Horizontal Subsurface Flow Systems Research Articles

Performance of bioretention systems by umbrella plant (Cyperus alternifolius L.) and common reed (Phragmites australis) for removal of microplastics

Domestic wastewater is one of the main sources of microplastic (MP) contamination in aquatic environment; however, most wastewater treatment plants (WWTPs) have not been designed for the removal of MPs. In this study, the release rate of MPs in the treated water from a WWTP into the river was estimated to be approximately 105 × 103 pcs/capita/day. Thus, bioretention systems are designed as tertiary wastewater treatment systems to reduce the number of MPs in water resources. The objective of this study was to evaluate the performance of bioretention systems using the umbrella plant (Cyperus alternifolius L.) and common reed (Phragmites australis) for MP removal. After 17 weeks, MPs were found in the common reed bioretention system. The common reed root system and substrate influence the MP retention process to a greater extent through physical filtration, substrate ratio, plant roots, and biofilms on the roots. Additionally, the common reed root system played an important role in the removal of low-density MPs. The accumulation of MPs in roots and root hairs inevitably impacts plants. The results showed that the common reed at a 3:2:9 ratio (gravel: sand: soil) had the highest relative height growth rate (RHGR) (1.8mmcm-1 week-1). These results show that the HSFs–3 at a ratio of 3:2:9 was able to reduce the number of MPs, with an average removal efficiency of 62.89% and 95.45% for sizes >1000µm, 89.21% for sizes 500–1000µm, and 44.16% for sizes <500µm. The highest average microbeads removal efficiency was 95.24%. Our results suggest that plant bioretention using Horizontal Subsurface Flow system is an effective treatment for removing MPs from wastewater.

A pilot-scale electrocoagulation-treatment wetland system for the treatment of landfill leachate

In the present study, the technical feasibility of an electrocoagulation-treatment wetland continuous flow system, for the removal of organic matter from landfill leachate (LL), was evaluated. The response surface methodology (MSR) was used to assess the individual and combined effects of the applied potential and distance between electrodes, on the removal efficiency and optimization of the electrocoagulation process. The hybrid treatment wetland system consisted of a vertical flow system coupled to a horizontal subsurface flow system, both planted with Canna indica. For a chemical oxygen demand (COD) concentration - without pretreatment of 5142.8 ± 2.5 mg L−1, the removal percentage for the electrocoagulation system was 79.4 ± 0.16%, under the optimal working conditions (Potential: 20 V; Distance: 2.0 cm). The COD removal efficiency in the treatment wetland with Canna indica showed a dependence with the hydraulic retention time, reaching 59.2 ± 0.2 % over 15 days. The overall efficiency of the system was about 91.5 ± 0.02 % removal of COD. In addition, a decrease in the biochemical oxygen demand (94.8 ± 0.14%) and total suspended solids (88.2 ± 0.22%), also related to the contamination levels of the LL, were obtained. This study, for the first time, shows that the coupling of electrocoagulation together with a treatment wetland system is a good alternative for the removal of organic contaminants present in LL.

Hybrid constructed wetland for treatment of power plant effluent polluted with hydrocarbons

Constructed wetlands (CWs) have good potential for application in the treatment of various types of polluted water in Iraq, including industrial wastewater, due to their low cost relative to the current conventional treatment technologies. Hybrid CW with a continuous-flow system was tested for the treatment of highly polluted industrial wastewater from the Al-Najibiyia Power Plant in Basrah City for 72 days with 5 days of retention time. The system consisted of a horizontal subsurface flow system (HSSF) planted with Phragmites australis (Cav.) followed by a surface flow (SF) system planted with Hydrilla verticillata (L.f.) Royle. A second system without plants served as a contaminant control system. Total petroleum hydrocarbons (TPHs), petroleum aromatic hydrocarbons (PAHs) and water quality were measured for both raw and treated wastewaters and plant status parameters were monitored. The presence of both plants and substrate had a significant effect on the removal efficiency and mass removal rate of all pollutants at (p < 0.05). The planted system performance showed a percentage removal of pollutants reaching to: 65.9 % for BOD5, 91.0 % for COD and 88.8 % for total suspended solids (TSS) while removal efficiency of BOD5, COD and TSS for unplanted systems was only 44.7, 64.5 and 68.7 %, respectively. The removal efficiencies of TPHs, and PAHs by the hybrid system were 96.5, and 96.0 %, compared to only 71.0 % and 51.0 % for unplanted system, respectively, showing that hybrid CW could enhance pollutant removal efficiency better than single CW. It is revealed also that the high efficiency in removing pollutants is the result of the plant and substrate presence and the interaction between plants and the surrounding microbial community. Thus, constructed wetlands (CWs) are a good option for industrial wastewater treatment due to its simple construction and effectiveness to remove hydrocarbons.

Evaluation the Efficiency of Subsurface Flow Constructed Wetland (SSF) for Wastewater Treatment and Reuse in Semi-arid Environment

The efficiency of subsurface flow (SSF) constructed wetlands was evaluated on the treatment of secondary treated wastewater to improve the quality of the effluent for reuse purposes. A horizontal SSF system was constructed to evaluate the efficiency to enhance the quality of secondary treated wastewater effluent from Ramtha wastewater treatment plant WWTP and its potential uses for crop production at Hydrulic retention time HRT of 1 day. The SSF was planted with barley crop (Hordium vulgare), retrieved from the Arab Center for the Studies of Arid Zones and Dry-land (ACSAD) variety followed by corn crop (Zea mays L.), using BONANZA, F1 variety in the other season. Weekly physicochemical and microbiological analyses were carried out on the outlet from the wetlands in addition to the TWW treated wastewater effluent (inlet) in order to assess the removal efficiency of each stage of the treatment process and the total treatment system and it was used for irrigation of a fodder crop field. The SSF wetland subsequently influenced the physicochemical parameters. The SSF reduced the concentration of COD, NO-3, and TKN by 48%, 18%, and 20% respectively. Water use efficiency (WUE) for corn and barley were improved tremendously compared to the traditional irrigation techniques used in the field. The results showed a great possibility of using the SSF wetlands for the growth and production of fodder crops.

Seasonal response of vegetation on pollutants removal in constructed wetland system treating dairy wastewater

Constructed wetland systems provide the ideal solution for small and medium dairy farms as they can be built close to the farm and are easy to manage and use. However, their perfomance is significantly affected by vegetation activity during the year. The aims of the present study were to assess the treatment of dairy wastewater (DWW) by a horizontal subsurface flow system (HSSFs) and the effect of plants in the removal efficiency (RE) of BOD5, COD, total N (TN) and total P (TP), in Sicily (Italy). The HSSFs treated 6/7 m3 per day of wastewater produced by a small dairy farm subsequent to biological treatment. The system included two units which were separately planted with Arundo donax L. and Cyperus alternifolius L. During a three-year study, the main chemical and microbiological characteristics were determined as well as pollutant RE. Plant growth analysis was carried out and biomass production was determined. All DWW parameters showed significant differences between inlet and outlet. In particular, for BOD5 and COD, average RE values were 77.8% and 61.6%, respectively. Arundo donax produced greater biomass than Cyperus alternifolius for both above- (4240.3 g m2/year) and below-ground (6996.3 g m2/year) plant parts. A seasonal variation in RE of BOD5, COD, TN and TP was recorded due to plant growth rates. Our findings highlight that the contribution of plants in pollutant RE tends to vary seasonally.

Performance of Pilot-scale Constructed Wetland for Treating Stormwater

Water scarcity and storm water management are two major challenges that effect the ecosystem and urban environment. In hot and humid country such as Malaysia, wastewater reuse should be encouraging whenever it is safe and economically feasible. Constructed wetlands (CW) have been recognized as one of the environmentally friendly technologies and successfully used for treating a diverse range of wastewaters. Constructed wetland can also be suitable habitat for native wetland plants and associated fauna. In an urban setting such as a university campus, a constructed wetland can also be landscaped as an educational and attractive green space, providing service learning and teaching opportunities for campus and surround community members. This study examines the performance of pilot-scale constructed wetlands as a sustainable wastewater treatment in Universiti Pertahanan Nasional Malaysia (UPNM) campus for treating and reusing the stormwater in the mini-reservoir. The pilot-scale of constructed wetlands have been designed and constructed in the laboratory using native wetland plant, the Cat-tail Typha Angustifolia. The pilot-scale of CW with vertical subsurface flow (VSF) system was able to remove all parameters better than horizontal subsurface flow (HSF) system. The highest percentage of removal of all parameters was at hydraulic retention time (HRT) of 5 hours and percentage of removal increased with an increase in HRT. The percentage of removal for total suspended solid (TSS), Chemical Oxygen Demand (COD), Biological Oxygen Demand (BOD), and Dissolved Oxygen (DO) approximately 84%, 71%, 68%, and 25%. Thus, the constructed wetland had the potential to increase the water quality level of stromwater in UPNM campus in order to support the sustainability and Green Campus environment campaign.

Evaluation of Tannery Wastewater Treatment by Integrating Vesicular Basalt With Local Plant Species in a Constructed Wetland System

Tannery wastewater is composed of a complex mixture of organic and inorganic components from various processes that can critically pollute the environment, especially water bodies if discharged without treatment. In this study, integrated vesicular basalt rock and local plant species were used to establish a horizontal subsurface flow constructed wetland system and to investigate the treatment efficiency of tannery wastewater. Four pilot units were vegetated with P. purpureum, T. domingensis, C. latifolius, and E. pyramidalis, and a fifth unit was left unvegetated (control). The constructed wetland units in horizontal subsurface flow systems were effective in removing total chromium (Cr), chemical oxygen demand (COD), and 5-day biological oxygen demand (BOD5) from the inflow tannery wastewater. The removal efficiency reached up to 99.38, 84.03, and 80.32% for total Cr, COD, and BOD5, respectively, in 6 days of hydraulic retention time (HRT). The removal efficiency of total suspended solid (TSS), total phosphorus (TP), and nitrate (NO3−) of the constructed wetland units reached a maximum of 70.59, 62.32, and 71.23%, respectively. This integrated system was effective for treating tannery wastewater, which is below the Ethiopian surface water standard discharge limit set to BOD5 (200 mg L−1), COD (500 mg L−1), total Cr (2 mg L−1), NO3− (20 mg L−1), TSS (50 mg L−1), and TP (10 mg L−1).

Evaluation of long-term phosphorus uptake by Schoenoplectus californicus and Phragmites australis plants in pilot-scale constructed wetlands

The aim of this study was to evaluate long-term phosphorus (P) retention in a pilot-scale system made of four horizontal subsurface flow (HSSF) constructed wetlands for wastewater treatment. Each wetland had an area of 4.5 m2 and was operated for nearly 8 years (2833 days). Two wetlands with Schoenoplectus californicus (HSSF-Sch) and the other two with Phragmites australis (HSSF-Phr) were planted. The P removal efficiency was 18% for both types of HSSF wetlands. The primary factors that correlated with long-term P retention efficiency in HSSF were phosphorus loading rate (PLR), hydraulic loading rate (HLR) and dissolved oxygen (DO). Average biomass production of HSSF-Phr and HSSF-Sch was 4.8 and 12.1 kg dry weight (DW)/m2, respectively. The P uptake by the plant increased over the years of operation from 1.8 gP/m2 to 7.1 gP/m2 for Phragmites and from 3.2 to 7.4 gP/m2 for Schoenoplectus over the same periods. Moreover, the warm season (S/Sm) was more efficient reaching 14% P uptake than the cold season (F/W) with 9%. These results suggest that both plants' P retention capacity in HSSF systems represents a sustainable treatment in the long term. Novelty statement Long-term (8 years) phosphorus uptake by Schoenoplectus californicus and Phragmites australis and retention in pilot-scale constructed wetlands are evaluated. Schoenoplectus californicus is an uncommon species that has been less studied for phosphorus uptake compared to Phragmites australis, a globally known species in constructed wetlands. Moreover, some studies evaluating the performance of constructed wetland systems for domestic wastewater treatment are usually limited in time (1–3 years). Therefore, this long-term study demonstrates that the plant plays an important role in phosphorus retention, especially the species Schoenoplectus californicus. So, the phosphorus uptake by plants can contribute between 9 and 14% of the phosphorus load of constructed wetland systems in early years of operation.

Hydraulic performance of horizontal constructed wetlands for stormwater treatment: A pilot-scale study in the Mediterranean

Horizontal subsurface flow (HSSF) constructed wetlands (CWs) are widely adopted as a highly effective technique for stormwater treatment. However, the cumulative clogging phenomenon in HSSF is a complex and challenging operative issue affecting removal efficiencies and the lifespan of CWs. This paper aims to evaluate the reliability of a combined approach for assessing the occurrence of clogging and its potential spatial and temporal evolution in two pilot-scale HSSF-CW. The experimental CW system was fed with stormwater runoff from a parking area during the rainy season and sequential batch reactor (SBR) wastewater (WW) during the dry season. The falling head (FH) method and a drainage equation were used to determine the hydraulic conductivity at saturation (Ks) of the porous medium and investigate the hydraulic performance of the system. A residence time distribution (RTD) analysis was also performed to evaluate the hydraulic flow dynamics and define the crucial parameters characterising the CW. The applied hydraulic measurement techniques highlighted that clogging was in the initial stages of development after 2.5 years of operation, likely associated with the presence of a pond and the partial retention of total suspended solids (TSS) by the HSSF system. Overall, the good consistency in the results of the applied methods supports their future application for predicting the occurrence of clogging phenomena in HSSF CWs.

Evaluate the performance of horizontal flow wetlands as an option for tertiary treatment of secondary sedimentation basins

Constructed wetlands (CWs) are simple low-cost wastewater treatment units that use natural process to improve the effluent water quality and make it possible for its reuse.in this study used the horizontal flow system for the tertiary treatment of wastewater effluent from secondary basins at Al-Rustamiya wastewater treatment plant / old project / Baghdad / Iraq. the Phragmites Australis plant was used for wastewater treatment and the horizontal subsurface flow system was applied. the experimental study was carried out in February 2020 to October 2020. the parameters were monitored for a period of five weeks, Concentration-based average removal efficiencies for HSSF-CW were COD,53% [NO]_3,41.3% [PO]_4,52% and TSS, 54.2%. Thus, constructed wetland can be considered as a sustainable alternative to the tertiary conventional treatment of wastewater, thus making it possible for reuse..

Treatment of Combined Dairy and Domestic Wastewater with Constructed Wetland System in Sicily (Italy). Pollutant Removal Efficiency and Effect of Vegetation

Dairy wastewater (DWW) contains large amounts of mineral and organic compounds, which can accumulate in soil and water causing serious environmental pollution. A constructed wetland (CW) is a sustainable technology for the treatment of DWW in small-medium sized farms. This paper reports a two-year study on the performance of a pilot-scale horizontal subsurface flow system for DWW treatment in Sicily (Italy). The CW system covered a total surface area of 100 m2 and treated approximately 6 m3 per day of wastewater produced by a small dairy farm, subsequent to biological treatment. Removal efficiency (RE) of the system was calculated. The biomass production of two emergent macrophytes was determined and the effect of plant growth on organic pollutant RE was recorded. All DWW parameters showed significant differences between inlet and outlet. For BOD5 and COD, RE values were 76.00% and 62.00%, respectively. RE for total nitrogen (50.70%) was lower than that of organic compounds. RE levels of microbiological parameters were found to be higher than 80.00%. Giant reed produced greater biomass than umbrella sedge. A seasonal variation in RE of organic pollutants was recorded due to plant growth rate Our findings highlight the efficient use of a CW system for DWW treatment in dairy-cattle farms.

TREATMENT EFFICIENCY OF PIGGERY WASTEWATER BY SURFACE AND HORIZONTAL SUBSURFACE FLOW CONSTRUCTED WETLANDS

Constructed wetlands have been used to treat various types of wastewaters such as urban runoff, acid mine drainage, municipal, industrial, and livestock wastewaters. This study is conducted to evaluate the effectiveness of two constructed wetlands (surface and horizontal subsurface flows) for piggery wastewater treatment after biogas process. The wetland plant Phragmites australis Cav. was used in 45 days for the experiments. The CWs were designed to treat up to 100 liters/day with the hydraulic retention time (HRT) of 3 days. Parameters including pH, COD, TSS, NH4+-N, total nitrogen (TN) and total phosphorus (TP) were measured. The pH of the CWs system was in the range of 6.7 to 7.3. The results showed that the horizontal subsurface flow CW had better treatment performance compared to the surface flow system. The removal efficiency of TP, TSS, COD, TN and NH4+-N by surface flow CW was 80, 60, 66, 60 and 65%, respectively while those by horizontal subsurface flow system was 86, 78, 74.6, 67.1 and 74.2%, respectively. The water quality of the effluents of both two CWs met the Vietnamese standards for livestock wastewater (QCVN62/2016-BTNMT, column B).

The performance of Pilot-scale Constructed Wetland for treating Stormwater

Constructed wetlands (CW) have been recognized as one of the environmental friendly technologies and successfully used for treating a diverse range of wastewaters. CW also suitable for native wetland plants and associated fauna habitat. In an urban environment likes university campus, a constructed wetland can provide as an educational and attractive green space for learning, teaching and research activities. This work focused on the performance of pilot-scale constructed wetlands as a sustainable wastewater treatment for treating and reusing the stormwater in the mini-reservoir situated in campus area. In this study, there were two tanks of pilot-scale CW with vertical subsurface flow (VSF) and horizontal subsurface flow (HSF) systems. Both was planted with the Cat-tail Typha Angustifolia and Tube Sedge in removal of total suspended solid (TSS), chemical oxygen demand (COD), biological oxygen demand (BOD) and dissolved oxygen (DO) of the stormwater in the mini-reservoir in campus. The CW without any plants referred as a control system. The results show that the CW with vertical subsurface flow (VSF) system able to remove all parameters better that horizontal subsurface flow (HSF) system. The highest percentage of removal of all parameters was at hydraulic retention time (HRT) of 5 hours and percentage of removal increased with an increase in HRT. The percentage of removal for total suspended solid (TSS), chemical oxygen demand (COD), biological oxygen demand (BOD) and dissolved oxygen (DO) approximately 85%, 70%, 68% and 25%. Thus, the constructed wetland had the potential to increase the waste water quality level.

Removal of Organic Micropollutants in Wastewater Treated by Activated Sludge and Constructed Wetlands: A Comparative Study

The aim of this study is to compare the removal of organic micropollutants (OMPs) in wastewater by activated sludge (AS) and constructed wetlands (CWs). This analysis was carried out in a wastewater treatment plant (WWTP) of a rural community where they implemented two technologies in parallel: AS and a pilot plant of horizontal subsurface flow (HSSF) constructed wetlands. In this case, these systems were fed by the same influent and the removal efficiencies of 14 OMPs, including analgesics/anti-inflammatories, anticonvulsants, stimulants, antifungals, fragrances, plasticizers, and transformation products, were evaluated in each system. Regarding the presence of OMPs in the wastewater, the concentrations of these compounds in the influent ranged from 0.16 to 7.75 µg/L. In general, the removal efficiencies achieved by the AS system were between 10%–95% higher than those values reported by HSSFs with values above 80% for naproxen, ibuprofen, diclofenac, caffeine, triclosan, methyl dihydrojasmonate, bisphenol-A, 2-hydroxyl ibuprofen, and carboxy ibuprofen (p &lt; 0.05). This behavior can be related to the aerobic conditions that promote the AS system with oxidation-reduction potential (ORP) and dissolved oxygen (DO) values above −281 mV and 0.24 mg/L, respectively. However, the removal of galaxolide was greater in HSSF system than in AS with significant difference of 70% (p &lt; 0.05). Despite these results, this study reveals that comparing both technologies, AS had the best removal performance of these OMPs studied.

Research focusing on plant performance in constructed wetlands and agronomic application of treated wastewater - A set of experimental studies in Sicily (Italy).

Constructed wetlands are sustainable technologies for the treatment of wastewater. These biological systems have been widely studied throughout the world for more than 30 years; however, most studies have focused on the effects of design and engineering on pollutant removal from wastewater. Undoubtedly, agro-technical aspects have been given too little consideration by research. This paper reports the main results of a set of experiments carried out on two pilot horizontal subsurface flow systems in Sicily (Italy). Festuca, Lolium and Pennisetum spp. in combination and three emergent macrophytes–Arundo donax L., Cyperus alternifolius L. and Typha latifolia L.–alone, were assessed. The aim of the study was to demonstrate that, under predetermined hydraulic and design conditions, the choice of plant species and the management of the vegetation can significantly affect the pollutant removal performance of constructed wetlands. In addition, wastewater (after treatment) can also be used for agricultural purposes leading to increased sustainability in agricultural systems. Arundo and Typha-planted units performed better than Cyperus-planted units in terms of chemical, physical and microbiological contaminant removal. All the species adapted extremely well to wetland conditions. Polyculture systems were found to be more efficient than monocultures in the removal of dissolved organic compounds. The reuse of treated wastewater for the irrigation of open fields and horticultural crops led to significant savings in the use of freshwater and fertilizers. The results of physical-energy characterization of A. donax above-ground plant residues and pellets highlighted the fact that a constructed wetland could also be a potential source of bioenergy.

Performance of Subsurface Flow Constructed Wetland Systems in the Treatment of Al-Rustumia Municipal Wastewater using Continuous Loading Feed

This study aimed at comparing the performance of vertical, horizontal and hybrid subsurface flow systems in secondary treatment for the effluent wastewater from the primary basins at Al-Rustumia wastewater treatment plant, Baghdad, Iraq. The treatments were monitored for six weeks while the testsduration were from 4 to 12 September 2018 under continuous wastewater feeding for chemical oxygen demand (COD), total suspended solid (TSS),ammonia-nitrogen(NH4-N) and phosphate (PO4-P) in comparison with FAO and USEPA standards for effluent discharge to evaluate the suitability of treated water for irrigation purposes. Among the systems planted with Phragmites Australia, the hybrid subsurface flow system which consisted of vertical unit followed by horizontal one, considerably removed the pollutants more efficiently than the single operated systems. The planted hybrid subsurface flow wetland system was achieved the highest removal with a mean removal rate of COD,TSS, NH4-N, and PO4-Pat 99.3, 83.2,67.4 and 53% respectively and these percentages were decreased in the other systems. The results proved that the planted vertical subsurface flow unit can be removed the COD, TSS, NH4-N and PO4-Pwith values of 93, 71.1, 43.3 and 30.7%, respectively while the achieved removals by horizontal subsurface flow unit of 99, 74.3, 54.5 and 20.3%, respectively. The planted horizontal subsurface flow wetland, however, showed a good efficacy for all parameters in the treatment process except for PO4-P when it is compared with vertical system, however, there is a clear increase in the NO3-N effluent concentration for all treatment units.

Performance of ornamental plants in monoculture and polyculture horizontal subsurface flow constructed wetlands for treating wastewater

The aim of this study was to evaluate the effect of two ornamental plants in monoculture and polyculture horizontal subsurface flow (HSSF) constructed wetlands for treating wastewater. Two pilot-scale HSSF systems each with a surface area of 4.5 m2 were operated over two years (2015 and 2016); a) one was planted with a mixture of Cyperus papyrus and Zantedeschia aethiopica (HSSF-Cyp/Zant), and b) the other was planted only with Cyperus papyrus (HSSF-Cyp). To compare the performance between monoculture and polyculture systems, in situ parameters and organic matter (chemical oxygen demand (COD) and biological oxygen demand (BOD5)), total suspended solids (TSS), nutrients (total nitrogen (TN) and total phosphorus (TP)) and pathogens (fecal coliform (FC) and total coliform (TC)) removal efficiencies were evaluated. Moreover, growth characteristics, biomass production and nutrients uptake of different plants used in HSSF systems were also compared. The removal efficiencies of organic matter, suspended solids, nutrients and pathogens during the operational years were above 60%, 90%, 10% and 1.8 Log most probable number (MPN)/100 mL, respectively, without significant differences between HSSF-Cyp/Zant and HSSF-Cyp. The biomass production and the density of both HSSF systems fluctuated between 19.7 and 21.5 kg dry weight (DW)/m2 and 454–684 individuals/m2. Regarding the nutrient content of different plants used, Zantedeschia aethiopica, which was planted in the polyculture system, had the highest TN and TP content in all plants tissues (59.6 g N/kg·DW and 8.28 g P/kg·DW, respectively). However, TN and TP mass balances determined that the effect of monoculture and polyculture systems was not significant. Despite these results, polyculture CWs represent a good alternative of treatment system because they provide social benefits to the community such the improving of the system landscape and a better habitat quality. Moreover, some authors reported that polyculture system enhance the resistance to environmental stress and disease and the system landscape.

Greenhouse gas emission from horizontal and vertical subsurface flow constructed wetlands in tropical climate

Abstract The aim of this study is to compare methane (CH4) and nitrous oxide (N2O) fluxes from horizontal subsurface flow (HSSF) and vertical subsurface flow (VF) systems treating municipal wastewater in tropical climates. The treatment performance from both systems was monitored simultaneously with CH4 and N2O fluxes to observe the relationships between them. Average CH4 fluxes of 5.4 mg·m−2·h−1 and 9.5 mg·m−2·h−1, and N2O fluxes of 0.32 and 0.21 mg·m−2·h−1 were measured from VF and HSSF systems, respectively. The average CH4 fluxes measured during the wet period were 63.5% and 44% less than those recorded during the dry period for HSSF and VF systems, respectively; those for N2O fluxes were 47% and 38% less than the dry period for these systems, respectively. The CH4 and N2O fluxes from both HSSF and VF dropped as a result of rainfall events and slowly increased after days with no rainfall. Influent total organic carbon (TOC) and total nitrogen (TN) concentrations are found to be the dominant factors regulating the fluxes where significant correlations between CH4 and N2O with the influent TOC and TN concentrations were found in both systems.

CONSTRUCTED WETLANDS AS BIOFILTERS IN CLOSED RECIRCULATING TANK CULTURE SYSTEMS OF ASIAN TIGER SHRIMP (PENAEUS MONODON)

The study was conducted to monitor the real-time status of toxic compounds to P. monodon in intensive recirculating aquaculture system integrated constructed wetlands (CWs) designed with surface flow (SF), vertical subsurface flow (VF) and horizontal subsurface flow (HF), and to examine removal efficiency of contaminants in different CWs. Plants used in the system were cattail (Typha sp.), elephant grass (Pennisetum purpureum) and unplanted systems used as referenced samples. Recirculating rate per day was 50 % of total water volume in tanks. Water from culture tanks was purified by passing through SF, VF and HF then return to original tanks without water exchange in entire study period. After 72 days, concentration of NO2-N, NH4-N and NO3-N was building up over study period and was not significantly different among treatment systems (except the concentration of NO3-N). At the end of study period, NH3 concentration was below the toxic threshold for P. monodon in according to Circular No. 45/2010/TT-BNNPTNT. P. monodon grew slowly and the survival rate was as low at 30 %, 43 % and 60,5 % in the HF, SF and VF systems, respectively. The average water volume added in each tank in entire study period was 393 ± 1,7 L. Despite of low survival and growth rates, the integration of CWs in intensively recirculating shrimp systems helps to improve water quality in accordance to Circular No. 45/2010, to diminish pollutant discharging and to maximize efficiency of water use which minimizes environmental pollution.

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.