Reed rootfelt for constructed wetlands

Abstract

The resources of lakes' overgrowth biomass increases in result of eutrofication process in
more than 2000 lakes in Latvia. Usage of lake reed rootfelt for filling of constructed wetlands
can improve leachate treatment at a beginning period of operation and especially applicable in
treatment plants with limited area. Physical and chemical properties of Reed rootfelt of lake
Zebras were investigated to evaluate possibilities for rootfelt usage in constructed wetlands.
The Reed rootfelt coalesces with the ground in coastal zone and is floating in the deeper areas
of lake. Thickness of floating reed rootfelt layer varies from 0.25 to 0.8 m. Density (without
gravitational water) of reed rootfelt varies from 550 kg/ml at a surface to 1058 kg/m' in
deeper layers if the rootfelt coalesces with ground. Investigated average density is 505 kg/ml
and 814 kg/ml for floated overgrowth and rootfelt coalesced with ground respectively. The
moisture content (without gravitational water, dry basis) of freshly removed floated rootfelt
changes from 523 % at a surface to 706 % in deeper layer. If rootfelt was dried and moistened
once more, moisture content remain practically same at a surface (498 %) and decreases 3
times in deeper layer (226 %). Investigated average organic matter content were 77 % for
floating rootfelt and 49 % for rootfelt coalescing with ground. The specific energy of rootfelt
cutting is 8,6 kJ/m2 for oscillating saw, 18.1 kJ/m2 for vertical blade and IO kJ/m2 for blade
sloped in 45°. Acceptable technology for rootfelt removal includes partitioning of overgrowth
in pieces and/or layers by manually operated or powered cutters and floating of pieces of
rootfelt to coastal stockpile. Pre-treatment of rootfelt includes washing out of inorganic
sediments, draining of the excess (gravitational) water and drying slightly only, to preserve
growing ability of rootfelt. Thickness of rootfelt pieces can be increased for filling of area
close to inlets in constructed wetlands to provide additional structure for enchanced
flocculation and sedimentation. Methods of rootfelt pieces removal, handling and
transportation avoid destruction of removed biomass and ensure high initial growing ability.