The benefits of plant-microbe interactions have been exploited extensively for nutrient removal. Radial oxygen loss in aquatic macrophytes potentially promotes nitrification and accelerates nitrogen removal through coupled nitrification-denitrification process. Nitrification is likely the limiting activity for an effective nitrogen removal in wetlands. In this work, we have quantified the effect of radial oxygen losses in Typha angustifolia plants in environments of contrasting salinities, including a temporary lagoon, a constructed wetland, and a river estuary. In all sites, radial oxygen diffusion occurred mainly at a narrow band, from 1 to 5 cm from the root tip, and were almost absent at the tip and basal sections of the root (> 5 cm). Root sections with active oxygen diffusion tended to show higher bacterial and archaeal densities in the rhizoplane according to 16S rRNA gene abundance data, except at higher salinities. Archaeal amoA /bacterial amoA gene ratios were highly variable among sites. Archaeal nitrifiers were only favoured over bacteria on the root surface of Typha collected from the constructed wetland. Collectively, radial oxygen loss had little effect on the nitrifying microbial community at the smaller scale (differences according to root-section), and observed differences were more likely related to prevailing physicochemical conditions of the studied environments or to long-term effects of the root microenvironment (root vs sediment comparisons).

• MeSH
• Ammonia metabolism   MeSH
• Plant Roots metabolism   MeSH
• Oxygen metabolism   MeSH
• Microbiota MeSH
• Nitrification physiology   MeSH
• Typhaceae metabolism   MeSH
• RNA, Ribosomal, 16S genetics   MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Ammonia MeSH
• Oxygen MeSH
• RNA, Ribosomal, 16S MeSH

Sludge treatment beds (STBs) have been used widely in many countries due to low energy consumption, low operating and maintenance costs, and better environmental compatibility. Penetration, evaporation, and transpiration are the main processes for sludge dewatering in STBs. However, the leachate quality from STBs usually cannot meet discharge limits. Moreover, such leachate has very low COD/N ratio, which makes it difficult to treat. In the present study, two subsurface flow (SSF) constructed wetlands (CWs) were investigated for the treatment of leachate from STBs under three different hydraulic retention time (HRT) (3 days, 4 days, 6 days), aiming for evaluating the effects of plants and HRT on treatment performance, as well as the potential of SSF CWs to treat sludge leachate with low COD/N ration. The results showed that plants play an important role in leachate treatment. The best treatment performance was achieved with HRT of 4 days. In this condition, the mean removal efficiencies of COD (chemical oxygen demand), NH4+-N, TN (total nitrogen), and TP (total phosphorus) in the planted and the unplanted CWs were 61.6% (unplanted - 3.7%), 76.6% (unplanted 43.5%), 70% (unplanted 41%), and 65.6% (unplanted 6%), respectively. Heavy metal concentrations were below the Chinese integrated wastewater discharge standard during the experimental period in the planted CW, and the removal efficiencies in the planted CW system were higher than in the unplanted CW system. In all, planted SSF CWs can be an effective approach in removing leachate from sludge treatment beds. Furthermore, considering to temperature and seasonal variation, the leachate from STBs needs to be further studied in pilot- and full-scale condition.

• Keywords
• Constructed wetland, Sludge leachate, Sludge treatment beds, Water purification,
• MeSH
• Water Purification MeSH
• Nitrogen analysis   MeSH
• Phosphorus analysis   MeSH
• Water Pollutants analysis   MeSH
• Biological Oxygen Demand Analysis MeSH
• Wetlands * MeSH
• Waste Disposal, Fluid methods   MeSH
• Wastewater MeSH
• Sewage MeSH
• Plants MeSH
• Metals, Heavy MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Nitrogen MeSH
• Phosphorus MeSH
• Water Pollutants MeSH
• Waste Water MeSH
• Sewage MeSH
• Metals, Heavy MeSH

Hydroponic root mats (HRMs) are ecotechnological wastewater treatment systems where aquatic vegetation forms buoyant filters by their dense interwoven roots and rhizomes, sometimes supported by rafts or other floating materials. A preferential hydraulic flow is created in the water zone between the plant root mat and the bottom of the treatment system. When the mat touches the bottom of the water body, such systems can also function as HRM filter; i.e. the hydraulic flow passes directly through the root zone. HRMs have been used for the treatment of various types of polluted water, including domestic wastewater; agricultural effluents; and polluted river, lake, stormwater and groundwater and even acid mine drainage. This article provides an overview on the concept of applying floating HRM and non-floating HRM filters for wastewater treatment. Exemplary performance data are presented, and the advantages and disadvantages of this technology are discussed in comparison to those of ponds, free-floating plant and soil-based constructed wetlands. Finally, suggestions are provided on the preferred scope of application of HRMs.

• Keywords
• Constructed wetland, Floating hydroponic root mats, Hydroponic root mat filters, Wastewater treatment,
• MeSH
• Biodegradation, Environmental MeSH
• Hydroponics * MeSH
• Plant Roots * MeSH
• Wetlands MeSH
• Waste Disposal, Fluid methods   MeSH
• Wastewater * MeSH
• Groundwater MeSH
• Rivers MeSH
• Ponds MeSH
• Water Pollution MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Waste Water * MeSH