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Views: 222 Author: Carie Publish Time: 2025-03-24 Origin: Site
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● The Role of Microorganisms in Wastewater Treatment
>> Types of Microorganisms Involved
>>> 3. Facultative Microorganisms
>> Key Processes in Sewage Treatment
>>> 1. Primary Treatment: Physical Separation
>>> 2. Secondary Treatment: Biological Degradation
>>> 3. Tertiary Treatment: Nutrient Removal
>> Microbial Identification and Monitoring
>>> 1. Temperature
>>> 2. pH
>>> 3. Toxicity
>>> 4. Oxygen Levels
>> Innovations in Microbial Wastewater Treatment
>>> 1. Bioelectrochemical Systems
>>> 2. Algal-Bacterial Synergy
● FAQ
>> 1. How long do microbes take to treat sewage?
>> 2. Can microbial treatments remove pharmaceuticals from wastewater?
>> 3. What happens if toxic chemicals enter a treatment plant?
>> 4. Why is methane from anaerobic digestion not always used?
>> 5. How do operators monitor microbial health in STPs?
Wastewater treatment is a critical process for protecting ecosystems and human health. Without effective treatment, sewage introduces harmful pathogens, excess nutrients, and toxic substances into water bodies, leading to diseases, algal blooms, and biodiversity loss. Microorganisms serve as nature's cleanup crew in sewage treatment plants (STPs), breaking down pollutants and converting waste into safer byproducts. This article explores the science behind microbial wastewater treatment, the types of microbes involved, and their indispensable roles in modern sanitation systems.
Microbes act as biochemical engineers in sewage treatment, transforming organic and inorganic contaminants into harmless substances through metabolic processes. The core equation governing aerobic wastewater treatment is:
Organic matter + 2O2 + 3NH3 + 4PO4-3 → New Cells + 6CO2 + 7H2O
Here, microbes consume organic waste (e.g., carbohydrates, proteins) and nutrients (nitrogen, phosphorus) to grow, while releasing carbon dioxide and water. Let's break down the microbial players and their functions.
Examples: Pseudomonas, Bacillus, Nitrosomonas
Aerobic bacteria require dissolved oxygen to degrade pollutants. These microbes dominate activated sludge systems and biofilters.
Mechanism:
- Oxidize organic matter into CO₂ and water.
- Convert ammonia (NH₃) to nitrate (NO₃⁻) via nitrification (Nitrosomonas and Nitrobacter).
Applications:
- Activated Sludge Process: Aerated tanks where bacteria form flocs to digest waste .
- Trickling Filters: Biofilms on porous media break down sewage as it percolates.
Examples: Methanogens, Clostridium, Desulfovibrio
Anaerobic bacteria thrive in oxygen-free environments, such as sludge digesters.
Mechanism:
- Hydrolyze complex organics into fatty acids, alcohols, and H₂/CO₂.
- Produce methane (CH₄) via methanogenesis, a renewable energy source.
Applications:
- Anaerobic Digesters: Convert sludge into biogas (60–70% methane).
- Phosphorus Removal: Candidatus Accumulibacter stores excess phosphorus as polyphosphate.
Examples: Escherichia coli, Enterobacter
These microbes switch between aerobic and anaerobic metabolism depending on oxygen availability.
Role:
- Stabilize systems during fluctuating oxygen levels.
- Aid in denitrification by reducing nitrate (NO₃⁻) to nitrogen gas (N₂).
- Screening and Sedimentation: Remove solids and grease.
- Microbial Pre-Treatment: Facultative bacteria begin breaking down soluble organics.
- Activated Sludge: Aerobic bacteria consume 85–90% of organic matter.
- Biofilm Systems: Microbes on rotating discs or membranes digest waste (e.g., MBBR, MBR).
- Nitrification/Denitrification: Nitrosomonas (aerobic) and Paracoccus (anaerobic) remove nitrogen.
- Phosphorus Uptake: Anaerobic-aerobic cycling enriches phosphorus-accumulating organisms (PAOs).
- Anaerobic Digestion: Methanogens reduce sludge volume by 30–50% and generate biogas.
- Composting: Thermophilic bacteria (e.g., Bacillus stearothermophilus) stabilize sludge for agriculture.
Microscopic analysis and DNA sequencing help identify microbial communities. Key indicators include:
| Microorganism | Significance |
|---|---|
| Stalked Ciliates | Healthy floc formation; low organic load |
| Filamentous Bacteria | Bulking sludge; poor settling |
| Rotifers | Advanced treatment stage; low BOD |
- Psychrophiles (45°C): Used in high-temperature digesters.
- Most bacteria prefer pH 6.5–8.5. Acidic conditions favor fungi (e.g., Fusarium).
- Heavy metals (e.g., Cu, Zn) inhibit enzymes.
- Solution: Bioaugmentation with metal-resistant strains like Ralstonia metallidurans.
- Dissolved oxygen (DO) must be 2–4 mg/L for aerobic systems.
- Microbial Fuel Cells (MFCs): Geobacter species oxidize organics while generating electricity.
- CRISPR-Edited Bacteria: Strains optimized for degrading pharmaceuticals or microplastics.
- High-Rate Algal Ponds: Algae (e.g., Chlorella) produce O₂ for bacteria, while absorbing CO₂ and nutrients.
Microorganisms are the unsung heroes of wastewater treatment, performing complex biochemical transformations that protect water resources. From aerobic oxidation to methane production, microbes enable cost-effective and sustainable sewage management. Advances in bioengineering and process optimization promise to enhance their efficiency further, making wastewater treatment a cornerstone of the circular economy.
Treatment times vary:
- Activated Sludge: 4–8 hours for secondary treatment.
- Anaerobic Digestion: 15–30 days for sludge stabilization.
Yes! Specialized consortia (e.g., White-Rot Fungi) degrade antibiotics and hormones via extracellular enzymes.
Toxins can kill microbes, causing system failure. Pre-treatment (e.g., ozonation) or bioaugmentation with resistant strains mitigates this risk.
Methane requires purification (removing H₂S and CO₂) before use. Small plants often flare it due to cost constraints.
They measure:
- MLSS (Mixed Liquor Suspended Solids): Indicates biomass concentration.
- Sludge Volume Index (SVI): Assesses settling ability.
- Microscopic Analysis: Identifies protozoa/metazoa ratios.
