Influence of Growth of Reeds on Evapotranspiration in Horizontal Subsurface Flow Constructed Wetlands

Abstract

In this study, the influence of growth of reeds on evapotranspiration (ET) was estimated, and a commonly used meteorological estimate of potential evapotranspiration (PET) was compared with direct measurements of ET. The salinity of the inside of HSF of the raw leachate inflow was 15.0±3.4g Cl -/L and that of the double diluted inflow was 9.3±1.9g Cl -/L. Although the growth of reeds in the raw leachate inflow was impeded remarkably compared to that of the double diluted leachate inflow, the reeds in the double diluted inflow bed showed healthy growth. The difference in the salinity gave rise to large differences in the growth of the reed. The annual ET rates in the poor vegetation bed, the dense vegetation bed and the unplanted bed were 656.5mm, 2,334.3mm and 22.2mm, respectively. The difference of the growth of the reed provided a large difference in the ET rate. The annual PET estimated on the basis of the Hamon equation was 751.6mm. The PET rate was much lower compared to the ET rate in the dense vegetation bed. It was necessary to consider site-specific factors such as the growth of plants in the evaluation of the water budget in the HSFs.

Effect of Reed Vegetation on Evapotranspiration and Treatment Performance with Vertical Subsurface Flow Constructed Wetlands in the Treatment of Landfill Leachate

“…Its degree of success has varied but not exceeded a 50% removal efficiency of such pollutants as COD, BOD, and nitrogen [22]. Most of landfill leachate in Japan contain a high salinity which is close to that of sea water [23][24][25]. Many kinds of plants are difficult to grow under high salinity conditions.…”

“…Mauchamp demonstrated that reed growth decreased as salinity increased (50% decrease at 4.6g・Cl -/L when compared to freshwater) and a 7-100% mortality depending on population, occurred at 9.1gCl -/ L and 12.1gCl -/L [28]. Although, there were few studies concerning the treatment of high salinity landfill leachate with constructed wetlands, several reports concerning horizontal subsurface constructed wetlands (HSFs) were given during past several years [23][24][25]. The ET capacity of reeds in VSSFs in different type of reed vegetation and the effect of reed vegetation on the treatment performance in the treatment of high salinity landfill leachate have not been thoroughly investigated.…”

Assessment of the Influence of Evaporation and Evapotranspiration on the Volume of Sludge Accumulation in The Sludge Drying Beds

“…2012, Nielsen 2007] [Herbst et al 1999] (Germany) the average monthly evapotranspiration of reed exceeds the evaporation from the free surface of the water by 1.5-2.0 times, depending on the climatic conditions. In another work [Tokuo Yano et al 2017] mentioned that if there is a favourable salt composition, the sludge evapotranspiration in 3 times higher than the reference evapotranspiration. The studies on different plant species show a significant difference in evaporation for different plant species [Milani et al 2019].…”

Estimated seasonal daily evapotranspiration rates for a horizontal subsurface flow constructed wetland

“…They did not find the exact reason for this extreme value. Yano et al [18] studied the influence of the plant growth on the evapotranspiration. The results showed that the evapotranspiration increased the growth of the plants, and that there were weeks when the water loss via evapotranspiration increased up to 80 % of the inflow rate.…”