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The aim of the study was to determine the technological reliability and to forecast the efficiency of wastewater treatment in a constructed wetland wastewater treatment plant (CW WWTP) in long-term operation. The research was conducted at a facility which in the mechanical part had a 3-chamber settling tank and the biological stage consisted of 4 constructed wetland beds with horizontal sewage flow, planted with common reed (Phragmites australis). During 12 years of the study, the WWTP was hydraulically loaded up to 97.7% of the designed mean daily inflow, equal to Qd,av. = 116 m3/d. The study showed that despite the high degree of reduction of such parameters as biochemical oxygen demand (BOD5) (90.0%), chemical oxygen demand (COD) (88.4%) and total suspended solids (TSS) (93.5%) the achieved reliability with respect to the limit values determined by the Weibull distribution model amounted to 48%, 62% and 77% for BOD5, COD and TSS, respectively. In the case of biogenic parameters, the technological reliability with respect to permissible values was 3% for total nitrogen and 13% for total phosphorus. Based on the performed analysis, it was concluded that the analyzed technological system did not guarantee the concentrations of pollutants in treated wastewater to reach the admissible levels defined in the related Polish legal act. In order to increase the efficiency of pollutants removal in the discussed wastewater treatment plant, the application of additional constructed wetland bed with vertical sewage flow (VF) preceding the horizontal beds (HF) was suggested. [ABSTRACT FROM AUTHOR]

Constructed wetlands are a kind of sewage treatment technology that requires simple equipment and low energy consumption. Intermittent influent vertical-flow constructed wetlands (VFCW) provide good pollutant control and are widely used. In order to clarify the mechanism of vertical flow constructed wetland in controlling pollutants, this study established a VFCW experimental system to investigate the removal rates of hydraulic load on CODCr, NH4-N, TN and TP. For the removal effect of pollutants, different factors included retention time, water inlet flow rate, water inlet cycle, and water distribution method were analyzed respectively. The experimental results revealed that the hydraulic load had the greatest impact on pollutant removal in the intermittent water intake system. The removal rates of CODCr, NH4-N and TN all increased with hydraulic load, and which had a tendency to increase first and then decrease. The optimal hydraulic load was 200 mm/d, at which the removal rates of CODCr, NH4-N and TN were 88.5%, 48.5% and 52.5%, respectively. Too short or too long a hydraulic retention time was not conducive to pollutant removal. The best hydraulic retention time was about 2 days, at which the removal rates of CODCr, NH4-N and TN were 89%, 48% and 53%, respectively. Increasing the water flow rate and the uniformity of water distribution can help improve CODCr, NH4-N and TN removal rates and the wetland utilization rate and processing load. [ABSTRACT FROM AUTHOR]

A vertical subsurface flow constructed wetland (VSSFCW) and a free surface flow constructed wetland (FSFCW) were set for the objective of comparison the performance of two systems in order to make a decision of the better one for future installation of wastewater treatment system and power generation. Both of the constructed wetlands were planted with Cyperus Alternifolius. During the observation period (19 days or 456 hours), environmental conditions such as pH, temperature, total chemical oxygen demand (COD), phosphate (PO4), nitrate (NO3) ,total suspended solids (TSS), total dissolved solids (TDS), Pb, Cu, and Cd removal efficiencies of the systems were determined. According to the results, final removal efficiencies for the VSSF and FWSF, respectively, were: COD (94.3% and 94.3%),PO4 (84.3% and 75.3%), NO3 (100% and 100%), TSS (96.8% and 85.6%), Pb (65.8% and 81.4%), Cu (more than 94.7% and 89.4%), Cd (85.7% and 88%). The treatment performances of the VSSF were better than that of the FWSF with regard to the removal of suspended solids and nutrients. In FWSF systems, electricity generation performed better than VSSF of 31.4 mV especially with batch system during one wastewater feed is loaded among all of the nineteen days with maximum voltage of 33.7 mV and decreased gradually as oxygen depletion in cathode chamber and less metabolism processes has occurred.

A vertical subsurface flow constructed wetland (VSSFCW) and a free surface flow constructed wetland (FSFCW) were set for the objective of comparison the performance of two systems in order to make a decision of the better one for future installation of wastewater treatment system and power generation. Both of the constructed wetlands were planted with Cyperus Alternifolius. During the observation period (19 days or 456 hours), environmental conditions such as pH, temperature, total chemical oxygen demand (COD), phosphate (PO4), nitrate (NO3), total suspended solids (TSS), total dissolved solids (TDS), Pb, Cu, and Cd removal efficiencies of the systems were determined. According to the results, final removal efficiencies for the VSSF and FWSF, respectively, were: COD (94.3% and 94.3%),PO4 (84.3% and 75.3%), NO3 (100% and 100%), TSS (96.8% and 85.6%), Pb (65.8% and 81.4%), Cu (more than 94.7% and 89.4%), Cd (85.7% and 88%). The treatment performances of the VSSF were better than that of the FWSF with regard to the removal of suspended solids and nutrients. In FWSF systems, electricity generation performed better than VSSF of 31.4 mV especially with batch system during one wastewater feed is loaded among all of the nineteen days with maximum voltage of 33.7 mV and decreased gradually as oxygen depletion in cathode chamber and less metabolism processes has occurred. [ABSTRACT FROM AUTHOR]

• Application of Vetiveria zizanioides and Oryza sativa in VF-CWs was analyzed. • The best effects of NO 3 −-N removal were for a hydraulic load No. 2 = 241 dm3·m−2·d−1. • The ratio of COD/NO 3 -N in wastewater affected the efficiency of NO 3 -N removal. • The best effects of COD removal in the VFCW-1 were for hydraulic load HL 2 – 55%. • The best effects of COD removal in the VFCW-2 were for hydraulic load HL 1 – 43%. • Vetiveria zizanioides has a good potential in NO 3 -N and COD removal from sewage. The aim of this work was to determine the potential of phytoremediation of Vetiveria zizanioides and Oryza sativa to nitrate (NO 3 −-N) and organic matter (COD – chemical oxygen demand) removal in subsurface vertical flow constructed wetland systems (VFCWs). The tests were carried out in models of 2 beds with a surface of 0.24 m2 and depth 0.70 m each at various hydraulic loads (H L) and COD constant in influente wastewater. The VFCW-1 bed was planted with the Vetiveria zizanioides and the VFCW-2 bed with the Oryza sativa. During the 22 weeks of research, the hydraulic load of the analyzed beds was: H L1 = 148 dm3·m−2·d−1, H L2 = 239 dm3·m−2·d−1, H L3 = 350 dm3·m−2·d−1, H L4 = 473 dm3·m−2·d−1. The VFCWs were fed from two reservoirs, one with mineral medium and nitrate, and the other one with fructose as organic matter. Based on the conducted tests, it was found that in both analyzed systems (VFCW-1 and VFCW-2) the highest NO 3 −-N removal rate was found under H L2 – the median is 59 and 42% respectively. The most effective removal of COD in the VFCW-1 system was obtained at a H L2 – 55%, while in the system VFCW-2 at a H L1 – 43%. The research shows that the low H L and high COD/NO 3 −-N ratio ensures good effects of nitrate and organic matter removal in VF type constructed wetland systems. It has been shown that the analyzed plants, especially Vetiveria zizanioides have good phytoremediation potential in the field of nitrate nitrogen and organic substance removal and can be recommended for use on a full scale of technology. [ABSTRACT FROM AUTHOR]

This paper outlines recent advances in the design, application, and operations and maintenance (O&M) of aerated treatment wetland systems as well as current research trends. We provide the first-ever comprehensive estimate of the number and geographical distribution of aerated treatment wetlands worldwide and review new developments in aerated wetland design and application. This paper also presents and discusses first-hand experiences and challenges with the O&M of full-scale aerated treatment wetland systems, which is an important aspect that is currently not well reported in the literature. Knowledge gaps and suggestions for future research on aerated treatment wetlands are provided.

The paper presents the results of research on the effects of removing pollution from domestic wastewater in two beds of constructed wetland systems with vertical flow. Bed I was planted with common reed (Phragmites australis Cav. Trin. Ex Steud.), whereas bed II with Glyceria maxima (Glyceria aquatica L.). The surface of each of the beds amounted to 30 m2, and the hydraulic load of each of them amounted to 0.033 m3·m-2·d-1. The study showed very good results in the removal of most of the analyzed indicators of contamination, which were similar in both analyzed beds. They were, respectively: 91 and 93% – for total suspended solids, 96 and 98% – for BOD5, 96 and 94% – for CODCr, 88 and 86% – for ammonia nitrogen and 87 and 88% – for total phosphorus. Much smaller effects were reported with regard to total nitrogen removal – 55% in bed I with common reed and 54% in bed II with Glyceria maxima. The tested beds also eliminated the number of coliform bacteria and faecal coliform bacteria quite effectively. Average effects of the removal of coliform bacteria in bed I and II were 99.74%, in the case of faecal coliform 98.06% and 97.94% respectively. Values of basic indicators of contamination (total suspended solids, BOD5 and CODCr) in the wastewater discharged from the analyzed beds met the requirements of the Regulation of the Minister of the Environment of 2014. The test results obtained in the first year of operation of the analyzed beds show that neither of the applied plants significantly improves the results of contaminant removal.

In order to investigate the potential of vertical flow constructed wetlands (VFCWs), a 24.5 m2 surface area filled with gravel and planted with Heliconia psittacorum, was implemented as an experimental system for domestic wastewater treatment in southern Brazil. The aims of the study were to (i) evaluate the performance of a full scale system septic tank (ST) and VFCW for decentralized domestic wastewater treatment, and (ii) identify the influence of Heliconia for hydraulic characteristics and consequent performance of the VFCW. The applied load rates in the VFCW were, on average, 10 g biochemical oxygen demand (BOD) m−2 day−1, 4 g NH4+-N m−2 day−1 and a hydraulic loading rate (HLR) of 60 mm day−1. Physicochemical analyses of wastewater treatment were carried out through grab sample methodology, for 5 months. Additionally, hydrodynamic tests were performed during plant development using rhodamine. The study demonstrated the viability of the system for decentralized wastewater treatment in Brazil, with average removal efficiencies of 78% for chemical oxygen demand (COD) and 84% for total suspended solids (TSS), according to national effluent discharge regulations. In spite of media's large size, the VFCW achieved good average removal efficiencies. The tracer test results showed that the VFCW average hydraulic detention time increased as plants grew. This may have occurred due to interception of wastewater applied on the macrophyte's leaves as well as a reduction in filter media permeability caused by the spread of roots and rhizomes. These results indicate that the plants played an important role in increasing wastewater contact time in wetlands with high hydraulic conductivity such as a gravel VFCW. [ABSTRACT FROM AUTHOR]

Eight wastewater samples from a university campus were analysed between May and July of 2014 to determine the concentration of 14 natural and synthetic steroid hormones. An on-line solid-phase extraction combined with ultra-high performance liquid chromatography coupled with mass spectrometry (on-line SPE-UHPLC-MS/MS) was used as extraction, pre-concentration and detection method. In the samples studied, three oestrogens (17β-estradiol, estrone and estriol), two androgens (boldenone and testosterone), three progestogens (norgestrel, progesterone and norethisterone) and one glucocorticoid (prednisone) were detected. The removal of hormones was studied in primary and secondary constructed wetland mesocosms. The porous media of the primary constructed wetlands were palm tree mulch. These reactors were used to study the effect of water flow, i.e. horizontal (HF1) vs vertical (VF1). The latter was more efficient in the removal of 17β-estradiol (HF1: 30%, VF1: 50%), estrone (HF1: 63%, VF1: 85%), estriol (100% both), testosterone (HF1: 45%, VF1: 73%), boldenone (HF1:-77%, VF1: 100%) and progesterone (HF1: 84%, VF1: 99%). The effluent of HF1 was used as influent of three secondary constructed wetland mesocosms: two double-stage vertical flow constructed wetlands, one with gravel (VF2gravel) and one with palm mulch (VF2mulch), and a mineral-based, horizontal flow constructed wetland (HFmineral). VF2mulch was the most efficient of the secondary reactors, since it achieved the complete removal of the hormones studied with the exception of 17ß-estradiol. The significantly better removal of BOD and ammonia attained by VF2mulch suggests that the better aeration of mulch favoured the more efficient removal of hormones. [ABSTRACT FROM AUTHOR]

The main aim of our study was to construct a two-stage vertical flow constructed wetland (VFCW) system to treat single household raw sewage water in India under tropical climate. For selecting the plant species different sets of lab experiments were carried out. Two different plant species ( Typha angustata and Canna indica ) were considered for their nutrient removal efficiency and biochemical methane potential (BMP) efficiency. Drum experiments were conducted to select the most suitable species for the constructed wetland. Batch assays were conducted in 100 ml bottles in order to determine BMP of plant biomass. The overall nutrient removal efficiency was the same in case of both the plant species that were tested. Typha angustata had been selected for planting in the single household wetland system as it is found in the natural wetlands of Goa and they have higher BMP than other species. The nutrient removal of pilot scale VFCW was monitored at two hydraulic loadings at 0.150 m/day and at 0.225 m/day. The removal of Chemical Oxygen Demand (COD), Biological Oxygen Demand (BOD), Total Kjeldahl Nitrogen (TKN), Ammoniacal Nitrogen (NH 3 -N), Total Phosphorous (TP), Total Dissolved Solid (TDS) and Total Volatile Solids (TVS) at 1st stage was 64%, 65%, 15%, 21%, 34% and 54% and for the 2nd stage reactor it is 90%, 88%, 50%,52%, 58% and 71% respectively on an average. After changing HLR (hydraulic loading rate) to 0.225 m/day the removal of COD, BOD, TDS, TVS, TKN and NH 3 -N at 1st stage was 61%, 62%, 33%, 40%, 35% and 58% and for the 2nd stage reactor it is 90%, 84%, 61%, 64%, 47% and 82% respectively on an average. As the loading rate increases there is no change in the treatment efficiency of TKN and NH 3 -N treatment efficiency increases. However marginal decrease in the treatment efficiency of COD and BOD of the system was observed. The overall footprint of the system got reduced from 1.5 m 2 per person to 0.79 m 2 per person under Goan climatic conditions. [ABSTRACT FROM AUTHOR]

Owing to legislation change (which made General Binding Rules effective from 1 January 2015) unless discharge is to specified environmentally sensitive sites, small sewage discharges (SSDs) in England – that is, <2 m3 d−1to ground; <5 m3 d−1to surface waters – no longer require an Environmental Permit (EP) and need not be registered for exemption, provided discharge to surface waters is preceded by treatment using equipment complying with BS EN 12566. This effectively excludes the use of treatment wetlands, unless covered by an EP, because the cost of certification to EN 12566 for bespoke designs is prohibitive. EPs take up to four months to obtain. Therefore, the new legislation has created a commercial disadvantage for constructed wetlands treating SSDs, compared with mass-produced sewage treatment plants. However, the UK statutory pollution regulators have maintained a dialogue with the Constructed Wetland Association (CWA), with a view to assessing whether treatment of SSD using constructed wetlands might be allowable, without requiring EPs. This paper presents treatment performance data obtained over 15 years, from a variety of full-scale operational treatment wetlands, as supporting evidence for design guidelines, proposed by the CWA to the UK regulators, for the implementation of constructed wetlands continuously passively treating SSD to 20:30:20 mg l−1BOD/SS/NH4-N under a wide range of loading rates. Relevant experience of UK designers, installers and operators since the early 1990s is included, resulting in recommended physical design criteria and loading rates for compact vertical flow reed beds, presented here as key elements of the draft guidelines. [ABSTRACT FROM AUTHOR]

The study was carried out in 4 concrete beds: two vertical subsurface flow beds (dimension of 1x1.4 x 0.6 m3) and twohorizontal subsurface flow beds (dimension of 0.6 x 2.3x 0.6 m3) planted with Cyperus alternifolius L. Under the averagewastewater temperature of 27°C, the hydraulic loading rates (HLR) were varied from 5 to 20 cm/d in order to obtain theoptimum operating conditions and compare the removal efficiency. The wastewater was intermittently fed into the verticalsubsurface flow beds (5 minutes on and 55 minutes off), and continuously into the horizontal subsurface flow beds. Themaximum removal efficiencies were found at the lowest hydraulic loading rate for both systems. The horizontal subsurfaceflow system had a higher removal rate than the vertical subsurface flow system in terms of COD (the removal rates at 5-20cm/d were 9.6-33.9 g/m2.d). The vertical subsurface flow system showed higher removal efficiency for TKN and NH4+-N, inevery hydraulic loading rate and the removal rates for TKN and NH4+-N were 0.4-1.1 g/m2.d, respectively. Furthermore, it wasfound that the uptake of N by plants in the horizontal flow system was higher than in the vertical flow system for everyhydraulic loading rate (HLR) but the loss of N via adsorption/denitrification was higher in the vertical flow system than inthe horizontal flow system, at 20 cm/d HLR. The removal rate constants in the horizontal subsurface flow system for COD andNH4+-N were 0.0166 and 0.0188 m/d and 0.0204 and 0.0287 m/d for the vertical subsurface flow system, respectively

Studies were conducted on pilot scale horizontal (HFCW) and vertical subsurface flow constructed wetland (VFCW) systems for the treatment of greywater. The fate of emerging contaminants in these systems was evaluated. Sodium dodecyl sulphate (SDS), propylene glycol (PG) and trimethyl amine (TMA) were selected as the target emerging contaminants. Pilot plants were designed to treat 2.5 m 3 /day of greywater generated in a student’s hostel, with a hydraulic retention time (HRT) ranging from 8.9 days to 14.9 days. The greywater passed through a pre-treatment (settling tank) unit before entering the horizontal and vertical flow constructed wetlands (10.1 m × 2.55 m × 1.2 m). The substrate material in wet land systems was a mixture of sand, brick bats and gravel, and systems were planted with reed plant ( Phragmites australis ). Performance of systems was evaluated for the removal of organics, nutrients, bacterial contamination and emerging contaminants. Accumulations of emerging contaminants in soil and plant tissues were also studied. Performance was monitored over a year to study the effect of operating conditions such as hydraulic retention time, external organic load, and the seasons. It was found that the vertical flow system was marginally more efficient in treating the pollutants when compared to horizontal flow system. Removal efficiencies of SDS, PG and TMA in VFCW for different operating conditions were around 89%, 95% and 98%, respectively. In the case of HFCW, removal efficiencies were 85%, 90% and 95% for SDS, PG and TMA, respectively. The treated water from both the systems was meeting the USEPA standard limits for reuse. [ABSTRACT FROM AUTHOR]

The paper presents the results of research on the effects of removing pollution from domestic wastewater in two beds of constructed wetland systems with vertical flow. Bed I was planted with common reed (Phragmites australis Cav. Trin. Ex Steud.), whereas bed II with Glyceria maxima (Glyceria aquatica L.). The surface of each of the beds amounted to 30 m², and the hydraulic load of each of them amounted to 0.033 m³·m-2·d-1. The study showed very good results in the removal of most of the analyzed indicators of contamination, which were similar in both analyzed beds. They were, respectively: 91 and 93% -- for total suspended solids, 96 and 98% -- for BOD5, 96 and 94% -- for CODCr, 88 and 86% -- for ammonia nitrogen and 87 and 88% -- for total phosphorus. Much smaller effects were reported with regard to total nitrogen removal -- 55% in bed I with common reed and 54% in bed II with Glyceria maxima. The tested beds also eliminated the number of coliform bacteria and faecal coliform bacteria quite effectively. Average effects of the removal of coliform bacteria in bed I and II were 99.74%, in the case of faecal coliform 98.06% and 97.94% respectively. Values of basic indicators of contamination (total suspended solids, BOD5 and CODCr) in the wastewater discharged from the analyzed beds met the requirements of the Regulation of the Minister of the Environment of 2014. The test results obtained in the first year of operation of the analyzed beds show that neither of the applied plants significantly improves the results of contaminant removal. [ABSTRACT FROM AUTHOR]

Vertical flow constructed wetland (VFCW) is a promising technique for removal of excess nutrients and certain pollutants from wastewaters. The aim of this study was to develop a STELLA (structural thinking, experiential learning laboratory with animation) model for estimating phosphorus (P) removal in an artificial VFCW (i.e., a substrate column with six zones) grown with umbrella papyrus ( Cyperus alternifolius ) species under a wetting-to-drying cycle. Simulations showed that rate of soluble P (SP) leaching was highest at the top zone (i.e., Zone 1) and decreased gradually with increasing zone number due to the adsorption, clogging, and plant uptake when the SP flowed through the zones. Our simulations further revealed that the best time for an optimal removal of SP from the wastewater was within the first week because the adsorption capacity of the substrate in the VFCW was highest at this time period. In general, the cumulative amounts of total P (TP) were in the following order: adsorption (53.3%) > leaching (13.5%) > uptake (0.49%). Adsorption of P was a major mechanism for P removal from the VFCW system. This study suggested that the STELLA model developed is a useful tool for estimating P removal from wastewater in VFCWs. [ABSTRACT FROM AUTHOR]

The aim of the present work is to study the performance of a constructed wetland for domestic wastewater depuration also working as a microbial fuel cell (MFC) under two different subsurface flow modes in the upper cathodic compartment (horizontal flow, HF, or vertical flow, VF), and to compare the efficiency under both situations. A pilot-scale subsurface constructed wetland treating domestic wastewater was used, and the installation also included the electrodes and devices needed to work as MFC. The system worked continuously during two years: under HF mode (first year) and under VF mode (second year). The Chemical Oxygen Demand (COD) removal results and the cell voltage production were continuously monitored. The wetland successfully worked as MFC generating electric power. The organic pollution was completely oxidized in the lower anaerobic compartment, and aerobic conditions were detected in the upper cathodic compartment, thus producing electrical current. No important differences were observed in COD removal efficiencies working under the two flow modes. The cathodic compartment showed higher redox potential and dissolved oxygen values working under VF mode. The maximum cell voltage measured was approximately 250 mV in both flow modes. Despite the higher oxygenation potential of the VF option, no important differences were observed in voltage generation. The process developed in the present work showed similar cell voltage, power density and current density to other previous works using photosynthetic MFC, benthic MFC and plant-type MFC. [ABSTRACT FROM AUTHOR]

Abstract: Subsurface oxygen availability tends to be one of the main rate-limiting factors for removal of carbonaceous and nitrogenous compounds in subsurface flow (SSF) wetlands used for domestic wastewater treatment. This paper reviews the pertinent literature regarding oxygen transfer and consumption in subsurface flow treatment wetlands, and discusses the factors that influence oxygen availability. We also provide first results from a pilot-scale research facility in Langenreichenbach, Germany (15 individual systems of various designs, both with and without plants). Based on the approach given in Kadlec and Wallace (2009), areal-based oxygen consumption rates for horizontal flow systems were estimated to be between 0.5 and 12.9g/m2-d; for vertical flow systems between 7.9 and 58.6g/m2-d; and for intensified systems between 10.9 and 87.5g/m2-d. In general, as the level of intensification increases, so does subsurface oxygen availability. The use of water or air pumps can result in systems with smaller area requirements (and better treatment performance), but it comes at the cost of increased electricity inputs. As the treatment wetland technology envelope expands, so must methods to compare oxygen consumption rates of traditional and intensified SSF treatment wetland designs. [Copyright &y& Elsevier]

Highlights: [•] A VFCW has been constructed to treat wastewaters from a WWTP with tertiary treatment. [•] The iron oxide (hematite) is a suitable material to remove TP in VFCW. [•] The role of the plants is significant in TP removal (35.6% of TP removed). [•] The percentage of TP removal is higher than 75%. [•] Other benefits are the complete nitrification of NH4 +, the removal of TN and COD. [Copyright &y& Elsevier]

The aim of this study was to investigate the efficiency of wastewater treatment by vertical flow constructed wetland systems under different hydraulic loadingrates (HLR). The comparison of two types of plants, Cyperus alternifolius (Umbrella sedge) and Vetiveria zizanioides (Vetiver grass), was also conducted. In this study, six circular concrete tanks (diameter 0.8 m) were filled with fine sand and gravel to the depth of 1.23 m. Three tanks were planted with Umbrella sedge and the other three tanks were planted with Vetiver grass. Settled domestic wastewater from Chiang Mai University (chemical oxygen demand (COD), NH4+-N and suspended solids (SS) of 127.1, 27.4 and 29.5 mg/L on average, respectively) was intermittently applied for 45 min and rested for 3 h 15 min. The HLR of each tank was controlled at 20, 29 and 40 cm/d. It was found that the removal efficiency of the Umbrella sedge systems was higher than the Vetiver grass systems for every parameter, and the lowest HLR provided the maximum treatment efficiency. The removal efficiency of COD and nitrogen in terms of total Kjeldahl nitrogen (TKN) was 76 and 65% at 20 cm/d HLR for Umbrella sedge compared to only 67 and 56% for Vetiver grass. Nitrogen accumulation in plant biomass was also higher in Umbrella sedge than in Vetiver grass in every HLR. Umbrella sedge was thus proved to be a suitable constructed wetland plant in tropical climates. [ABSTRACT FROM AUTHOR]

Using constructed wetlands (CWs) with vertical flow and intermittent loading, high organic matter and ammonium removal can be achieved. In the case of additional requirements for phosphorus removal, which in Austria often occurs if the treated wastewater is discharged into small sensitive receiving waters, additional measures have to be taken. The objective of this work was to investigate the applicability of conventional phosphorus pre-precipitation with sodium aluminate for a CW system. The experiment was carried out at a full-scale CW in Oberwindhag in Lower Austria, a twostage vertical flow CW with intermittent loading designed for a size of 60 person equivalents (PE). The goal was to reach the required value of 1.6 mg/L PO4-P for the effluent of the system. Prior to the experiments the plant was in operation for 3 years without measures for phosphorus removal. After pre-precipitation with sodium aluminate was activated, three different dosages were investigated. Satisfying results in the preliminary treatment chambers were not obtained until a high dosage (β =3.5, i.e. 3.5 times the dose required from stoichiometry) was applied. After an adaptation time of several months the required effluent concentration of 1.6 mg PO4-P/L could be reached and maintained. However, the additional phosphorus pre-precipitation increases the yearly operating costs of a vertical flow CW system significantly, e.g. for 60 and 25 PE, by 15 and 38%, respectively, thus indicating the need for optimizing the dosing of the chemical. [ABSTRACT FROM AUTHOR]

Abstract: An integral solution for the recovery of fertilizer elements contained in swine farm slurry is the joint composting of diverse solid wastes generated in the installation and surroundings, in which the composting material was watered with swine slurry. In such a system, a high percentage of the water contained in the slurry is evaporated while nutrients are, in part, retained in the compost produced. This paper presents the results of a pilot vertical flow constructed wetland (VFCW) treating the high strength leachate generated from the compost piles. The VFCW was provided with effluent recycling in order to deal with high influent concentrations of nitrogen compounds, which reached up to 459mg NH3-N/L and 904mg TKN/L without the need for dilution with clean water. After start-up, and operating at 10°C with surface loading rates (SLRs) of 9.2, 17.9, 4.8 and 1.9g/m2 d of TSS, TCOD, BOD5 and TN, respectively, the VFCW reduced the concentration of all these parameters by more than 93%. Effluent concentration of nitrate was high during the two first months of operation (178mg NO3-N/L), but afterwards simultaneous nitrification and denitrification developed, reaching total nitrogen removal of 93% and low effluent nitrogen concentration (16mg NH3-N/L and 10mg NO3-N/L). Furthermore, options to avoid clogging or to facilitate the application of higher SLR are discussed. [Copyright &y& Elsevier]

Abstract: This study aimed to investigate nitrogen mass removal rates and microorganisms in planted columns that simulate vertical flow constructed wetlands. Two synthetic wastewaters, with mean NH4–N concentrations of 471±19 and 475±17mg/L, were treated in six individual columns. Under steady hydraulic and pollutant loading, average NH4–N removal rate was in the range of 21–47g/m2d, and average TN removal was 0–27g/m2d. Higher redox potential values benefitted ammonia removal but limited TN removal. The supply of organic carbon, by adding glucose into the synthetic wastewater, slightly reduced ammonia removal rate, but significantly enhanced TN removal. The variation of temperature between 14°C and 20°C had no effect on nitrogen removal. The seeding of microorganisms using diluted activated sludge, and submerging the columns with treated effluent for three days per week, appeared to intensify aerobic microbial degradation activities; oxygen consumption reached 53–363g O2/m2d, which was equivalent to upward air flux of 0.18–1.21m3/m2d in individual columns. Fluorescence in situ hybridization analysis of bacterial mass revealed the population densities of nitrifying bacteria, and specific denitrifying bacteria (Azoarcus-Thauera-cluster, genus Hyphomicrobium, genus Paracoccus, and family Saprospiraceae). Denitrifier Azoarcus-Thauera-cluster was the dominant bacterial group (58% of all cells) when organic carbon is available. Without organic carbon, ammonium oxidizing bacteria (AOB) dominate microbial populations in the columns. [Copyright &y& Elsevier]