As Sri Lanka’s cities expand and industries grow, wastewater treatment systems are under increasing pressure to perform consistently, comply with tighter discharge norms, and support long-term environmental sustainability. Among the various technologies used nationwide, the biological sewage treatment plant remains the most efficient and widely adopted solution for removing organic pollutants and stabilising wastewater.
However, the performance of a biological system depends heavily on proper operation and routine maintenance. When not maintained, issues such as odour, sludge overflow, foaming, and poor effluent quality can arise — often leading to violations of discharge standards and increased operational cost.
Here are essential maintenance tips to keep biological sewage treatment plants running efficiently across Sri Lanka.
Why Biological Treatment Is So Effective?
A biological sewage treatment plant uses microorganisms to break down organic pollutants in wastewater. These microorganisms consume organic matter, reducing Biological Oxygen Demand (BOD) and improving water clarity and quality.
This makes biological systems ideal for:
- Municipal wastewater
- Hotels and resorts
- Hospitals
- Commercial buildings
- Housing projects
- Industrial estates
They are essential in Sri Lanka’s tourism-driven regions, where clean surroundings and adherence to environmental norms are critical.
Key Maintenance Tips for Reliable Operation
1. Ensure Steady Influent Flow & Loading
Biological systems are sensitive to sudden shock loads. Maintain consistent influent flow and avoid large fluctuations in organic matter, oils, chemicals, or toxic compounds.
2. Monitor Dissolved Oxygen Levels
Aerobic units must maintain sufficient oxygen. Low DO leads to foul odours, poor BOD reduction, and biomass die-off.
Target DO levels: 2–4 mg/L (depending on design).
3. Maintain Proper Sludge Age & MLSS
The concentration of microorganisms (MLSS) must be kept within an optimum range.
Too high = bulking, poor settling
Too low = insufficient treatment
Routine sludge wasting is essential to maintain balance.
4. Regularly Check Blowers, Diffusers, and Pumps
Mechanical failures directly affect biological performance. Routine servicing ensures an uninterrupted oxygen supply and stable operations.
5. Avoid Toxic Chemicals Entering the Plant
Detergents, grease, disinfectants, and industrial chemicals can inhibit microbial activity. Source control and pre-treatment help protect the biological process.
6. Track BOD & COD Reduction
The core function of a biological oxygen demand sewage treatment plant is to lower BOD. Regular sampling ensures that microbes remain healthy and that treatment efficiency remains stable.
7. Maintain Clarifiers & Prevent Sludge Overflow
Poor clarifier maintenance can cause suspended solids carry-over — a common reason for non-compliance.
8. Prevent Foaming & Bulking Issues
Foaming may indicate overgrowth of filamentous bacteria or surfactant overload. Proper nutrient balance and aeration adjustments help manage these issues.
9. Calibrate Sensors & Instruments
pH meters, DO sensors, flow meters, and online analysers must be calibrated frequently to maintain data accuracy.
10. Implement SCADA or Remote Monitoring
Automated monitoring helps detect anomalies early, reduces manual errors, and supports compliance with Sri Lanka’s environmental discharge norms.
Common Problems & How to Prevent Them
Odour Issues
Often caused by low oxygen or septicity.
Solution: Improve aeration, check DO, and prevent stagnant zones.
Poor Effluent Clarity
Usually due to sludge bulking or improper settling.
Solution: Control MLSS, adjust aeration, and maintain clarifier performance.
High BOD in Treated Water
Indicates a stressed or unhealthy microbial population.
Solution: Check for toxins, adjust sludge age, and maintain nutrient balance.
Foaming
Caused by surfactants or filamentous growth.
Solution: Identify the source, adjust the aeration pattern, and dose anti-foam if required.
Importance of Professional O&M Support
Routine maintenance ensures compliance with national regulations set by the Central Environmental Authority (CEA). In Sri Lanka’s hospitality, commercial, and industrial sectors, professional O&M services help avoid:
- Penalties for non-compliance
- Guest complaints (especially in hotels)
- Equipment downtime
- High operational cost
- Environmental damage
Well-managed biological systems consistently achieve BOD and COD targets while ensuring long-term reliability.
Unveiling Ion Exchange’s Pioneering Solutions for Chemical Treatment of Wastewater
For over six decades, Ion Exchange has been delivering comprehensive water and wastewater treatment solutions to a diverse range of industries, institutions, municipalities, and communities worldwide. Our solutions include customized and pre-engineered water treatment plants designed to meet critical quality requirements for various uses.
Coagulation and Flocculation
Coagulation and flocculation are essential processes for removing colloidal particles from water. Our range of synthetic cationic, anionic, and non-ionic organic coagulants and flocculants is effective in clarifying and filtering water and removing heavy metals and color from wastewater and process fluids. Additionally, our chemical dosing systems, available in various capacities, ensure precise chemical treatment applications. Ion Exchange offers a complete range of coagulants and flocculants for solid-liquid separation in various applications, benefiting from:
– Removal of suspended solids and colloidal silica in pre-treatment
– Elimination of colloidal organics
– Solid-liquid separation in effluent treatment equipment
– Color removal in distillery and textile effluents
– De-oiling in refinery effluents
– Pre-treatment for reverse osmosis to reduce SDI
– Brine clarification
– Miscellaneous process applications
Conclusion
A biological sewage treatment plant remains one of the most effective solutions for wastewater treatment in Sri Lanka. With proper maintenance, careful monitoring, and efficient operation, these systems can perform reliably for years — ensuring safe discharge, environmental protection, and sustainable development.
Connect with Ion Exchange experts to optimise, upgrade, or maintain your biological sewage treatment plant for long-term performance in Sri Lanka.
