Vertical Flow Constructed Wetland System Research Articles

Long-term behaviour of a two-stage CW system regarding nitrogen removal

In the first two years of operation a nitrogen removal efficiency of 53% and a high average elimination rate of 1,000 g N m(-2) yr(-1) could be observed for a two-stage vertical flow (VF) constructed wetland (CW) system. The two-stage system consists of two VF beds with intermittent loading operated in series, each stage having a surface area of 10 m2. The first stage uses sand with a grain size of 2-3.2 mm for the 50 cm main layer and has a drainage layer that is impounded; the second stage sand with a grain size of 0.06-4 mm and a conventional drainage layer (with free drainage). The two-stage VF system was designed for and operated with an organic load of 40 g COD m(-2) d(-1) (i.e. 2 m2 per person equivalent). Data from the following years of operation showed that from the third year nitrogen elimination increased and stabilized. The median values of the nitrogen elimination rate in the first five years of operation have been 3.51, 2.76, 4.20, 3.84 and 4.07 g N m(-2) d(-1), the median value of the last three years being 3.8 g N m(-2) d(-1) and 1,380 g N m(-2) yr(-1), respectively, and the nitrogen removal > 60%. It can be assumed that the vegetation as well as the biofilm development in the two-stage VF CW system plays the major role for the enhancement of the nitrogen elimination rate.

Study of a Novel Vertical Flow Constructed Wetland System with Drop Aeration for Rural Wastewater Treatment

Constructed wetlands are recognized as a reliable technology for rural wastewater treatment. However, conventional constructed wetlands face problems with low pollutant removal efficiency and limited oxygen transfer capability. Therefore, a novel vertical flow constructed wetland (VFCW) system with drop aeration was developed in this study. Two pilot-scale vertical flow constructed wetlands of 0.75 m2 each were constructed with the same dimensions and configuration but different media, one of which (named as CW1) was filled with a 1:1 mixture (by weight) of zeolite and dolomite and the other (named as CW2) with the same zeolite only. The oxygen transfer capability of a multilevel two-layer drop aeration device, organics and nitrogen removal of CW1 and CW2, and pollutant distribution along the depths of CW1 and CW2 in different operational phases were studied. The results demonstrated that compared with the direct drop aeration process, the multilevel, two-layer drop aeration device supplied 2–6 mg/L higher dissolved oxygen per meter of drop height, and after installation of the six-level, two-layer drop aeration devices, the 5-day biochemical oxygen demand removal load was improved from 8.1 to 14.2 g m−2 day−1 for CW1. With regard to the different filter media, nitrogen removal was improved by the adsorption of zeolite in the first year, with 5–36% higher NH 4 + –N removal efficiency of CW2 compared with that in CW1. Since it did not have a significant positive effect on phosphate removal, dolomite can be replaced by zeolite. The chemical oxygen demand removal mainly took place in the upper 15-cm filter layer in different operational phases, while nitrogen distribution along the depths of the VFCWs was different in different operational phases. In addition, as no operational problems occurred, the vertical flow constructed wetland system with drop aeration is an appropriate alternative for rural wastewater treatment, with numerous advantages of low capital and operation costs, no energy consumption, easy maintenance, high hydraulic loading rate, high pollutant removal efficiency, and no clogging.

Evaluating performance of vertical flow constructed wetland under various hydraulic loading rates in effluent polishing

The discharge of untreated wastewater or partially treated effluent and runoff from agricultural fields into water bodies is a major source of surface water pollution worldwide. To mitigate this problem, wastewater treatment using wastewater stabilization ponds and constructed wetlands have been promoted. The performance of such wastewater treatment systems is strongly dependent on their hydraulics, which if not properly considered during design or operation, may result in the partially treated effluent being discharged into water bodies. This paper presents results from a study that was carried out to evaluate the performance of a vertical flow constructed wetland system under varying hydraulic loading regimes. The influent and effluent samples from the constructed wetland were collected and analysed for physical, chemical and biological parameters of importance to water quality based on recommended standard laboratory methods. The data collected was useful in determining the treatment efficiency of the wetland. The hydraulic loading rate applied ranged between 0.014 and 0.174 m/day. Phosphorus reduction for the different hydraulic loading rates ranged between 92 and 47% for lowest and highest loading rates applied respectively. However, ammonium nitrogen reduction was not significantly affected by the different hydraulic loading rates, since the reduction ranged between 97 and 94%.

STELLA software as a tool for modelling phosphorus removal in a constructed wetland employing dewatered alum sludge as main substrate

A dynamic simulation model was developed for the removal of soluble reactive phosphorus (SRP) from the vertical flow constructed wetlands (VFCW) using a dynamic software program called STELLA (structural thinking, experiential learning laboratory with animation) 9.1.3 to aid in simulating the environmental nature and succession of relationship between interdependent components and processes in the VFCW system. In particular, the VFCW employed dewatered alum sludge as its main substrate to enhance phosphorus (P) immobilization. Although computer modelling of P in treatment wetland has been well studied especially in recent years, there is still a need to develop simple and realistic models that can be used for investigating the dynamics of SRP in VFCWs. The state variables included in the model are dissolved phosphorus (DISP), plant phosphorus (PLAP), detritus phosphorus (DETP), plant biomass (PLBI) and adsorbed phosphorus (ADSP). The major P transformation processes considered in this study were adsorption, plant and microbial uptake and decomposition. The forcing functions which were considered in the model are temperature, radiation, volume of wastewater, P concentration, contact time, flow rate and the adsorbent (i.e., alum sludge). The model results revealed that up to 72% of the SRP can be removed through adsorption process whereas the uptake by plants is about 20% and the remaining processes such as microbial P utilization and decomposition, accounted for 7% SRP removal based on the mass balance calculations. The results obtained indicate that the model can be used to simulate outflow SRP concentration, and it can also be used to estimate the amount of P removed by individual processes in the VFCW using alum-sludge as a substrate.

Phosphorus removal by laboratory-scale unvegetated vertical-flow constructed wetland systems using anthracite, steel slag and related blends as substrate

This research aimed to investigate the phosphorus (P) removal of a series of laboratory-scale unvegetated vertical-flow constructed wetland systems using anthracite, steel slag and related blends as substrate in treatment of low concentration domestic sewage. The long-term performance of P removal was firstly studied by using single substrate of anthracite or steel slag, and three systems applying various combined substrates were investigated when the average P loading rate varied between 0.9 and 1.5 g TP/m2 x d. The results demonstrated that both anthracite and steel slag systems were highly effective in removing total P (CTP, 77.17 +/- 23.34% and 90.26 +/- 4.48%) and soluble reactive P (SRP, 92.14 +/- 12.56% and 96.20 +/- 2.58%). The system filled with anthracite, vermiculite and steel slag from the top down removed 82.45 +/- 9.52% and 87.83 +/- 8.58% of TP and SRP, respectively. However, other combined substrate systems showed comparative low and fluctuant P removal. The effluent pH was maintained at 7-9, which met environmental requirements of China. Therefore, anthracite provides a long-term high efficiency of P removal and may be a promising substrate from the standpoint of the effluent pH, and the arrangement of combined substrate has a prominent effect on P removal.

Estimation of nitrogen dynamics in a vertical-flow constructed wetland

The vertical-flow constructed wetland (VFCW) is a promising engineering technique for removal of excess nutrients and certain pollutants from wastewater and stormwater. The aim of this study was to develop a model using the STELLA software for estimating nitrogen (N) dynamics in an artificial VFCW (i.e., a substrate column with six zones) associated with a growing Cyperus alternifolius species under a wetting (wastewater) -to-drying ratio of 1:3. The model was calibrated by our experimental data with a reasonable agreement prior to its applications. Simulations showed that rates of NH 4 +-N and NO 3 −-N leaching decreased with increasing zone number (or column depth), although such a decrease was much more profound for NH 4 +-N. Our simulations further revealed that rate of NH 4 +-N leaching decreased with time within each zone, whereas rate of NO 3 −-N leaching increased with time within each zone. Additionally, both the rates of NH 4 +-N and NO 3 −-N leaching through zones followed the water flow pattern: breakthrough during wetting period and cessation during drying period. In general, the cumulative amounts of total nitrogen (TN) were in the following order: leaching > denitrification > uptake > settlement. About 54% of the TN from the wastewater flowed out of the VFCW system, 18% of TN lost due to denitrification, 6% of TN was taken up by roots of a single plant (one hill), and the rest of 22% TN from the wastewater was removed from other mechanisms, such as volatilization, adsorption, and deposition. This study suggested that to improve the overall performance of a VFCW for N removal, prevention of N leaching loss was one of the major issues.

Enhanced removal of organic matter and ammonia nitrogen in a one‐stage vertical flow constructed wetland system

AbstractA modified cyclic batch constructed wetland was innovated to examine the removal of organic matter and ammonia nitrogen from rural wastewater in the eastern area of China. The results demonstrated that mean percentage removal of BOD5 and NH‐N in the modified cyclic batch constructed wetland treating rural wastewater were 80 and 97%, respectively. Compared with conventional constructed wetland systems, the quality of effluent from the modified cyclic batch constructed wetland was higher when treating rural wastewater. The predominant process for BOD5 removal was aerobic biodegradation and biomass assimilation in the system, which accounted for more than 99% of total removal. Mass balance calculation of NH‐N showed that the average rate of nitrification was 6.247 g m−2 day−1, which was 7.5 times more than the amount removed by biomass assimilation. The supply of oxygen by the modified methods in the modified cyclic batch constructed wetland was significantly high for available oxygen, which was 76.984 g m−2 day−1, much higher than the demand for rural wastewater treatment. © 2009 American Institute of Chemical Engineers Environ Prog, 2010

Comparison of single-stage and a two-stage vertical flow constructed wetland systems for different load scenarios

Constructed wetlands (CWs) are known to be robust wastewater treatment systems and are therefore very suitable for small villages and single households. When nitrification is required, vertical flow (VF) CWs are widely used. This contribution compares the behaviour and treatment efficiencies of a single-stage VF CW and a two-stage VF CW system under varying operating and loading conditions according to standardized testing procedures for small wastewater treatment plants as described in the European standard EN 12566-3. The single-stage VF CW is designed and operated according to the Austrian design standards with an organic load of 20 g COD m(-2) d(-1) (i.e. 4 m(2) per person equivalent (PE)) The two-stage VF CW system is operated with 40 g COD m(-2) d(-1) (i.e. 2 m(2) per PE). During the 48 week testing period the Austrian threshold effluent concentrations have not been exceeded in either system. The two-stage VF CW system showed to be more robust as compared to the single-stage VF CW especially during highly fluctuating loads at low temperatures.

Seasonal and Spatial Changes of Microorganism Communities in Constructed Wetlands: A Community Level Physiological Profiling Analysis

In constructed wetlands, microorganisms associated with plants are assumed to play a major role. A one-year survey was conducted in five vertical flow constructed wetland systems that had been operating from 2 months to 8 years in small French villages (100–500 People Equivalent) to provide a better understanding of microbiological activity. The objective of our study was to highlight the most important factor generating variability between microorganisms communities compared to treatment performances. Results of community level physiological profiling using Biolog Ecoplates were analyzed using principal component analysis. The greatest microbial activity was observed in the oldest wetland during summer. Profiles of fed and rest bed were differentiated by the nature of the main carbon source metabolized. Whereas carbohydrates and carboxylic acids appeared to be better assimilated with fed beds, it seemed that phosphate compounds as well as amines allowed better growth in the plates inoculated with samples of rest beds. In all fed beds, the most important parameters affecting the diversity were the season and the age of the wetlands. There were only slight profile differences between surface and subsurface samples and between the first and second stage samples.

Hydraulic behaviour of vertical‐flow constructed wetland under different operating conditions

Five vertical‐flow constructed wetland (VFCW) units planted with cattail (Typha augustifolia) were used to study the effects of feeding (continuous and batch), hydraulic loading rates (HLR) and drainage patterns (free drainage and percolate impounding) on hydraulic behaviour. The tracer studies were divided into two parts: (i) continuous feeding at an HLR of 0.005, 0.025, 0.05, 0.075, 0.1 and 0.3 m3 m−2 d−1 operating at different drainage patterns (i.e. free drainage and percolate impounding) and (ii) batch feeding at different water levels of percolate impounding (20, 30 and 40 cm). The results revealed that although the hydraulic behaviour of VFCW systems was strongly dependent on the operating pattern (feeding and drainage), it was not significantly affected by the hydraulic loading rate. The results of continuous feeding study concluded that (a) percolate impounding achieved an increase in HRT that was 1.6 times the HRT with free drainage, (b) the dispersion in both drainage patterns were moderate, and (c) the results from the tank‐in‐series (TIS) model correlated more closely with the data observed than with the dispersion plug flow (DPF) model. For batch feeding and percolate impounding, a uniform flow distribution of the tracer occurred in the water column after 2.1, 3.1 and 4.4 days for 20, 30 and 40 cm, respectively.

High-rate nitrogen removal in a two-stage subsurface vertical flow constructed wetland

A two-stage constructed wetland (CW) system consisting of two vertical flow (VF) beds with intermittent loading operated in series has been investigated. The first stage uses sand with a grain size of 2–3.2mm for the main layer and has a drainage layer that is impounded; the second stage uses sand with a grain size of 0.06–4mm and a conventional drainage layer. The two-stage system was operated with an organic load of 40 gCODm−2d−1 for the whole system, that is with a specific surface area requirement of 2 m2 per person equivalent. The system was operated over a period of 2 years including two full winter seasons. No operational problems occurred, and the Austrian effluent standards for organic matter and ammonium nitrogen could be met during the whole investigation period. Additionally, average nitrogen removal efficiencies of 53% and average nitrogen elimination rates of 2.7 g Nm−2d−1 and 986 g Nm−2yr−1, respectively, could be achieved without recirculation, thus allowing construction with energy-free loading systems. It can be concluded that a better effluent quality can be reached with such two-stage systems as compared to a conventional single-stage VF CW system with intermittent loading, even if the two-stage system is loaded with the double organic load and therefore has only half of the specific surface area requirement.

Forms, patterns and extractability of phosphorus retained in alum sludge used as substrate in laboratory-scale constructed wetland systems

This study examined the form, pattern and extractability of phosphorus (P) retained in alum sludge (an aluminium-containing drinking water treatment residual in dewatered cake form), which was used as substrate in laboratory-scale constructed wetland systems for P-rich wastewater treatment. Used alum sludge samples from successive depth ranges in the laboratory-scale vertical flow constructed wetland systems were examined for KCl extractable P. The samples were also sequentially fractionated into two main categories consisting of readily available P and P forms that are not easily decomposed. The extracted fractions included labile P, microbial P, (Fe + Al) P, humic P, (Ca + Mg) P and residual P. A major proportion of P retained in the used alum sludge was in forms that are not easily decomposed. Of the P forms that are not easily decomposed, the P associated with Ca and Mg accounted for a higher proportion of the inorganic fraction as compared to the P associated with the Fe and Al. The results also show that in most cases, the concentration of the P forms decreased with increasing depth from the topmost surface of the alum sludge in the systems.

Treatment of high-strength wastewater in tropical vertical flow constructed wetlands planted with Typha angustifolia and Cyperus involucratus

The ability of vertical flow (VF) constructed wetland systems to treat high-strength ( ca. 300 mg L −1 of COD and ca. 300 mg L −1 total-nitrogen) wastewater under tropical climatic conditions was studied during a 5-month period. Nine 0.8-m diameter experimental VF units (depth 0.6 m) were used: three units were planted with Typha angustifolia L., another three units were planted with Cyperus involucratus Rottb and three units were unplanted. Each set of units were operated at hydraulic loading rates (HLRs) of 20, 50 and 80 mm d −1. Cyperus produced more shoots and biomass than the Typha, which was probably stressed because of lack of water. The high evapotranspirative water loss from the Cyperus systems resulted in higher effluent concentrations of COD and total-P, but the mass removal of COD did not differ significantly between planted and unplanted systems. Average mass removal rates of COD, TKN and total-P at a HLR of 80 mm d −1 were 17.8, 15.4 and 0.69 g m −2 d −1. The first-order removal rate constants at a HLR of 80 mm d −1 for COD, TKN and total-P were 49.8, 30.1 and 13.5 m year −1, respectively, which is in the higher range of k-values reported in the literature. The oxygen transfer rates were ca. 80 g m −2 d −1 in the planted systems as opposed to ca. 60 g m −2 d −1 in the unplanted systems. The number of Nitrosomonas was two to three orders of magnitude higher in the planted systems compared to the unplanted systems. Planted systems thus had significantly higher removal rates of nitrogen and phosphorus, higher oxygen transfer rates, and higher quantities of ammonia-oxidizing bacteria. None of the systems did, however, fully nitrify the wastewater, even at low loading rates. The vertical filters did not provide sufficient contact time between the wastewater and the biofilm on the gravel medium of the filters probably because of the shallow bed depth (0.6 m) and the coarse texture of the gravel. It is concluded that vertical flow constructed wetland systems have a high capacity to treat high-strength wastewater in tropical climates. The gravel and sand matrix of the vertical filter must, however, be designed in a way so that the pulse-loaded wastewater can pass through the filter medium at a speed that will allow the water to drain before the next dose arrives whilst at the same time holding the water back long enough to allow sufficient contact with the biofilm on the filter medium.

Enhanced removal of organic matters and ammonia nitrogen in a one-stage vertical flow constructed wetland system

Enhanced removal of organic matters and ammonia nitrogen in a one-stage vertical flow constructed wetland system

A two-stage subsurface vertical flow constructed wetland for high-rate nitrogen removal

By using a two-stage constructed wetland (CW) system operated with an organic load of 40 gCOD.m(-2).d(-1) (2 m2 per person equivalent) average nitrogen removal efficiencies of about 50% and average nitrogen elimination rates of 980 g N.m(-2).yr(-1) could be achieved. Two vertical flow beds with intermittent loading have been operated in series. The first stage uses sand with a grain size of 2-3.2 mm for the main layer and has a drainage layer that is impounded; the second stage sand with a grain size of 0.06-4 mm and a drainage layer with free drainage. The high nitrogen removal can be achieved without recirculation thus it is possible to operate the two-stage CW system without energy input. The paper shows performance data for the two-stage CW system regarding removal of organic matter and nitrogen for the two year operating period of the system. Additionally, its efficiency is compared with the efficiency of a single-stage vertical flow CW system designed and operated according to the Austrian design standards with 4 m2 per person equivalent. The comparison shows that a higher effluent quality could be reached with the two-stage system although the two-stage CW system is operated with the double organic load or half the specific surface area requirement, respectively. Another advantage is that the specific investment costs of the two-stage CW system amount to 1,200 EUR per person (without mechanical pre-treatment) and are only about 60% of the specific investment costs of the singe-stage CW system.

The use of vertical flow constructed wetlands for on-site treatment of domestic wastewater: New Danish guidelines

Official guidelines for the on-site treatment of domestic sewage have recently been published by the Danish Ministry of Environment as a consequence of new treatment requirements for single houses and dwellings in rural areas. This paper summarises the guidelines for vertical constructed wetland systems (planted filter beds) that will fulfil demands of 95% removal of BOD and 90% nitrification. The system can be extended with chemical precipitation of phosphorus with aluminium polychloride in the sedimentation tank to meet requirements of 90% phosphorus removal. The necessary surface area of the filter bed is 3.2 m 2/person equivalent and the effective filter depth is 1.0 m. The filter medium must be filtersand with a d 10 between 0.25 and 1.2 mm, a d 60 between 1 and 4 mm, and a uniformity coefficient ( U = d 60/ d 10) less than 3.5. The sewage is, after sedimentation, pulse-loaded onto the surface of the bed using pumping and a network of distribution pipes. The drainage layer in the bottom of the bed is passively aerated through vertical pipes extending into the atmosphere in order to improve oxygen transfer to the bed medium. Half of the nitrified effluent from the filter is recirculated to the first chamber of the sedimentation tank or to the pumping well in order to enhance denitrification and to stabilise the treatment performance of the system. A phosphorus removal system is installed in the sedimentation tank using a small dosing pump. The mixing of chemicals is obtained by a simple airlift pump, which also circulates water in the sedimentation tank. The vertical flow constructed wetland system is an attractive alternative to the common practice of soil infiltration and provides efficient treatment of sewage for discharge into the aquatic environment.

The performance of vertical flow constructed wetland systems with special reference to the significance of oxygen transfer and hydraulic loading rates

The paper reviews the development of the vertical flow (VF) reed beds/constructed wetlands over the past 20 years. The performance of VF systems (and their use within hybrid systems) is analysed by reference to a number of brief case studies. The oxygen transfer rate (OTR) achieved is absolutely critical to the sizing of the systems. The author reviews the reported OTRs and comments on the existing design equations proposed for calculation of the area of beds. The 1st generation of VF systems used a set of parallel beds that were dosed one at a time in rotation and then rested for a period of days because there was considerable concern (based on early experience) that they would become clogged. In the past 10 years a number of new designs of 2nd generation VF beds have been built which make use of a single bed and hence operate without any resting periods. The hydraulic loading rate and the selection of the bed media, which are critical to the design and hence successful operation of these 2nd generation compact VF beds, are described. It is now possible to produce a very high quality of effluent from VF beds alone sized at 2 m2/pe when treating domestic sewage.

Removal of indicator bacteria from municipal wastewater in an experimental two-stage vertical flow constructed wetland system

The removal of sanitary indicator bacteria (total coliforms, faecal coliforms, and faecal streptococci) was studied in an experimental constructed wetland system consisting of (1) a 2-m3 three-chamber sedimentation tank, (2) a 5 m2 vertical flow constructed wetland, (3) a filter-unit with calcite aimed at removing phosphorus, and (4) a 10 m2 vertical flow constructed wetland. The indicator bacteria were enumerated before and after each unit of the wetland system during four monitoring episodes with different loading conditions. At a hydraulic loading rate of 520-1,370 mm/d, the first-stage vertical flow beds removed about 1.5 log-units of total coliforms, 1.7 log-units of faecal coliforms and 0.8 log-units of faecal streptococci. In the second stage bed receiving lower loadings both in term of concentration and quantity (260-690 mm/day), the eliminations were lower. It was not possible in the present study to identify any seasonal effects, but no measurements were done during summer. Recycling of treated effluent back to the sedimentation tank did not affect elimination. Area-based rate constants for the vertical flow wetland receiving effluent from the sedimentation tank averaged 3.2 m/d for total coliforms, 3.3 m/d for faecal coliforms and 2.1 m/d for faecal streptococci. The rate constants depended on loading rates. It is suggested that filtration is a major removal mechanism for bacterial indicator organisms in vertical flow constructed wetland systems.

Phosphorus removal from municipal wastewater in an experimental two-stage vertical flow constructed wetland system equipped with a calcite filter

Laboratory studies have indicated that calcite may be used in separate, exchangeable filter units in constructed wetland systems to remove phosphorus. Based on these studies we built a full-scale experimental constructed wetland with a calcite-based filter unit to study its performance, under real-life conditions. The system consists of a 2-m3 sedimentation tank and two vertical flow constructed wetlands. The system has three 0.09 m3 calcite filter-units to study phosphorus removal. The hydraulic loading rate varied between 1.7 and 6.2 m3/d. The residence time in filters ranged from 28 to 99 minutes. Overall the system removed 62 +/- 18% of phosphorus. The removal in the calcite filter was initially good, but after three months all P-filters were saturated. The calcite increased pH by approximately half a unit and released calcium. A total of about 2.2 kg P/m3 calcite was removed by the filter. The first-stage bed receiving effluent from the sedimentation tank consistently removed phosphorus, whereas the second bed sometimes released phosphorus. The first order area-based removal rate constant for total-P in the vertical bed averaged 0.24 +/- 0.20 m/d and was highly dependent on the loading rate. This shows that first order removal kinetics do not satisfactorily describe removal of phosphorus in vertical flow constructed wetland systems with unsaturated flow.

Compact vertical flow constructed wetland systems - first two years’ performance

In order to move towards optimising wastewater treatment performance by vertical down-flow reed beds, user and installer demands were applied to design, resulting in the "compact vertical flow reed bed" (CVF bed). Performance data are presented for the two years since commissioning a CVF bed and pond system serving eight residents. Particular emphasis was placed on investigating oxygen transfer rate and susceptibility to hydraulic overloading. Average percentage concentration reduction effected by single passage through the bed exceeded 97% for suspended solids and biochemical oxygen demand, and 90% for ammoniacal nitrogen and total Kjeldahl nitrogen. The occurrence of nitrification and denitrification (up to 58%) within the same bed was clearly indicated. Percentage ortho-phosphate removal averaged 92% over the first 17 months' operation and thereafter fell to approximately 45%. Faecal coliform density underwent an almost four log reduction. Oxygen transfer rate within the reed bed was between 28-36 gO2/m2 x d. Normal operation was maintained until six times dry weather hydraulic load rate was exceeded, at which point surface flooding occurred. The capacity of a single vertical flow reed bed to achieve effective treatment of domestic sewage was demonstrated, with no requirement for reduced load rates, promising substantial advantages over established approaches.