Vertical Flow Constructed Wetland System Research Articles

Assessment of pathogen removal efficiency of vertical flow constructed wetland treating septage

Septage refers to the semi-liquid waste material that accumulates in septic tanks and other onsite sanitation systems. It is composed of a complex mixture of human excreta, wastewater, and various solid particles. Septage is a potential source of water pollution owing to presence of high organic content, significant pathogen concentrations, and a range of nutrients like nitrogen and phosphorus. The harmful impacts of septage pollution poses significant risks to public health through the contamination of drinking water sources, eutrophication of water bodies and spread of water borne diseases. Conventional septage treatment technologies often face limitations such as high operational costs, energy requirements, and the need for extensive infrastructure. Therefore, with an aim to treat septage through an alternative cost effective and energy-efficient technology, a laboratory-scale constructed wetland (CW) system (0.99 m2) consisting of a sludge drying bed and a vertical flow wetland bed was utilized for the treatment of septage. The sludge drying bed and vertical flow beds were connected in series and filled with a combination of gravel with varying sizes (ranging from 5 to 40 mm) and washed sand. Canna indica plants were cultivated on both beds to facilitate phytoremediation process. The system was operated with intermittent dosing of 30 Ltrs of septage every day for 2 months. The HRT of the system was fixed at 48 h. The average inlet loads of Biochemical Oxygen Demand (BOD5), Chemical Oxygen Demand (COD), and Total Suspended Solids (TSS) were measured as 150 ± 65.7 g m−2 day−1, 713 ± 443.9 g m−2 day−1, and 309 ± 66.3 g m−2 day−1, respectively. After treatment, the final effluent had an average load of 6 g m−2 day−1 for BOD5, 15 g m−2 day−1 for COD, and 51 g m−2 day−1 for TSS, indicating that the CW system achieved an average removal efficiency of 88% for BOD, 87% for COD, and 65% for TSS. The average load of total coliforms and helminthes eggs in the influent was recorded as 4 × 108 Colony-Forming Units (CFU) m−2 day−1 and 3 × 107 eggs m−2 day−1, respectively. However, the CW system demonstrated significant effectiveness in reducing microbial contamination, with an average removal efficiency of 99% for both total coliforms and helminthes eggs. The vertical flow constructed wetland system, equipped with pretreatment by sludge drying bed, has proven to be efficient in treatment of septage.

Application of the Monte-Carlo Method to Assess the Operational Reliability of a Household-Constructed Wetland with Vertical Flow: A Case Study in Poland

The objective of this study was to model the operation of a vertical-flow constructed wetland (VF-CW) for domestic wastewater, using Monte-Carlo simulations and selected probability distributions of various random variables. The analysis was based on collected wastewater quality data, including the values of the pollutant indicators BOD5 (biochemical oxygen demand), CODCr (chemical oxygen demand), and TSS (total suspended solids), in the 2017–2020 period. Anderson–Darling (A–D) statistics were applied to assess the fit of the theoretical distributions to the empirical distributions of the random variables under study. The selection of the best-fitting statistical distributions was determined using the percentage deviation (PBIAS) criterion. Based on the analyses that were performed, the best-fitting statistical distributions for the pollution indicators of the raw wastewater were the generalised extreme value distribution for BOD5, the Gaussian distribution for CODCr, and the log-normal distribution for TSS. For treated effluent, the log-normal distribution was the best fit for BOD5 and CODCr; the semi-normal distribution, for TSS. The new data generated using the Monte-Carlo method allowed the reliability of the VF-CW operation to be assessed by determining the reliability indices, i.e., the average efficiency of the removal of pollutants (η), the technological efficiency index (R), the reliability index (CR), and the risk index of the negative control of the sewage treatment plant operation (Re). The obtained results indicate that only in the case of CODCr, the analysed treatment facility may fail to meet the requirements related to the reduction of organic pollutants to the required level, which is evidenced by the values of the indicators CR = 1.10, R = 0.49, and η = 0.82. In addition, the risk index of the negative operation of the facility (Re) assumes a value of 1, which indicates that during the period of its operation, the VF-CW system will not operate with the required efficiency in relation to this indicator. The novelty of this work is the implementation of the indicated mathematical simulation methods for analysing the reliability of the operation of the domestic wastewater treatment facility.

The impact of external plant carbon sources on nitrogen removal and microbial community structure in vertical flow constructed wetlands

The present study was developed to explore nitrogen removal performance and associated microbial mechanisms of action in vertical flow constructed wetlands (VFCWs) when using external carbon sources. These analyses ultimately revealed that alkali-soaked Phragmites australis (P. australis) could serve as an effective plant carbon source, exhibiting the lower levels of total nitrogen (TN) release and the highest chemical oxygen demand (COD) of all tested carbon sources. Nitrogen removal efficiency improved following the addition of plant carbon sources, and under carbon/nitrogen (C/N) rations of 2, 4, 5, and 7, the VFCW system was able to remove 43.69%–75.76% TN, with the highest removal rate being observed at a C/N of 5. The abundance of denitrifying microorganisms such as Thiobaillus and Halomonas were also more enriched in VFCW1 than VFCW0, with stronger correlations in the microbial network community. A qPCR approach was used to analyze functional genes involved in denitrification, revealing that the addition of plant carbon sources was associated with increases in total gene abundance and the abundance of the denitrifying gene nirS, whereas no corresponding increase in amoA or nxrA abundance was observed. Higher total gene, amoA, and nxrA abundance were observed in the upper levels of these VFCW systems as compared to the lower layers, whereas nirS exhibited the opposite abundance pattern. Overall, these findings suggested that short-range denitrification is likely to be the primary denitrification process active in this VFCW system.

Application of hybrid vertical flow constructed wetland systems to treatment of greywater for their use to irrigation in rural areas

Access to water supply is currently one of the biggest social and economic challenges in many parts of the world. Iran is currently experiencing serious water problems. One of the appropriate solutions to overcome the existing challenge is to pay attention to alternative water sources such as treated greywater. In the present study the performance of greywater treatment system consists of a vertical flow constructed wetland followed by column filled with combined inexpensive adsorbents in a series was investigated. The absorption capacity of incinerator bottom ash (IBA), rice husk, pumice, dried stems of Phragmites Australis (PA) and activated carbon (as control) absorbents were assessed by analyzing the quality of the influent and effluent streams through testing COD, PO4−3, NO3−, EC and TSS in greywater. After evaluating the treatment capacity of the above absorbents, it was concluded that IBA and dried stems of PA are the most effective material to reach the irrigation water quality. Then, using them, a hybrid pilot-scale experimental system was designed to study the treatment of greywater. This hybrid system efficiently removes COD, NO3− –N and PO4−3 by up to 90.35%, 100% and90.2%, respectively.

Effectiveness of the tropical plants Rhynchospora corymbosa and Coix lacryma-jobi in vertical flow constructed wetlands for municipal primary sewage effluent treatment

The performance of two tropical plants, Rhynchospora corymbosa L. (RC) and Coix lacryma-jobi, L (CL) in treatment of primary sewage effluent in lab-scale vertical-flow constructed wetlands (VFCW) along with no plant control wetland was investigated. A batch-flow VFCWs were operated under batch fill and drain hydraulic loading system with hydraulic retention times (HRT) of 0.5, 1, and 2 days and fill rate of 8 L/day. Removal of solids, organics, nutrients, and pathogens were monitored. The volumetric contaminant removal rates were best described by 1st order kinetics except for ammonia and phosphate, which was best described by Stover-Kincannon kinetics. Influent TSS, PO4 3−, COD, BOD5, and total coliform concentration were low but high in NH4 + concentration. CL was better in nutrient removal as HRT increases compared to RC. RC was more efficient at TSS, turbidity, and organics removal. Pathogen removal was independent of plant type but HRT. Solids and organic removal were lower in CL planted CWs due to preferential flow paths created by their bulky root. CL planted CWs removed more nutrients followed by RC planted CWs and then no-plant control CWs. The results of these tests demonstrate that both CL and RC are suitable for the treatment of municipal wastewater in VFCW system.

Nitrogen removal performance and bacterial community analysis of a multistage step-feeding tidal flow constructed wetland

A multistage mesocosm vertical flow constructed wetland system was designed to treat synthetic domestic wastewater with a high nitrogen (N) load. The study aim was to determine the impact of design and operational variables on N removal efficiency in such systems. A tidal flow operational strategy enhanced aeration and was coupled with a step-feeding approach to promote N removal. Over the 420-day running period N removal rates were between 70 and 77 gN/m3/d, for a step-feeding ratio range of 60:40 to 80:20. The system was able to remove 91–95% of chemical oxygen demand, 74–91% of ammonium and 66–81% of total-N. Tidal flow and step-feeding strategies significantly impacted nitrogen removal with the best performance at a step-feeding ratio of 80:20 providing a carbon to nitrogen (COD/N) ratio of 4–5. The bacterial diversity increased at each stage throughout the system with dominating phyla Proteobacteria, Firmicutes, Planctomycetes, Bacteroidetes, Chloroflexi, Verrucomicrobia and Acidobacteria. Dominant bacteria at the genus level were Thiothrix, Planctomyces, Azonexus, Pseudoxanthomonas, Hydrogenophaga, Gemmobacter and other genera suggesting that N removal was accomplished via diverse metabolic pathways, including autotrophic nitrification, heterotrophic denitrification, autotrophic denitrification, and possibly anammox. This study shows benefits of step-feeding strategies in tidal flow constructed wetlands as a cost-effective solution for minimizing external carbon input to achieve effective N removal.

Kinetics and mineralization fraction of organic matter from sewage sludge mixed with soil under controlled laboratory conditions

The objective of this work was to evaluate the kinetics and mineralization fraction of organic matter from sewage sludge mixed with the soil under controlled laboratory conditions. For this, organic material samples accumulated in layers 0–5 cm, 5–10 cm and 10–15 cm in relation to the surface of a vertical flow constructed wetland system (VF-CW) used for treatment of septic tank sludge, in addition to samples of dewatered sludge from a septic tank and a UASB reactor and non-dewatered sludge from an anaerobic digester were mixed with material collected from the surface layer of a Red Yellow Argisol at rates equivalent to the applications, via organic residues, of 300 and 600 kg ha−1 year−1 of total nitrogen. It was found that the two-phase kinetic equation fit better to the mineralization data of labile and recalcitrant organic carbon. For the lowest nitrogen application rate in the mixtures, the mineralization fractions of the total organic carbon were higher than 73%, while at the highest dose there was a reduction in the mineralization of organic matter by 17% and 63%, respectively in samples collected in layer 10–15 cm from the VF-CW and in the septic tank sludge dewatered in the drying bed.

Removal of Methylene Blue dye from textile wastewater using vertical flow constructed wetland

The aim of this study is to assess the performance of vertical flow constructed wetland system to treat synthetically prepared textile wastewater containing Methylene Blue dye (MB) of two different dye concentrations of 50 mg/L and 100 mg/L. Three lab scale Vertical Flow Constructed Wetland systems (CW1, CW2 and CW3) of size 30 cm diameter and 60 cm depth each were fabricated. CW1, acted as a control system without plants and was packed with sand, zeolite and gravel. CW2 and CW3 were planted with wetland plants - Canna Indica. CW2, was filled with packing media: sand, zeolite and gravel and CW3, with sand and gravel. The wetlands were operated in batch and continuous mode. The systems were evaluated by measuring Colour removal, Chemical Oxygen Demand (COD), pH and Electrical Conductivity (EC). The absorbance of the Methylene Blue dye in the wastewater before and after treatment was measured at the wavelength of maximum absorption using UV/visible spectrophotometer. The results showed that the wetlands CW1, CW2 and CW3 reduced colour by 85 %, 93 % and 74 % for 50 mg/L of MB and 89 %, 99 % and 74 % respectively for 100 mg/L of MB. COD removal of 70 %, 93 % and 89 % was achieved in CW1, CW2 and CW3 respectively for 50 mg/L MB. At 100 mg/L MB, COD removal was 65 %, 89 % and 83 % in CW1, CW2 and CW3 respectively. This study shows that the constructed wetland system with zeolite is a promising technique for the colour removal of methylene blue dyeing textile effluents.

Nitrogen removal performance and microbiological characteristics for the landfill leachate treatment in a three-stage vertical flow constructed wetlands system

Landfill leachate (LL) has the characteristics of high NH 4 + -N and low C/N ratio, increasing the cost and difficulty of efficient treatment. Constructed wetlands system (CWs) has proven to be feasible for the treatment of LL. A constructed three-stage series of vertical flow CWs (termed CW1, CW2, and CW3) based on effluent recirculation (T-VF) was used to treat LL, and nitrogen removal effect and microbiological characteristics was investigated. The results show that the nitrogen removal efficiency showed a increased trend from CW1 to CW3. The average removal efficiencies of TN, NH 3 + -N, and NO 3 − -N in T-VF were 91.43%, 94.19%, and 98.11%, respectively, which showed good nitrogen removal performance. Furthermore, application of the combined CW1, CW2 and CW3 increased diversity of substrate bacterial communities and decreased the relative abundances of the dominant nitrifying(e.g. Nitrosomonas , Nitrobacter ) and heterotrophic denitrifying bacteria (e.g. Thauera ). The relative abundances of autotrophic denitrification (e.g. Thiobacillus ) increased. Pathway of nitrogen metabolism and functional genes analysis showed that the abundance of enzymes associated with the denitrification and dissimilatory nitrate reduction increased and that the abundance of enzymes associated with the nitrification decreased. Application of the combined CW1, CW2 and CW3 could be respectively formed corresponding nitrogen removal microbial community, influent quality and pathways of nitrogen to enhance the nitrogen removal effect of T-VF to treat LL. • The removal rate of nitrogen was over 90% in vertical flow constructed wetlands. • Nitrosomonas and Nitrobacter were the dominant nitrification bacteria. • Denitrifying bacteria Thauera , Thiobacillus , and Lautropia predominated.

Performance evaluation of different macrophytes in small‐scale vertical flow constructed wetlands for greywater treatment using principal component analysis

AbstractThe scarcity of water is perceived as a systematic global risk due to increasing water demand. Vertical flow constructed wetland (VFCW) is proposed as an energetically efficient and economical process to treat greywater (GW) for non‐potable purposes. Macrophyte contributes a significant amount to the treatment process, and it depends on species, and their ecology. In this study, four single‐stage VFCW systems were planted with locally available plant species named Hymenocallis littoralis as Plant 1, Phragmites australis as Plant 2, Canna indica Plant as 3, and Colocasia as Plant 4, which were used for the treatment of GW. The mean removal efficiencies associated with Plant 1, Plant 2, Plant 3, and Plant 4 are 55.13%, 48.11%, 52.53%, and 56.39% for chemical oxygen demand (COD); 45.35%, 35.36%, 64.10%, and 56.39% for ammonia; and 32.97%, 20.85%, 71.57%, and 33.40% for phosphate, respectively. All systems show significant removal efficiency (more than 40%) of all pollutants, except TDS and pH. Among all the observed plants, C. indica achieved the highest removal efficiency for COD, ammonia, and phosphate. The obtained results were analyzed for the dependency of correlations with effluent, influent, and macrophytes used in the treatment system. The principal component analysis (PCA) identified two principal components from 13 variables and explained 50.25%, 47.47%, and 45.62% variance of normalized datasets in VFCW. The PCA also shows significant correlations of plant species with different targeted effluent parameters.

Study of domestic wastewater treatment using Moringa oleifera coagulant coupled with vertical flow constructed wetland in Kibera Slum, Kenya.

The domestic wastewater collection and treatment rate of Nairobi, Kenya are not high. The wastewater in the Kibera slum on the outskirts of the city that is directly discharged to the environment and pollution of the surrounding water body is a serious problem. This paper takes the domestic wastewater in the slum area as the research objective and researches on the wastewater characteristics, collection, and treatment, therefore providing the reference for the wastewater collection and treatment technology in the region. In this paper, domestic wastewater in the Kibera slum of Nairobi was sampled and investigated to find out the characteristics of wastewater discharged, the way of discharge of the household wastewater, and the management in this area. The study shows that there are differences in the concentration of main pollutants such as nutrients and organic matter in the wastewater from the household discharged to the residential river in the slum area. The domestic wastewater in this slum area contained a high concentration of nutrients such as nitrogen and phosphorus and other organics, total suspended solids (TSS), total coliforms and color, and with no treatment methods. Therefore, economic and feasible treatment technology needs to be developed. A pilot study was conducted on the treatment of domestic wastewater in the slum area by combining the seed extract of the natural plant Moringa oleifera as a coagulant and vertical flow constructed wetland (VFCW) at Tongji University, Shanghai, China. The VFCW system was efficient in chemical oxygen demand (COD), TSS, turbidity, total phosphorus (TP), and phosphates (PO4-P) removal, but the removal efficiency of nitrogen (total nitrogen (TN), ammonium nitrogen (NH4-N), and nitrate (NO3-N)) was poor, and the effluent pH reached the required discharge country's standard of the water. The average removal efficiencies for COD (79.99%), TSS (86.84%), turbidity (87.35%), TP (61.29%), PO4-P (65.66%), TN (14.11%), NH4-N (18.17%), and NO3-N (93%) were achieved by the treatment system. Furthermore, the removal efficiencies of pollutants such as TP, PO4-P, TN, and NH4-N were carried out by using the fruit extract of Moringa oleifera as raw material and zeolite as an auxiliary agent. The comprehensive effect of zeolite combined with VFCW and natural coagulant in the treatment of domestic wastewater was investigated. The COD removal efficiency was increased by (9%). TN by (46%), NH4-N by (67%), TP by (19%), and turbidity improved by (9%). In short, the domestic wastewater in the Kibera slum was collected and pretreated with natural plant coagulant, and then purified by vertical flow constructed wetland, which can not only significantly reduce the pollutant concentration but also basically meet the discharge standards. It is a low-cost sewage treatment technology suitable for poor areas.

Development and performance assessment of a castor-based vertical flow constructed wetland system for utilization of landfill leachate

Development and performance assessment of a castor-based vertical flow constructed wetland system for utilization of landfill leachate

Effect of Plant Species on the Performance and Bacteria Density Profile in Vertical Flow Constructed Wetlands for Domestic Wastewater Treatment in a Tropical Climate

Bacteria are frequently studied due to their involvement in pollutants transformation processes during wastewater treatment. In this study, the treatment efficiency, bacteria densities and their vertical profile were investigated in pilot-scale vertical flow constructed wetlands (VFCW) planted with different plant species under a tropical climate in west Africa. Five beds were planted with local plant species, i.e., Andropogon gayanus, Chrysopogon zizanioides, Echinochloa pyramidalis, Pennisetum purpureum and Tripsacum laxum, while one bed remained unplanted. These species have been rarely used in CWs while some (e.g., T. laxum) are tested for the first time. After a 7-month trial, bacteria densities were measured in substrate samples separated into six layers along the bed depth. Plants presence enhanced the bacterial density and VFCW efficiency; the removal rates of organic matter (90.9–95.9%; COD and 95.2–98.5%; BOD5), nitrogen (74.3–84%; TN and 76–84%; NH4-N) and phosphorus (77.4–96.9%; PO4-P) were higher by 5.9–24.1% compared to the control bed, providing an overall excellent treatment performance for a single-stage VFCW system. Small numbers of anaerobic bacteria were obtained in the VFCWs, explaining the low-to-zero NO3-N removal, except for the VFCWs with T. laxum and P. purpureum. Aerobic bacteria decreased from the upper to bottom layers from 17.4 to 0.1 × 106 CFU/g in the planted beds, while anaerobic bacteria increased from 0.1 to 2.1 × 106 CFU/g. Anaerobic bacteria were more abundant in the unplanted than in the planted beds. The total bacteria count was dominated by aerobic bacteria, and decreased from the surface towards the bottom. Overall, the VFCW with P. purpureum demonstrated the highest efficiency, indicating that this design is an effective and sustainable nature-based solution for wastewater treatment in a tropical climate.

Effects of matrix modification and bacteria amendment on the treatment efficiency of municipal tailwater pollutants by modified vertical flow constructed wetland

Although vertical flow constructed wetland (VFCW) has great potentials for degradation of water contaminants, traditional VFCW has limited removal efficiencies for pollutants. This study constructed three sets of modified VFCW systems, including VFCW-A with matrix-modification using mixture of biochar and activated carbon, VFCW-B with microbial amendment using denitrifying bacteria, and VFCW-C with combined treatments of both. Their removal efficiencies for various pollutants in synthetic municipal tailwater were investigated. Results showed that the removal efficiencies for NH4–N, NO3–N, total nitrogen (TN), total phosphorus (TP), and chemical oxygen demand (COD) by VFCW-C were higher than VFCW-B throughout the experimental period, indicating that matrix-modification could improve the VFCW performance. The higher removal efficiencies for TN, TP, and COD by VFCW-C than VFCW-A also suggested the effectiveness of microbial amendment in VFCW. However, the improved removal for NO3–N by VFCW-C over VFCW-A became less obvious at later operation stage due to insufficient carbon source. All three VFCWs achieved their best removal efficiency when carbon source was supplemented at CH3COO−/TN ratio of 0.5. Our study suggested that the combined treatment of matrix-modification using biochar/activated carbon mixture and microbial amendment using denitrifying bacteria could effectively enhance the treatment efficiency of VFCW systems for tailwater pollutants from sewage plant.

Performance of a novel vertical flow constructed wetland for greywater treatment in rural areas in Jordan

ABSTRACT Jordan is facing severe challenges in terms of water scarcity and wastewater management. Thus, there is a growing need for adopting innovative approaches to overcome these challenges. Within the framework of this study, a pilot project was implemented to treat household greywater in rural areas in Jordan with a purpose of reuse for irrigation. The project consists of designing and developing four vertical flow constructed wetland (VFCW) systems located in different sites and integrating them in a decentralized treatment system. The project work aims particularly to present a model of an innovative, compact and effective modified VFCW system. The performance of the systems was assessed by analyzing the quality of the influent and effluent streams through testing 19 water quality parameters. The results revealed that the design was adequate and efficient in treating greywater as exemplified by removal efficiencies of 90%, 90% and 92% for BOD, COD and TSS respectively. Moreover, the other physico-chemical parameters (T-N, T-P, N-NO3-, Turbidity, Ca, Mg, SO4-, and heavy metals) measured in the effluent streams complied all with the Jordanian standards for unrestricted irrigation. Therefore, the outcomes of the current study can be invested to support the use of constructed wetlands in Jordan as a sustainable technology to improve the wastewater management practices and reinforce the decentralized wastewater treatment approach in rural areas.

Modeling and Economic Analysis of Greywater Treatment in Rural Areas in Jordan Using a Novel Vertical-Flow Constructed Wetland.

Water scarcity in Jordan is becoming more severe with time, which resulted in an indispensable need for economic innovative approaches to maximize the utilization of nonconventional water resources through reuse options. Within the framework of the current study, a novel vertical flow constructed wetland system was implemented for greywater treatment in four different rural areas in Jordan. In this paper, the primary objective was to develop a regression-based nonlinear model to predict BOD effluent concentration from the proposed system. The model obeyed the first-order kinetics and found to provide an efficient tool in predicting the effluent BOD value as exemplified by an R2 of 0.78. Moreover, a cost analysis was carried out to verify the feasibility of the proposed system. The economic results revealed a NPV range of 295-1209 JOD (420-1730$), IRR range of 6-10.7%, and a payback period range of 8.8-15.5 years. The average calculated costs of greywater treatment using the VFCWs were found to be 0.391 (USD/m3 treated) and 0.672 (USD/kg BOD removed). Finally, the energy saving from using the proposed system was quantified and an estimate of 70 JOD (100$)/year household was obtained.

Operational Performances and Enzymatic Activities for Eutrophic Water Treatment by Vertical-Flow and Horizontal-Flow Constructed Wetlands

In this study, pilot-scale vertical-flow constructed wetland (VFCW) and horizontal-flow constructed wetland (HFCW) were constructed to treat eutrophic water, and dissolved oxygen (DO) distributions, decontamination performances and key enzymes activities were compared under different influent loads. The influent load increase caused reductions of DO levels and removal efficiencies of chemical oxygen demand (COD), total nitrogen (TN), NH4+−N and organic nitrogen, but it had no remarkable effect on the removal of NO3−−N and total phosphorus (TP). The interior DO concentrations of VFCW were higher than those of HFCW, indicating a vertical hydraulic flow pattern was more conducive to atmospheric reoxygenation. The VFCW and HFCW ecosystems possessed comparable removal capacities for TN, NO3−−N and TP. VFCW had a remarkable superiority for COD and organic nitrogen degradation, but its effluent NH4+−N concentration was higher, indicating the NH4+−N produced from organic nitrogen degradation was not effectively further removed in the VFCW system. The activities of protease, urease and phosphatase declined with the increasing depth of substrate layers, and they were positively correlated with DO concentrations. The enzymatic activities of VFCW were significantly higher than that of HFCW in the upper layers. Taken together, VFCW and HFCW presented a certain difference in operational properties due to the different hydraulic flow patterns.

A small-scale study of plant orientation in treatment performance of vertical flow constructed wetland in continuous flow

In constructed wetland (CW) ecology, plants play a vital role in wastewater treatment. The plants provide an adequate surface to various microorganisms, transfers oxygen and uptake nutrients to treat wastewater. This study deals with the treatment of greywater by using vertical flow constructed wetland system (VFCW). In the present study, two reactors were prepared for two different orientations in monoculture (S-1) and mixed culture (S-2) by using four types of macrophytes (Canna indica, Colocasia, Hymenocallis littoralis, and Phragmites australis). The reactors were operated in continuous mode for 90 days by maintaining the 10 mL/min flow rate and 1-day retention time. The mean removal efficiency of S-1 is 40.70, 33.69, 27.13, 48.17, 66.76, and 50.82% for ammonia, total kjeldahl nitrogen (TKN), phosphate, sulfate, turbidity, and chemical oxygen demand (COD), respectively. The mean removal efficiency of S-2 CW is 53.06, 34.54, 37.49, 48.64, 69.26, and 58.26% for ammonia, TKN, phosphate, sulfate, turbidity, and COD, respectively. ANOVA showed significant differences among both VFCWs in removal efficiency for all measured parameters. The performance of the two systems was compared with each other with the significance level of p = 0.05. The results indicated that the orientation of plant plays a major role in the removal of various physicochemical parameters.

Coliform removal in a constructed wetland system used in post-swine effluent treatment

This study evaluated the efficiency of a constructed wetland system (CWS) in removing total coliforms (TC) and thermotolerant coliforms (ThC) of swine wastewater, as a complementary treatment to an anaerobic system. At Stage 1, the experimental system was combined using a vertical flow constructed wetland system (VFCWS) cultivated with Tifton 85 grass in series with a horizontal subsurface flow constructed wetland system (HFCWS1) cultivated with Taboa. In HFCWS1, the hydraulic detention times (HDT) were 4.7, 3.1 and 2.3 days and the surface application rates (SAR) were 294, 319 and 397 kg ha-1 d-1 of COD, in Phases I, II and III, respectively. At Stage 2, the experimental system was combined using a horizontal subsurface flow constructed wetland system (HFCWS2) cultivated with Tifton 85 grass, HDT were 6.1, 2.0 and 0.5 days and the SAR were 850, 656 and 6.34 kg ha-1 d-1 of COD, in Phases I, II and III, respectively. In Stage 1, it was verified that the VFCWS was more efficient in coliform removal when compared to HFCWS1. When only HFCWS were compared, coliform removal in Stage 1 was between 1 and 2 log units in HFCWS1. In the stage 2, the HFCWS2 was more limited, with the highest removal efficiencies during Phase I of 1.6 and 0.8 log units for TC and ThC, respectively. In general, the association resulted in efficiencies that ranged from 96.4 to 99.0% for TC, 94.2 and 97.6% for ThC, equivalent to the average removal of 1.2 to 2 log units, considered satisfactory.

Phytoremediation potential of Vetiveria zizanioides and Oryza sativa to nitrate and organic substance removal in vertical flow constructed wetland systems

The aim of this work was to determine the potential of phytoremediation of Vetiveria zizanioides and Oryza sativa to nitrate (NO3−-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 (HL) 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: HL1 = 148 dm3·m−2·d−1, HL2 = 239 dm3·m−2·d−1, HL3 = 350 dm3·m−2·d−1, HL4 = 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 NO3−-N removal rate was found under HL2 – the median is 59 and 42% respectively. The most effective removal of COD in the VFCW-1 system was obtained at a HL2 – 55%, while in the system VFCW-2 at a HL1 – 43%. The research shows that the low HL and high COD/NO3−-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.