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In this paper, we analysed the pollutant removal efficiency and reliability of a vertical and horizontal flow hybrid constructed wetland (CW) planted with giant miscanthus and Jerusalem artichoke. The wastewater treatment plant, located in south-eastern Poland, treated domestic sewage at an average flow rate of 1.2 m3·d−1. The tests were carried out during. 5-years of operation of the sewage treatment plant (2011–2016). During this period, sewage samples were collected from three stages of wastewater treatment in four seasons (winter – February, spring – May, summer – August, and autumn – November). The following parameters were measured: BOD5, COD, total suspended solids, total nitrogen, and total phosphorus. The average effectiveness of organic pollutant removal expressed by BOD5 and COD was 98.8 and 97.6%, respectively, and the removal efficiency for total suspended solids was 93%. The average values of BOD5, COD, and total suspended solids in wastewater discharged to the receiver were significantly lower than the limit values required in Poland. The efficiency of total nitrogen and total phosphorus removal was 64.1 and 68.1%, respectively, and the average values of these components in the outflow from the treatment plant exceeded the standard levels. A reliability analysis performed using the Weibull probability model showed that the reliability of pollutant removal in the tested CW system was very high for BOD5 and COD (100%). It was also demonstrated that the tested CW did not provide effective elimination of biogenic elements (nitrogen and phosphorus), as evidenced by the low reliability values – 32 and 28%, respectively. The investigated hybrid CW system with giant miscanthus and Jerusalem artichoke removed organic and biogenic pollutants with a similar efficiency as systems using classic plant species such as reed and willow.

This paper is a review of research and experiences related to the application of constructed wetland systems (CWs) in southeastern Poland in 1992–2016. On the basis of literature data, a comparison between pollutant removal efficiencies of one-stage and hybrid CWs was made. Some problems regarding the operation of these treatment plants were also presented. Data from various facilities indicate that one-stage CWs with horizontal or vertical flow were characterised by a quite high (80–89%) efficiency of removal of BOD5, COD and total suspended solids, but were less efficient in removing of biogenic compounds nitrogen and phosphorus – respectively 59 and 66%. Significantly higher removal efficiencies for the basic pollutants (above 92%) were observed in hybrid CWs with a VF–HF bed configuration. Those facilities removed ca. 65% of total nitrogen and 89% of total phosphorus. A statistical analysis revealed that hybrid VF–HF type CWs were characterised by a very high, about 99%, operation reliability. Lower reliabilities were achieved by one-stage CWs, especially those with a VF bed. Twenty five years of research on and experiences in the application of CWs in southeastern Poland indicate that one-stage CWs can be used on a larger scale in Polish conditions in rural areas with a scattered housing structure. Hybrid systems, on the other hand, can be applied successfully in recreational centres or in protected areas, especially in national parks, where a high pollutant removal efficiency is required. It has been shown that the use of hybrid CWs is consistent with the idea of sustainable development.

The paper presents the results of a study of selected parameters of common osier (Salix viminalis) biomass sampled annually, over a 12-year period, from a constructed wetland wastewater treatment plant. The focus of the study was on parameters that were relevant to biomass energy management. The study was conducted in a constructed wetland wastewater treatment plant consisting of one horizontal flow bed with a total area of 186 m2, planted with osier willows. The following biomass parameters were analysed: biomass yield, volume, humidity, ash content, higher and lower heating values, and contents of N, P, K in different parts of plant stems. The study showed that osier biomass harvested from the investigated constructed wetland system could be used as an energy source in thermochemical processes. The higher and lower heating values were similar to those obtained by other authors (18.13 and 17.38 MJ·kg−1, respectively). The energy yield (17.49 MJ·m−2) and energy density (3486–5411 MJ·m−3) were also calculated. Young shoot parts had higher ash and micronutrient contents and lower energy parameters than old parts.

Recent years have seen an increasing interest in hybrid constructed wetland (HCW) systems for domestic sewage treatment. This paper is focused on kinetics of removal of the main pollutants occurring in wastewater i.e. organics expressed as chemical oxygen demand, biochemical oxygen demand and total nitrogen. The purpose of the article is to compare different HCW configurations in terms of mass removal rates (MRR) and removal rate coefficients (kA and kv). Analysed data have been collected at two wetland systems, each composed by two subsurface flow beds: horizontal flow (HF) and vertical flow (VF). Reliable evaluation was achieved by using the same composition of influent wastewater in both HCWs. Performance of opposite configurations HF + VF vs. VF + HF was compared after each stage and the overall HCW system. The average mass removal rates of COD, BOD5 and TN in both systems were similar, respectively: 2.30, 0.98 and 0.40 g m−2 d−1. However, removal rates differ between single wetland beds after each treatment stage.

tThe aim of the study was to determine the influence of the particle size of carbonate–silica rock (opoka)used in rock filters on the efficiency of phosphorus removal from domestic wastewater. The investigationswere carried out in a laboratory using a model consisting of three vertical flow filters with carbonate–silicarock of different particle sizes (G1= 1–2 mm; G2= 2–5 mm; G3= 5–10 mm). The tested rock was subjectedto decarbonising at 900◦C and consisted primarily of 51.7% SiO2, 23.2% CaO, and 7.6% Al2O3. In the firstthree weeks of the study (1–3), the hydraulic load of each filter was Q1= 0.72 l/day and the hydraulicresidence time was HRT1= 24 h; in the next three weeks (4–6) Q2= 1.08 l/day and HRT2= 16 h, and duringthe last three weeks (7–9) Q3= 1.44 l/day and HRT3= 12 h. A significant influence of the size of rock parti-cles and the hydraulic load (hydraulic residence time) on the efficiency of total phosphorus removal andon phosphorus concentration in the wastewater discharged from the system was observed ( = 0.05).Statistically, the best removal of phosphorus from wastewater – an average of 97%, was found in thesubstrate with the smallest particle size (rock G1, 1–2 mm) at the lowest hydraulic load of 0.72 l/dayand at a hydraulic residence time of 24 h. The lowest phosphorus removal efficiency was observed inthe filter containing rock G3with a particle size of 5–10 mm (mean

In recent years, constructed wetland systems are used widely for the purification of small amounts of wastewater because they provide very high effects of removing impurities. The existing research results show that constructed wetland systems can be used not only for highly efficient wastewater treatment, but at the same time in order to produce biomass for energy purposes. The aim of this paper was to determine the possibilities of energy use of the plants: common reed, willow, Jerusalem artichoke, giant miscanthus, obtained from constructed wetland system. The yield of common reed was the highest compared to the other plant species used in analyzed object and amounted to 13.6 Mg DM ha −1 and then 8.7 Mg DM ha −1 for willow. The lowest dry matter yield was 5.9 Mg DM ha −1 in the case of Jerusalem artichoke. High Heating Value was similar in all analyzed plants (17.9–19.2 MJ kg −1 ), the highest results were obtained from willow. Biomethane production during anaerobic digestion was the highest from common reed (108 m 3 Mg −1 FM) and the lowest from Jerusalem artichoke (66 m 3 Mg −1 FM). The methane concentration in biogas was rather low (50.9–54.9) comparing to other typical substrates for biogas production.