Microbiology for Environmental Engineering

Microbiology for environmental applied scienceBy Georgios TzelepisMicroorganisms play a major role in arbitrary water and waste quality and every biological cognitive operation is base on the action of microorganisms. Bacteria constitute an all important(predicate) group of microorganisms which ar directly related to Environmental Engineering beca single-valued function of their crucial role in sewer water treatment. They ar single cadreed prokaryotic organisms with a structurally and functionally artless form and various shapes, such as spherical, rod-shaped or spiral. One master(prenominal) characteristic of the bacteriuml cell is the lack of building block tissue layer constitution with exception the cytoplasmic membrane. The identification of bacterium is ground on a number of different criteria including their morphological (shape, size), physiological and inherited characteristics. Their re fruit is found on the binary split with formation cartridge clip of ab come to the fore 20 minutes. Bacteria nuclear number 18 sensitive to pH changes and they deliver the goods under neutral conditions, although some of them shadow survive in a highly acidic environment. Regarding their survival temperature, they atomic number 18 divided into psychrophilic, mesophilic and thermophilic. Bacteria be very sensitive to temperature changes and they view as an optimum out elicitth temperature. (Darakas, 2016)Bacteria aim the capacity to degrade the constitutive(a) substances (pollutants) and this is the reason why they be the intimately important group of organisms in scathe of the public health engineering, since biological waste water treatment processes are based on their activities. The socialisation of pollutants is mainly achieved by the biological self-cleaning of the water thanks to microorganisms and specifically bacterium. The main three points of interest in the sewer water treatment is the microorganisms (bacteria), the include d complete matter which constitutes diet for microorganisms and the oxygen which is necessary for the zilch and survival of microorganisms. ecumenicly, the metabolous diversity of organisms, and more specifically of bacteria, firstly depends on the postal code parentage. cogency is important for the chemical reactions and is arrive ated from environmental sources. When the sources are chemicals, the species are called chemotrophs, time when the slide fastener is derived from the light they are called phototrophic species. However, some bacteria have the ability to routine both zero sources based on conditions.Second classification is based on the deoxycytidine monophosphate source. When they are natural fertiliser compounds they are called chemoheterotrophs or photoheterotrophs respectively. early(a) than when in constitutional compounds are accustomd, bacteria are called chemoautotrophs or photoautotrophs.Finally, chemotroph bacteria which metabolize organic chemic als for energy are called chemoorganotrophs. Contrariwise, those that use inorganic chemicals are called chemolithotrophs. thither are two basic types of metabolism for chemoorganotrophs fermentation, in which the metabolism of the substratum is without outer oxidizing agent, and respiration, in which there is an external oxidizing agent. Both types of metabolism fecal matter convert a primary source of energy to unitary which can be used by the cells.2.1.1 Carbon sourceBacteria that use hundred dioxide for the majority (or all) of their carbon readments are called autotrophs. The obligate autotrophs that are adapted to use only when CO2 as a source of carbon use simple energy substrates and they are either chemolithotrophs or photolithotrophs. (Singleton, 2005) In autotroph bacteria carbon dioxide from the environment is used to form interlinking compounds, but also there is the situation that carbon dioxide is incorporated in these compounds and called fixed. There are two vernacular pathways for this fixation, the Calvin cycle and the reductive TCA cycle. Autotrophs are able to succeed in very harsh environments, such as deep sea vents, repayable to their lack of habituation on extraneous sources of carbon other than carbon dioxide. (Yates et al., 2016)On the other hand, some of the know species of bacteria are heterotrophic, both aerobic and anaerobic. They use as a main source of carbon complex carbon compounds derived from other organisms, with the most significant the glucose, alcohol, and organic acids. However, there are specialised heterotrophic bacteria capable also of decomposing cellulose (actinomycetes), keratin, hydrocarbons, and other substances. Heterotrophs are only able to thrive in environments that are capable of sustaining other forms of action due to their dependence on these organisms for carbon sources. (Lester Birkett, 1999)2.2 Energy sourceMicroorganisms, and more specifically bacteria, require food to obtain energy. Phototrophic bacteria are mostly aquatic organisms and obtain energy using radiant energy (light), usually via photo price reduction. This happens through vary pigments that they comprise in order to form energy molecules. Generally, photosynthetic bacteria can be divided in two categories, these who accomplish the photosynthesis with production of oxygen (aerobically) and those without (unaerobically). (Singleton, 2005)Chemotrophs are organisms that obtain their energy by metabolisng chemicals from the environment, through the oxidisation of inorganic molecules, such as iron and magnesium. They are divided in two different categories, chemoautotrophs and chemoheterotrophs, with their difference already been described. (Boundless, 2016)Carbon source of heterotrophic bacteria can be either oil-soluble and colloidal organics of untreated waste (BOD) or endogenous carbon microorganisms, i.e. the carbon putrescent light cells or methanol (CH3OH), which is the best organic substrat e to the denitrification. (Darakas, 2016)2.3 Electron acceptorAs mentioned, all the bacterial cells have to convert a primary source of energy into forms that can be used. Some cells can convert a primary energy source to an electrochemical form which constitutes of a gradient of ions between the two proves of cytoplasmic membrane. Chemotroph and phototroph bacteria form high-energy compounds from a primary energy source using different techniques. (Singleton, 2005)Respiration is a type of metabolism in which a substrate is metabolized with the help of an external oxidizing agent. Oxygen can work as the exogenous oxidizing agent having aerobic respiration, or organic oxidizing agents can be used instead in an anaerobic respiration. Despite the fact that the oxidizing agent can be inorganic or organic, in chemoorganotrophs, the substrate is always an organic compound. (Singleton, 2005)Oxygen is the concluding electron acceptor for the aerobic respiration. The sugar is have it aw ayly broken bulge to carbon dioxide and water, yielding a maximum of 38 molecules of ATP per molecule of glucose. Electrons are transferred to oxygen using the electron transport chain (ETC), a system of enzymes and cofactors located in the cytoplasmic membrane and arranged so that the conversion of electrons down the chain is coupled with the cause of protons (hydrogen ions) across the membrane and out of the cell. ETC induces the movement of positively charged hydrogen ions to the outside of the cell and negatively charged ions to its interior. This ion gradient results in the acidification of the external medium and an energized plasma membrane with an electrical charge of 150 to 200 millivolts. The generation of ion gradients is a normal aspect of energy generation and storage in all living(a) organisms. The gradient of protons is used directly by the cell for many processes, including the prompt transport of nutrients and the rotation of flagella. The protons also can mov e from the exterior of the cell into the cytoplasm by passing through a membrane enzyme called the F1F0-proton-translocating ATPase, which couples this proton movement to ATP synthesis. (Kadner Rogers, 2015)Bacteria that are able to use respiration enkindle far more energy per sugar molecule than do fermentative cells, because the complete oxidation of the energy source allows complete extraction of all of the energy available. (Kadner Rogers, 2015)Respiration can also occur under anaerobic conditions. anaerobiotic respiration uses external oxidizing agents such as nitrate (NO3), nitrite (NO2), sulfate (SO42), or fumarate in place of oxygen. Depending on the different types or conditions, the electron bestower (substrate) used by chemoorganotrophs in anaerobic respiration is of various organic compounds. The energy yields available to the cell using these acceptors are lower than in respiration with oxygen, but they are still substantially higher than the energy yields availabl e from fermentation. The utilization of CO2as a terminal electron acceptor is limited to a group of bacteria called methanogens and this process requires a strongly reduced environment. This use produces methane (CH4) which can be a problem in some instances akin landfill sites. (Maier, 1999)All the bacteria have an optimum growth temperature where their growth is faster, era they also have a specific range of temperature into which they can only grow. Most of the bacteria are mesophilic and they grow in temperatures between 15 and 45 degrees of Celsius. Thermophilic are bacteria with growth temperature over 45 degrees of Celsius, temporary hookup psychrophilic are the bacteria with growth temperature under 15 degrees.3.1 Low temperatureIt is healthful known that bacteria as well as various other forms of life survive and thrive optimally in crack conditions of temperature, pressure, pH and other environmental parameters. However, there is also evidence of bacteria life in ext reme environments. For example bacteria were found to exist in the very acidic river Rio Tino while also bacteria were detected in subzero environments like in Lake Vostok even in depth of 3600 meters, on a lower floor the surface ice. (Chattopadhyay Sengupta, 2013)At low temperature, bacteria are challenged with a number of difficulties due to decrease in the rate of biochemical reactions that sustain the life. Bacteria interpreted from low temperature environments were found with increased branched chain, short chain, anteiso and unsaturated oleaginous acids. They were also found to synthesize more cis fatty acids in gustatory perception to trans fatty acids. All these factors are contributing in the increase of membrane fluidity. Moreover, in order to adjust with the low enthalpy and the reduced atomic and molecular motions at low temperature, they achieve flexibility through simplification in strength and number of non-covalent interactions. Finally a high take aim of post- transcriptional modification of t-RNA by dihydrouridine also has a major role in psychrophiles. Dihydrouridine unsettles the stacking that stabilizes the RNA. (Chattopadhyay Sengupta, 2013)3.2 High temperatureThermophilic bacteria are common in soil and volcanic habitats and have a limited species configuration. Examination of metabolic pathways and regulatory mechanisms in thermophiles proves that thermophilic bacteria have almost the same properties commonly found in mesophilic bacteria, with the main difference being specific molecular mechanisms, important in high temperature biological stability and activity. As a consequence of growth at high temperature and unique macromolecular properties, thermophilic bacteria can consume high metabolic rates, physically and chemically stable enzymes than similar mesophilic species. Thermophilic processes come forward more stable, rapid and facilitate reactant activity and product recovery. Analysis of important biomolecules in thermophi lic bacteria has revealed subtle structural differences in proteins, nucleic acids and lipids. Some of these differences have not been observed in mesophilic bacteria. For instance the membrane lipids of extreme thermophiles contain more saturated and straight chain fatty acids than mesophiles. This allows thermophilic bacteria to grow at higher temperatures by providing the correct degree of fluidity requisite for membrane function. Finally the explanation for high temperature stability of tRNA in Thermus species is that Thermus transfer RNA contains more guanine plus cytosine bases in the specific base-p subscriber lineed division, which endures greater hydrogen bonding and increased thermal stability. Also, the base-paired region in tRNAs from Thermus contains more thiolated thymidine which provides a stronger stacking force inside the molecule. (Zeikus, 1979)The restoration, nutrition and protection of the environment with the help of biological agents in general and bacteri a more specifically are significantly important in terms of sustainability in the environment. Hence, in many cases, bacteria and environmental engineering go hand in hand and both are interdependent on each other. Their main connection is the removal and treatment of the wastes, unassailable or liquid, from various sources like the industrial, domestic and other. There are many examples of the use of bacteria especially in waste and effluent treatment, where some reclaimable characteristics of bacteria are used. 4.1 sewer water treatmentBiological treatment is one of the most widely used removal methods as well as for partial or complete stabilization of biologically degradable substances in wastewaters. General characteristics of wastewaters are measured in terms of Chemical Oxygen ask (COD), Biochemical Oxygen Demand (BOD), and Volatile Suspended Solids (VSS). Bacteria provide the largest component of the microbial community in all biological wastewater treatment processes, a nd numbers in excess of 106 bacteria/ml of wastewater are frequently encountered.4.1.1 Activation SludgeActivated sludge is a process that has been adopted worldwide as a secondary biological treatment for domestic wastewaters. In the activated sludge process the immersion wastewater is complex and aerated with existing biological sludge (microorganisms). Organics in the wastewater come into contact with the microorganisms and are utilized as food and oxidized to CO2, and H2O. The microorganisms using the organics as food they reproduce, grow, and die. While the microorganisms grow, are mixed together by the movement of air so individual organisms gist an diligent mass of microbes called activated sludge. The wastewater flows continuously into an aeration tank where air is injected to mix the activated sludge with the wastewater and to supply oxygen require for microbes to breakdown the organic materials. This mixture of activated sludge and wastewater in the aeration tank is ca lled mixed liquor suspended solids and mixed liquor quicksilver(a) suspended solids. The mixed liquor is sent to the sludge handling governing body (second part of activation sludge method). A part of this mass precipitates while the rest flows back to the aeration tank in order to maintain able microbial population levels. This is the called activated sludge. The microorganisms in activated sludge principally are composed of 70 to 90% organic and 10 to 30% inorganic matter. The microorganisms generally found in activated sludge consist of bacteria (mostly), fungi and protozoa.4.1.2 Nitrogen and Phosphorus removalNitrogen and daystar are two essential elements in terms of the waste treatment. The north compounds and the phosphates existing in wastewaters are very important for the survival of the bacteria although they should be removed in order to avoid problems of deoxygenation and eutrophication in the nett recipient. (Bitton, 2010)NitrificationThe principal organisms invol ved in nitrification processes belong into two categories, Nitrosomonas and Nitrobacter. These bacteria are considered to be strictly autotrophs since they derive energy for growth and synthesis from the oxidation of inorganic newton and carbon (CO2) compounds. Nitrosomonas catalyse oxidation of ammonia to nitrite using molecular oxygen, while Nictobacter further oxidize nitrite to nitrate using oxygen derived from the water molecule. It should be mentioned that some some soluble forms of c-BOD can inhibit the activity of nitrifying bacteria since they are able to land the cells of nitrifying bacteria and inactivate their enzyme systems. (Horan, 1989)DenitrificationDenitrification is a process by which certain species of bacteria under anoxic conditions reduce nitrate nitrogen to the gaseous end-products of N2, NO, or N2O which can then escape from solution to the atmosphere. Unlike other nitrogen compounds, the gaseous forms of nitrogen have no significant effect on environmental quality. The presence of oxidized nitrogen and organic carbon are essential properties for denitrification to proceed. Denitrifying bacteria are composed of heterotrophic organisms. The most common denitrifying bacteria are Bacillus denitrijicans, Micrococcus denitrijicans and more. (Horan, 1989)Phosphorus removalThe anaerobic-oxic process (most commonly used), consists of a modified activated sludge system that includes an anaerobic upstream of the conventional aeration tank. During the anaerobic shape, inorganic the Tempter is released from the cells as a result of polyphosphate hydrolysis. The energy liberated is used for the uptake of BOD from wastewater. (Bitton, 2010)Removal efficiency is high when the BOD/phosphorus ratio exceeds 10. During the aerobic phase, soluble phosphorus is taken up by bacteria that synthesize polyphosphates using the energy released from BOD oxidation. The anaerobic-oxic process results in BOD removal and produces sludge which is bass in phosphor us. The key features of this process are the relatively low solid retention time and high organic loading rates. (Cheremisinoff, 1997)4.1.3 Anaerobic Digestion major applications of anaerobic digestion are the stabilization of concentrated sludges produced from the treatment of especially industrial wastes. The digestion is a complex biochemical process in which several groups of anaerobic and facultative organisms over again simultaneously absorb and break down organic matter and can be described as a two-phase process. In the first phase, acid-forming organisms convert the complex organic substrate to simple organic acids. Little change occurs in the total amount of organic material in the system, with decrease in ph . Second phase involves conversion of the organic acids to principally methane and carbon dioxide. The anaerobic process is essentially controlled by the methane producing bacteria. Methane formers are very sensitive to pH, substrate composition, and temperature. If the pH drops below 6,methane formation stops, and there is no decrease in organic gist of the sludge. One characteristic of the methane bacteria is that they are highly active in the mesophilic and thermophilic ranges. (Cheremisinoff, 1997)4.2 Solid Waste Treatment4.2.1 CompostingComposting is the biological decomposition and stabilization of organic substrates. Each gram of decaying compost contains millions of beneficial microorganisms that work to break down organic matter. Of the microorganisms present, 80 to 90 percent are bacteria, including actinomycetes and aerobic bacteria. oxidative are separated in three different varieties, each of which is active at different phases of the decomposition process. Psychrophilic bacteria (during winter) work on the initial organic matter, at temperatures around 12 degrees Celsius. These bacteria raise the temperature to 20 C, at which time, the mesophilic bacteria take over. These bacteria work at moderate to warm temperatures between 2 0 and 38 C. At 38 C, the thermophilic bacteria take over, raising the temperature to 70 C. Once this happens, the process starts over again with the addition of new materials. Actinomycete bacteria appear during the late stages of composting to clean up remaining materials that are difficult for aerobic bacteria to break down. 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