Abstract
Landfill leachate is a typical large source of nitrogenous wastewater. We have revealed that nitrification reaction occurs in the leachate lagoons at two sea landfill sites, “Sakai 7－3” and “Izumiotsuoki”, located in Osaka Bay. By using nitrifying bacteria which are thought to be present in the lagoon sludge, it was expected that efficient nitrogen treatment could be performed in the leachate lagoon. In sea landfill sites, it is common that the salt concentration of leachate changes with the passage of time. In this study, a continuous nitrification test using synthetic leachate with a swim-bed reactor was conducted on the sludge samples of “Sakai 7－3” and “Izumiotsuoki” lagoons, and the effect of salinity on the treatment efficiency was investigated. It was confirmed that the ammonia oxidation occurred promptly in the synthetic leachate containing 0.5% or 3.0% sodium chloride. In contrast, the inhibition of nitrite oxidation was remarkable in the Izumiotsuoki sludge under high salinity of 3.0%. Then, the microbial community during continuous nitrification test, especially ammonia oxidizing bacteria and nitrite oxidizing bacteria were investigated. From these results, the nitrogen cycle in the lagoons was discussed.
