Treatment train for mature landfill leachates: Optimization studies

Area of Science:

• Environmental Engineering
• Water Treatment Technologies
• Chemical Engineering

Background:

• Urban mature leachates pose significant environmental challenges due to high organic and nitrogen content and low biodegradability.
• Existing treatment methods often struggle to meet stringent legal discharge limits for pollutants like chemical oxygen demand (COD) and total nitrogen (TN).

Purpose of the Study:

• To evaluate a multi-stage treatment train strategy for urban mature leachate to achieve full legal compliance.
• To optimize biological and physicochemical processes for efficient removal of organic carbon, nitrogen, and other pollutants.

Main Methods:

• A sequential batch reactor (SBR) was used for total nitrogen (TN) removal, followed by a coagulation stage for dissolved organic carbon (DOC) removal.
• A photo-Fenton (PF) oxidation process was employed to enhance leachate biodegradability.
• Final treatment involved a conventional activated sludge process in continuous mode.

Main Results:

• The SBR achieved higher TN removal efficiency with increased temperature (20-30°C).
• Coagulation at pH 3.0 with 240mg Fe3+/L yielded 64% DOC removal and 33 NTU turbidity.
• Photo-Fenton oxidation significantly improved biodegradability, enabling final biological treatment to meet COD discharge limits (<150mg O2/L).
• The final activated sludge process achieved COD (107±3 mg/L) and TSS (50±2 mg/L) below legal limits.

Conclusions:

• A sequential treatment train combining SBR, coagulation, photo-Fenton oxidation, and activated sludge is effective for urban leachate treatment.
• Process parameters like temperature, coagulant dosage, pH, and UV energy significantly impact treatment efficiency.
• The developed strategy successfully meets legal discharge limits for COD, TN, and turbidity.