Basics of qualitative research: Grounded theory procedures and techniques

The term ''urban stream syndrome'' describes the consistently observed ecological degra- dation of streams draining urban land. This paper reviews recent literature to describe symptoms of the syndrome, explores mechanisms driving the syndrome, and identifies appropriate goals and methods for ecological restoration of urban streams. Symptoms of the urban stream syndrome include a flashier hy- drograph, elevated concentrations of nutrients and contaminants, altered channel morphology, and reduced biotic richness, with increased dominance of tolerant species. More research is needed before generaliza- tions can be made about urban effects on stream ecosystem processes, but reduced nutrient uptake has been consistently reported. The mechanisms driving the syndrome are complex and interactive, but most impacts can be ascribed to a few major large-scale sources, primarily urban stormwater runoff delivered to streams by hydraulically efficient drainage systems. Other stressors, such as combined or sanitary sewer overflows, wastewater treatment plant effluents, and legacy pollutants (long-lived pollutants from earlier land uses) can obscure the effects of stormwater runoff. Most research on urban impacts to streams has concentrated on correlations between instream ecological metrics and total catchment imperviousness. Recent research shows that some of the variance in such relationships can be explained by the distance between the stream reach and urban land, or by the hydraulic efficiency of stormwater drainage. The mech- anisms behind such patterns require experimentation at the catchment scale to identify the best management approaches to conservation and restoration of streams in urban catchments. Remediation of stormwater impacts is most likely to be achieved through widespread application of innovative approaches to drainage design. Because humans dominate urban ecosystems, research on urban stream ecology will require a broadening of stream ecological research to integrate with social, behavioral, and economic research.

https://www.jstor.org/stable/10.1899/04-028.1

The urban stream syndrome: current knowledge and the search for a cure

Membranes have an increasingly important role in alleviating water scarcity and the pollution of aquatic environments. Promising molecular-level design approaches are reviewed for membrane materials, focusing on how these materials address the urgent requirements of water treatment applications.

Materials for next-generation desalination and water purification membranes

As photovoltaic penetration of the power grid increases, accurate predictions of return on investment require accurate prediction of decreased power output over time. Degradation rates must be known in order to predict power delivery. This article reviews degradation rates of flat-plate terrestrial modules and systems reported in published literature from field testing throughout the last 40 years. Nearly 2000 degradation rates, measured on individual modules or entire systems, have been assembled from the literature, showing a median value of 0·5%/year. The review consists of three parts: a brief historical outline, an analytical summary of degradation rates, and a detailed bibliography partitioned by technology. Copyright © 2011 John Wiley & Sons, Ltd.

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Photovoltaic Degradation Rates—an Analytical Review

In the last few decades, pharmaceuticals, credited with saving millions of lives, have emerged as a new class of environmental contaminant. These compounds can have both chronic and acute harmful effects on natural flora and fauna. The presence of pharmaceutical contaminants in ground waters, surface waters (lakes, rivers, and streams), sea water, wastewater treatment plants (influents and effluents), soils, and sludges has been well doccumented. A range of methods including oxidation, photolysis, UV-degradation, nanofiltration, reverse osmosis, and adsorption has been used for their remediation from aqueous systems. Many methods have been commercially limited by toxic sludge generation, incomplete removal, high capital and operating costs, and the need for skilled operating and maintenance personnel. Adsorption technologies are a low-cost alternative, easily used in developing countries where there is a dearth of advanced technologies, skilled personnel, and available capital, and adsorption appears to be the most broadly feasible pharmaceutical removal method. Adsorption remediation methods are easily integrated with wastewater treatment plants (WWTPs). Herein, we have reviewed the literature (1990-2018) illustrating the rising environmental pharmaceutical contamination concerns as well as remediation efforts emphasizing adsorption.

Pharmaceuticals of Emerging Concern in Aquatic Systems: Chemistry, Occurrence, Effects, and Removal Methods.

SUMMARY: A decision-making framework (DMF) for stormwater management based on a stochastic watershed model has been developed by the CRC for Catchment Hydrology. The DMF predicts stormwater flows and loads of pollutants (total suspended solids, phosphorus, nitrogen and gross pollutants) exported from urbanized catchments with varying types and levels of stormwater abatement techniques. The utility of the DMF is limited by the lack of prediction as to the effects of these changes on the ecology of receiving waters. This paper places the DMF within a conceptual model of stormwater physico-chemical impacts on stream ecosystems. Emerging methods are identified and described for in- serting predictive models of ecological indicators (community composition) into the DMF, and to include the assimila- tive capacity of the stream ecosystem as part of the 'treatment train'. Current research using the catchment ecosystem approach to quantify in-stream biogeochemical processes is described, and areas of research need are identified, such as the effects of the spatial arrangement of catchment urbanization on stream ecology and the interactions between engi- neering solutions, stream condition and human behaviour.

Developing predictive ecological capacity for a stormwater management decision-making framework

Background. Arsenic and heavy metals pollution in water is a worldwide problem. Onsite, cost-effective, low impact treatment technologies are required to remove heavy metals to avoid further degradation of aquatic ecosystems. Constructed wetlands have been successfully applied to treat several types of wastewater and their application has accelerated, primarily due to rising costs of fossil fuel-derived energy sources. They also offer low cost/easy maintenance and a wildlife habitat (Lee et al., 2009). In particular, subsurface flow constructed wetlands have the potential to remove different metals and metalloids from water, but few studies have been performed to investigate As removal (Lizama A. et al., 2011). In addition, the use of alternative media has been suggested but not sufficiently studied. Zeolite, limestone and cocopeat substrates have been found to be more effective than conventional gravel substrate under neutral to slightly acidic conditions (Lizama Allende et al., 2011), but under highly acidic conditions, their performance is unknown. These acidic conditions are generally associated with the presence of As and metals. The Azufre River, northern Chile, was selected as the case-study for its elevated levels of As and low pH (Rios et al., 2011) to test the alternative substrates and the conventional gravel as wetland supporting media.

Subsurface flow constructed wetlands for the removal of arsenic and metals from acidic contaminated water

Simplified modelling of the hydraulic behaviour of vertical flow constructed stormwater wetlands

Resume Les ouvrages d'infiltration sont de plus en plus utilises pour la gestion des eaux pluviales aussi bien en milieu routier qu'en milieu urbain. Bien que ces techniques d'infiltration soient largement utilisees, elles sont encore suspectees de dysfonctionnements persistants et notamment de se colmater facilement provoquant une stagnation de l'eau dans le systeme et une diminution importante des capacites d'evacuation. L'objet de la publication est de presenter une contribution permettant de connaitre l'evolution temporelle du colmatage, d'expliquer son evolution par les apports d'eau, de matiere en suspension ou de matiere organique et enfin de circonscrire les zones de developpement des depots a partir du suivi d'un ouvrage en service. Pour cela nous suivons la resistance hydraulique (indicateur de colmatage), et les facteurs influents tels comme la frequence des apports, le contenu en matiere organique et en matieres en suspension, ainsi que la distribution de ces apports sur la surface du bassin. Resumo Os dispositivos de infiltracao sao cada vez mais utilizados para gerenciamento das aguas pluviais, tanto em zonas rodoviarias como em areas urbanas.Embora as tecnicas de infiltracao sejam amplamente usadas, elas ainda sao suscetiveis a disfuncionamentos persistentes,

https://hal.archives-ouvertes.fr/hal-01115297/document

Caractérisation des apports sur un bassin d'infiltration et impact sur son fonctionnement hydraulique

Biofilters (also called biofiltration or bioretention systems) have been proven to be an effective option for the treatment of pollutants in urban stormwater. The aim of this study was to independently test an alternative sand based filter media, which could be reliably and easily specified and constructed from inert material, and which would (i) sustain adequate plant growth, (ii) maintain hydraulic conductivity, and (iii) achieve effective pollutant removal. Twenty biofilter columns were constructed for this experiment, using two fine sands of different initial drainage rates, tested in vegetated and non-vegetated configurations. The results showed that, independently of the type of sand used, plant growth was sustained in all biofilters, and that after one year (i.e. at the time of the last sampling event), the pollutant treatment performance of vegetated columns was comparable to loamy sand based biofilters, which are typically used in current practice. However, the results also showed that after one year of exposure to stormwater, the hydraulic conductivity of the filters had greatly deteriorated, in particular for the vegetated configurations. The results of this study demonstrated that sand based biofilters, built according to these simple filter media specifications, could be used as a viable option for stormwater treatment. The main advantages of this alternative specification are its reproducibility and reduced variability.

http://documents.irevues.inist.fr/bitstream/handle/2042/35835/23302-018BRA.pdf?sequence=1

Hydraulic and pollutant treatment performance of sand based biofilters Conductivité hydraulique et rendement épuratoire de filtres de biorétention à base de sable

Tim D. Fletcher

Papers

Developing predictive ecological capacity for a stormwater management decision-making framework

Subsurface flow constructed wetlands for the removal of arsenic and metals from acidic contaminated water

Simplified modelling of the hydraulic behaviour of vertical flow constructed stormwater wetlands

Caractérisation des apports sur un bassin d'infiltration et impact sur son fonctionnement hydraulique

Hydraulic and pollutant treatment performance of sand based biofilters Conductivité hydraulique et rendement épuratoire de filtres de biorétention à base de sable