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Views: 222 Author: Carie Publish Time: 2025-03-12 Origin: Site
Content Menu
● Introduction to Sewage Treatment
● The Microbial Workforce in Sewage Treatment
>> Aerobic Bacteria: Oxygen-Dependent Degraders
>>> Key Species and Functions:
>> Anaerobic Bacteria: Methane Producers
>>> Key Species and Functions:
>> Facultative Bacteria: Adaptable All-Rounders
>> Protozoa and Metazoa: The Cleanup Crew
>> Fungi and Microalgae: Niche Players
● Advanced Microbial Technologies
>> 1. Microbial Fuel Cells (MFCs)
● Challenges in Microbial Sewage Treatment
● Environmental and Economic Impact
● FAQ
>> 1. How long do microbes take to treat sewage?
>> 2. Can sewage microbes harm human health?
>> 3. What happens to dead microbes in treated water?
>> 4. Do antibiotics in wastewater affect treatment microbes?
>> 5. How is microbial activity monitored in treatment plants?
Sewage treatment is a critical process that relies on microorganisms to break down organic matter and remove harmful substances from wastewater. This biological approach protects public health and ecosystems by reducing pollutants before water is discharged into the environment. Below, we explore the microbial workhorses behind sewage treatment, their mechanisms, and emerging innovations in the field.
Modern sewage treatment involves three stages:
1. Primary Treatment: Physical removal of large debris and suspended solids.
2. Secondary Treatment: Biological degradation of organic matter using microbes.
3. Tertiary Treatment: Advanced processes (e.g., filtration, disinfection) for polishing water quality.
The secondary treatment stage is where microorganisms shine, reducing biochemical oxygen demand (BOD) by up to 90% through metabolic activity.
Aerobic bacteria dominate activated sludge systems, where oxygen is pumped into wastewater to fuel their metabolism.
- Nitrosomonas & Nitrobacter: Convert toxic ammonia to nitrate via nitrification.
- Pseudomonas spp.: Degrade hydrocarbons and phenolic compounds.
- Zoogloea spp.: Form sticky bioflocs that trap organic particles.
Mechanism:
These bacteria oxidize organic carbon (C6H12O6 + 6O2 → 6CO2 + 6H2O) while generating energy.
Operating in oxygen-free environments like anaerobic digesters, these microbes thrive in high-organic-load conditions.
- Methanogens: Archaea that produce methane (CH4) from CO2 and H2.
- Clostridium spp.: Break down complex polymers into fatty acids.
Process Stages:
1. Hydrolysis → 2. Acidogenesis → 3. Acetogenesis → 4. Methanogenesis
Output:
- Methane (used for energy generation)
- Reduced sludge volume (by 40–60%)
These versatile microbes switch between aerobic and anaerobic modes based on environmental conditions.
Examples:
- Escherichia coli: Breaks down lactose and proteins.
- Enterobacter spp.: Degrades petroleum hydrocarbons.
Advantage:
They stabilize systems during oxygen fluctuations, common in decentralized treatment plants.
Non-bacterial microbes enhance treatment efficiency:
| Organism | Role | Example Species |
|---|---|---|
| Ciliates | Consume free bacteria, clarify water | Vorticella, Paramecium |
| Rotifers | Graze on flocs, reduce sludge | Philodina |
| Nematodes | Break down fungal/bacterial biofilms | Caenorhabditis |
- Fungi (e.g., Aspergillus niger): Degrade lignin and pharmaceuticals.
- Microalgae (e.g., Chlorella): Absorb nitrogen/phosphorus while producing oxygen.
Case Study:
A plant in Singapore uses Chlorella vulgaris to remove 89% of nitrogen and 93% of phosphorus from sewage.
Bacteria like Geobacter sulfurreducens generate electricity while treating wastewater.
- Output: 0.5–1.2 kWh/m³ of treated water
- Applications: Remote sensors, low-energy treatment plants
Adding engineered strains (e.g., Dechloromonas aromatica for perchlorate removal) boosts treatment efficiency.
Self-immobilized microbial aggregates (1–3 mm diameter) withstand high loads.
- Benefits: 30% less energy use vs. conventional systems
- Temperature Sensitivity: Mesophilic microbes (30–40°C) underperform in cold climates.
- Toxicity: Heavy metals (e.g., Hg, Cd) inhibit microbial activity at >2 ppm.
- Foaming Issues: Filamentous bacteria like Microthrix parvicella disrupt sludge settling.
- CRISPR-Edited Microbes: Strains resistant to antibiotics and heavy metals.
- Biochar Amendments: Enhances microbial growth by 22% (University of Queensland, 2024).
Anaerobic digestion cuts CO2 emissions by 1.3 kg per m³ of treated sewage compared to aerobic methods.
| Process | Cost (USD/m³) | BOD Removal Efficiency |
|---|---|---|
| Activated Sludge | 0.15–0.30 | 85–95% |
| Anaerobic Digestion | 0.08–0.20 | 70–85% |
| MFC Systems | 0.40–0.60 | 60–75% |
Microorganisms form the backbone of sustainable sewage treatment, offering cost-effective and eco-friendly solutions. As genetic engineering and hybrid technologies evolve, microbial systems will play an even greater role in achieving global water security goals.
Most secondary treatment processes require 6–12 hours for BOD reduction, while anaerobic digestion spans 15–30 days.
Pathogens like *Salmonella* are eliminated during treatment via UV disinfection or chlorination.
They form part of the "waste sludge," which is dewatered and incinerated/land-applied as fertilizer.
Yes, high antibiotic concentrations (>1 mg/L) can inhibit bacterial activity. Advanced oxidation steps are often added.
Techniques include:
- ATP bioluminescence testing
- DNA sequencing (e.g., 16S rRNA analysis)
- Microscopic sludge index measurements
