Abstract
Based on 4 years of performance of phosphorus removal in a multi-stage constructed wetland with autoclaved lightweight aerated concrete (ALC) treating milking parlor wastewater, potential of constructed wetland as an advanced treatment and effect of vegetation on sustainability of phosphorus removal were evaluated. Although a higher phosphorus removal was observed in growing period compared to dry-up period for the first 2 years, such tendency was reversed from the third year. The phosphorus removed per unit area was higher at upper treatment stages. Transition of phosphorus load to down treatment stages with the years, however, equalized phosphorus removal performance per unit area at each treatment stage. The difference in treatment performances between planted and unplanted wetland suggested that vegetation had a delay effect on saturation of phosphorus sorption by ALC and on transition of phosphorus load to down treatment stages, resulting in endurance of high phosphorus removal performance for 4 years. Advanced treatment of phosphorus was possible by constructed wetland without a plant harvesting process. Annual phosphorus removal efficiency for 4 years treatment reached 87.6% under planted condition.
