Reed rootfelt for constructed wetlands

Abstract

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