Reed Bed System Research Articles

Designing a Small-scale Infra-free (IF) System for Community Applications: Managing Energy, Water and Waste

abstractThis paper explores alternative infra(structure)-free (IF) scenarios at a community level to promote machi-zukuri (community/neighborhood planning), a bottom-up decentralization approach improving citizen’ and municipality involvement in city planning in Japan. Demographic analysis in Japan shows that the population is becoming more urbanized, with an increasingly centralized infrastructure, but that per capita waste generation is increasing because the number of people in each household is decreasing; therefore, integration of the energy, water and waste (EWW) cycles becomes more important. For residents who are unconnected to centralized sewage treatment in Japan, mainly concentrated in municipalities whose population is less than 100,000, there is a lack of alternatives for wastewater treatment, except the current technically-demanding ‘joukasou’ on-site treatment system. The authors evaluated the 30-year life-cycle cost performance of three current systems with alternative (integrated-technology) IF scenarios focusing on wastewater treatment for a small community (20 households). These systems are; wastewater gardens with biogas production, an anaerobic digester gas system integrated with fuel cell technology and a heat and power unit (CHP) combined with a biogas-producing reed bed system, all of which treat wastewater and result in useful end products-, closing the life cycle with low maintenance, a lower environmental load-, and two to four times smaller development cost than centralized options in both rural and urban communities.

Use of dewatered alum sludge as a substrate in reed bed treatment systems for wastewater treatment

In this paper, two laboratory-scale simulated reed beds were investigated for the purpose of assessing the feasibility and effectiveness of using dewatered alum sludge as a possible substrate for wastewater treatment reed bed systems. One horizontal subsurface flow setup and one vertical flow setup were used. The horizontal flow system was planted with Phragmites australis while the vertical flow system was left unplanted. Thus, the latter was more akin to a sand filter system, but was examined with the potential use as a planted vertical reed bed system. The influent source used was farmyard wastewater. It is expected that the present study will provide the basis for long-term and large-scale trials in realizing the concept of integrating “waste” into treatment processes. Results obtained so far have shown that the dewatered alum sludge holds great promise as a low-cost resource media for use in reed bed treatment systems. Appreciable and stable performance was obtained during the continuous operation at high hydraulic, organic and phosphorus loadings. In particular, both wetlands achieved over 90% phosphorus removal, reflecting the significant advantage of this novel approach over conventional reed bed treatment systems. However, extensive research into possible surface clogging and possible release of some substances from the sludge to the treated effluent is necessary to ensure reliability of the system. This will help to make the alum sludge-based reed bed environmentally and economically justifiable.

Helsinge sludge reed bed system: reduction of pathogenic microorganisms

Reduction of pathogenic bacteria: Salmonella, enterococci and Escherichia coli was investigated using the sludge reed bed system. The system at Helsinge was established in 1996 and has a capacity of 630 tonnes dry solids per year and consists of 10 basins. Since 2000 the individual basins have been subjected to an average area-specific loading rate of 46-56 kg dry solids/m2/year. The total sludge residue height in April 2006 was approximately 1.40 m. The sludge (approximately 0.5-0.8% dry solids), with which the individual basins were loaded, contained a large number of bacteria. Salmonella, enterococci and E. coli were found in the sludge in the following quantities: 10-300/100 g (wet weight), 7,000-25,000 CFU/g (wet weight) and 800,000-10,000,000 CFU/100 g (wet weight), respectively. The analysis of the reduction in pathogens in the sludge residue through a period of 3-4 months after the last loading indicated that the pathogen content was reduced down to < 2/100 g (Salmonella), < 10 CFU/g (enterococci) and < 200 number/100 g (E. coli). For enterococci and E. coli the reduction was approximately log 5 and log 6-7, respectively. In the same period the sludge residue achieved a dry solids content of approximately 20-35%.

Performance of vegetated and non-vegetated vertical flow reed beds in the treatment of diluted leachate

This study was undertaken to investigate the behaviour of a vertical flow reed bed system with 3 kind of wastewaters (W1, W2 and W3) and for two hydraulic retention times (3 and 7 days) as well as to assess the role of Phragmites Australis in constructed wetland treatment processes. The adopted batch experimental system consisted of six vertical flow filters, filled with granular media and planted with reeds. For each vegetated reactor there was a correspondent blank in order to make a comparison. Wastewaters were obtained mixing tap water, MSW landfill leachate and activated sludge in different percentages. W1, W2 and W3 were designed in order to reproduce treated or untreated wastewaters not in compliance with legislation in force (Directive 91/271/EEC), with increasing level of NH4 +-N from W1 (16.3 mg/L) to W3 (76.0 mg/L). In average terms, 3 days was sufficient for W1 and W2 to face the compliance limits; while, for W3 even 7 days was not sufficient to respect the compliance limit for ammonia nitrogen (1.4 times greater). The obtained results shown that the vegetation played an essential role especially in the removal of nitrogen: for the wastewater with the highest loads the contribution of reeds in the removal of nitrogen was greater than that of biofiltration processes. The contribution of the vegetation was also detectable in the removal of orthophosphate, but with minus efficiency.

Sludge treatment and drying reed bed systems

Sludge Reed beds have been used for dewatering (draining and evapotranspiration) and mineralisation of sludge in Denmark since 1988 when the first sludge processing system was introduced. Sludge from wastewater treatment plants (2500–125 000 PE) is treated in sludge reed bed systems with 1–18 basins with loading rates of 25–2200 tonnes dry solids/year for 10 years. In 2002, approximately 95 systems were in operation. Dimensioning and design of reed bed systems depends on the sludge production rate, sludge type, quality and regional climate.The maximum sludge loading rate is approximately 50–60kg DS m−2 year−1. Loading cycles are related to the sludge type and the age of the sludge reed systems. The sludge residue will, after approximately 10 years of operation, reach an approximate height of 1.2–1.5 metres with dry solids content of 30%. The concentration of LAS and NPE (total) in the sludge residue was reduced by a total of approximately 98% and 93%, respectively. Experience has shown that the quality of the final product with respect to heavy metals, hazardous organic compounds and pathogen removal after 10 years of treatment make it possible to recycle the biosolids to agriculture as an Enhanced treated product.

Reed-Bed Technology for Treating Oil- Production Water in the Sultanate of Oman

This article, written by Technology Editor Dennis Denney, contains highlights of paper SPE 98548, "The Use of Reed-Bed Technology for Treating Oil-Production Waters in the Sultanate of Oman," by A. Al Mahruki, Sultan Qaboos U.; B. Alloway, U. of Reading; and H. Patzelt, Sultan Qaboos U., prepared for the 2006 SPE International Conference on Health, Safety, and Environment in Oil and Gas Exploration and Production, Abu Dhabi, UAE, 2–4 April. Safe and environmentally benign disposal of produced water is a major concern in the Sultanate of Oman. Petroleum Development Oman (PDO) produces 600 000 m3/d of water, which is contaminated with petroleum hydrocarbons (10 to 800 mg/L), traces of phenols, emulsifiers, and a wide range of metals at varying concentrations. It also shows a relatively high electrical conductivity. The current methods of disposal into shallow and deep aquifers are no longer meeting environmental regulations. The use of reed-bed technology for the treatment of produced water significantly reduced organic- and inorganic-contaminant concentration in the effluents. Introduction Oil production in Oman is associated with large volumes of water, termed oil-production water (OPW), and the water/oil ratio can be as high as 1:6 after preliminary separation. The volume of water produced by PDO is predicted to rise to 900 000 m3/d by 2013. Only 40% of the OPW is used to maintain reservoir pressure by injection, while the remainder is disposed of into shallow and deep aquifers. Over the last 3 decades, these methods of disposal became progressively unacceptable for various environmental reasons. A major concern was the possibility of contaminating the groundwater resources with toxic organic and inorganic contaminants. PDO's environmental policy is to invest in research projects aimed at better use of the OPW. Water-treatment and reuse plans were developed, driven by the concept of "greening the desert" by use of reed beds to treat the OPW. Reed-Bed Biotechnology There has been increasing interest in environmental biotechnologies because of their potential in removing organic and inorganic contaminants from soil, water, and waste water. For instance, reed beds are used to treat water, waste water, and effluent from different sources including household, agricultural, industrial, and mining effluents contaminated with toxic organic contaminants and heavy metals. Recent literature on phytoremediation discussed the interaction between the soil matrix, plants, and microbial population that brings about many processes responsible for cleanup of contaminants including phytoextraction, phytostabilization, rhizofiltration, and phytovolatilization. Materials and Methods A large-scale reed-bed system was set up in Nimr, in south Oman. It comprised eight beds, with each reed bed being 75×48 m (3600 m2). Each line of four reed beds is called a train and is expected to treat 1500 m3/d after the reed beds have matured. Initially, two trains were constructed (Train A and B) to treat 3000 m3/d with gradual expansion to 170 000 m3/d.

Sludge dewatering using the reed bed system in the Gaza Strip, Palestine

AbstractSludge treatment using reed beds is more attractive in the Gaza Strip than traditional sludge drying beds. Sludges having solids contents of 1–2% can be applied to reed beds at a loading of 40 cm/m2 every 2 weeks. The infiltration rate for a reed bed system is high, and the evapotranspiration rate is typically 170% of pan evaporation. The cost of sludge treatment using reed beds is 0.34 US$/m3 compared with 1.01 US$/m3 for treatment using conventional drying beds. This paper presents the results of using reed beds for sludge treatment in the Gaza Strip for 3 years.

SLUDGE TREATMENT AND DRYING REED BED SYSTEMS IN DENMARK

ABSTRACTSludge Reed beds have been used for dewatering (draining and evapotranspiration) and mineralisation of sludge in Denmark since 1988 when the first sludge processing system was introduced. Sludge from wastewater treatment plants (2,500‐125,000 pe) is treated in sludge reed bed systems with 1–18 basins with loading rates of 25–2,200 tonnes dry solids/year for ten years. In 2002, approximately 95 systems were in operation. Dimensioning and design of reed bed systems depends on the sludge production rate, sludge type, quality and regional climate.The maximum sludge loading rate is approximately 50–60 kg DS/m2/year. Loading cycles are related to the sludge type and the age of the sludge reed systems. The sludge residue will, after approximately ten years of operation, reach an approximate height of 1.2–1.5 metres with dry solids content of 30–40%. Experience has shown that the quality of the final product with respect to heavy metals, hazardous organic compounds and pathogen removal after ten years of treatment make it possible to recycle the biosolids to agriculture as an enhanced treated product.

Incidence of Class 1 Integrons in a Quaternary Ammonium Compound-Polluted Environment

Samples of effluent and soil were collected from a reed bed system used to remediate liquid waste from a wool finishing mill with a high use of quaternary ammonium compounds (QACs) and were compared with samples of agricultural soils. Resistance quotients of aerobic gram-negative and gram-positive bacteria to ditallowdimethylammomium chloride (DTDMAC) and cetyltrimethylammonium bromide (CTAB) were established by plating onto nutrient agar containing 5 microg/ml or 50 microg/ml DTDMAC or CTAB. Approximately 500 isolates were obtained and screened for the presence of the intI1 (class 1 integrase), qacE (multidrug efflux), and qacE Delta1 (attenuated qacE) genes. QAC resistance was higher in isolates from reed bed samples, and class 1 integron incidence was significantly higher for populations that were preexposed to QACs. This is the first study to demonstrate that QAC selection in the natural environment has the potential to coselect for antibiotic resistance, as class 1 integrons are well-established vectors for cassette genes encoding antibiotic resistance.

人工ヨシ湿地における植栽基盤が下水処理水の栄養塩除去に及ぼす影響

人工ヨシ湿地における植栽基盤が下水処理水の栄養塩除去に及ぼす影響

Constructed wetlands in Flanders: a performance analysis

During the last decade, the number of constructed wetlands in Flanders (Belgium) increased exponentially. Extensive data collection resulted in a database of 107 constructed wetlands that was used to evaluate certain trends and treatment performances. Design sizes vary between 1 and 2000 population equivalents (PE), with the majority of reed beds having a size smaller than 500 PE. Most reed beds are used as single treatment units, although they are sometimes also combined with other reed beds or even conventional systems. The main purpose is to treat domestic and dairy wastewater. Average removal efficiencies were lowest with free-water-surface (FWS) reed beds (chemical oxygen demand (COD), 61%; suspended solids (SS), 75%; total nitrogen (TN), 31% and total phosphorus (TP), 26%). The best overall performance was obtained with vertical flow (VF) wetlands (COD, 94%; SS, 98%; TN, 52%; TP, 70%), except for total nitrogen removal where combined reed bed systems even did better (COD, 91%; SS, 94%; TN, 65%; TP, 52%). Despite this considerable achievement in removal, the effluent nutrient concentrations of many systems remain too high and entail a tangible danger of eutrophication.

Optimising the performance of a lab-scale tidal flow reed bed system treating agricultural wastewater

A gravel-based tidal flow reed bed system was operated with three different strategies in order to investigate its optimal performance for the treatment of a high strength agricultural wastewater. According to the three strategies, individual reed beds were saturated and unsaturated with the wastewater for different periods while reasonably stable hydraulic and organic loadings were maintained. Experimental results demonstrated that the system produced the highest pollutant removal efficiencies with a relatively short saturated period and long unsaturated period, highlighting the importance of oxygen transfer into reed bed matrices during the treatment. Significant removals of some major organic and inorganic pollutants were achieved under all three operational conditions. Nitrification was not the major route of ammoniacal-nitrogen removal when the system was under high organic loading. Due to the filtration of suspended solids and the accumulation of biomass, gradual clogging of the reed bed matrices took place, which caused concerns over the long-term efficiency of the tidal flow system.

Purification capacity of a highly loaded laboratory scale tidal flow reed bed system with effluent recirculation

The purification capacity of a laboratory scale tidal flow reed bed system with final effluent recirculation at a ratio of 1:1 was investigated in this study. In particular, the four-stage reed bed system was heavily loaded with strong agricultural wastewater. Under the hydraulic and organic loading rates of 0.43 m 3/m 2·d and 1055 gCOD/m 2·d, respectively, the average removal efficiencies obtained for COD, BOD 5, SS, NH 4–N and P were 77%, 78%, 66%, 62% and 38%, respectively. Even with the high loading rates, approximately 30% of NH 4–N was converted into NO 2–N and NO 3–N from the mid-stage of the system where nitrification took place. The results suggest that the multi-stage reed bed system could be employed to treat strong wastewater under high loading, especially for the substantive mass removal of solids, organic matter and ammoniacal-nitrogen. Tidal flow combined with effluent recirculation is a favourable operation strategy to achieve this objective.

Reedbeds for greywater treatment—case study in Santa Elena-Monteverde, Costa Rica, Central America

In much of rural Latin America, untreated greywater is piped straight to the nearest street or stream while only the blackwater from the toilet is plumbed to a rudimentary septic system. This practice constitutes a discernible health risk with significant environmental impact, such as in the case of Monteverde, Costa Rica. In this case study, we present a low-cost reedbed system for the treatment of domestic greywater designed upon ecological sanitation principles. A locally available plant, Coix lacryma-jobi, has proven to be a resilient and viable emergent macrophyte in reedbed systems and is to our knowledge the first time this species has been used for wastewater treatment. An environmental services contract (ESC) was also established in an attempt to provide a sustainable maintenance scheme. The quality of the treated greywater from this system achieves the Costa Rican guidelines for wastewater reuse which indicate that the design criteria for the treatment of greywater using reedbeds will be guided by pathogen removal.

Sediment accumulation in newly constructed vegetative treatment facilities along a new major road

The A34 Newbury bypass was opened in England in November 1998. This 15 km of roadway has nine constructed vegetative treatment systems incorporating oil separators, silt traps, grass filters for primary filtration and chemical absorption, reed wetlands for secondary biofiltration, a deep water pool and outflow device to control the rate of water discharge into existing watercourses. Two of these facilities discharge stormwater into the Lambourn sites of special scientific interest (SSSI) river. An evaluation of the heavy metal levels in these two ponds (Ponds J and K) has been undertaken in the 39-month period after the opening of the bypass. Motorway-derived contaminants including Pb, Cd, Cu and Zn were evaluated within pond sediment throughout these treatment facilities. Results reveal that heavy metal levels within the treatment system that possesses a well-established reed bed system decrease rapidly though the facility. It is postulated that the high reed biomass within this facility may be primarily responsible for reducing hydraulic flow thus allowing a greater residence time for sedimentation, filtration and bioaccumulation processes.

Anti-sized reed bed system for animal wastewater treatment: a comparative study

This paper presents a comparative study on the treatment of high-strength animal wastewater in two parallel lab-scale constructed reed bed systems, namely progressively-sized system and anti-sized system, which have same configuration but different arrangement of bed media. The reed bed systems were operated in a tidal flow pattern to treat diluted pig slurry. Detailed analyses were carried out for the removal of some key pollutants including COD, BOD 5, NH 4-N, P and suspended solids. The results showed that both systems have considerable capacity for the removal of solids, organic matter and inorganic nutrients. The formation of biofilms on the surfaces of gravel media in both reed bed systems was monitored by scanning selected gravel samples using scanning electron microscopy. In general, no significant difference was detected with regard to the percentage pollutant removal in the systems. However, the anti-sized system demonstrated a clear advantage in its ability to slow down the clogging of bed media and avoid the impairment of long-term functioning and sustainability of the beds. A conceptual model was developed to predict the occurrence of the clogging. The validity of the model was tested using data from this study and from the literatures.

Removal of ammoniacal-nitrogen from an artificial landfill leachate in downflow reed beds

The fate of ammoniacal-nitrogen (NH 4-N) was studied in a lab-scale downflow reed bed system treating an artificial landfill leachate. Individual reed beds were saturated by the leachate, then drained and rinsed by tap water. NH 4-N was removed by a two-stage process, adsorption onto the reed bed media followed by nitrification into nitrite-nitrogen (NO 2-N) and nitrate-nitrogen (NO 3-N). Decrease of the NH 4-N level of the leachate was observed when the reed beds were saturated. By rinsing the beds, part of the NH 4-N adsorbed inside the bed matrices was released into the rinse water. The presence of NO 2- and NO 3-N in the rinse water demonstrated that nitrification took place while NH 4-N was retained inside the bed matrices. For artificial leachates with NH 4-N levels of 150±5 mg/l, an average removal rate of 44% in a 3 h treatment was achieved. Mass balance analysis indicated that adsorption, transformations into NO 2- and NO 3-N accounted for 64, 4 and 24% of the NH 4-N removal, respectively. This study also demonstrated that in general a greater rate of effluent recirculation around downflow reed beds gives higher NH 4-N removal.

Assessing the environmental impact of two options for small-scale wastewater treatment: comparing a reedbed and an aerated biological filter using a life cycle approach

Different options for wastewater treatment have different performance characteristics and also different direct impacts on the environment. These impacts occur over the whole life cycle of the treatment system. Natural wastewater systems such as the reedbed may offer reduced whole life cycle environmental impacts compared to systems with more technical and material sophistication. This paper describes a study of the life cycle impacts of two options for small-scale wastewater treatment which are a horizontal flow reedbed system and a package bio-filtration plant. The study is limited to impacts during the construction and operation phases. Energy use, CO 2 emission and solid emissions were chosen as the environmental aspects. It was found that overall the reedbed and conventional systems were quite similar in terms of life cycle energy use. Transport occurring during construction and operational maintenance was a key contributor to energy use and CO 2 emissions. The environmental impact of the reedbed reduced if the soil excavated on site was suitable for re-use in the infill. The effect on the results of the different assumptions made during the study was checked using sensitivity analysis. This analysis also helped us to identify recommendations for reducing the life cycle impact of the reedbed system.

Nitrogen removal from domestic effluent using subsurface flow constructed wetlands: influence of depth, hydraulic residence time and pre-nitrification

This paper describes two studies into the BOD and TN removal performance of horizontal subsurface flow wetlands (reed beds) in subtropical Australia. The aim of the first study was to determine the influence of HRT and vertical position on BOD and TN concentration and removal performance in a 0.5 m deep reed bed (System 1) by taking samples from three levels (or layers) in the water column at five points along the length of the bed. The aim of the second study was to investigate the TN removal performance of a treatment train consisting of a vertical flow intermittently dosed sand filter preceding a reed bed (System 2). Both systems were dosed with primary settled municipal wastewater (BOD 194 mg L(-1); TN 49 mg L(-1)). System 1 achieved a TN load removal of 58% under a HLR of 22 mm day(-1) (HRT 10.5 days), producing effluent BOD concentrations consistently less than 8 mg L(-1). There was no significant difference in BOD attenuation rate between the three layers. While there were differences in both the nitrification and denitrification rates between the three layers, the TN concentration was found to decline steadily in all layers up to an HRT of 8.7 days. System 2 reduced TN influent load by 33%, less than half of which was removed by the reed bed. The lack of substantial TN removal within this reed bed was attributed to the low concentrations of BOD and consequent lack of dissolved organic carbon to drive the denitrification process.

Effect of effluent recirculation on the performance of a reed bed system treating agricultural wastewater

Effluent recirculation was investigated in a vertical flow reed bed system treating an agricultural wastewater. A comparison was made for the efficacy of this system before and after recirculation was adopted. Recirculation considerably improved the removal of BOD 5, COD, suspended solids (SS) and NH 4-N. The most significant improvement was made for NH 4-N, and nitrification of NH 4-N into NO 2-N and NO 3-N only took place when recirculation was employed. The removal of PO 4-P, however, was only slightly improved by recirculation. Generally, the removal rate of NH 4-N increased proportionally with its loading onto the system. With recirculation the pH value of the wastewater gradually decreased as a result of alkalinity being consumed during the nitrification process, whereas without recirculation the pH remained virtually unchanged. When recirculation was employed, the ambient temperature did not have a significant influence on the removal of BOD 5 but appeared to affect NH 4-N removal.