Overview of Anaerobic Microorganisms in Wastewater Treatment

During wastewater treatment, microorganisms play a central role in degrading organic pollutants. In particular, anaerobic bacteria are capable of functioning in environments without oxygen, helping convert organic matter into biogas and simpler end-products. Understanding the characteristics and classification of anaerobic bacteria is essential for operating anaerobic wastewater treatment systems efficiently.

1. What Are Anaerobic Microorganisms?

Anaerobic microorganisms are a group of microbes that can grow and develop in environments without oxygen. They not only tolerate the absence of oxygen but are also inhibited or killed when exposed to oxygen. These microorganisms typically live in places such as pond sediments, the digestive tracts of animals, or within wastewater treatment systems.

Anaerobic microorganisms degrade organic matter and treat waste.

This group of microorganisms plays an important role in biological processes such as fermentation, organic matter degradation, and wastewater treatment. In industry, they are applied to produce biogas, ethanol, organic acids, and many other valuable compounds. Anaerobic microorganisms are classified as follows:

• Obligate anaerobic bacteria: These bacteria can only exist in completely oxygen-free environments; the presence of oxygen inhibits or kills them.
• Aerotolerant anaerobic bacteria: These bacteria can survive in the presence of oxygen, but they do not use oxygen for metabolism and rely solely on anaerobic pathways.
• Facultative anaerobic bacteria: These bacteria can live in both oxygenated and oxygen-free environments, and when oxygen is available, they can use it to generate energy.

2. Factors Affecting Anaerobic Microorganisms

The growth and activity of microorganisms in anaerobic environments are influenced by various physical, chemical, and biological factors. Proper control of these factors helps optimize the anaerobic degradation process and enhance biogas production efficiency in treatment systems.

• Nutrients: Essential for the growth of anaerobic microorganisms. They require macronutrients such as carbon, nitrogen, phosphorus, and micronutrients like iron, nickel, and cobalt to maintain enzyme activity. Nutrient deficiencies slow down degradation rates and reduce conversion efficiency.
• Temperature: Directly affects metabolic rates and enzyme activity. Anaerobic processes operate most effectively at 30–38°C (mesophilic) or 50–55°C (thermophilic). Sudden temperature changes can shock the microbial community and reduce degradation efficiency.
• pH: A key parameter to maintain biological balance in anaerobic systems. Most anaerobic microorganisms thrive at pH 6.8–7.2. If pH is too low or too high, enzyme activity is inhibited, reducing biogas production and organic matter degradation.
• Hydraulic retention time (HRT): Determines the contact duration between microorganisms and substrates. Anaerobic bacteria need sufficient retention time to complete degradation phases. If retention is too short, organic matter may remain untreated, lowering system efficiency.
• Toxic substances: Compounds such as ammonia, sulfide, heavy metals, or toxic organics can inhibit or kill anaerobic microorganisms. When these substances exceed tolerance limits, degradation activity is disrupted or halted. Therefore, toxic compounds must be controlled or pretreated before entering the system.

3. What Is the Role of Anaerobic Microorganisms in Wastewater Treatment?

Anaerobic microorganisms are widely used in wastewater treatment systems with high organic loads such as domestic wastewater, food processing wastewater, and livestock effluent. During treatment, they break down complex organic compounds into simpler substances while producing methane (CH₄) and carbon dioxide (CO₂). This method is highly efficient because it reduces environmental pollution and simultaneously recovers renewable energy.

Anaerobic treatment offers several advantages such as energy savings, reduced sludge generation, and low operating costs. Common models include UASB reactors, fixed-bed anaerobic systems, and anaerobic stabilization ponds. Besides treating wastewater, anaerobic technology contributes to renewable energy recovery and promotes sustainable development in the environmental sector.

Anaerobic treatment provides benefits such as energy savings, reduced sludge, and low operating costs.

Overall, anaerobic bacteria not only help reduce pollution but also create economic benefits through biogas production. Each type of anaerobic bacteria—from obligate to facultative—plays a unique role in the sequence of organic matter degradation in wastewater. Scientific research and proper application of these microorganisms enhance treatment efficiency, save energy, and support sustainable environmental management.