Effect of air and water on the release of chlorine from semi-aerobic landfill

Landfill leachate has a high chloride (Cl-) content. Because it is highly mobile, and cannot be sorbed or transformed bio-chemically, it is important to have detailed information about how it migrates in landfill sites. In this study, we set up four lab-scale simulated landfills, including an anaerobic landfill (AL), an anaerobic landfill with leachate recirculation (RAL), an anaerobic/semi-anaerobic landfill with leachate recirculation (RASL), and an anaerobic/semi-aerobic landfill (ASL), to explore how, when regulated, moisture and air affected the migration of chlorine. We found that water and air had a strong influence on the release of Cl-. Leachate obviously promoted Cl- dissolution in refuse when recirculated. When air was introduced into landfill, thereby changing it from anaerobic to semi-aerobic, the leachate Cl- concentration increased sharply from around 4-9 g L-1 (RASL) and 18 g L-1 (ASL), respectively. In principle, Cl- is released continuously when leachate is recirculated in landfills (RAL and RASL), but it can also be found a terminal when the leachate recirculation stops (AL and ASL). Cumulative amounts of 64, 66, 27, and 53 g of Cl- were released from the AL, RAL, RASL, and ASL, respectively. Lower COD/Cl and NH4+-N/Cl ratios in ASL and RASL after day 175 indicated that lower Cl- pollution risk than that in AL and RAL.

Automated summary

The study investigated the impact of moisture and air on the migration of chloride ions in landfills, finding that water and air significantly influenced the release of chloride ions in leachate. The results showed that continuous release of chloride ions occurs when leachate is recirculated in landfills.