Advanced treatment of landfill leachate through combined Anammox-based biotreatment, O/HO oxidation, and activated carbon adsorption: technical performance, surrogate-based control strategy, and operational cost analysis.

The complexity of landfill leachate makes it difficult to treat it with a single biological/ physical/chemical process. Moreover, the dynamic leachate characteristics pose a challenge for effective process control. Therefore, a combined treatment, consisting of a one-stage partial nitrification-Anammox process, an O/HO process, and a granular activated carbon filtration (GAC) process, was investigated. Meanwhile, a novel surrogate-based ozone dose control strategy for O/HO process was evaluated. Results show that this three-stage process offers high removal of total nitrogen (> 90%), COD (chemical oxygen demand, 60-82%), and micropollutants (atrazine, alachlor, carbamazepine, and bisphenol A, > 96%), satisfying discharge requirements. In the combined post-treatment, ozone dosing for COD removal can be real-time controlled by UVA reduction monitoring, based on a specific correlation between COD and UVA changes. On the other hand, O/HO pre-treatment controlled at a 50% UVA reduction shows to be the optimal point, when adsorption is designed as the main step for COD removal. Cost analysis shows that post-treatment with low (high) organic load i.e., COD ≤ (≥)540 mg/L, a combination with O/HO (GAC) as the main step appears to be more cost-effective. Therefore, a dynamic operation strategy in response to the leachate change is recommended.