripping process 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 from a liquid phase to a gas phase. The basic principle of this process of nitrogen removal is illustrated in Fig. 7.1. Stripping unit for instance a packed tower Effluent to pH adjustment or other treatment processes Figure 7.1. The principle...

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...

Reverse osmosis

The permeate flux, F, through a semipermeable membrane is given by Ds * Cw * V Cw the concentration of water AP the driving pressure (see Fig. 10.2) The equation (10.3) indicates that the water flux is inversely proportional to the thickness of the membrane. These terms can be combined with the coefficient of water permeation, Wp, and equation (10.3) reduces to For the solute flux, Fs, the driving force is almost entirely due to the concentration gradient across the membrane, which leads to the...

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...

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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

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...

The Influence of pH on the Denitrification Rate

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...

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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

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

Daily Quantity Sludge

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...

Vl

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 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...

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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

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

Typical Sewage System Diagram

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

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

Step Aeration

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...