How to Solve Persistently High COD in Leachate?

13 Apr, 2026 11:58am

At large landfill sites, leachate COD often exceeds 5,000 mg/L. Without effective treatment, the risk of surface water and groundwater contamination rises rapidly. Persistently high COD not only causes biological treatment failure and severe membrane fouling, but also significantly increases operating costs.

As a global leading water treatment solution provider, WTEYA offers systematic leachate COD treatment solutions. Through scientifically integrated process combinations, WTEYA helps customers achieve stable compliance discharge and water reuse, transforming leachate from a burden into a manageable and recoverable resource.

Core Reasons Why Leachate COD Remains High

Leachate is a high-strength wastewater generated during landfill operations or industrial waste disposal. The main reasons why COD remains persistently high include:

Cause	Description	Impact
Complex Organic Matter	Large molecular organics, colloids, oils mixed together	Difficult for microorganisms to degrade, low biological efficiency
Poor Biodegradability	Organic compounds inhibit microbial activity	Unstable biological reactions, fluctuating effluent quality
Large Water Quality Fluctuation	Rainfall or waste composition changes affect flow and quality	High shock load, unstable system operation
Interfering Substances	Heavy metals, suspended solids, oils	Microbial inhibition, intensified membrane fouling

⚠️ Summary: The root cause of persistently high COD lies in the combination of complex pollutants and high operational pressure. A single treatment process is rarely enough to solve the problem completely.

Systematic Solution: Biological Treatment → Membrane Treatment → Evaporation System

WTEYA believes that high-COD leachate treatment must be approached as a system engineering project, rather than relying on one single technology.

To remove refractory COD effectively, multi-stage collaborative treatment is required to gradually reduce COD and achieve long-term stable compliance.

1️⃣ Biological Treatment: Remove Biodegradable Organics

Biological treatment is the core stage of COD removal. Traditional activated sludge systems often fail under high COD loading. WTEYA adopts optimized technologies for stable and efficient performance:

• Two-stage A/O Optimization: Enhances microbial activity and buffers water quality fluctuations

• MBR Membrane Bioreactor: Separates biomass from water, improving COD removal stability under high loading

• Specialized Microbial Enhancement: High-COD resistant bacteria improve treatment efficiency

💡 Technical Highlight: Optimized biological treatment effectively removes degradable organics and creates ideal influent conditions for downstream membrane systems.

2️⃣ Membrane Treatment: Advanced Purification and Water Reuse

Even after biological treatment, leachate may still contain small organic molecules and salts. Membrane treatment is used for deep purification:

• Nanofiltration (NF): Removes macromolecular pollutants

• Reverse Osmosis (RO): Removes dissolved salts and small organics, enabling water reuse or compliant discharge

💡 Operational Keys:

• Stable influent water quality

• Precise process parameter control

• Intelligent monitoring systems for long-term efficiency

3️⃣ Evaporation System: Achieve Full Wastewater Reduction

For ultra-high salinity wastewater or refractory pollutants, WTEYA uses evaporation systems to achieve zero liquid discharge:

• MVR Falling Film Evaporation: Concentrates leachate while recovering thermal energy for energy savings

• Forced Circulation Crystallizer: Crystallizes salts

• Mother Liquor Recirculation & Drying: Final residual liquid solidification

4️⃣ Intelligent Operation Management: Ensure Long-Term Stability

Stable COD compliance depends not only on technology, but also on smart management systems:

• Online Monitoring: Real-time tracking of COD, ammonia nitrogen, TDS, and pH

• Automatic Adjustment: Dosing amount, membrane pressure, and evaporation temperature controlled automatically

• Data Analysis: Early warning and optimization to reduce unplanned downtime

✅ Result: Long-term stable system operation, lower maintenance costs, and consistently high treatment efficiency.

Conclusion: From COD Control to Resource Recovery

Persistently high leachate COD is the result of complex wastewater characteristics and system stress. WTEYA emphasizes that systematic multi-stage treatment + intelligent management is the real solution.

Through the full-process treatment chain of:

Biological Treatment → Membrane Treatment → Evaporation System

customers can achieve:

• Stable COD compliance

• Full wastewater reduction

• Water reuse and resource recovery