Constructed Wetland Model Research Articles

Machine learning assisted combined systems of wastewater treatment plants with constructed wetlands optimal decision-making

This study proposed an efficient framework for optimizing the design and operation of combined systems of wastewater treatment plants (WWTP) and constructed wetlands (CW). The framework coupled a WWTP model with a CW model and used a multi-objective evolutionary algorithm to identify trade-offs between energy consumption, effluent quality, and construction cost. Compared to traditional design and management approaches, the framework achieved a 27 % reduction in WWTP energy consumption or a 44 % reduction in CW cost while meeting strict effluent discharge limits for Chinese WWTP. The framework also identified feasible decision variable ranges and demonstrated the impact of different optimization strategies on system performance. Furthermore, the contributions of WWTP and CW in pollutant degradation were analyzed. Overall, the proposed framework offers a highly efficient and cost-effective solution for optimizing the design and operation of a combined WWTP and CW system.

Constructed wetlands as nature based solutions – hands-on activities to highlight their potential to minimize ocean pollution

This work presents an engaging hands-on activity designed to teach school students about nature based solutions (NBS) and their role in achieving high-quality water systems within a sustainable circular economy. Through this activity, students actively participate in building a small constructed wetland (CW) and test its effectiveness under various contamination scenarios. The activity was tested with school teachers, undergoing refinements based on their feedback. This iterative development process has ensured the activity’s effectiveness in engaging both school students and the public. Further, the CW model can be scaled-up for specific school projects focused on improving water quality. This activity offers valuable opportunities to enhance ocean literacy, promote understanding on NBS and raise awareness about aquatic ecosystems contamination and the importance of environmental sustainability.

Comparing The Ability to Treat Artificial Cow Wastewater by Constructed Wetland Model Using Sorghastrum nutans and Brachiaria humidicola

In addition to meat production, the cattle industry generates significant waste, including bedding materials, wastewater, animal manure, and losses related to feed. If not managed correctly, these byproducts can have adverse environmental impacts. Constructed wetlands (CWs) offer a cost-effective and eco-friendly solution for sustainable wastewater treatment. By virtue of their extensive root systems and filtration matrices, CWs effectively reduce pollution by eliminating suspended particles, organic matter, heavy metals, and pathogens from wastewater. This research aims to assess pollutants present in cattle wastewater and evaluate the efficacy of Sorghastrum nutans and Brachiaria humidicola in purifying contaminants within constructed wetlands (CWs). CWs planted with B. humidicola exhibited higher removal rates for nutrient pollutants compared to CWs utilizing S. nutans. After a week of treatment, B. humidicola-based CWs demonstrated removal percentages of 94.07% for total nitrogen and 91.58% for phosphate (PO₄³⁻). Constructed wetlands also prove effective in eliminating biological contaminants like Escherichia coli and Shigella sp. This study highlights that the CW model incorporating B. humidicola outperforms the S. nutans model, achieving 100% removal of E. coli and 97.37% removal of Shigella sp. In conclusion, cow wastewater contains nutrient and biological pollutants, both effectively mitigated by CWs using selected plant species. Notably, B. humidicola surpasses S. nutans in its capacity for pollutant removal.

Attenuation of erythromycin-laden waste water using the constructed wetland technique

Erythromycin (ERY) is environmentally resilient because of its aromatic nature, which hinders degradation. In the present study, silty–sandy soil, with a saturated hydraulic conductivity (K) value of 1.66 × 10−7 m/s, was studied for its potential to remove aqueous ERY using a laboratory-scale constructed wetland. With a dose of 10 g/l, a concentration of 25 mg/l and a contact time of 30 min, the maximum adsorption reached 89.79 ± 1.5%, as found from batch experiments. The Freundlich isotherm (R 2 = 0.983, n = 0.575, K f = 0.04 mg/g) was the best fitting among different user models. In the kinetic study, the pseudo-second-order model (q e = 1.297 mg/g, K 2 = 0.182 g/(mg min)) had the best fit with experimental data. A one-dimensional vertical column study exhibited an exhaustion time of 2.7 days for a 40 mm deep soil bed to remove ERY. A laboratory-scale constructed wetland model composed of silty–sandy soil showed a reduction of ERY of 92.44%. Finally, the results were validated with the CW2D wetland model of the Hydrus software, which corroborated the experimental results. The outcome exhorts that constructed wetlands with silty–sandy soil may be an effective technique for the reduction of ERY present in waste water, which has profound importance from a social health perspective.

Spatial characterization of microbial sulfur cycling in horizontal-flow constructed wetland models

Constructed wetlands (CWs) are a cost-effective technology for wastewater treatment in which plant-microorganism relationships play a key role in transforming pollutants. However, there is little knowledge about the spatial organization of microbial metabolic processes in CWs. Here we show the structuring of microbial transformation of inorganic sulfur compounds (ISCs) in two horizontal subsurface-flow CW models fed with sulfate-rich artificial wastewater. One model was fully planted with Juncus effusus, while the other was planted only in the middle to investigate further the influence of the plant on ISC transformations. Chemical analyses revealed that sulfate reduction and re-oxidation of sulfide/sulfur occurred simultaneously along the flow paths, with net reduction at the beginning of the CWs, where organic carbon from the influent was still present, and predominant re-oxidation in the downstream sections. Porewater ISC concentrations hardly differed between the two CWs. However, analysis of the bacterial communities showed that sulfur cycling in the fully planted CW was much higher. Total bacterial abundances were about 50 times and 3–4 orders of magnitude higher in the rhizoplane than in porewater and on gravel, respectively, as quantified by qPCR determination of the 16S rRNA gene. Sequencing of 16S rRNA gene amplicons revealed that bacterial communities on the roots and in the porewater differed substantially, apparently a consequence of the fluxes of oxygen and exudates from the roots. Furthermore, we observed partitioning of ISC transforming bacteria into different niches of the CWs. The results of the chemical and microbial analyses collectively support that extensive sulfur cycling occurred in the rhizospheres of the CW models. The study is relevant to the treatment of sulfur-containing wastewater and the elucidation of microbial communities involved in biogeochemical activities to improve water quality.

Constucted Wetland sebagai Model Ruang Publik untuk Memperbaiki Ekologi pada Kawasan Permukiman di Tepian Sungai Kapuas Pontianak

The residential areas on the banks of the Kapuas River have a poor domestic sewage system. Domestic waste that pollutes the Kapuas River needs to be filtered before entering the river. Constructed wetland is a solution for filtering hydrological waste by using water plants. Hydrological analysis related to tides and levels of river water quality as well as analysis of endemic water vegetation are the basis for determining the concept of a constructed wetland model which ecologically functions to filter waste, and also socially functions as a public space. With a suitable constructed wetland design, it is hoped that it can improve the ecology of the residential area on the banks of the Kapuas River and can also become a public space destination for people in residential areas on the banks of the Kapuas. This research produces a visual prototype of constructed wetlands in the area, and this research is also expected to produce outputs in the form of research reports, national journal publications and Appropriate Technology, which can be adopted by the government or society.

Effects of restoration strategies on wetland: A case‐study of Xinqiang River National Wetland Park

AbstractAccurately understanding the characteristics of a wetland ecological restoration plant communities and their species diversity relationships is the key to improving wetland management and biodiversity protection. To see the effects of restoration strategies implemented in Xinqiang River National Wetland Park, China, we studied 4 models for ecological restoration, namely protection and conservation (PC), reasonable utilization (RU), restoration and reconstruction (RR) and the building of constructed wetland (CW). We then analyzed the features of the plant communities, species diversity and soil properties, and carried out a correlation analysis between plant communities and the species diversity. Finally, we selected four key communities and analyzed their features and soil properties using a symmetric matrix. Results showed that the soil in the PC model had the highest amount of available phosphorus, available nitrogen and pH value. The soil had higher moisture content in the RU model and CW model than the other 2 models. Based on the correlation analysis, we found that there are obvious common characteristics among different ecological restoration types, that is, the diversity characteristics of tree layer, shrub layer and herb layer have obvious differentiation characteristics. We identified four features of the community characteristics that could improve species diversity: SA, TH, HH and SCD. The results of this study have provided a theoretical basis that there is a coupling relationship between ecological community characteristics and species diversity. The above coupling results have practical significance for maintaining good ecological structure and diversity protection.

Subsurface flow constructed wetland model for phytoremediation of chromium from tannery wastewater using Echinodorus palaefolius

In the leather tanning process or tannery, Cr solution is usually used to modify leather properties. This results in Cr containing wastewater, which becomes a crucial issue. One promising method for removing Cr from tannery wastewater is by using subsurface flow constructed wetland (SSF-CW). A combination of adsorption and phytoremediation that occurs in the SSF-CW removes Cr from wastewater. In this research, the effect of vegetation and media on Cr removal was investigated. Echinodorus palaefolius was used as a phytoremediation agent, while wood charcoal and natural zeolite were used as media. The experiment was conducted in 4-different SSF-CW reactor configurations, namely CTT (wood charcoal-zeolite; no plant), CDT (wood charcoal-zeolite; with plant), ZDT (zeolite; with plant) and ADT (wood charcoal; with plant). Each reactor was filled with 70 L Cr contained water that was recirculated within the reactor for 15 days. Evidence revealed that Echinodorus palaefolius significantly increases the removal of Cr from wastewater, compared to that of without those plants (wood charcoal-zeolite medium only). Using an initial concentration of Cr of 2.05 mg/L, removal percentage is 63.7, 86.83, 70.37, and 83.05% for CTT, ZDT, ADT, and CDT, respectively. It is also found that zeolite media performed much better than charcoal. A combination of zeolite medium and Echinodorus palaefolius (ZDT) produced the highest Cr removal. In addition to that, despite its Cr intoxication indication, the Echinodorus palaefolius was able to grow/regenerate during the experiment.

Modeling the impacts of plants and internal organic carbon on remediation performance in the integrated vertical flow constructed wetland

The integrated vertical flow (IVF) constructed wetland consists of two or more chambers with heterogeneous flow patterns and strong aeration capability, possesses favorable remediation performance. The Constructed Wetland Model No.1 (CWM1) embedded in the OpenGeoSys # IPHREEQC was applied to investigate the wetland plant effects on treatment efficiency. Two fundamental functions of the plant roots (i) the radial oxygen loss (ROL) and (ii) exudation of internal organic carbon (IOC), are developed and implemented in the model to simulate the treating processes of planted laboratory-scale IVF wetlands fed by the synthetic wastewater. The good agreement between simulated results and measurements of the planted IVF wetland and the unplanted filters mimicking wetland demonstrates the combined effects of ROL and IOC and the model reliability. In summer the ammonia (NH4-N) and total nitrogen (TN) removals are high as above 90% in both IVF wetlands, and in winter they decline significantly to around 55% and 45% in unplanted wetland, contrastively to about 85% and 78% in the planted wetland. The nitrogen removal - COD/N ratio relation curves of IVF wetlands are proposed and obtained by modeling to evaluate organic carbon loading status. Based on the curves, the COD/N ratios of unplanted and planted wetlands are about 3∼7 and 3∼10 gCOD/gN for high TN removal respectively. Planted wetlands can tolerate a wider range of COD/N ratio influents than unplanted ones. The ROL in the unplanted wetland promotes COD and NH4-N removal, while may inhibit denitrification under low-temperature conditions. The single addition of IOC enhances the oxygen-consuming and restrains the nitrification under the full loaded COD condition. Summing up all organic carbon releases from substrate and roots as IOC, the quantification of IOC acts on nitrogen treatment was simulated and compared with the external organic carbon (EOC) loading from influent. IOC performs higher efficiency on TN removal than EOC at the same organic loading rates. The results provide the thoughts of the solution for low TN removal in the carbon deficient constructed wetlands.

Removal of Antibiotics and Nutrients by Vetiver Grass (Chrysopogon zizanioides) from a Plug Flow Reactor Based Constructed Wetland Model.

Overuse of antibiotics has resulted in widespread contamination of the environment and triggered antibiotic resistance in pathogenic bacteria. Conventional wastewater treatment plants (WWTPs) are not equipped to remove antibiotics. Effluents from WWTPs are usually the primary source of antibiotics in aquatic environments. There is an urgent need for cost-effective, environment-friendly technologies to address this issue. Along with antibiotics, nutrients (nitrogen and phosphorus) are also present in conventional WWTP effluents at high concentrations, causing environmental problems like eutrophication. In this study, we tested vetiver grass in a plug flow reactor-based constructed wetland model in a greenhouse setup for removing antibiotics ciprofloxacin (CIP) and tetracycline (TTC), and nutrients, N and P, from secondary wastewater effluent. The constructed wetland was designed based on a previous batch reaction kinetics study and reached a steady-state in 7 days. The measured concentrations of antibiotics were generally consistent with the modeling predictions using first-order reaction kinetics. Vetiver grass significantly (p < 0.05) removed 93% and 97% of CIP and TTC (initial concentrations of 10 mg/L), simultaneously with 93% and 84% nitrogen and phosphorus, respectively. Results show that using vetiver grass in constructed wetlands could be a viable green technology for the removal of antibiotics and nutrients from wastewater.

NUMERICAL MODELING OF HORIZONTAL SUBSURFACE FLOW CONSTRUCTED WETLAND SYSTEM

This is the first study looking at the wastewater treatment system created at Basrah University, Iraq. This study aims to investigate the effectiveness of horizontal subsurface flow (HSSF) constructed wetland (CW) system for treating municipal wastewater, and to understand the inner processes presented in the wetland to distinguish and define the function of each component of the treatment and to create wastewater treatment built using MATLAB programming language to represent the biochemical phenomena systems similar to the treatment system and implement them throughout Iraq. To do this, a mathematical model based on one dimensional constructed wetland model number 1 (CWM1) matrix and the optimum CWs operational parameters was occurring in the CWs. The CWM1 was used to simulate processes in horizontal subsurface flow (HSSF) constructed wetlands. Results of the simulation had a very good fit to measured NH4-N as well as a good fit to measured chemical oxygen demand (COD) concentration after changing the values of the concentration autotrophic nitrifying bacteria (XA) and acetotrophic methanogenic bacteria (XAMB).

Comparison and assessment of the nutrient removal capacity by reed grass (Phragmites australis L.) and vetiver (Vetiveria zizanioides L.)

The paper presented results of the comparative assessment of nutrient absorption capacity by plants, including reed grass (Phragmites australis L.) and vetiver (Vetiveria zizanioides L.). The constructed wetland models were designed with experiments (i) - Loading 1 (T1): reed grass (S1), vetiver (V1) + control (C1); (ii) - Loading 2 (T2): reed grass (S2), vetiver (V2) + control (C2); (iii) - Load 3 (T3): reed grass (S3), vetiver (V3) + control (C3). The study investigated the surface water quality parameters including nutrients such as TKN (Total Kieldalh Nitrogen), ammonium (NH4-N), nitrite (NO2-N), nitrate (NO3-N), total phosphorus (TP) and phosphate (PO43-). Results showed that there was significantly decreasing change related to pollutant concentration in the tanks. The studied results showed that the water treatment efficiency of Loading 1 (T1) possessed highly nutrient absorption capacities such as nitrogen and phosphorus. Comparing the nitrogen and phosphorus removal efficiency, there was no statistically significant difference between reed grass and vetiver in the same loading (P&gt;0.05). In general, in the same loading levels, the plants’ nutrient removal efficiencies were often higher than the control experiments (P&lt;0.05). The effluent findings illustrated some parameters of water quality that met to National Technical Regulation of surface water quality for agricultural irrigation purposes (QCVN 08-MT:2015/BTNMT). Therefore, the constructed wetland technology obtained highly effective characteristics and supplying the environmental friendly advantages.

Benzylsuccinate Synthase is Post-Transcriptionally Regulated in the Toluene-Degrading Denitrifier Magnetospirillum sp. Strain 15-1.

The facultative denitrifying alphaproteobacterium Magnetospirillum sp. strain 15-1 had been isolated from the hypoxic rhizosphere of a constructed wetland model fed with toluene. This bacterium can catabolize toluene anaerobically but not aerobically. Here, we used strain 15-1 to investigate regulation of expression of the highly oxygen-sensitive glycyl radical enzyme benzylsuccinate synthase, which catalyzes the first step in anaerobic toluene degradation. In cells growing aerobically with benzoate, the addition of toluene resulted in a ~20-fold increased transcription of bssA, encoding for the catalytically active subunit of the enzyme. Under anoxic conditions, bssA mRNA copy numbers were up to 129-fold higher in cells growing with toluene as compared to cells growing with benzoate. Proteomics showed that abundance of benzylsuccinate synthase increased in cells growing anaerobically with toluene. In contrast, peptides of this enzyme were never detected in oxic conditions. These findings show that synthesis of benzylsuccinate synthase was under stringent post-transcriptional control in the presence of oxygen, which is a novel level of regulation for glycyl radical enzymes.

Assessing the Ability to Treat industrial Wastewater by Constructed Wetland Model Using the Brachiaria mutica

The speed of urbanization—industrialization in Vietnam is increasing, which helps to boost the economy and at the same time create great environmental pressure. Industrial wastewater from production processes is always abundant and discharged continuously every day with diverse pollution components. Wastewater treatment of by simple and low-cost methods has been concerned. In this study, constructed wetland (CW) model using the Brachiaria mutica has been researched to evaluate the performance of Horizontal subsurface flow (HSSF) CW in treating industrial effluents. The model built with dimensions is 1.2 m × 0.4 m × 0.6 m and operated under 4 research organic load rates respectively 40; 60; 80; 100 kgCOD/ha.day. Average treatment efficiency of pollution parameters through study is COD 93.86%, T–N 97.46%, T–P 91.12%, TSS 83.07%, BOD5 97.72%. The output concentration values of the pollution parameters are smaller than the allowable values in column A QCVN 40: 2011/ BTNMT. The results of this study will be the premise to find solutions for industrial wastewater treatment with easy to operate and environmentally friendly. The process of industrial wastewater treatment using CW planning B. mutica is simple and efficient. The success of this work is possible to expand research on wastewater treatment capacity of CW planning B. mutica with different kinds of wastewater such as domestic wastewater, livestock wastewater, medical wastewater.

Selection of Suitable Filter Materials for Horizontal Subsurface Flow Constructed Wetland Treating Swine Wastewater

This research aims to assess different filter materials in horizontal subsurface flow constructed wetland (CW) planted with combined Phragmites australis Cav. and Cyperus alternifolius L. for treatment of real swine wastewater at a large pig farm in Vietnam. Four CW models including CW1 (gravel), CW2 (gravel, limestone), CW3 (gravel, limestone, and sand), and CW4 (gravel, limestone, and rice husk) were designed and conducted during 90 days of the experiments. The results showed that the removal efficiencies of chemical oxygen demand (COD), total suspended solids (TSS), nitrogen, and phosphorus from swine waster by the CW3 and CW4 models were higher than those by CW1 and CW2. The highest removal efficiency of COD, NH4+-N, TN, and TP by CW3 was 82 ± 2%, 82 ± 4%, 77 ± 1%, and 82 ± 3%, respectively. The result of this study indicates the capacity of combined gravel, limestone, and sand as suitable substrate filter for swine wastewater treatment.

Modeling the relationship of aeration, oxygen transfer and treatment performance in aerated horizontal flow treatment wetlands

Mechanical aeration is commonly used to improve the overall treatment efficacy of constructed wetlands. However, the quantitative relationships of air flow rate (AFR), water temperature, field oxygen transfer and treatment performance have not been analyzed in detail until today. In this study, a reactive transport model based on dual–permeability flow and biokinetic formulations of the Constructed Wetland Model No. 1 (CWM1) was developed and extented to 1) simulate oxygen transfer and treatment performance for organic carbon and nitrogen of two pilot–scale horizontal flow (HF) aerated wetlands (Test and Control) treating domestic sewage, and, 2) to investigate the dependence of oxygen transfer and treatment performance on AFR and water temperature. Both pilot–scale wetlands exhibited preferential flow patters and high treatment performance for chemical oxygen demand (COD) and NH4–N at AFRs of 128–700 L m−2 h−1. A reduction of the AFR in the Test system from 128 to 72 L h−1 m−2 substantially inhibited NH4–N removal. Conservative tracer transport as well as reactive transport of dissolved oxygen (DO), soluble and total chemical oxygen demand (CODs, CODt), NH4–N and NOx–N measured in pilot–scale experiments were simulated with acceptable accuracy (E1¯=0.39±0.26). An equation to estimate the volumetric oxygen transfer coefficient was found to be: kLa,20=0.511ln(AFR). Simulated treatment performance depended on kLa,20 in a non–linear manner. A local sensitivity analysis of the calibrated parameters revealed porosity, hydraulic permeability and dispersion length of the fast flow field as well as kLa,20 as most important. An optimal AFR for a spatially and temporally continuous aeration pattern for treatment wetlands treating similar influent was estimated to 150–200 L h−1 m−2. This study provides insights into aeration mechanisms of aerated treatment wetlands and highlights the benefits of process modeling for in–depth system analysis.

Potential use of aquatic plants in constructed wetlands for simultaneous removal of Phosphate and COD from laundry wastewater

One component of household wastewater that has a bad impact on the environment is waste that comes from washing which uses detergent, due to a fairly high phosphate and chemical oxygen demand (COD) concentration. The purpose of this study was to determine the potential of using aquatic plants to reduce phosphate and COD levels from laundry waste. This research was carried out using constructed wetlands model of laboratory scale using the combination of flow types of subsurface flow systems (SFS) and the type of vertical flow system (VFS) with a waste residence time of 5 days and 10 days. Based on the results, for model I, the average percentage of COD levels reduction is 67.62% and phosphate is 13.89%, while in model II, the average percentage of COD reduction is 59.93% and phosphate is 14.36%, after 10 days of waste residence time. Aquatic plants used in the modeling of constructed wetland can grow and reproduce well, this can be indicated by the growth of new shoots and flowers of these plants.

Performance of tropical vertical subsurface flow constructed wetlands for leachate treatment at different hydraulic loading rates

This study is focused on the investigation of three different types of plant species namely; Narrow leaf Cattail (Typha angustifolia), Green Bulrush (Scirpus atrovirens) and Umbrella Palm (Cyperus alternifolius) for treatment of leachate. Twelve laboratory scale subsurface flow constructed wetland models were operated in batch mode. Four models, each containing similar plant species were fed with synthetic leachate having four different concentrations (25%, 50%, 75% and 100%) and 7 days HRT was given. The duration of a batch run was 12 weeks. Removal efficiencies of BOD5, COD, PO43-, TC, and TN were measured. Evapotranspiration (ET) loss of each test run was also assessed. According to the results, the constructed wetland planted with Umbrella palm and fed with 25% leachate showed the best pollutant removal efficiencies of 99.26% for BOD5, 99.61% for COD, 98.78% for TN and 97.34%for TC. Highest ET potential of 93.57% was also observed from the constructed wetland with umbrella palm fed with 25% leachate. Two way ANOVA analysis was carried out for each plant species and leachate concentration and the Umbrella Palm species was identified as the best for leachate treatment. Key words: Constructed wetlands, landfill leachate, plant species and pollutant removal

Evapotranspiration versus oxygen intrusion: which is the main force in alleviating bioclogging of vertical-flow constructed wetlands during a resting operation?

Clogging is the most significant challenge limiting the application of constructed wetlands. Application of a forced resting period is a practical way to relieve clogging, particularly bioclogging. To reveal the alleviation mechanisms behind such a resting operation, evapotranspiration and oxygen flux were studied during a resting period in a laboratory vertical-flow constructed wetland model through physical simulation and numerical model analysis. In addition, the optimum theoretical resting duration was determined based on the time required for oxygen to completely fill the pores, i.e., formation of a sufficiently thick and completely dry layer. The results indicated that (1) evapotranspiration was not the key factor, but was a driving force in the alleviation of bioclogging; (2) the rate of oxygen diffusion into the pores was sufficient to oxidize and disperse the flocculant biofilm, which was essential to alleviate bioclogging. This study provides important insights into understanding how clogging/bioclogging can be alleviated in vertical-flow constructed wetlands. Graphical abstract Evapotranspiration versus oxygen intrusion in alleviating bioclogging in vertical flow constructed wetlands.

The sulfur depot in the rhizosphere of a common wetland plant, Juncus effusus, can support long-term dynamics of inorganic sulfur transformations

The sulfur cycle in the rhizosphere of constructed wetlands is frequently interlaced with transformations of carbon and nitrogen. Knowledge about the manifold sulfur transformations may thus aid in improving treatment performance of constructed wetlands. In this study, two laboratory-scale constructed wetland models (planted fixed bed reactors; PFR1 and PFR2) were used to investigate inorganic sulfur transformations at various total loads of sulfate and organic carbon. Sulfate, sulfide and elemental sulfur were the most abundant sulfur compounds detected, thus providing evidence for the simultaneous occurrence of dissimilatory sulfate reduction and sulfide oxidation. This co-occurrence was likely enabled by oxygen micro-gradients in the root-near environment, i.e. aerobic sulfide and elemental sulfur oxidation took place mostly at the roots while sulfate and elemental sulfur reduction occurred in the pore water under reduced redox conditions. The rhizosphere was found to be first sink, then source for sulfur during the course of the experiment. Immobilization of reduced sulfur was triggered by catabolism of organic matter coupled to dissimilatory sulfate reduction and the subsequent partial oxidation of generated sulfide. Good plant status was critical for sulfur deposition in the systems. Without externally provided sulfate the sulfur depot of the rhizosphere was a prolonged source for sulfur, which was remobilized into the pore water. Oscillations between sulfide and sulfur (PFR1) or sulfide and sulfate (PFR2) suggested a dynamic interplay between plants and various microbial guilds, i.e. dissimilatory sulfate and sulfur reducers on one side and sulfide and sulfur oxidizers on the other.