Get Best Essay Written by US Essay Writers
Phone no. Missing!

Please enter phone for your order updates and other important order related communication.

Add File

Files Missing!

Please upload all relevant files for quick & complete assistance.


Microbial ecology can be described as the interaction of microorganisms with the environment. Despite their size, they have a huge impact on humans and the environment (Flandroy et al., 2018). They are present in almost all ecological niches and show vast diversity and distribution. They are involved in a vast range of ecological interactions and also with higher life forms. Microbes play a huge role in human life. The human body hosts a large number of microorganisms. They are responsible for digestion, breakdown of foods to produce nutrients, and detoxifying harmful chemicals (Medfu Tarekegn, Zewdu Salilih, & Ishetu, 2020). Microbes are also an important constituent of various industries like alcohol, bakery, dairy, and leather (Feng, Chen & Chen, 2018). They are used in the production of enzymes, antibiotics, vaccines, and vitamins. They also play a key role in waste management. They are responsible for the breakdown of organic matter into simpler substances like methane, carbon dioxide, and water. They are commonly used in the treatment of domestic and industrial waste. They play an important role in biological waste management. It also plays a key role in wastewater management (Duan, et al., 2020). This process is conducted in a process called the Activated Sludge process which consists of multiple chambers having high concentrations of microbes that are involved in the degradation of organic matters and removal of biotic wastes present in wastewater. This process is used in the treatment of both municipal and industrial wastewater.

The following essay shall discuss in detail the growth of microorganisms and the various factors that are responsible for their growth and multiplication. It shall contain detailed information regarding the ecological factors that facilitate the growth of different kinds of microbes in the environment. Further, it shall discuss the activated sludge process for the treatment of wastewater and how microorganisms play a key role in it. A critical analysis of the advantages and disadvantages of the activated sludge process has also been done in the essay.

Microbial Growth

Various factors play a role in maintaining microbial ecology. The most common abiotic factors that affect the growth of microbes are temperature, moisture, pH levels, nutrition levels, and oxygen levels (Al-Hawash et al., 2018). For microbes like fungi, dampness plays an important role. They cannot grow without enough moisture in their ecology. That is why leaking pipes, stagnant water, and damp furniture are easy breeding grounds for fungi (Andersen et al., 2021). Similarly, each microorganism has different environmental factors that support its growth. Their cell structure and replication process are based on the environment they strive in. Some of the common factors affecting microbial ecology are described in the following sections.


Microorganisms tend to grow better in warm environments. Temperature closer to human body temperature proves to be optimum for the growth of microbes. Cooler conditions slow the growth. As the temperature increases, the rate of catalysis also increases (Nottinghan et al., 2019) The enzymatic reactions double with the increase of every 10 degrees Celcius. All these factors favour the growth and multiplication of microbes. Higher temperature is also lethal for microbes. An excess increase in temperature damages the enzymes, cells, and proteins that are responsible for the growth (Cavicchioli et al., 2019). The cardinal temperature of each microbe governs its growth. Cardinal temperature also varies with different microbes. It depends on the other environmental factors like pH and nutrients available. Depending on the cardinal temperature, microbes are differentiated into various classes: 


These microbes grow the best at an optimum temperature range of 10oC to 20 oC. Their enzymes catalyze the best at low temperatures and the cell membranes remain fluid at this temperature range (Bhatia et al., 2021). Bacillus and Arthobacter fall under this category.


These microbes grow at an optimum temperature of 20o C to 40o C. they usually thrive the best in warm-blooded animals like human beings (Liu et al., 2017). Common bacteria that fall under this category are Staphylococcus aureus, and Escherichia coli.


Certain microbes grow the best at a temperature higher than 55o C (Atalah et al., 2019). They are mostly found in hot springs and composts. Thermus aquaticus, Cyanidium caldarium are some examples of this type of microbes.


Some microbes can thrive at a temperature range of 90oC. Their optimum temperature range is observed as 80°C and 113°C. Such microbes fall under the category of hyperthermophiles (Liu et al., 2017). They cannot sustain at a temperature less than 55oC. Pyrococcus abyssi & Pyrodictium occultum are hyperthermophiles that are found in seafloor hotbeds.

Environmental pH

Certain microbes, especially bacteria are sensitive to the number of hydrogen ions they find in the environment. Large enzymes or proteins in them are greatly affected by pH. The proteins tend to denature when present in an environment with different ion concentrations compared to their natural habitat (Jim & Kirk, 2018). Microbes tend to grow well in a neutral pH environment. An acidic or basic environment tends to harm the growth of the microbes. Based on the optimum pH, there are three  categories of microbes:


These microbes show the highest growth in a neutral pH environment which means they grow optimally at a pH of around 7 (Ratzke & Gore, 2018). They are the most common type of microbes. They are well suited to the human body, hence most bacteria that cause disease in the human body are neutrophils. Escherichia coli is a common example of neutrophiles.


Microorganisms growing optimally at a pH lower than 5.5 are called acidophiles. They belong to diverse groups like archaea, bacteria, protozoa, and algae. Most of these are commonly found in geysers, sulphuric pools, coal mines, and other metal ore mines (Jim & Kirk, 2018). Metallosphaera, Stygiolobus, and Sulfolobus are common archaea falling under this category. Some gut microbes are also acidophiles that can survive at such a high concentration of hydrochloric acids.


Microorganisms growing optimally at a pH range of 8 to 10.5 are called alkaliphiles. They are dependent on an alkaline environment and the presence of sodium ions for growth, sporulation, and germination (Ratzke & Gore, 2018). Alkaliphilic microorganisms like Bacillus, Micrococcus, Pseudomonas, and certain eukaryotes like yeasts and fungi have been isolated. From various alkaline habitats like Soda Lake in Africa and Lonar Lake in India.

Oxygen Content

The growth of various microorganisms depends on the oxygen concentration. The oxygen is related to the metabolic process of the microbes. Depending on the need for oxygen, bacteria and other microorganisms can be divided into two types.

Aerobic Microorganisms

Aerobic bacteria throve best in the presence of oxygen. In these microbes, aerobic respiration is followed to derive energy from oxidative phosphorylation and the Krebs's cycle (Berg et al., 2022). In these microbes, oxygen acts as a terminal electron acceptor during respiration. Hence, they cannot survive in the absence of molecular oxygen. Mycobacterium tuberculosis, Bacillus cereus are classic examples of aerobic microbes.

Anaerobic Microorganisms

Such bacteria do not require oxygen for their survival. Rather oxygen acts as a toxic substance and hinders their growth. They derive their energy following the lactic acid fermentation process. they use Nicotinamide Adenine Dinucleotide Hydrogen (NADH) as their electron carrier in place of oxygen (Buckel & Thauer, 2018). During the process of glycolysis, the NADPH traps electrons and converts them into ATP or energy but the energy produced is usually less than that in aerobic respiration. Clostridium, Bacteroides fall under this category of microbes.

Moisture Content

The majority of fungus and bacteria require a minimum relative humidity of 60 percent to survive and multiply. Less availability of water inhibits microbial activity by lowering intracellular water potential and reducing the activity of enzymes (Mendell, Macher, & Kumagai, 2018). This factor overall reduces the multiplication and growth of microbes. Thus the growth of microbes happens the maximum during the monsoon season and in tropical lands.


High pressure generally does not favor the growth of microbes. Excess pressure inhibits cellular processes and the formation of structures and proteins. High hydrostatic pressure inhibits cell division, DNA replication, transcription, and various enzymatic reactions. Certain exceptions are also there. Few microbes live deep down in the oceans around 1000 meters in depth where the average hydrostatic pressure is around 600 to 1000 atm and the average temperature is 2-3oC. These are called the Barotolerant (Sum, 2018). They survive in high-pressure environments but can survive in less extreme environments as well. Barophiles are those microbes that cannot survive outside such environments.

Nutrition Content

Every organism requires carbon, hydrogen, oxygen, and electrons for growth.  The nutrients that are required in larger concentrations are called macronutrients. These are elements are the major constituents of the microbial cells, proteins, and enzymes. Examples of macronutrients are carbon, nitrogen, oxygen, hydrogen, sulfur, phosphorus, calcium, and magnesium. The nutrients that are required in fewer amounts but are vital for the growth of microorganisms are called micronutrients (Savarino, Corsello, & Corsello, 2021). Manganese, copper, chlorine, and iron are examples of micronutrients.


Wastewater can be defined as a polluted form of water generated by human activities. it can also be termed sewage. They are mainly generated from domestic waste, industrial waste, and rainwater. The major components of sewage are inorganic wastes (plastics, rags, and metals), organic wastes (urine, feces, and solid organic matters), pathogens, oils and greases, heavy metals (mercury, lead, chromium, and arsenic), and toxic chemicals (pesticides, phenols, PCBs, and chlorinated compounds) (Kumar & Dutta, 2019). These contaminated water are breeding grounds of multiple disease-causing microbes like Salmonella typhi, Vibrio cholerae, Clostridium botulinum, and Escherichia coli (Fitzmorris-Brisolara et al., 2022). These microbes are responsible for waterborne diseases which are most common in tropical countries where the temperature and moisture content in the atmosphere favours the growth of the microbes. Diseases like Cholera and Typhoid have caused pandemics in countries of central Africa, Southeast Asia, Brazil, and India and resulted in the loss of millions of lives.
Other than microbes, chemicals, and heavy metals found in wastewater also causes disbalance in the ecology. Biomagnification of toxic elements takes place harming the lives of humans the most. It leads to diseases like kidney dysfunction, nervous disorders, skin lesions, and cancer (Ziarati et al., 2018). At the correct time, heavy metal poisoning is a critical health issue in humans.

Waste Water Treatment

Wastewater treatment is converting wastewater into water that can be discharged back into the environment or can be used for different purposes. It is one of the most common forms of pollution (Rao, 2018). Untreated water if released into natural water bodies can impact the entire ecology of the water body system. They can harm the lives of fishes and other lifeforms in water, can cause oxygen depletion, and lead to poisoning of natural water bodies. The fish inhabiting the toxic water bodies may contain toxic chemicals in their body (McCallum et al., 2019). The consumption of these fishes can lead to poisoning in the human body. The most common forms of toxicity observed are lead and mercury poisoning.

Treatment of wastewater is important for the environment. Water from industries should be treated before releasing it into the environment to reduce the level of water pollution. Industrial wastewater also contains various toxic chemicals. Water treated by plants can also be recycled to be re-used in factories and industries (Kazour et al., 2019). This overall saves a huge quantity of water every year. The sludge separated from water can also be used in energy production since they contain a large number of biodegradable materials. They can be used for the production of electricity or can be used as manures in fields.

Activated Sludge Treatment

Activated sludge treatment is a process of treatment of wastewater with the use of microorganisms. It is composed of aerobic and anaerobic microbes like bacteria, fungi, archaea, and protists. These microbes are capable of breaking organic compounds into simpler components. It is one of the efficient ways of treating wastewater in large volumes. It contains multi-chamber reactor units. It removes particles like inorganic or organic wastes that are toxic and unwanted harmful microorganisms from the sewage wastes (Wilen et al., 2018). The entire process is divided into three basic steps – the primary, secondary, and tertiary steps. The primary treatment involves manual removal of macroparticles like leaves, graves, plastics, and sands. The secondary step is the biological treatment which removes soluble organic matter with the help of bacteria. The final step is the chemical method that involves disinfecting the secondary effluent with the help of chlorine gas.

Primary Treatment

The initial step of this process is the screening of the wastewater to remove materials like rags, plastics, debris, and large solid wastes (Karballa et al., 2017). This step efficiently removes floating matters and algae. The next step is passing the wastewater through grit chambers where sand, gravel, and smaller particles are screened based on their size and densities.

Secondary Treatment

This is the biological treatment and the most essential part of the wastewater treatment process. it starts with a pre-treatment process that involves the sedimentation of heavy organic solids. This step ensures the elimination of 50-70 percent of the suspended solids. The next step is the filtering of effluents. The Activated sludge involves two separate processes – aeration and sludge settlement.

Aeration Tank

In a bioreactor, the raw sludge is taken along with the microbial suspension. It consists of an air compressor which helps to maintain continuous airflow in the tank. Air is blown and mixed with wastewater by surface agitation or via diffusers using compressed air. The main purpose of pumping air and oxygen is to meet the oxygen demands of microorganisms present in the tanks (Amin, Hawash & Abdel-Fatah, 2019). Other than that, air also helps the microbial colonies to stay in continuous suspension. This ensures maximum contact of the microbial flocs with the wastewater. The microbes decompose and break the raw, unsettled solid sewage into smaller and simpler components along with carbon dioxide and water.

Secondary Sedimentation

It involves the use of a clarifier settler. The sewage liquor produced in aeration tanks is discharged into the clarification chamber where the live bacteria settle at the bottom along with the flocculated biomass while the dead bacteria float above (Zlateva, & Dimitrova, 2022). In the middle, a layer of clear liquid or clarified fluid is formed. This clean water is discharged into a soakaway or a watercourse. The live bacteria are resent into the activated sludge chamber for the treatment of a new batch of wastewater. The dead bacteria are removed by processes like vortexing.

Tertiary Treatment

The clean water discharged is collected and chemically treated to ensure high-quality effluent. The remaining dissolved solutes and microbes are separated by the ultrafiltration or microfiltration process (Hafiz et al., 2021). Finally, the water is treated by processes like UV disinfection, ozonation or chlorination to ensure its quality before it is discharged into nature or reused.

Microbes In Activated Sludge

The major groups of microbes that are used in the activated sludge process are bacteria, metazoan, protozoa, filamentous bacteria, and algae and fungi. The bacteria are primarily responsible for the removal of organic nutrients from the wastewater. They are capable of digesting organic compounds like benzene, toluene, and benzopyrene. Aerobic bacteria are mostly used in aeration tanks which can use the oxygen in the tanks and break down the organic matters into energy that they use for their growth and multiplication (Xia et al., 29018) The protozoa are responsible for digesting the suspended particles and removing the free dispersed bacteria. The metazoan does not contribute much to the digestion of organic matters but they are present in larger amounts than bacteria and protozoa. Their presence symbolizes the treatment system conditions. the presence of algae and fungi indicates problems with pH and sludge. They do not cause much harm to the activated sludge process.

Advantages And Disadvantages

The activated sludge treatment process is crucial in the field of wastewater treatment. The process successfully removes the undesirable sludge in water effectively (Buaisha, Balku & Ozalp-Yaman, 2020). The process favours the growth of good bacteria that are responsible for the breakdown of organic matters in the process. hence, after every cycle,  no microbes are required to be fed in tanks externally.  The entire process is simple, reliable, and odorless. The chances of error are also less in this process. The biggest advantage of the activated sludge process is its cost-effectiveness (Jafarinejad, 2017). For these reasons, the most activated sludge process is one of the most common water treatment processes.

There are certain disadvantages of the process too. Though the running cost is low, the initial cost for set up and operation is very high. This plant cannot be handled by common men. Skilled personnel is required for the handling, running, and maintaining the treatment of activated sludge. Energy consumption is huge for the running of this plant. Electricity is required constantly throughout the process (Crini & Lichtfouse, 2019). A solution to this issue can be obtained by using the organic sludge separated for the production of renewable energy and then using it for the running of the plant.

If compared, the advantages of the activated sludge process of water treatment are much higher than the disadvantages. Studies suggest that it is a far better process than percolating filtration or wetland systems. Thus, it can be considered an effective method and can be practiced without any concern.
From the entire essay, it can be concluded that multiple factors affect the ecology of a microorganism. Every microorganism is different and grows the best in its niche. In the case of artificially culturing the microbes, the optimum ecology needs to be provided to get the best outcome. The essay further stated how various microorganisms play an important role in waste management. In the industry of waste management of water, the activated sludge process is the most common process that is followed throughout the world. It proves to be highly efficient and has shown effective results in treating wastewater. It is also a cost-effective process if the sludge generated can be used to generate electricity that is consumed by the plant. the factor that the activated sludge chamber re-seeds the microbes responsible for breakdown is also a vital advantage of this process. Though the activated sludge treatment process has been commonly practiced, there is yet a lot to be done. There are still industries that do not perform waste management before discharging them into the environment. The Government must make this compulsory for every industry, no matter big or small and ensure that not much waste is generated in the environment. Municipal wastes should also be treated else it may lead to the spreading of diseases like cholera, dengue, typhoid, and dysentery. Thus, following proper waste management techniques shall help to arrest spreadable diseases to a large extent and make the environment pollution free.

Al-Hawash, A. B., Dragh, M. A., Li, S., Alhujaily, A., Abbood, H. A., Zhang, X., & Ma, F. (2018). Principles of microbial degradation of petroleum hydrocarbons in the environment. The Egyptian Journal of Aquatic Research, 44(2), 71-76.
Amin, A., Hawash, S. I., & Abdel-Fatah, M. A. (2019). Model of Aeration Tank for Activated Sludge Process. Recent Innovations in Chemical Engineering (Formerly Recent Patents on Chemical Engineering), 12(4), 326-337.
Atalah, J., Cáceres-Moreno, P., Espina, G., & Blamey, J. M. (2019). Thermophiles and the applications of their enzymes as new biocatalysts. Bioresource technology, 280, 478-488.
Berg, J. S., Ahmerkamp, S., Pjevac, P., Hausmann, B., Milucka, J., & Kuypers, M. M. (2022). How low can they go? Aerobic respiration by microorganisms under apparent anoxia. FEMS microbiology reviews, 46(3), fuac006.
Buaisha, M., Balku, S., & Özalp-Yaman, S. (2020). Heavy metal removal investigation in conventional activated sludge systems. Civil Engineering Journal, 6(3), 470-477.
Buckel, W., & Thauer, R. K. (2018). Flavin-based electron bifurcation, ferredoxin, flavodoxin, and anaerobic respiration with protons (Ech) or NAD+ (Rnf) as electron acceptors: a historical review. Frontiers in microbiology, 9, 401.
Carballa, M., Alvarino, T., Buttiglieri, G., Choubert, J. M., & Pons, M. N. (2017). Innovative primary and secondary sewage treatment technologies for organic micropollutants abatement.
Crini, G., & Lichtfouse, E. (2019). Advantages and disadvantages of techniques used for wastewater treatment. Environmental Chemistry Letters, 17(1), 145-155.
Duan, H., Gao, S., Li, X., Ab Hamid, N. H., Jiang, G., Zheng, M., ... & Yuan, Z. (2020). Improving wastewater management using free nitrous acid (FNA). Water research, 171, 115382.
Feng, R., Chen, L., & Chen, K. (2018). Fermentation trip: amazing microbes, amazing metabolisms. Annals of Microbiology, 68(11), 717-729.
Fitzmorris-Brisolara, K., Maal-Bared, R., Worley-Morse, T., Danley-Thomson, A., & Sobsey, M. (2022). Monitoring coliphages to reduce waterborne infectious disease transmission in the One Water framework. International Journal of Hygiene and Environmental Health, 240, 113921.
Flandroy, L., Poutahidis, T., Berg, G., Clarke, G., Dao, M. C., Decaestecker, E., ... & Rook, G. (2018). The impact of human activities and lifestyles on the interlinked microbiota and health of humans and of ecosystems. Science of the total environment, 627, 1018-1038.
Jafarinejad, S. (2017). Cost estimation and economical evaluation of three configurations of activated sludge process for a wastewater treatment plant (WWTP) using simulation. Applied Water Science, 7(5), 2513-2521.
Jin, Q., & Kirk, M. F. (2018). pH as a primary control in environmental microbiology: 1. thermodynamic perspective. Frontiers in Environmental Science, 6, 21.
Kazour, M., Terki, S., Rabhi, K., Jemaa, S., Khalaf, G., & Amara, R. (2019). Sources of microplastics pollution in the marine environment: Importance of wastewater treatment plant and coastal landfill. Marine Pollution Bulletin, 146, 608-618.
Kumar, S., & Dutta, V. (2019). Constructed wetland microcosms as sustainable technology for domestic wastewater treatment: an overview. Environmental Science and Pollution Research, 26(12), 11662-11673.
Liu, H. C., Xia, J. L., Nie, Z. Y., Liu, L. Z., Wang, L., Ma, C. Y., ... & Wen, W. (2017). Comparative study of S, Fe and Cu speciation transformation during chalcopyrite bioleaching by mixed mesophiles and mixed thermophiles. Minerals Engineering, 106, 22-32.
McCallum, E. S., Nikel, K. E., Mehdi, H., Du, S. N., Bowman, J. E., Midwood, J. D., ... & Balshine, S. (2019). Municipal wastewater effluent affects fish communities: A multi-year study involving two wastewater treatment plants. Environmental Pollution, 252, 1730-1741.
Medfu Tarekegn, M., Zewdu Salilih, F., & Ishetu, A. I. (2020). Microbes used as a tool for bioremediation of heavy metal from the environment. Cogent Food & Agriculture, 6(1), 1783174.
Mendell, M. J., Macher, J. M., & Kumagai, K. (2018). Measured moisture in buildings and adverse health effects: a review. Indoor air, 28(4), 488-499.
Nottingham, A. T., Bååth, E., Reischke, S., Salinas, N., & Meir, P. (2019). Adaptation of soil microbial growth to temperature: Using a tropical elevation gradient to predict future changes. Global change biology, 25(3), 827-838.
Rao, M. N. (2018). Waste water treatment. Oxford and IBH Publishing.
Ratzke, C., & Gore, J. (2018). Modifying and reacting to the environmental pH can drive bacterial interactions. PLoS biology, 16(3), e2004248.
Savarino, G., Corsello, A., & Corsello, G. (2021). Macronutrient balance and micronutrient amounts through growth and development. Italian Journal of Pediatrics, 47(1), 1-14.
Wilén, B. M., Liébana, R., Persson, F., Modin, O., & Hermansson, M. (2018). The mechanisms of granulation of activated sludge in wastewater treatment, its optimization, and impact on effluent quality. Applied microbiology and biotechnology, 102(12), 5005-5020.
Xia, Y., Wen, X., Zhang, B., & Yang, Y. (2018). Diversity and assembly patterns of activated sludge microbial communities: a review. Biotechnology advances, 36(4), 1038-1047.
Ziarati, P., Shirkhan, F., Mostafidi, M., & Zahedi, M. T. (2018). An overview of the heavy metal contamination in milk and dairy products. Acta scientific pharmaceutical sciences, 2(7), 1-14.
Zlateva, P., & Dimitrova, N. (2022, April). Analysis of Some Properties of an Activated Sludge Wastewater Treatment Model. In IOP Conference Series: Earth and Environmental Science (Vol. 1008, No. 1, p. 012023). IOP Publishing.

Hurry and fill the order form

Say goodbye to dreadful deadlines