Last Updated on May 11, 2025 by Kevin Chen
In industrial wastewater treatment, chloride ion (Cl⁻) concentration fluctuations are a critical factor. As high-chloride wastewater becomes more common in industries such as chemicals, food processing, and textiles, many operators are asking: Does high chloride content affect the stability and efficiency of MBR (Membrane Bioreactor) systems?
The answer is yes — excessive chloride levels can significantly disrupt biological treatment processes, reduce COD removal rates, and even lead to complete system failure.
How Does Chloride Affect Microorganisms?
The core of any MBR system is activated sludge, consisting of a diverse microbial community. These organisms are highly sensitive to osmotic pressure:
- In high osmotic pressure environments (e.g., Cl⁻ > 5000 mg/L), water molecules move out of microbial cells, causing dehydration, plasmolysis, and cell death.
- When Cl⁻ exceeds 8000 mg/L, sludge bulking and excessive foaming can occur, followed by massive microbial die-off.
- Sudden increases are more harmful than gradual changes. Abrupt spikes in chloride concentration do not give microbes time to adjust, resulting in rapid system destabilization.
What Are the Signs of Chloride Impact?
- Decreased COD removal, lowering overall treatment efficiency
- Interrupted nitrification, with nitrite accumulation
- Sludge disintegration, poor settling, increased SS, and sludge loss
- Microbial diversity collapses, with filamentous bacteria and protozoa disappearing
- System failure, requiring time and intervention to recover
How Can High Chloride Wastewater Be Managed?
As a professional MBR membrane system manufacturer, we recommend a multi-pronged strategy:
01. Acclimate Activated Sludge
Gradually increasing chloride levels in the influent allow microorganisms to adapt. The acclimation period typically lasts 7–10 days. Monitor biomass concentration and COD removal during this time to ensure a stable transition.
02. Dilute High-Chloride Wastewater
Diluting high-chloride wastewater with fresh or low-salt water can lower Cl⁻ concentrations below inhibitory levels (typically <2000 mg/L). This method is simple and effective for facilities where source control is feasible.
03. Optimize Treatment Processes
Introducing anaerobic stages or multi-phase processes can reduce the chloride load on the aerobic zone and improve system stability.
04. Maintain DO and Nutrient Supply
Increasing dissolved oxygen and supplementing essential nutrients (e.g., nitrogen, phosphorus) support microbial metabolism and keep the activated sludge healthy and active.
05. Strengthen Sludge Management
Regularly wasting excess sludge ensures the biomass stays in the logarithmic growth phase, enhancing system resilience against chloride shocks.
The above information is about the impact of high chloride concentration. If you still have any questions, please feel free to contact SPERTA.
Shanghai SPERTA Environmental Technology Co., Ltd. has specialized in producing water treatment products for many years. The company has its own MBR membrane technology, a complete technical team, and pre-sales and after-sales service. If you have any needs, please feel free to contact us.
