Treatment of landfill leachate with high levels of ammonia by constructed wetland systems

Abstract

Landfill leachate treatment can be expensive and energy-intensive when achieved in advanced wastewater treatment plants. One possible method to reduce cost and energy requirements is to treat the leachate on-site using constructed wetlands. In this study, we investigated the feasibility of treating the leachate from a 10-year-old landfill site, with high levels of ammonia, by lab-scale constructed wetland microcosms. Five different types of wetland systems were used in the test: P1, P2 and CS-1 systems fed by original leachate, P3

and CS-2 systems fed by secondarily treated leachate. The CS systems were used as control without vegetation. Each system contained two basins connected in series: one installed as free water surface (FWS) wetland microcosm, and the other as subsurface flow (SSF) wetland microcosm. After one year of operation, the experimental results showed that P2 system performed better than both P1 and P3 systems by comparing their removal efficiencies of ammonia, which were measured equal to 94%, 84% and 60%, respectively. However, for total nitrogen removal, all three systems exhibited lower values, which meant that the process denitrification was insignificant in the wetland systems treating aged leachate. According to the experimental results of adding extra BOD into the systems, we found that the reason was due to lack of organic carbon sources in aged leachate for denitrification, which might cause nitrate buildup in the effluents.

Keywords:

• Constructed wetland treatment systems
• denitrification
• landfill leachate
• microcosm