Investigations on phosphorus retention in subsurface flow constructed wetlands

2003 ◽  
Vol 48 (5) ◽  
pp. 67-74 ◽  
Author(s):  
H. Rustige ◽  
I. Tomac ◽  
G. Höner
Keyword(s):  
Constructed Wetlands ◽  
Warm Season ◽  
Reed Beds ◽  
Loading Rates ◽  
Output Concentration ◽  
Reed Bed ◽  
Performance Rate ◽  
Filter Bed ◽  
Positive Effect ◽  
Small Positive Effect

62 SSF sand-based constructed wetlands in Germany, Austria and Switzerland have been evaluated for their phosphorus performance. In addition intensive investigations on the removal of phosphorus and its accumulation within the filter bed were conducted at five wetlands. For the performance of horizontal flow (HF) reed beds a regression equation could be derived. This was not possible for vertical flow (VF) reed beds. The best removal efficiency was observed from HF systems with hydraulic loading rates of 10 mm d-1 or less. 50 percent of all investigated HF wetlands had an average P output concentration of less than 2.1 mg l-1 in comparison to 3.3 mg l-1 of VF wetlands. Saturation, seasonal and redox effects could be derived from time series analysis of the performance rate and further investigations of a well monitored VF reed bed. The retention of phosphorus was highest during the warm season. A small positive effect on phosphorus removal was observed with intermittent low redox levels. Soil analyses showed the highest accumulation of P within the influent zone of either HF or VF wetlands.

Nutrient removal in subsurface flow constructed wetlands for application in sensitive regions

2001 ◽  
Vol 44 (11-12) ◽  
pp. 149-155 ◽  
Author(s):  
H. Rustige ◽  
Chr. Platzer
Keyword(s):  
Drinking Water ◽  
High Performance ◽  
Treatment Plant ◽  
Filter Medium ◽  
Water Filter ◽  
Multi Stage ◽  
Reed Bed ◽  
One Year ◽  
Performance Rate ◽  
Filter Bed

One of the most interesting sites for research on CWs in Germany has been established in Wiedersberg (Saxonia). The multi-stage concept with primary settling, vertical and horizontal flow reed bed followed by UV-disinfection and a special phosphorus filter bed, allows numerous ways of operation and investigations. Denitrification can be improved by recirculation through VF bed and sedimentation tank or by means of adding carbonaceous water from the primary stage to a second level within the VFB or directly to the following HF bed. In order to investigate the efficiency of P-elimination four kinds of natural sands containing different amounts of iron have been used. To maintain a long-term capacity for P-reduction an additional filter bed is filled with gravelly sand which had been used for the precipitation of iron from drinking water before. After saturating with P this filter medium can be exchanged easily. A result of more than one year of operation is the high performance rate for adsorption of phosphorus by enriched iron on drinking water filter sand. At a total loading rate of 350 g P/m3 filter medium 250 g P/m3 have been adsorbed. Design considerations can not be given yet. The median denitrification rate at VFB is 1.3 g N m-2d-1 and at HFB is 0.25 g Nm-2d-1. The low denitrifcation rate of HFB might be due to a very high quota of wastewater dilution by storm- and ground-water of 100 to 200 percent. The investigations on this wastewater treatment plant will be continued until June 2001 and experiments with filter columns will be added.

Design of a Hybrid Reed Bed System to Achieve Complete Nitrification and Denitrification of Domestic Sewage

1999 ◽  
Vol 40 (3) ◽  
pp. 283-289 ◽  
Author(s):  
Paul Cooper ◽  
Paul Griffin ◽  
Stuart Humphries ◽  
Adrian Pound
Keyword(s):  
Horizontal Flow ◽  
Vertical Flow ◽  
Total N ◽  
Reed Beds ◽  
Loading Rates ◽  
Flow Systems ◽  
Reed Bed ◽  
And Performance ◽  
Sludge Drying ◽  
Complete Nitrification

The design of vertical-flow (VF) reed beds is reviewed and the performance of the few worldwide existing hybrid systems, combining both horizontal- and vertical-flow beds, is assessed. Horizontal-flow (HF) beds are good for suspended solids removal and will remove BOD5 up to a set loading. Vertical-flow beds can achieve BOD5 removal at much higher loading rates and they are capable of complete nitrification as tertiary or secondary treatment systems. It is possible to achieve biological denitrification in horizontal-flow beds. By combining horizontal- and vertical-flow systems in the appropriate process sequence it is thus possible to produce a system which removes BOD5, TSS and achieves complete nitrification as well as substantial removal of nitrate and hence a lowered Total N. The paper discusses the possible process options for combining horizontal- and vertical-flow systems. One example of these systems will be described in more detail. This is a flexible hybrid system being built by Severn Trent Water. Designed to treat the flow for a small village with a population of 129 it will have vertical-flow beds followed by horizontal-flow beds. The design allows for flexibility such that the size of the vertical-flow and horizontal-flow stages can be altered (for experimental purposes) to allow the design arrangement to be stressed and performance evaluated with the intention of defining the optimum loading rates for each of the stages. The same site also has sludge drying reed beds for treating the primary sludge.

Constructed reed beds: appropriate technology for small communities

1995 ◽  
Vol 32 (3) ◽  
pp. 339-348 ◽  
Author(s):  
M. B. Green ◽  
J. Upton
Keyword(s):  
Sewage Treatment ◽  
Appropriate Technology ◽  
Great Promise ◽  
High Quality ◽  
Reed Beds ◽  
Small Communities ◽  
Operational Information ◽  
Reed Bed ◽  
Small Sites ◽  
Very High

Reed bed treatment is put in the context of a major water company’s need to provide reliable, high quality, effluents from small sewage treatment works whilst seeking to minimise running costs. Design and operational information is given for reed bed applications in Severn Trent Water. Performance details are provided for application to secondary, tertiary and storm overflow treatment. The results give particular confidence in the system’s ability to deliver very high quality effluents when used for tertiary treatment, the company’s biggest application. Reed beds work well against less demanding criteria for secondary treatment at small sites and show great promise for storm overflow treatment.

Experiences with a top layer of gravel to enhance the performance of vertical flow constructed wetlands at cold temperatures

2009 ◽  
Vol 59 (6) ◽  
pp. 1111-1116 ◽  
Author(s):  
Guenter Langergraber ◽  
Alexander Pressl ◽  
Klaus Leroch ◽  
Roland Rohrhofer ◽  
Raimund Haberl
Keyword(s):  
Organic Matter ◽  
Constructed Wetlands ◽  
Common Reed ◽  
Treated Wastewater ◽  
Second Phase ◽  
Vertical Flow ◽  
Cold Temperatures ◽  
Main Layer ◽  
Gravel Layer ◽  
Filter Bed

In a first phase of this study it was shown that the Austrian effluent standards for organic matter could not be met in winter for vertical flow (VF) beds designed for and loaded with 27 g COD.m−2.d−1 (3 m2 per person equivalent). The aim of this second phase of the study was to investigate, if the performance of a constructed wetland can be enhanced, i.e. if the effluent requirements can be met, when an additional gravel layer (15 cm, 4–8 mm) is added on top of the main layer of the VF bed. The hypothesis was that this top layer would increase the thermal insulation and consequently the temperatures in the filter bed during cold periods, thus resulting in higher removal efficiencies during winter. Two VF beds were operated in parallel; one bed with such a 15 cm top layer, one without. Otherwise the construction of both beds was identical: surface area of about 20 m2, 50 cm main layer (grain size 0.06–4 mm, d10=0.2 mm; d60=0.8 mm), planted with common reed (Phragmites australis). The beds were intermittently loaded 4 times per day with mechanically pre-treated wastewater (hydraulic loading: 47 mm.d−1; median value of the influent concentration: 505 mg COD.L−1). Despite a better performance during the first winter, the bed with additional top layer showed in general a very unstable performance. It is assumed that the main reason for this was that the oxygen transfer was reduced by the additional top layer so far that suspended organic matter could not any longer be degraded in between loadings. Therefore clogging of the filter occurred.

The application of wetland technology for copper removal from distillery wastewater: a case study

2009 ◽  
Vol 60 (11) ◽  
pp. 2759-2766 ◽  
Author(s):  
C. Murphy ◽  
P. Hawes ◽  
D. J. Cooper
Keyword(s):  
Metal Removal ◽  
Copper Removal ◽  
Ionic Form ◽  
Reed Beds ◽  
Organic Species ◽  
Treatment Processes ◽  
Distillery Wastewater ◽  
Reed Bed ◽  
Performance Results

The ability of reed beds to remove significant levels of metals from effluent streams is well cited in the literature. Various methods of removal have been postulated and demonstrated including physical methods such as filtration and settlement, precipitation when the metal is present as a salt and adsorption to organic species or take up by macrophytes when the metal is in a soluble or ionic form. Consequently, reed beds have been used in a variety of applications for metal removal in water treatment processes. The distillation process for whisky generates an effluent containing a significant amount of copper which is scoured from the copper stills during the process and cleaning operations. High soluble copper concentrations can breach discharge consents. A horizontal subsurface flow reed bed system has been designed and installed for copper removal at a distillery in Scotland. This paper presents the findings of the literature search, outlines the design of the bed and reviews the performance results.

On-site domestic wastewater treatment by reed bed in the moist subtropics

2001 ◽  
Vol 44 (11-12) ◽  
pp. 353-360 ◽  
Author(s):  
L. Davison ◽  
T. Headley ◽  
M. Edmonds
Keyword(s):  
New South ◽  
Domestic Wastewater ◽  
Moisture Loss ◽  
Reed Beds ◽  
Treatment Performance ◽  
South Wales ◽  
Domestic Wastewater Treatment ◽  
Australian State ◽  
North Eastern ◽  
Reed Bed

This paper summarises the results of studies on four subsurface flow wetlands (reed beds) located in the moist sub-tropical north eastern corner of the Australian state of New South Wales. The reed beds, which are subjected to a variety of effluent types, all have a gravel substrate planted with Phragmites australis. All four units were found to maintain satisfactory treatment performance year round. Mean removal efficiencies ranged from 56% to 90% (SS), 70% to 93% (BOD), 38% to 66% (TN), 87% to 99.8% (Faecal coliforms), and 42% to 70% (TP - with one seasonal result of 0% for the eight year old unit) for the four reed beds. After eight years in operation the oldest reed bed was showing signs of phosphorus saturation with outlet TP concentrations exceeding inlet concentrations on some occasions. The youngest reed bed studied appeared to be operating efficiently after five months. A summer water balance on one of the reed beds revealed an average crop factor of 1.6 and a moisture loss to atmosphere of 40% of influent flow. Treatment performance (particularly for TN and SS) was found to be negatively correlated with rainfall during one study. The paper discusses the implications of the above results for on-site system designers and regulators and identifies areas for further investigation.

Removal Efficiency of Three Cold-Climate Constructed Wetlands Treating Domestic Wastewater: Effects of Temperature, Seasons, Loading Rates and Input Concentrations

1999 ◽  
Vol 40 (3) ◽  
pp. 273-281 ◽  
Author(s):  
Trond Mæhlum ◽  
Per Stålnacke
Keyword(s):  
Organic Matter ◽  
Constructed Wetlands ◽  
Domestic Wastewater ◽  
Cold Climate ◽  
Treatment Efficiency ◽  
Loading Rates ◽  
P Sorption ◽  
Percentage Points ◽  
Effects Of Temperature ◽  
Pre Treatment

This paper outlines the influence of temperature, flow rate and input concentrations on the treatment efficiency of organic matter and nutrients in constructed wetlands (CWs). Three integrated 10 PE systems with horizontal subsurface flow (HSF) treating domestic wastewater are described. Particular attention is devoted to: (1) aerobic pre-treatment in vertical-flow filters, (2) filter media with high phosphorus (P) sorption capacity, and (3) the treatment efficiency during winters. Aerobic pre-treatment followed by CW units including P sorption media removed most organic matter (BOD> 75%), P (> 90%) and total and ammonia N (40-80%). P retention was relatively stable in wetland filters, both with lightweight aggregates and ferruginous sand during 3-6 years of monitoring. Iron-rich sand from Bsh and Bs horizons of ferro-humic podzols was efficient for P sorption, but removal efficiencies of COD, TOC and SS were negative. The differences in efficiency between cold and warm periods were less than 10 percentage points for all parameters. It is anticipated that temperature effects are partially compensated by the large hydraulic retention time. The findings suggest that HSF systems do not require vegetation.

Lessons from Thailand: universal healthcare achievements and challenges

2018 ◽  
Vol 45 (2) ◽  
pp. 387-401
Author(s):  
Ravikan Nonkhuntod ◽  
Suchuan Yu
Keyword(s):  
Healthcare System ◽  
Healthcare Utilization ◽  
Design Methodology ◽  
Meta Analysis ◽  
Selection Criterion ◽  
Policy Makers ◽  
Content Type ◽  
Universal Healthcare ◽  
Positive Effect ◽  
Small Positive Effect

Purpose The purpose of this paper is to discuss the successes of Thailand’s healthcare system along with challenges it is facing, examining documents and policies used by those charged with developing and implementing health services. Design/methodology/approach The search pool comprised PubMed and Google Scholar from the period 2001-2015. Selection criterion for inclusion was sources dealing with out-of-pocket (OOP) expenditure and healthcare utilization in Thailand. In total, 33 studies met the criterion of containing sufficient data to be included in the meta-analysis. Findings The authors found a small positive effect size on OOP expenditure and healthcare utilization, obtaining values of 0.1604 (95% CI 0.1320-0.1888, p<0.0001) and 0.2788 (95% CI 0.0917-0.4659, p=0.0035), respectively. Originality/value To review and meta-analyze the literature dealing with the outcomes of Thailand’s healthcare system to understand whether Thailand’s healthcare system is achieving its mandate or not. The results of this paper can help policy makers to understand and evaluate Thailand’s healthcare system.

scholarly journals Impact of Electronic Monitoring on Employees: A Meta-Analysis

2021 ◽  
Author(s):  
Rudolf Siegel ◽  
Cornelius J. König ◽  
Veronika Lazar
Keyword(s):  
Job Satisfaction ◽  
Electronic Monitoring ◽  
Negative Impact ◽  
Meta Analysis ◽  
Well Being ◽  
Negative Effect ◽  
And Performance ◽  
Relationship Of ◽  
Positive Effect ◽  
Small Positive Effect

Electronic monitoring is more and more widespread and affects many employees around the globe. The current meta analysis collected data of 59 independent samples (with 223 effect sizes) to estimate the effect of electronic monitoring on job satisfaction, stress, and performance. A random-effects model indicated a small negative effect of monitoring on job satisfaction, r=-.09, and a small positive effect on stress, r=.12. There was no relationship with performance, r=-.01. Even if the effects of monitoring on job satisfaction and stress are small, taking the large number of employees who are monitored for several hours a day into account, these effects may have a severe and negative impact on employees’ well-being. Performance maintenance is the main justification for the use of electronic monitoring, but the non-existing relationship of monitoring with performance questions the validity of this justification.

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