Potential of hybrid constructed wetland system in treating milking parlor wastewater under cold climatic conditions in northern Hokkaido, Japan

Abstract

A real scale hybrid constructed wetland (CW) system (656 m2), with a configuration of VFA-VFB-HF beds constructed in series is operating since November 2006 in northern Hokkaido, Japan. The system was experimented to assess its capability in purifying 4.5 m3d−1 of high strength milking parlor wastewater under colder climate. Annual mean air temperature at site was recorded as 6.4 oC (extremes vary as -22.8 oC at lowest and 30.6 oC at highest). From the monthly sampling from November 2006 to January 2010, average loading and removal rates of TSS, CODcr, BOD5, TN and TP were 5.4 g m−2 d−1 (98%), 30.3 g m−2 d−1 (88%), 11.5 g m 2 d−1 (89%), 1.2 g m−2 d−1 (76.4%) and 0.2 g m−2 d−1 (76%). System did not stop for a single day, efficiently worked even during snow covered periods and was tolerant to the load fluctuations.