subsurface
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elektronický časopis
- MeSH
- inženýrství MeSH
- Konspekt
- Patologie. Klinická medicína
- NLK Obory
- radiologie, nukleární medicína a zobrazovací metody
- technika
- NLK Publikační typ
- elektronické časopisy
Critical factors leading to arsenic release and attenuation from the shallow subsurface were studied with multidisciplinary approach in the natural gold-arsenic geochemical anomaly at Mokrsko (Czech Republic). The results show that microbial reduction promotes arsenic release from Fe(III) (hydr)oxides and Fe(III) arsenates, thereby enhancing dissolved arsenic in the shallow groundwater at average concentration of 7.76 mg/L. In the organic-rich aggregates and wood particles, however, microbial sulfate reduction triggers the formation of realgar deposits, leading to accumulation of As in the distinct organic-rich patches of the shallow subsurface. We conclude that precipitation of realgar in the shallow subsurface of soil/sediment depends on specific and non-trivial combination of water and rock chemistry, microbial community composition and spatial organisation of the subsurface zone, where speciation in saturated environments varied on a centimeter scale from reduced (decomposed wood, H2S and realgar present) to oxidized (goethite and arsenate minerals are present).
- MeSH
- arsen analýza metabolismus MeSH
- chemické látky znečišťující vodu analýza metabolismus MeSH
- mikrobiologie vody * MeSH
- podzemní voda chemie mikrobiologie MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Geografické názvy
- Česká republika MeSH
The constructed wetland (CW) for 326 PE with horizontal subsurface flow at Kotenčice, Central Bohemia, Czech Republic, was built in 1994. Despite the relatively high efficiency of the CW, the filtration beds suffered from clogging, and therefore it was decided in 2011 to rebuild the whole system. The new treatment system was built as an experimental system consisting of four different combinations of horizontal and vertical beds. The major aim of the design was to determine the best hybrid combination which then could be used in the future for refurbishment of older horizontal flow CWs or for the new systems. The mechanical pretreatment consists of mechanical bar screens, a new Imhoff tank, and the original settling tank which has been converted into the accumulation tank from where the wastewater is pumped into the wetlands. The filters are planted with Phragmites australis, Phalaris arundinacea, Iris pseudacorus, Iris sibirica, Glyceria maxima and Lythrum salicaria in order to evaluate and compare various plant species' effect on the treatment process. The new technology includes a tertiary treatment which consists of a greenhouse with a photo-reactor for the cultivation of algae and hydroponic systems (residual nutrients removal), sludge reed-beds and a composting field.
- MeSH
- čištění vody metody MeSH
- mokřady * MeSH
- odpad tekutý - odstraňování metody MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Geografické názvy
- Česká republika MeSH
The effect of Typha latifolia and its litter on density and abundance of three denitrifying genes (nirS, nirK and nosZ) were investigated in six laboratory-scale SSF CW microcosms. Results showed that the copy numbers of nirS, nirK and nosZ in wetland microcosms were ranged between 10(8)-10(9), 10(6)-10(7) and 10(7)-10(8) copies g(-1), respectively. The presence of T. latifolia encouraged the growth of nirK containing bacteria. Addition of cattail litter could greatly stimulate the growth of bacteria containing nirS and nosZ gene. Path analysis illustrated that the presence of plants and litters had no significant direct impact on denitrifying genes, while it affected the denitrifying genes via alteration of dissolved oxygen and carbon sources.
- MeSH
- Bacteria enzymologie genetika MeSH
- bakteriální geny * MeSH
- biologické modely MeSH
- biomasa * MeSH
- denitrifikace genetika MeSH
- mokřady * MeSH
- nitrátreduktasa genetika metabolismus MeSH
- RNA ribozomální 16S genetika MeSH
- rostliny mikrobiologie MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Nitrate is commonly found in the influent of subsurface-batch constructed wetlands (SSB CWs) used for tertiary wastewater treatments. To understand the effects of plants and the litter on nitrate removal, as well as on nitrogen transformation in SSB CWs, six laboratory-scale SSB CW microcosms were set up in duplicate and were operated as batch systems with hydraulic residence time (HRT) of 5d. The presence of Typha latifolia enhanced nitrate removal in SSB CWs, and the N removed by plant uptake was mainly stored in aboveground biomass. Typha litter addition greatly improved nitrate removal in SSB CWs through continuous input of labile organic carbon, and calculated enrichment factors (ε) were between -12.1‰--13.9‰ from the nitrogen stable isotope analysis, suggesting that denitrification plays a dominant role in the N removal. Most significantly, simultaneous sulfur-based autotrophic and heterotrophic denitrification was observed in CWs. Finally, mass balance showed that denitrification, sedimentation burial and plant uptake respectively contributed 54%-94%, 1%-46% and 7.5%-14.3% to the N removal in CWs.
- MeSH
- biodegradace MeSH
- biomasa MeSH
- chemické látky znečišťující vodu metabolismus MeSH
- denitrifikace * MeSH
- dusičnany metabolismus MeSH
- izotopy dusíku metabolismus MeSH
- mokřady * MeSH
- odpad tekutý - odstraňování * MeSH
- orobincovité metabolismus MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Three different flow regimes were carried out in a pilot-scale horizontal subsurface flow constructed wetland-treating sulfate rich wastewater contaminated with monochlorobenzene (MCB) and perchloroethene (PCE). The three regimes were continuous flow, 7-day cycle discontinuous flow, and 2.5-day cycle discontinuous flow. The results show that intensifying the tidal regime (2.5-day cycle) significantly enhanced MCB removal before 2 m from the inlet and increasing PCE removal efficiency at 0.5 m. The PCE dechlorination process was promoted with tidal operation, especially under the 2.5-day cycle regime, with significant increases of cis-1,2- dichloroethenes (DCEs), vinyl chloride (VC), and ethene, but trans-1,2-DCE was significantly decreased after tidal operation. Due to the high sulfate concentration in the influent, sulfide was observed in pore water up to 20 and 23 mg L(-1) under continuous flow and 7-day cycle regime, respectively. However, sulfide concentrations decreased to less than 4 mg L(-1) under intensified tidal operation (2.5-day cycle). The increase of oxygen concentration in pore water through intensified tidal operation resulted in better MCB removal performance and the successful inhibition of sulfate reduction. In conclusion, intensifying tidal operation is an effective approach for the treatment of chlorinated hydrocarbons and inhibiting sulfide accumulation in horizontal subsurface flow constructed wetland.
- MeSH
- biodegradace MeSH
- chemické látky znečišťující vodu analýza MeSH
- chlorované uhlovodíky analýza MeSH
- čištění vody metody MeSH
- mokřady * MeSH
- odpadní voda chemie MeSH
- pilotní projekty MeSH
- sírany analýza MeSH
- sulfidy analýza MeSH
- Publikační typ
- časopisecké články MeSH
- Geografické názvy
- Německo MeSH
Sulfate is frequently found in the influent of subsurface-flow constructed wetlands (SSF CWs) used as tertiary treatments. To reveal the effects of plants and litters on sulfate removal, as well as the competition for organic carbon among microorganisms in SSF CWs, five laboratory-scale SSF CW microcosms were set up and were operated as a batch system with HRT 5 d. The results showed that the presence of Typha latifolia had little effect on sulfate removal in CWs, with or without additional carbon sources. Cattail litter addition greatly improved sulfate removal in SSF CWs. This improvement was linked to the continuous input of labile organic carbon, which lowers the redox level and supplies a habitat for sulfate reducing bacteria (SRB). The presence of SRB in cattail litter indicated the possibility of sulfate removal around the carbon supplier, but the quantity of microbes in cattail litter was much lower than that in gravel. Stoichiometry calculations showed that the contribution of SRB to COD removal (21-26%) was less than that of methane-producing bacteria (MPB) (47-61%) during the initial stage but dominated COD removal (42-65%) during the terminal stage. The contributions of aerobic bacteria (AB) and denitrification bacteria (DB) to COD removal were always lower than that of SRB. It was also observed that the variations in COD: S ratio had a great influence on the relative abundance of genes between SRB and MPB and both of them could be used as good predictors of carbon competition between SRB and MPB in CWs.
- MeSH
- Bacteria metabolismus MeSH
- biomasa MeSH
- chemické látky znečišťující vodu chemie metabolismus MeSH
- čištění vody metody MeSH
- mokřady * MeSH
- odpad tekutý - odstraňování * MeSH
- orobincovité fyziologie MeSH
- RNA ribozomální 16S MeSH
- sírany chemie metabolismus MeSH
- uhlík chemie metabolismus MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem 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.
The removal efficiencies and the kinetics of disinfection byproducts (DBPs) were studied in six greenhouse laboratory-scale SSF CWs. Cattail (Typha latifolia) and its litter (collected from the aboveground samples of cattail in autumn) were used as a potential phytoremediation technology and as a primary substrate, respectively, for DBP removal. Results showed that most of the 11 DBPs (except chloroform and 1, 1-dichloropropanone) were efficiently removed (>90%) in six SSF CWs with hydraulic retention time of 5 d and there were no significant differences among the systems. Under the batch mode, the removal of DBPs in SSF CWs followed first-order kinetics with half-lives of 1.0-770.2 h. As a primary DBP in wastewater effluent, removal efficiencies for chloroform were higher in planted systems than in unplanted ones and plant uptake accounted for more than 23.8% of the removal. Plant litter greatly enhanced the removal of trihalomethanes (THMs) by supplying primary substrates and reducing conditions, and the formation of dichloromethane supported the anaerobic biodegradation of THMs via reductive dechlorination in SSF CWs. Trichloroacetonitrile was completely removed within 10 h in each system and hydrolysis was considered to be the dominant process as there was a rapid formation of the hydrolysis byproduct, trichloroacetamide.
- MeSH
- anaerobní bakterie metabolismus MeSH
- biodegradace MeSH
- chemické látky znečišťující vodu analýza metabolismus MeSH
- čištění vody metody MeSH
- dezinfekce metody MeSH
- kinetika MeSH
- mokřady * MeSH
- odpadní produkty analýza MeSH
- orobincovité MeSH
- podzemní voda chemie MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
