Dairy Wastewater Treatment by Constructed Wetland Planted with Carex under Cold Climate

摘要

Hokkaido is located in the northernmost area of the Japanese islands,and the climate in Hokkaido is dry and moderate in the Summer but very cold in the Winter.One of the main industries of Hokkaido is dairy farming,and its wastewater causes serious problem on the water environment.In several years,constructed wetlands have been installed and are treating dairy wastewater in Hokkaido region.In this research,the free water surface constructed wetland which processes the dairy wastewater was investigated to determine the treatment capabilities of a constructed wetland under the weather condition in Hokkaido.The wastewater from the milking parlor of the barn in our research center and imitation wastewater only containing inorganic nitrogen and phosphorus were supplied to the free water surface wetlands (16 m2,Carox rhynchophisa was planted) on 100L/day.The water depth was maintained around 20 cm during summer to fall,and around 40 cm during winter to maintain of the stream by freezing only the surface.Accumulation of the pollutants to soil was investigated.Although the change in the quantity in the soil was stable few about nitrogen,phosphorus differed in the speed of increase and decrease by the layer.Also in order to prevent the out-flow of a contamination substance,it seemed that the further observation is required.