Reed Beds Research Articles

Reed bed treatment systems for sewage treatment in the United Kingdom — The first 10 years' experience

The UK Water Industry first became interested in Reed Bed Treatment Systems for sewage in 1985. Early problems were experienced with soil-based horizontal-flow systems of the Root Zone type. The problems were overcome by national co-ordination of a development programme and international co-operation by an EC Expert Contact Group. A number of different types of systems have now been developed and the systems are now being accepted. The paper reviews the development of these systems for secondary and tertiary treatment and nitrification and mentions development of systems for other forms of treatment. The design changes made to overcome the problems are described. These include the gradual move to the use of gravel-based systems because of the difficulty experienced with over-land flow in the soil systems. The sizing of the systems is described together with performance data for the original horizontal-flow and the more recently developed vertical-flow systems. Treatment at secondary and tertiary levels is illustrated and the potential for nitrification. Early problems with reed growth have been overcome by planting with port-grown seedlings.After 10 years the process is generally accepted by the Water Industry as an appropriate treatment for villages and there are now between 200 and 300 systems in operation.

Constructed wetland systems for water pollution control in North China

Constructed wetland systems are a low-cost, low-energy-consumption and effective technology for water pollution control used increasingly in recent years in China. In this paper, the land treatment systems in China are introduced, the constructed wetland systems in North China are detailed, and the integrated reed bed wetland-lagoon system, as an advanced constructed wetland system, is compared with other land treatment systems. Lastly, the authors elaborate their opinion on problem “wetlands occupy larger lands” and energetically advocate to develop this new land treatment technique in China.

Using reed beds for winter operation of wetland treatment system for wastewater

If a Constructed Infiltration Wetland Treatment System (CIW-TS) with reed beds for wastewater could regularly operate and get the desired treatment efficiency during cold winter, the system would realize all-year-round operation. The technology presented is the result of a pilot scale treatment system in Tianjin, north China, one that successfully operated for two years. A characteristic of the technology is that the system could regularly operate under ice layers when the average temperature was lower than −4°C. Wastewater percolates through the thick soil layer in a horizontal direction. Effluent quality is better than secondary treatment level, e.g. BOD5<20 mg/l, SS<20 mg/l, TN<15 mg/l, TP<0.6 mg/l. A yearly hydraulic loading rate of 14–20 m is appropriate.

Natural treatment systems

Natural treatment systems

Late and middle pleistocene climatic change and forest development in Colombia: pollen record Funza II (2–158 m core interval)

Late and middle pleistocene climatic change and forest development in Colombia: pollen record Funza II (2–158 m core interval)

Choice of singing sites by male bushcrickets (Tettigonia viridissima) in relation to signal propagation

The spatial dispersion of singing male bushcrickets (Tettigonia viridissima) in a marshland habitat was found to be significantly clumped. Males clustered in patches of taller vegetation, buth within such clusters, males were regularly spaced with a mean distance of 6 m between nearest-neighbours. Males occupied perches on plants that were, on average, 0.3 m above the top of surrounding vegetation. Physical and acoustical interactions between males were observed more frequently when males were singing from higher sites. Excess attenuation of the male song was found to increase with frequency but decreased markedly with increasing elevation of the singing male above the ground. The maximum detection range of the song, realized when the insect was singing > 1 m above the surrounding vegetation, was estimated as 60 m for the fundamental frequency (10 kHz), 38 m for the 1st harmonic (20 kHz) and 14 m for the second harmonic (30 kHz). By contrast, when males sang from the middle of dense reed beds, the estimated detection distance was only 8 m, 6 m and 4 m for each frequency band, respectively. Males could have increased the detection range of their songs almost three fold by singing from higher positions than those usually observed in the field. This suggests that there may be a cost of singing at higher elevations such as an increased risk of predation and/or increased aggression from neighbours. We suggest the spacing strategy adopted by males reflects a compromise between maximizing the range over which their songs can be detected and accurately localized by females and minimizing interference from competing males.

Dynamics of Heavy Metals in Soils of a Reed Bed System

Abstract Heavy metal balances of a reed bed system (soil pH > 7, carbonate content about 30%) continuously flooded with sewage during 5 years indicate that only Pb, Zn, Cd and Cu were partly stored in the soil. Strong reductive conditions, high sewage percolation and metal complexation with soluble organic compounds caused a considerable leaching of Fe, Mn, Ni and Cr from the soil and formation of amorphous iron oxides. The results indicate that continously flooded reed bed systems with high percolation rates are not suitable for the elimination of heavy metals. Conversely, it should be possible to purify metal contaminated soils through percolation of sewage with low metal content.

The Effects of Conservation Management of Reed Beds. II. The Flora and Litter Disappearance

1. The effects of management were determined by comparing pairs of adjacent cut and uncut reed (Phragmites australis) beds at 12 sites, and by a randomized block experiment at a further site in which plots of reed were cut, burnt or left unmanaged. 2. Most plant species were more abundant in the managed reed beds than the unmanaged ones, and only three were more abundant in the unmanaged beds. Several were more common in burnt than cut plots. 3. Reeds were shorter and at higher densities where cut or burnt than where unmanaged. The proportion of reed flowering stems was highest in burnt plots. 4. The rate of decomposition of reed leaf litter at the experimental site was determined by weight loss from litter bags and leaf bundles. There was no difference in weight loss and no difference in associated soil invertebrates between treatments. 5. However, weight loss was inversely related to water depth in the plots and after 6 weeks correlated with the number of Oligochaetes, Psychodid larvae and some Coleoptera. 6. Cutting and burning positively affected floristic diversity and most marsh plants, but had no effect on the rate of litter breakdown.

The Effects of Conservation Management of Reed Beds. I. The Invertebrates

1. A replicated experiment was done in plots in a stand of reed (Phragmites australis) which were cut, burnt or left unmanaged. Invertebrates in the soil were sampled by heat extraction and hand-sorting, and those above ground by water traps, dissection of reed stems and in situ counting. 2. Only a few families showed differences between treatments, and this number declined with time after treatment. After 1 year, no soil invertebrates and only a few families of above-ground invertebrates showed any significant treatment effects. 3. Most treatment effects were between the unmanaged control and both cut and burnt plots. A significant difference between cut and burnt treatments was recorded for only one family, with numbers lower in the cut plots. 4. Total number of invertebrates, species-richness, species diversity and evenness showed no relationship with treatment. 5. Many soil invertebrates were more abundant in drier parts of the reed bed, but there was no similar effect on above-ground invertebrates.

Treatment of dairy farm wastewaters in engineered reed bed systems

The objective of an engineered reed bed is to manage the natural growth of the reeds in order to optimise the processing of the wastewater to be purified. Downflow reed beds, with two treatment stages, have been added in front of a previously installed horizontal flow bed on a dairy farm to treat parlour washings and standing yard wastewater. Recent results have shown that the BOD is being reduced from an average of 1006 mg/litre at the inlet to only 57 mg/litre at the exit from the small final lagoon.

A botanical approach to the treatment of wastewaters

A number of investigations are in progress worldwide into the ability of aquatic plants to purify wastewaters from domestic, industrial and agricultural sources. Most of the studies in the U.K. are being conducted by the Water Authorities into the treatment of sewage using engineered beds of the common reed, Phragmites australis, under horizontal flow conditions. At the University of Birmingham Phragmites are being studied for the treatment of agricultural effluents which are significantly more polluting than sewage. Two reed beds have been constructed on farms and some initial results are given in the paper. The use of reed beds employing downward flow of wastewater may give improved treatment performance in the future.

Fish predation and habitat complexity: are complexity thresholds real?

Empirical data have suggested the existence of a substratum complexity threshold below which predation rates are not affected by variations in habitat complexity. Complexity thresholds might either be real, resulting from switching of predator behavior, or artifacts of experimental designs, resulting from too few experimental treatments broadly separated in habitat complexity or from inadequate statistical power of the experiment. Experimental work with perch Perca fluviatilus L. and stickleback Pungitius pungitius L. prey in simulated reed beds utilized extensive replication (20) of 11 habitat complexity treatments to examine this question. Predation rates were a linear function of habitat complexity level. This linear function accurately predicted predation rates for higher complexity levels than initially used, suggesting that no complexity threshold occurred for perch. Although these results argue against the existence of habitat complexity thresholds, additional tests with other predators will be necessary to answer this question.

The use of Reed Bed Treatment Systems in the UK

This paper summarises the British experience of Reed Bed Treatment Systems (RBTS) for sewage treatment over the past three years. It includes a list of the 26 systems which have been built together with their design details including, length, width, slope, media and the loading that they are designed for. Comment is made about the use of soil and gravel growth media. Different inlet and outlet arrangements are described. The alternative propagation and planting methods are reviewed. The paper closes with the performance data from a number of the UK systems. The performance of the British beds indicates that RBT Systems may be adequate for BOD and SS removal but the removal of phosphorus and nitrogen is not as high as predicted elsewhere.

Gas exchange through the soil-atmosphere interphase and through dead culms of phragmites australis in a constructed reed bed receiving domestic sewage

The decomposition processes of organic matter during winter in a 3-year old soil-based constructed reed bed with lateral sub-surface water flow were evaluated by quantifying the in- and efflux of metabolic gases and by considering input-output budgets and relating these to storages within the bed. The total flux of gaseous oxygen into the bed was 5.86 g m −2 day −1 of which 2.08 gm −2day −1 was through the cavities of dead, still standing culms of Phragmites australis. The respiratory oxygen consumption of the roots and rhizomes almost perfectly balanced the oxygen influx through the culms leaving only 0.02 g O 2 m −2 day −1 to be released to the surrounding soil. The macrophyte-induced rhizosphere oxygenation was therefore of no quantitative importance for aerobic BOD degradation and microbial nitrification. Organic matter was degraded aerobically by means of oxygen delivered directly from the atmosphere and anaerobically by methanogenic bacteria in the upper layers of the soil. Some nitrogen and phosphorus was retained with sludge deposition on the surface of the bed and in the inlet trench. The constructed reed bed under study did not function according to the theory of the root-zone process. The majority of the wastewater moved along preferred pathways on the surface of the bed because of low soil hydraulic conductivity. Changes in the physical design and the operational practice of constructed reed beds needed to improve and optimize performance efficiency for nutrients are discussed.

Den postglaciale landskapsutviklingen på Dragvoll universitetsområde, Trondheim

Stratigraphic studies, pollen analyses and 14C-datings have revealed the landscape evolution at the university area at Dragvoll since it was deglaciated. In the central bog area the nearly 50 m deep glaciofluvial clay is overlain by (a) marine clay mud deposited 11,500 years ago, when the area up to 175–180 m was a branch of Trondheimsfjorden, (b) limnic nekron mud precipitated after 10,500 BP, when the central part of the area became a lake, (c) telmatic peat formed after 8500 BP, when the lake changed into a reed and sedge swamp, and (d) terrestric peat formed after the sedge swamp 6000 years ago shifted into a peat bog. Open birch-juniper forest shifted 9500 years ago into dominant pine forest and 8500 years ago into local alder forest surrounded by hazel and elm groves which culminated 6500 years ago. Elm and hazel had disappeared 4000 years ago, whereas only pine, birch and alder remained. After 1300 BP spruce became dominant. Local grain raising might have started in the Bronze Age, but a more radic...

Sewage Treatment in Constructed Reed Beds – Danish Experiences

The working experiences from twenty-five Danish constructed reed beds are summarised. The removal efficiency with respect to BOD is typically 70-90% after one growing season producing a consistent effluent concentration of less than 20 mg/l. The typical reduction of total-nitrogen and total-phosphorus is 25-50% and 20-40%, respectively. The poor performance with respect to nitrogen and phosphorus can be ascribed to (a) surface run-off (low permeability of the soil) which prevents the sewage from getting into the rhizosphere, and (b) insufficient release of oxygen from the root-system of the reeds to secure a quantitative significant nitrification. The nutrient removal is therefore dependent on the hydraulic loading rate. Only reed beds with loading rates of less than 2 cm/d show a purifying effect in respect of nitrogen and phosphorus better than 50%. The hydraulic permeability of the soil develops slowly, if ever. Even after four growing seasons overland flow predominates, typically forming a pattern covering only a part of the reed bed area. However, as most of the Danish reed beds are constructed on sites with no demand for nutrient removal, the systems function satisfactorily from the point of view of meeting the discharge standards.

Land‐Treatment Systems: Design and Performance with Special Reference to Reed Beds

AbstractThe principles of design of a land treatment system are explained on the basis of determining the land area requirements of particular constituents in terms of the supply rate and assimilative capacity. Illustrative data are provided for the design and performance of slow‐rate and overland flow systems.The paper includes a comprehensive report on the design and performance of pilot studies carried out on a reed‐bed treatment system at Valleyfield, Fife, Scotland. This provides valuable insight into the choice of the bed substrate and the problems of reed establishment. Of the media tested, coarse pulverized fuel ash appeared to be promising in terms of its hydraulic conductivity and reduction in biochemical oxygen demand. For a domestic sewage of typical strength, a bed area of 5 m2 per population equivalent yielded an effluent having a BOD of less than 20 mg/1, but did not provide conditions which were conducive to significant nitrogen removal.

Sewage Treatment by Reed Bed Systems

ABSTRACTIn the past five years sewage‐treatment systems, based on artificial reed beds, have created much interest in Europe. In the UK, reed bed treatment systems have attracted this interest because of their potential for producing cost‐effective treatment for small communities. In 1985 a UK coordinating group was established to produce an integrated research and development programme for evaluating the process.This paper briefly describes the principles lying behind reed bed treatment systems, and outlines the progress which has been made to January 1988. The results of performance from eight full‐scale and pilot‐scale systems are presented in detail.

OILED SEDIMENTS IN THE HUMBER ESTUARY FOLLOWING THE SIVAND INCIDENT

ABSTRACT The Sivand oil spill of September 28, 1983, was unusual in that 6,000 t of crude oil were spilled in a highly turbid estuary. This study aimed to contribute to knowledge of spatial and temporal oil distribution and to examine its degradation. The role of suspended particulate matter (SPM) in the fate of oil is discussed, but the study concentrates on stranded oil in two sedimentologically distinct shorelines where ecological and conservation interests are high. The sites were Humberston Fitties, a sand flat, and Blacktoft Sand, a muddy shore in the inner estuary. Methods used were replicate sediment core sampling followed by gas liquid chromatography (GLC) and included ancillary sediment analyses. Soon after the spill, the sand total hydrocarbon (THC) concentration was greater than 50,000 ppm. Over 12 months this concentration decreased to about 3,000 ppm, as expected in coarser sediments. The muds were initially less contaminated (about 2,000 ppm), with only slight reductions in concentration over 12 months. However, there was strong evidence of sediment mobility at this site, and natural cleanup was in fact nearly complete after 9 months; the oil found at 12 months was due to transport of Sivand oil-contaminated muds from nearby reed beds. Good drainage at both sites permitted initial oil penetration. Root macropores at the muddy site encouraged penetration, weathering, and release of oil more easily than if it had been found in the sediment matrix. Sediment mobility at the muddy site contrasted with the firmness of the oiled sandflat, and contrary to vulnerability indices, may imply more rapid oil removal under some circumstances. Water washing was implicated as a major process in oil degradation at the sandy site, but no dramatic sediment turnover or erosion occurred that might have removed the oil. The steep gradients in oil concentration and composition with depth contrasted with the muddy site, where oil penetrated as a coherent mass via root macropores. The study illustrates the importance of sedimentological factors in the fate, effects, and mass balance of spilled oil. Published work on the Sivand has emphasized the effectiveness of cleanup and the lack of biological effects, but may have underestimated the amount of oil trapped in sediments.

A low-cost effective trap for use in sampling aquatic fauna

Reed beds, rocky shores and undercut bands are difficult to sample faunistically, using standard netting equipment. Traps, however, provide an effective means for sampling such areas. We have developed a variation based on the popular cylindrical trap design, using commercially available plastic mesh. The resulting trap is efficient, low-cost, easy to construct, light weight, and not subject to corrosion.