Nitrification

Introduction to Nitrification

Nitrosomonas And Nitrobacter

Biological nitrification is the conversion or oxidation of ammonium ions to nitrite ions and then to nitrate ions. During the oxidation of ammonium ions and nitrite ions, oxygen is added to the ions by a unique group of organisms, the nitrifying bacteria (Figure 6.1). Nitrification occurs in nature and in activated sludge processes. Nitrification in soil is especially important in nature, because nitrogen in absorbed by plants as a nutrient in the form of nitrate ions. Nitrification in water is...

TABLE 121 Ammonium Ion Loss and Production in an Aeration Tank

Clarifier Denitrification

Mechanism for Ammonium Ion Loss Ammonium Ammonium Ion or Production Ion Loss Production Air-stripping of ammonia at high pH x Deamination of amino acids and proteins x Degradation of cationic polymers x Nutrient source for nitrogen for bacteria x dissolved oxygen are consumed by nitrifying bacteria as they oxidize ammonium ions and nitrite ions. Therefore, when nitrification occurs, a significant biomass demand for dissolved oxygen occurs, and the dissolved oxygen level within the aeration tank...

TABLE 141 Types of Biochemical Oxygen Demand

Biochemical Oxygen Demand Diagram

There are several types of BOD that enter an activated sludge process. Total BOD is the sum of all types of BOD found in the influent to the activated sludge process. Forms of particulate BOD are the solids such as cellulose that can be degraded. Much particulate BOD is removed in the primary clarifier, and unless adequate HRT is provided in the aeration tank, par-ticulate BOD is adsorbed to the surface of floc particles in the aeration tank and is not degraded. Forms...

The Wastewater Nitrogen Cycle

Life Cycle Rhizobum Radiobacter

Because of the large number of valences or oxidation states of nitrogen, many nitrogenous compounds exist in the environment and the activated sludge process (Table 9.1). The majority of nitrogen found in the environment exists as molecular nitrogen. Approximately 80 of dry air by volume contains molecular nitrogen and represents an inexhaustible reservoir of this essential element. Although constituting much less of the biomass than carbon or oxygen, nitrogen is an essential element for all...

Classification of Nitrification Systems

Nitrification systems within activated sludge processes may be classified according to the degree of separation of cBOD and nBOD oxidation or removal. The removal of cBOD and nBOD may occur in the same aeration tank or in separate aeration tanks. If cBOD and nBOD removal occur in the same aeration tank, the treatment system is termed a single-stage system (Figure 20.1). If cBOD and nBOD removal occur in separate aeration tanks, the treatment system is termed a separate-stage or two-stage system...

Ing Accidental Denitrification

Nitrofixation Imgais

There are several indicators of denitrification. Indicators of denitrification in the secondary clarifier include presence of numerous bubbles, rising solids that have numerous bubbles on their surface, increase in alkalinity, and possibly, pH across the clarifier, and reduction in redox potential across the clarifier. Because the atmosphere contains approximately 80 molecular nitrogen, the capture and measurement of escaping molecular nitrogen from the surface of the clarifier to demonstrate...

The Activated

Final Product Nitrification

Figure 5.1 The activated sludge process. In the activated sludge process, a tank (aeration tank) or series of tanks is used to degrade or oxidize wastes. The oxidation of the wastes is achieved by mixing the wastes, with air and a high concentration of bacteria, for sufficient time. When the wastes are oxidized more bacteria are produced. The bacteria in the form of floc particles leave the aeration tank and enter a clarifier. Here the floc particles settle to the bottom of the clarifier and...

Benefits of Denitrification

The benefits of denitrification are significant if denitrification is used properly. The benefits include protecting the quality of the receiving water, permit compliance, strengthening of the floc particles, control of undesired filamentous growth, return of alkalinity to the treatment process, and cost-savings for the treatment or degradation of cBOD. By denitrifying, the quantity of nitrite ions and nitrate ions discharged to the receiving water is greatly reduced. The ions are used as a...

Organicnitrogen

Oblique Cylinder Drawing

A large number of algae, including those that grow in tetrad formation (colony of four) can fix molecular nitrogen. When algae fix molecular nitrogen, the nitrogen is converted to ammonium ions and then incorporated in an organic molecular to form amino acids and proteins. Municipal, activated sludge processes receive large quantities of organic-nitrogen wastes. Some of the organic-nitrogen wastes release ammonium ions in the sewer system as they are...

TABLE 151 Oxygen Requirement Groups of Bacteria

Nitrification Oxygen Curve

CBOD removal Denitrification Floc formation Methane production in anaerobic digesters biological and operational purposes. These purposes are (1) the oxidation of cBOD to provide carbon and energy for cellular activity, growth, and reproduction (production of MLVSS), (2) oxidation of cBOD to provide energy for endogenous respiration (destruction of MLVSS), and (3) oxidation of nBOD or nitrification. Of the many operational requirements known to affect nitrifying bacteria or nitrification,...

Temperature

Of all operational factors affecting nitrification, temperature has the most significant influence on the growth of nitrifying bacteria and, consequently, the rate of nitrification (Table 17.1). The rate of nitrification usually is expressed as pounds of ammonium ions oxidized per pound of MLVSS per day. Because nitrifying bacteria are temperature sensitive, nitrification is temperature sensitive. There is a significant reduction in the rate of nitrification with decreasing temperature and,...

TABLE 183 Inhibitory Threshold Concentrations of Some Organic Wastes

Photosynthetic Bacteria Tank

Organic Waste Concentration, mg l Free ammonia inhibits Nitrosomonas and Nitrobacter. Free ammonia can inhibit Nitrosomonas at concentrations as low as 10 mg l. Free ammonia can inhibit Nitrobacter at concentrations as low as 0.1 mg l. The conversion of nitrite ions to free nitrous acid and its accumulation are a function of nitrite ion concentration and aeration tank pH. With decreasing pH, nitrite ions are more easily converted to free nitrous acid (Equation 18.2). Free nitrous acid inhibits...

Methemoglobinemia

Methemoglobinemia

The term ''methemoglobinemia'' or ''blue baby syndrome'' refers to the disease experienced by an infant who consumes groundwater contaminated with nitrate ions. When an infant consumes formulae made with groundwater contaminated with nitrate ions, the ions are easily converted to nitrite ions in the infant's digestive tract. The nitrite ions that enter the infant's circulatory system bond quickly to the iron in the hemoglobin or red blood cells (Figure 1.4). Figure 1.4 Methemoglobinemia. If...

TABLE 113 Limiting Factors Responsible for Incomplete Nitrification

High influent ammonium ion concentration Short retention time in the aeration tank Temporary low dissolved oxygen level As the bacteria in the mixed liquor suspended solids are removed, the filtrate will not contain ammonium ions used as the nitrogen nutrient that may have been released by the bacteria during testing. Therefore these ammonium ions are not measured. Since the mixed liquor effluent is used, no significant loss of nitrite ions or nitrate ions would have occurred through...

Nitrite Ion Accumulation

The production and accumulation of nitrite ions in an activated sludge process can occur during some forms of incomplete nitrification. The accumulation of nitrite ions is due to partial inhibition of enzymatic activity within nitrifying bacteria. This inhibition prevents the rapid oxidation of nitrite ions to nitrate ions. Operational factors responsible for this inhibition include cold temperature, deficiencies in key nutrients, high influent ammonium ion concentration, inhibitory and toxic...

Sources of Nitrite Ions and Nitrate Ions

Unless nitrite ions and nitrate ions are discharged to an activated sludge process in specific industrial waste streams, nitrite ions and nitrate ions that are found in an activated sludge process must be produced in the aeration tank. The production of nitrite ions and nitrate ions is achieved through the biologically mediated reactions of nitrification. The reactions involve the oxidation of ammonium ions and nitrite ions. Industrial waste streams that contain relatively high concentrations...

Introduction to Denitrification

The term denitrification was first used in France in 1886 to describe the use of nitrate ions by some bacteria to degrade substrate. The bacterial use of nitrate ions (and nitrite ions) to degrade substrate actually evolved before the use of free molecular oxygen. Wastewater denitrification describes the use of nitrite ions or nitrate ions by facultative anaerobes (denitrifying bacteria) to degrade cBOD. Although denitrification often is combined with aerobic nitrification to remove various...

Substrate or cBOD

The quantity of substrate or cBOD rather than the quantity of nitrite ions or nitrate ions is considered to be the most important factor that determines denitrification. The larger the quantity of cBOD especially simplistic, soluble cBOD the greater is the demand for electron acceptors, such as free molecular oxygen, nitrite ions, and nitrate ions. The greater the demand for electron acceptors is, the greater the chances are that denitrification occurs even under an aerobic condition. If the...

TABLE 191 Operational Factors Favoring Nitrification

MCRT > 8 days (increasing with decreasing temperature) HRT > 10 hours during cold temperatures F M 0.5 pounds ammonium ions per pound MLVSS There are several advantages of maintaining as many nitrifying bacteria as possible. First, having more nitrifying bacteria in the aeration tank can offset the reduction in nitrification due to cold temperature. Second, by increasing the MCRT to provide for more nitrifying bacteria, the increased MCRT also provides for more or-ganotrophs and more rapid...

Free Molecular Oxygen

Single Deck Pontoon Floating Roof

Free molecular oxygen inhibits denitrification by virtue of its competition with nitrite ions and nitrate ions as an electron acceptor for the degradation of cBOD. If free molecular oxygen is in the environment of the bacterial cell and enters the bacterial cell, the cell uses free molecular oxygen (Equation 29.1). The use of free molecular oxygen is preferred over the use of nitrite ions and nitrate ions, because the use of free molecular oxygen yields more cellular energy and cellular growth....

Troubleshooting Key and Tables

To identify the factor responsible for the loss of nitrification in an activated sludge system, answer question 1 below in the troubleshooting key. Continuing answering each question, until yes is obtained. Proceed with a review of the table or corrective measure indicated by the yes. 1. Is the wastewater temperature 16 C Yes See Table 21.1. No Go to question 2. TABLE 21.1 Corrective Measures for Cold Wastewater Temperature TABLE 21.1 Corrective Measures for Cold Wastewater Temperature Increase...