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In this paper the nitrogen elimination rates of different constructed wetland (CW) designs reported in literature are compared with those obtained for outdoor and indoor 2-stage vertical flow (VF) systems. The outdoor system is located about 150 km west of Vienna. Both stages are planted with Phragmites australis and the system has been operated for 4 years continuously. During this period the average value of the nitrogen elimination rate was 3.30 g N m(-2) d(-1). The indoor system comprises three parallel operated 2-stage VF systems and is located in the technical lab hall at BOKU University. The design of the indoor system resembles the outdoor system. However, there are a few differences: (1) the indoor systems are not planted, and (2) different filter media have been used for the main layer of the first stages. With the indoor system the highest nitrogen elimination rate achieved was 2.24 g N m(-2) d(-1) for the system with zeolite and impounded drainage layer. Similar results have been found in France for treating raw wastewater with VF and horizontal flow (HF) beds in series with nitrogen elimination rates of 1.89 and 2.82 g N m(-2) d(-1) for differently designed HF beds. The highest nitrogen elimination rates of 15.9 g N m(-2) d(-1) reported were for pilot-scale VF CWs treating high-strength synthetic wastewater (total nitrogen of 305 mg L(-1) in the influent) in Thailand. It has been shown that the outdoor two-stage VF CW system has one of the highest nitrogen elimination rates of CWs treating domestic wastewater.

To evaluate the performances of a controlled drainage system in optimizing water use and reducing nutrient losses from agricultural fields, an experimental facility was set up in north-eastern Italy in 1996. Water table management was tested in combination with surface (open ditches) and subsurface (pipe) drainage systems. Data were collected from 2007 to 2013 on: water table depth, drained volumes, nitrogen and phosphorus concentrations in groundwater and in drainage water. Nitrogen in groundwater showed higher concentrations when controlled drainage was combined with open ditches system, with a median of 13.43 mg L −1 for NO 3 -N and 18.68 mg L −1 for total N. Drainage water showed an opposite trend: subsurface pipes with free drainage provided highest concentrations due to extensive leaching (a median of 20.7 mg L −1 for NO 3 -N and 24.0 mg L −1 for total N). Phosphorus concentrations showed notable differences in drainage water, with higher values in the controlled drainage – open ditches system due to surface runoff (a median of 0.190 mg L −1 for PO 4 -P and 0.536 mg L −1 for total P). In general, the most hazardous period for surface water pollution was autumn-winter, due to rainy weather and fertilizer application on bare soil. Overall, water table management reduced total water discharge by 81% compared to free drainage. On average, with controlled drainage annual nitrogen losses were lowered by 92% (from 29 to 2 kg NO 3 -N ha −1 ) and annual phosphorus losses by 65% (from 0.14 to 0.05 kg PO- 4 P ha −1 ). Free drainage with subsurface pipe was the worst combination from the environmental point of view: annual nitrogen and phosphorus losses were 46 kg NO 3 -N ha −1 and 0.10 kg PO 4 -P ha −1 respectively. Water table management clearly proved to be a reliable tool to improve both water usage and quality. [ABSTRACT FROM AUTHOR]

The aim of this study was to evaluate the agronomical and environmental effects of digestate solid fraction (DSF) used as fertiliser in a vegetable crop succession (green bean, savoy cabbage, cabbage and cauliflower) in Northeast Italy (45°20' N; 11°57' E). Three fertilisation treatments were tested using DSF to substitute 0% (Tmin), 50% (T50) and 100% (T100) optimal level of mineral nitrogen fertilisation. The experiment was carried out from 22nd May 2014 (green bean sowing) to 3rd June 2015 (cabbage harvest). Summer and spring crops did not show significantly different marketable yield among fertilisation treatments with an average value (±standard error) of 9.0±0.5, 9.9±1.2 and 51.3±6.4 Mg ha-1 for green bean, cauliflower and cabbage, respectively. Lower DSF fertilisation effect was monitored on winter crop (savoy cabbage) with a marketable yield reduction of -35.1% than mineral fertilisation (25.9 Mg ha-1), whereas the T50 treatment was not significantly different compared to the two previous ones. Crop species significantly influenced the N use efficiencies with negative recovery and use efficiency indexes for the DSF fertilisation treatments. Soil CO2 emissions were not significantly influenced by fertilisation in all studied crops with median values always lower than 1 g m-2 h-1. [ABSTRACT FROM AUTHOR]

This experiment assesses the aptitude of 18 species in treating the digestate liquid fraction (DLF) in a floating wetland treatment system. The pilot system was created in NE Italy in 2010 and consists of a surface-flow system with 180 floating elements (Tech-IA®) vegetated with ten halophytes and eight other wetland species. The species were transplanted in July 2011 in basins filled with different proportions of DLF/water (DLF/w); periodic increasing of the DLF/w ratio was imposed after transplanting, reaching the worst conditions for plants in summer 2012 (highest EC value 7.3 mS cm/L and NH-N content 225 mg/L). It emerged that only Cynodon dactylon, Typha latifolia, Elytrigia atherica, Halimione portulacoides, Salicornia fruticosa, Artemisia caerulescens, Spartina maritima and Puccinellia palustris were able to survive under the system conditions. Halophytes showed higher dry matter production than other plants. The best root development (up to 40-cm depth) was recorded for Calamagrostis epigejos, Phragmites australis, T. latifolia and Juncus maritimus. The highest nitrogen (10-15 g/m) and phosphorus (1-4 g/m) uptakes were obtained with P. palustris, Iris pseudacorus and Aster tripolium. In conclusion, two halophytes, P. palustris and E. atherica, present the highest potential to be used to treat DLF in floating wetlands. [ABSTRACT FROM AUTHOR]

Abstract: Five macrophyte species, Carex elata All., (Cae), Juncus effusus L. (Jue), Typhoides arundinacea (L.) Moench (syn. Phalaris arundinacea L.) (Pha) var. picta, Phragmites australis (Cav.) Trin. (Phr), and Typha latifolia L. (Ty), have been grown in mesocosms fed with a synthetic wastewater to acquire information on nitrogen balance and assess their capacity to abate nitrogen. The experiment, conducted during the growing seasons 2008–09 with four replicates, also included an unvegetated control. The mesocosms, filled with gravel, were fed with a solution of 105ppm of NO3–N and 100ppm of NH4–N in 2008 for a cumulative nitrogen load of 86g/m2 and with increased concentration in 2009 from 104ppm of NO3–N and 119ppm NH4–N, to 200ppm of NO3–N and 207ppm of NH4–N for a cumulative nitrogen load of 222g/m2. At the end of the experiment plants were harvested and N content in the above and belowground biomass was determined along with the amount of N contained in the roots and gravel microbial communities. In the first growing season (8 months) Ty removed 82g/m2 (96% of the cumulative load) of TOT N, followed by Cae (94%), Jue (82%), Pha (81%), Phr (77%) and the control (48%). In the second growing season (6 months) all the vegetated treatments, except Jue, increased their efficiency, with Pha removing 216g/m2 (98% of the cumulative load) of TOT N, followed by Phr and Ty (97%), Cae (93%), Jue (75%) and the control (63%). Jue showed lower tolerance than the other species to high N concentration. Depending on the species, plants absorbed 53–75% of the two-seasons load and allocated 51–83% of this amount in the aerial tissues, showing the benefit of harvesting to remove N from the treatment site, at least in the medium short term. Application of the N balance allowed the gaseous losses to be estimated, giving values ranging from 51g/m2 in Ty to 114g/m2 in Pha, 17% and 37% of the total load respectively. If the target is the definitive elimination of the maximum amount of N from the treatment site, the sum of nitrogen harvested in the aerial part and the gaseous losses has to be considered. This value was maximum with Cae, with 227g/m2 over the two years. [Copyright &y& Elsevier]

The performance of a constructed surface flow wetland in reducing diffuse N pollution coming from croplands is being investigated in an ongoing experiment, begun in 1998 in NE Italy. The 0.32 ha wetland is vegetated with Phragmites australis (Cav.) Trin. and Typha latifolia (L.). It receives drainage water from 6 ha of land managed for an experiment on drainage systems, where maize, sugarbeet, winter wheat and soybean are cultivated. During the period 1998–2002, the wetland received from 4698 to 8412 mm of water per year (on average, about 9 times the environmental rainfall); its water regimen was discontinuous and flooding occurred on a variable number of days per year (from 13 to 126). Nitric nitrogen was the most important form of element load. Its concentration in the inflow water over time was rather discontinuous, with median values ranging from 0.2 (in 2001) to 4.5 (in 2000) mg L−1. Inflow nitric N concentrations were occasionally in the 5–15 mg L−1 range. Concentrations reduced passing through the wetland, with a more evident effect in the last year. Over 5 years, the wetland received slightly more than 2000 kg ha−1 of nitrogen, 87% in nitric form mostly from farmland drainage. The remaining 13% of N was applied as organic slurry directly onto the wetland, with 5 distributions during 1998 to assess wetland performance in treating occasional organic loads. Field drainage loads had a discontinuous time pattern and occurred mostly during autumn–winter, with the exception of the 2001–2002 season which was a very dry. The wetland discharged 206 kg ha−1 of N, over the 5-year period, with an apparent removal efficiency of about 90%. The disappearance was mostly due to plant uptake (1110 kg ha−1) and soil accumulation (570 kg ha−1), with the contribution of denitrification being estimated at around 7%. [Copyright &y& Elsevier]

Abstract: Buffer strips are an efficient and economical way to reduce agricultural nonpoint source pollution. Local researches are necessary to gain information on buffer performance, with particular emphasis on narrow buffers. The effect of a 6m buffer strip (BS) in reducing runoff, suspended solids and nutrients from a field growing maize, winter wheat and soybean was assessed in a field experiment conducted in North-East Italy during 1998–2001. The BS was composed of two rows of regularly alternating trees (Platanus hybrida Brot.) and shrubs (Viburnum opulus L.), with grass (Festuca arundinacea L.) in the inter-rows. The BS reduced total runoff by 78% compared to no-BS, in which cumulative runoff depth was 231mm over 4 years. With no-BS runoff appeared to be influenced mostly by total rainfall, while with BS maximum rainfall intensity was more important. The filtering effect of the BS reduced total suspended solids (TSS), particularly after the second year, when the median yearly concentrations ranged from 0.28 to 0.99mgL-1 and were smaller than 0.14mgL-1, with no-BS and with BS respectively. The combination of lower concentrations and runoff volumes significantly reduced TSS losses from 6.9 to 0.4tha-1 over the entire period. A tendency to increased concentrations of all forms of N (total, nitrate and ammonium) while passing through the BS was observed, but total N losses were reduced from 17.3 to 4.5kgha-1 in terms of mass balance. On the contrary, P concentrations were unmodified (soluble P), or lowered (total P) by the BS, reducing total losses by about 80%. The effect on total P, composed mainly of sediment-bound forms, was related to particulate settling when passing through the BS. A numerical index (Eutrophic Load Index), integrating water quality and runoff volumes, was created to evaluate the eutrophication risk of runoff with or without the BS. It showed that the BS effect was mostly due to a reduction of runoff volumes rather than improving the overall water quality. [Copyright &y& Elsevier]

Surface flow constructed wetlands (SFCWs) can be effectively used to treat agricultural drainage waters, reducing N and P surface water pollution. In the Venice Lagoon drainage basin (northeastern Italy), an SFCW was monitored during 2007–2013 to assess its performance in reducing water, N, and P loads more than 10 years after its creation. Nitrogen concentrations showed peaks during winter due to intense leaching from surrounding fields. Phosphorus concentrations were higher after prolonged periods with no discharge, likely due to mobilization of P of the decomposing litter inside the basin. Over the entire period, N removal efficiency was 83% for NO3–N and 79% for total N; P removal efficiency was 48% for PO4–P and 67% for total P. Values were higher than in several other studies, likely due to the fluctuating hydroperiod that produced discontinuous and reduced outflows. Nitrogen outlet concentrations were reduced by the SFCW, and N removal ratios decreased with increasing hydraulic loading, while no strong correlations were found in the case of P. The SFCW was shown to be an effective long-term strategy to increase water storage and reduce N and P loads in the Venice Lagoon drainage basin. [ABSTRACT FROM AUTHOR]