Pilot-scale Horizontal Subsurface Flow Research Articles

Development and evaluation of a constructed pilot-scale horizontal subsurface flow wetland treating piggery wastewater

Abstract This paper reports on the development and evaluation of a pilot horizontal subsurface flow constructed wetland (HSSFCW) for removal of biochemical oxygen demand (BOD), chemical oxygen demand (COD), total dissolved solids (TDS), total nitrogen (TN) and total phosphorus (TP) from primary piggery wastewater. Two locally available plants, Pennisetum clandestinum and Pennisetum purpureum, were planted in two of three cells while the remaining unplanted cell served as the control. Monitoring of the wetland influent and effluent wastewater was carried out every two weeks for 7 months. The study revealed successful treatment of the wastewater by the wetland in terms of BOD, COD, TDS, TN and TP effluent compliance with Nigerian discharge standards. Average removal efficiencies were 66.53, 64.95, and 60.27% for BOD5; 44.85, 41.61 and 36.37% for COD; 63.61, 58.27 and 52.88% for TDS; 62.49, 58.89 and 50.14% for TN and 48.53, 44.91 and 41.27% for TP for the three wetland cells including the control respectively. Planted cells achieved the highest removal efficiency with no significant difference in pollutant removal between the two planted cells indicating their suitability for use as wetland plants. Effluent concentrations were within FEPA discharge limits except TP. The performance of the constructed wetland suggests that HSSFCW could be a suitable alternative technology for on-farm treatment of piggery wastewater in Nigeria. The study has provided a starting point for the use of HSSFCW and gives insight of the potential application of this technology for on- farm pollution control in Nigeria.

Combining tracer studies and biomimetic design principles to investigate clogging in constructed wetlands

In this study, we suggest a clogging maintenance strategy and design alteration for constructed wetlands. Such a system could benefit rural communities who rely solely on constructed wetland systems for provision of household and agricultural water and for whom regular system shut-down for maintenance is essentially not viable. A newly established, pilot-scale horizontal subsurface flow constructed wetland was investigated by means of step-change tracer experiments. Sampling was carried out at multiple points down the length of the wetland and at three depths for each location. The mean residence time datawere used to generate velocity profiles. This methodology enabled the development of a three-dimensional hydraulic model to identify dead zones and regions of short-circuiting within the system. Biomimetic principles were then incorporated to propose improvements to conventional constructed wetland design, which would potentially allow for better clogging management and continuous operation. In particular, modularizing the regions of the wetland most prone to clogging (those containing dead space) would accommodate isolation, removal and replacement of such sections, while still allowing treatment of wastewater in adjacent sections.

Growth and Treatment Performance of Three Macrophytes in a Pilot-Scale Horizontal Subsurface Flow Constructed Wetland for Slaughterhouse Wastewater

Growth and Treatment Performance of Three Macrophytes in a Pilot-Scale Horizontal Subsurface Flow Constructed Wetland for Slaughterhouse Wastewater

S-metolachlor herbicide removal in pilot-scale horizontal subsurface flow constructed wetlands

The aim of this study was to explore the efficiency of three horizontal subsurface flow (HSF) constructed wetlands (CWs) to remove S-metolachlor from contaminated water. The three CWs, with code names MG-R, MG-C and MG-Z, all contained medium gravel as porous media. MG-R and MG-C were planted with Phragmites australis and Typha latifolia, respectively, and MG-Z was left unplanted and used as control unit to study the effect of vegetation. The CWs units in this experiment operated continuously for one year but they were mature systems operating in various experiments for more than fourteen years. The results showed that the mean percent S-metolachlor removal values were 68.9%, 47.8% and 40.8% for MG-R, MG-C and MG-Z units, respectively. The vegetation (Phragmites australis) and the hydraulic residence time were found as the most important parameters affecting the CW capacity in herbicide removal. The current data suggest that HSF CWs are an efficient and low-cost technology in treating S-metolachlor-contaminated surface runoff in agricultural areas.

Post-treatment of tannery wastewater using pilot scale horizontal subsurface flow constructed wetlands (polishing)

In the present study, a pilot scale horizontal subsurface flow constructed wetland (CW) system planted with Phragmites karka; longitudinal profile was studied. The wetland was fed with tannery wastewater, pretreated in a two-stage anaerobic digester followed by a sequence batch reactor. Samples from each CW were taken and analyzed using standard methods. The removal efficiency of the CW system in terms of biological oxygen demand (BOD), chemical oxygen demand (COD), Cr and total coliforms were 91.3%, 90%, 97.3% and 99%, respectively. The removal efficiency for TN, NO3- and NH4+-N were 77.7%, 66.3% and 67.7%, respectively. Similarly, the removal efficiency of SO42-, S2- and total suspended solids (TSS) were 71.8%, 88.7% and 81.2%, respectively. The concentration of COD, BOD, TN, NO3-N, NH4+-N, SO42 and S2- in the final treated effluent were 113.2 ± 52, 56 ± 18, 49.3 ± 13, 22.75 ± 20, 17.1 ± 6.75, 88 ± 120 and 0.4 ± 0.44 mg/L, respectively. Pollutants removal was decreased in the first 12 m and increased along the CW cells. P. karka development in the first cell of CW was poor, small in size and experiencing chlorosis, but clogging was higher in this area due to high organic matter settling, causing a partial surface flow. The performance of the pilot CW as a tertiary treatment showed that the effluent meets the permissible discharge standards.

Wastewater management using a pilot-scale horizontal subsurface flow system in Western Sicily (Italy) for irrigation of Paspalum vaginatum Sw. turf

The reuse of treated wastewater represents an attractive prospect for sustainable water management in urban areas. The aim of this study was to evaluate the reuse of treated wastewater from constructed wetland systems for the irrigation of Seashore paspalum turf (Paspalum vaginatum Sw.) and assess the effects of treated wastewater on the soil and turfgrass. The research was carried out in Sicily (Italy) in a pilot-scale horizontal subsurface flow system (HSSF). Seashore paspalum plots were irrigated with freshwater and treated wastewater. In treated wastewater-irrigated plots, we estimated the amounts of nitrogen and potassium, supplied by irrigating with treated wastewater. The productive and qualitative characteristics of Seashore paspalum were not significantly influenced by irrigation with treated wastewater compared to freshwater. There was no significant variation in soil salinity and organic matter with the application of treated wastewater. The results confirm that treated wastewaters provide an additional water source and fertilizer for turf management in urban areas where the supply of freshwater is often limited.

Effects of plants and temperature on nitrogen removal and microbiology in pilot-scale horizontal subsurface flow constructed wetlands treating domestic wastewater

Two pilot-scale intermittently operated horizontal subsurface-flow constructed wetlands (HSSFCWs), one planted with Acorus calamus L. and one with Phragmites australis (Cav.) Trin. ex Steud., were implemented for the polishing treatment of domestic wastewater from Huazhong Agricultural University dormitories, Hubei Province, China. The characteristics of nitrogen removal between the plant rhizosphere and non-rhizosphere were assessed from 19 September to 12 December 2012 to address the effect of plants. The mean removal efficiency of total nitrogen (TN) was 45.2% for the two HSSFCWs with a hydraulic loading rate of 0.15m3m−2d−1. In both pilot-scale HSSFCWs, the nitrification intensity and numbers of nitrite-oxidizing bacteria and ammonia-oxidizing bacteria in the rhizosphere were significantly higher than in the non-rhizosphere, associated with oxygen release from plant roots. In contrast, the denitrification intensity and number of denitrifying bacteria were higher in the non-rhizosphere. Although significantly higher dissolved oxygen concentration at the root surface and greater numbers of nitrogen-processing bacteria in the rhizosphere occurred for Acorus calamus compared to Phragmites australis, very similar nitrogen removal efficiencies were observed in the two HSSFCWs, probably due to the relatively low N concentration of the wastewater treated in the wetlands. In addition, the removal efficiencies of NH4+-N and NO3−-N were significantly positively correlated with water temperature in both HSSFCWs.

Organic Matter and Nutrients Removal in Tropical Constructed Wetlands Using Cyperus ligularis (Cyperaceae) and Echinocloa colona (Poaceae)

In tropical countries like Colombia, a large variety of available aquatic plants have yet to be investigated for phytodepuration processes. The aim of this study was to assess the effect of Cyper-us ligularis and Echinocloa colona¸ two local plants of Colombian Caribbean region, on removal of dissolved organic matter (COD) and nutrients (N-NH4 +, N-NO3 − and P-PO4 −3) from domestic wastewater. Experiments were conducted in replicate pilot-scale Horizontal Subsurface Flow Constructed Wetlands (HSSF CWs) (0.66 m2). Four wetland treatment units were installed in parallel. Two were planted with C. ligularis and the other two remained with E. colona. The experimental system was connected to a 0.76-m3 primary sedimentation tank that fed experimental wetland treatment units. Wetlands were filled with granite gravel (~8 mm and 0.4 of porosity). During a period of 4 months, each treatment unit received a continuous loading at the rate of 42 L day−1 and a hydraulic retention time of 2.3 days approximately. Wastewater samples from influent and effluents were collected three times each week in order to monitor temporal/spatial changes in removals efficiencies of COD, N-NH4 +, N-NO3 −, and P-PO4 −3. Results showed that removals of COD, N-NH4 +, and N-NO3 − were not significantly different between treatments (p > 0.05). Nevertheless, P-PO4 −3 removal for E. colona was significantly higher than C. ligularis (p < 0.05), showing that this plant can assimilate important amounts of P. Further investigations must be conducted to evaluate the potential of native aquatic macrophytes for phytodepuration.

Triazophos (TAP) removal in horizontal subsurface flow constructed wetlands (HSCWs) and its accumulation in plants and substrates

Triazophos (TAP) is a widely used phosphorus pesticide in China that possesses a potential risk for water pollution. We have studied the removal efficiency of TAP using pilot-scale horizontal subsurface flow constructed wetlands (HSCWs) as well as the contribution of plants, substrates and other pathways to its removal. For TAP concentrations of 0.12 ± 0.04 mg L−1, 0.79 ± 0.29 mg L−1 and 3.96 ± 1.17 mg L−1, the removal efficiencies were 94.2 ± 3.7%, 97.8 ± 2.9% and 84.0 ± 13.5%, respectively, at a hydraulic loading rate (HLR) of 100 mm d−1; at an HLR of 200 mm d−1, the removal efficiencies were 96.7 ± 1.3%, 96.2 ± 1.7% and 61.7 ± 11.1%, respectively. The isopleth maps of TAP along the direction of flow indicate that most of the TAP removal occurred in the front and middle regions, while the major removal region would move forward with increasing influent TAP. Plant and substrate accumulation accounted for 0.035 ± 0.034% and 4.33 ± 0.43% of the total removal, respectively, indicating that over 95% of the TAP removal was achieved through other mechanisms. Thus, these results suggest HSCWs can be an effective approach with which to treat TAP contaminated water. Furthermore, the longitudinal scale and hydraulic conditions, as well as the roles of plants, substrates and microbes and their interactions, should be further considered in the design and application of CWs for pesticide pollution control.

The salinity effects on the performance of a constructed wetland-microbial fuel cell

The objective of the present work is to study the influence of the wastewater salinity concentration on the performance of a Constructed Wetland-Microbial Fuel Cell (CW-MFC) for simultaneous water pollution control and electricity generation. The work has been carried out under the hypothesis that increasing the salinity may improve the electricity production because of a lower internal ohmic resistance, although it could damage the microbiological processes or the plants. A pilot-scale horizontal subsurface flow CW, modified to function as an MFC, was operated under a continuous operation mode over five consecutive experimental periods of approximately 2 months each. The wastewater salinity was increased in each new period by steeply increasing the NaCl concentration in the synthetic wastewater from 0.51 to 9.51gL−1. The CW-MFC performance was monitored during every stationary period. The increasing salinity first improved the cell voltage, and the resultant maximum voltage (130mV) under continuous operation corresponded to a salinity concentration between 4 and 5gL−1. However, subsequently higher salinity levels caused the opposite effect. The maximum voltage was obtained in an unstable condition, as microbiological inhibition in the anode zone appeared early, at approximate salinity levels of only 3gL−1. Batch experiments confirmed the results, and higher cell voltage values up to 600mV were obtained if longer retention times were allowed. The wetland plants (Phragmites australis) were only damaged at a salinity concentration of 9.51gL−1.

The use of constructed wetlands for the treatment and reuse of urban wastewater for the irrigation of two warm-season turfgrass species under Mediterranean climatic conditions.

Constructed wetlands (CWs) represent low-cost technology for the treatment and reuse of wastewater in urban areas. This study aimed to evaluate the pollutant removal efficiency of a CW system and to assess the effects of irrigation using treated urban wastewater on soil and on two warm-season turf species. The research was carried out in Sicily (Italy) on a pilot-scale horizontal subsurface flow system which was fed with treated urban wastewater following secondary treatment from an activated-sludge wastewater treatment plant. The pilot system was located in an open urban park and comprised two separate parallel planted units. Experimental fields of Cynodon dactylon (L.) Pers. and Paspalum vaginatum Sw. were set up close to the system and irrigated with both treated wastewater (TWW) and freshwater (FW). Irrigation with TWW did not result in a significant variation in soil pH and soil salinity in the topsoil. The turf species tolerated high sodium levels in the soil due to TWW irrigation. Savings in FW and mineral fertilizers were deemed significant. The results highlight the fact that use of CW systems for the treatment and reuse of wastewater can represent a sustainable way to obtain alternative water resources for turfgrass irrigation in urban areas.

Treatment of agricultural equipment rinsing water containing a fungicide in pilot-scale horizontal subsurface flow constructed wetlands

Boscalid is a carboxamide fungicide, developed as an alternative reagent to classic fungicides, which acts against several ascomycetous fungal species. The use of boscalid is continuously on the rise due to its unique mode of action and low toxicity to mammals and birds. However, boscalid can be transported from the application sites and contaminate the environment. Recent studies have reported detection of boscalid in air, precipitation, streams and groundwater samples. Moreover, boscalid was the fourth most frequently encountered pesticide residue in food according to the latest European Union report. Thus, the aim of this study was to explore the efficiency of two pilot-scale horizontal subsurface flow (HSF) constructed wetlands (CWs) to remove boscalid from rinsing water produced during the cleaning of pesticide spraying equipment. The two CWs were planted with common reeds (Phragnites australis). One contained fine gravel (code name FG-R) and the other cobbles (CO-R). Both CWs were loaded daily with water containing boscalid at concentrations similar to those usually detected in rinsing water near sites where pesticide mixing, loading and washing takes place. The results showed that the removal in both systems ranged from 49 to 100%. In the first two months, the removal ranged from 75–94% and 95–100% for CO-R and FG-R, respectively. From April up to the next February, the mean removal was 76.3% and 72.4% for FG-R and CO-R, respectively. It seems that HSF CWs are efficient systems in treating boscalid-polluted agricultural equipment rinsing water in agricultural areas. Therefore, their construction and use near sites where pesticide mixing, loading and washing takes place is recommended.

Management of irrigation water and nutrient demands of tomato (Lycopersicon esculentum Mill.) using urban treated wastewater from a pilot-scale horizontal subsurface flow system constructed wetland in Sicily (Italy)

Management of irrigation water and nutrient demands of tomato (Lycopersicon esculentum Mill.) using urban treated wastewater from a pilot-scale horizontal subsurface flow system constructed wetland in Sicily (Italy)

Horizontal subsurface-flow constructed wetland removal efficiency using Cyperus articulatus L.

Constructed Wetlands (CW) are a suite of natural wastewater treatment systems that are governed by biological, chemical and physical processes. These processes, in tandem, regulate the removal of organic and inorganic wastewater pollutants. Both aquatic microorganisms and aquatic macrophytes can transform and uptake contaminants from wastewater and achieve higher removal efficiencies. The aim of this study was to evaluate the effect of Cyperus articulatus, a Colombian native aquatic macrophyte, on removal of dissolved organic matter and nitrogenous compounds from domestic wastewater. Experiments were conducted in replicate pilot-scale Horizontal Subsurface Flow Constructed Wetlands (HSSF CWs). Four (4) wetland treatment units were installed in parallel. Two were planted with C. articulatus and the other two remained as unplanted controls. The experimental system was hydraulically connected to a 760L septic tank, which functioned as a primary treatment module and fed experimental wetland treatment units. Each wetland unit was filled with granite gravel (8mm average diameter and approximately 40% porosity) to a depth of 0.5m. During a period of four-months, each treatment unit was provided with 29Lday−1 of clarified domestic wastewater, ensuring a Hydraulic Retention Time of three (3) days. Wastewater samples from influent and effluents were collected twice each week in order to monitor temporal/spatial changes in concentration of chemical oxygen demand (COD), ammonium nitrogen (NH4+-N) and nitrate nitrogen (NO3−-N). At the end of the experiment, plant biomass was collected and dried to constant weight to facilitate calculations and reporting of plant biomass on a dry matter basis. Although this was a preliminary study of short duration, results showed that high organic matter removal efficiency can be achieved (91% in systems planted with C. articulatus, compared with 80% in unplanted wetlands). NH4+-N removal was significantly improved in planted systems, averaging 85% vs. 40% for unplanted systems (p<0.05). Total biomass production by C. articulatus was 5.0 (±0.16) kg.m−2. In conclusion, results obtained in this short duration study indicate that C. articulatus could be a promising species for treating domestic wastewater in the Colombian Caribbean region.

A comparison of three different residence time distribution modelling methodologies for horizontal subsurface flow constructed wetlands

In this paper three different residence time distribution modelling methodologies for horizontal subsurface flow constructed wetlands were compared and these were the impulse response, step change derivative and step change integral modelling methodologies. Impulse response and step change tracer studies were conducted on pilot scale horizontal subsurface flow constructed wetlands to generate the concentration-time data to be fed into the impulse response and step change modelling approaches, respectively. For the unplanted reactor, the two step change modelling methodologies suggested the same fluid flow behaviour reflected by almost identical values for the mean residence time (t¯m) and the same value for the number of stirred tanks in series (N) and Peclet number (Pe). The impulse response modelling approach suggested a 7% higher t¯m and a lower degree of dispersion. For the planted system each modelling methodology suggested different fluid flow behaviour. Practical limitations were attempted to be identified for the two types of tracer experiments. The limitations of the experiments could be considered limitations of the modelling methodologies as they depended on the tracer experiments for data generation. We were unable to collect sufficient data on the peak of the impulse response curve for the unplanted reactor and may have affected the impulse response modelling methodology results. Sampling down the length of the reactor revealed that tracer dispersion had an effect of broadening the impulse response curves to the extent that it was almost impossible to identify non-ideal flow behaviour such as short-circuiting. The mathematical techniques employed by each modelling methodology were also critically assessed. We found that varying the size and hence number of subintervals used in Simpson’s 1/3 rule for numerical integration resulted in different values for t¯m/τ for each modelling approach. The lower the sensitivity of the modelling methodology the better as choosing a parameter as arbitrary as subinterval size should not have a noticeable effect on reported hydraulic behaviour. For both reactor systems the step change derivative approach was least sensitive to subinterval selection, reporting a 1% and 4% variation in t¯m/τ for the planted and unplanted system, respectively whereas t¯m/τ determined by the step change integral and impulse response modelling methodologies varied by 10% or more in some cases. We highlighted the differentiation of F(t) to obtain E(t) to be a potential weakness of the step change derivative methodology as it had the capability to amplify background noise which may have affected the calculation of the hydraulic parameters. It was concluded that each modelling methodology had the potential to output a different reactor model for the same reactor and that each approach has its own inherent strengths and weaknesses. The choice of modelling methodology is ultimately dictated by availability of experimental equipment and the designer’s confidence in using each of the respective approaches.

Effects of tidal operation on pilot-scale horizontal subsurface flow constructed wetland treating sulfate rich wastewater contaminated by chlorinated hydrocarbons.

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 2m from the inlet and increasing PCE removal efficiency at 0.5m. 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 23mgL-1 under continuous flow and 7-day cycle regime, respectively. However, sulfide concentrations decreased to less than 4mgL-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.

Performance of pilot-scale horizontal subsurface flow constructed wetlands treating groundwater contaminated with phenols and petroleum derivatives

Groundwater contaminated with various organic and inorganic pollutants is a major issue especially in historic industrial areas with chemical industries and refineries. In this study, Constructed Wetlands, as an ecological and environmentally sustainable alternative, were tested at pilot-scale for the removal of phenolic compounds and petroleum derivatives from contaminated groundwater in a pump-and-treat remediation research facility in Germany. Three horizontal subsurface-flow Constructed Wetlands (two planted, one unplanted) were fed with contaminated groundwater containing methyl tert-butyl ether (MTBE), benzene and ammonia. In two of the beds, a solution of phenol and m-cresol (15 and 2mg/L or 314.5 and 45.5mg/m2/d, respectively) was injected to the groundwater inflow. Results showed a complete removal of the two phenolic compounds in the beds without any alteration in the MTBE and benzene removal rates. This indicated that Constructed Wetlands are versatile and can be used to effectively treat different pollutants simultaneously. Higher contaminant removal efficiency of planted systems confirms the positive role of plants presence and their ability to promote biodegradation. Spatial distribution analyses showed that the major portion of the removal took place in the first part of wetland length, which indicated that the systems could potentially deal with higher loads and can be used to optimize the system design.

Effect of operational and design parameters on performance of pilot-scale horizontal subsurface flow constructed wetlands treating university campus wastewater.

Three horizontal subsurface flow (HSF) pilot-scale constructed wetland (CW) units operated for 3years treating municipal wastewater originating from a university campus. The main objective of the study was the evaluation of the performance of these systems under several operational, design, and climatic conditions. Several parameters and factors were investigated, including the influence of temperature, vegetation, and hydraulic residence time. The results were compared to those of a previous study conducted in the same pilot-scale units and under the same operational conditions where synthetic municipal wastewater was used. Results show the satisfying overall performance of the CW units. Performance seems to be influenced by vegetation, temperature, and hydraulic residence time (HRT). The planted units produced better results than the unplanted one while, generally, all units operated better under warmer conditions. In addition, longer HRTs contributed to higher removal efficiencies. Finally, the systems showed higher removal efficiencies in the previous study (synthetic wastewater) regarding organic matter removal, while for the other pollutants, the present study (real wastewater) showed higher or comparable performance in most cases and especially in the planted units. The study also shows the overall good, continuous, and long-term operation of CW systems, since these systems operate for about 13years.

Reuse of urban-treated wastewater from a pilot-scale horizontal subsurface flow system in Sicily (Italy) for irrigation of Bermudagrass (Cynodon dactylon (L.) Pers.) turf under Mediterranean climatic conditions

Constructed wetlands (CW) are one of the most important biological technology for the treatment and reuse of wastewaters. The aim of this study was to evaluate the reuse of treated wastewater (TWW) from CW for irrigation of Bermudagrass turf (Cynodon dactylon (L.) Pers.) and assess the effects of TWW on the biometric and qualitative parameters of the turfgrass and on chemical–physical soil properties. The research was carried out in Sicily (Italy) in a pilot-scale horizontal subsurface flow system which was fed with urban TWW following secondary treatment from an activate sludge wastewater treatment plant. The pilot-system included three separate parallel units. The outflow TWW flowed downhill into three storage tanks which were connected to sprinkler systems. Bermudagrass plots were irrigated with freshwater (FW) and with TWW from planted units and unplanted unit. The TWW quality did not affect the visual turf quality and colour. The above-ground biomass yield of Bermudagrass was on average 1.31 kg m−2 in the TWW-irrigated plots. There was not a significant variation of soil pH, but an increase in organic matter content and salinity were recorded in TWW-irrigated plots. The results confirm that TWW provides an additional water source and fertilisers where the supply of FW is limited.

Pollutant removal efficiency of a pilot-scale Horizontal Subsurface Flow in Sicily (Italy) planted with Cyperus alternifolius L. and Typha latifolia L. and reuse of treated wastewater for irrigation of Arundo donax L. for pellet production—Results of two-year tests under Mediterranean climatic conditions

Constructed wetland systems (CWs) are developed biological technologies for the treatment and reuse of wastewater. The aims of this study were to evaluate the treatment performance of a pilot Horizontal Subsurface Flow system (HSSFs), to evaluate the reuse of treated wastewater (TWW) from CWs for the irrigation of giant reed (Arundo donax (L.)) and to assess the effects of TWW on the biomass yield of giant reed grown for pellet production. The research was carried out in Sicily (Italy) in a pilot-scale HSSFs which was fed with urban-treated urban wastewater following secondary treatment from an activated sludge wastewater treatment plant. Giant reed plots were irrigated with TWW from plantedunits, TWW from an unplanted-unit and with freshwater (FW). The pilot system was found to have excellent removal efficiency for all the parameters examined. The different treatment levels of irrigation did not affect significantly the growth and yield of giant reed ecotypes. Differences between heating values of above-ground biomass irrigated with FW and TWW were negligible. TWW from CWs can be used for the irrigation of species grown for energy purposes, thereby providing an alternative source of water, particularly in areas where water deficit in the agricultural sector is significant.