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.

/pdf/photovoltaic-degradation-rates-an-analytical-review-a86in1nx10.pdf

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.

Development of the enviss filtration media: preliminary results

Stormwater management strategies increasingly recognise the need to emulate the pre-development flow regime, in addition to reducing pollutant concentrations and loads. However, it is unclear whether current design approaches for stormwater source-control techniques are effective in restoring the whole flow regime, and in particular low flows, towards their pre-development levels. We therefore modelled and compared a range of source-control stormwater management strategies, including some specifically tailored towards enhancing baseflow processes. The strategies were assessed based on the total streamflow volume and three low flow metrics. Strategies based on harvesting tanks showed much greater volume reduction than those based on raingardens. Strategies based on a low flow rate release, aimed at mimicking natural baseflow, failed to completely restore the baseflow regime. We also found that the sensitivity of the low flow metrics to the proportion of catchment treated varied amongst metrics, illustrating the importance of metrics selection in the assessment of stormwater strategies. In practice, our results suggest that realistic scenarios using low flow release from sourcecontrol techniques may not be able to fully restore the low flow regime, at least for perennial streams. However, a combination of feasibly-sized tanks and raingardens is likely to restore the baseflow regime to a great extent, while also benefitting water quality through the retention and filtration processes.

http://documents.irevues.inist.fr/bitstream/handle/2042/51322/3B81-182HAM.pdf;sequence=1

The impact of stormwater source-control strategies on the (low) flow regime of urban catchments L'impact des stratégies de contrôle à la source sur le débit d'étiage des bassins versants urbains

Selecting tree species with high transpiration and drought avoidance to optimise runoff reduction in passive irrigation systems.

Despite the demonstrated treatment efficiency of biofiltration, nitrogen remains a challenging pollutant to remove from urban stormwater runoff. This difficulty stems from the multiple forms in which nitrogen may be present, varying from bioavailable and inorganic to an array of largely uncharacterised organic compounds. Additionally, complex environmental influences on nitrogen transformation and removal processes affect nitrogen removal efficiency. An experiment with 245 biofilter columns of varied design indicated nitrate dictated performance variation during wet periods, suggesting differing rates of nitrification, denitrification or plant uptake. In dry months, organic nitrogen removal was additionally problematic, but displayed minimal variation between treatments. The results suggest that alternative biofilter design features are required to facilitate microbial processing of re-released organic nitrogen from plants.

Stormwater biofiltration-the challenges of inorganic and organic nitrogen removal

Increasingly, urban water managers in Australia are seeking to make significant decisions about the use of stormwater management measures that improve waterway health (e.g. constructed wetlands and bioretention systems) within the context of the so-called 'triple-bottom-line'. That is, such decisions are based on financial, social and ecological considerations. The Cooperative Research Centre (CRC) for Catchment Hydrology has developed and is trialling draft guidelines on how to undertake triple-bottom-line assessments of proposed stormwater projects that aim to improve waterway health (e.g. assessments that involve the design and/or the location of new infrastructure). For the sake of practicality, these guidelines provide different levels of assessment which are commensurate with the scale and complexity of the project. To assist the financial element of the assessment, a life-cycle costing module has been built into version 3 of the CRC's MUSIC model (i.e. the 'Model for Urban Stormwater Improvement Conceptualisation'). This module allows users to estimate the likely value of cost elements and the overall life-cycle cost of common structural stormwater measures that aim to improve waterway health. This module was developed following an analysis of the cost of Australian measures and the development of algorithms that relate the size of measures to their cost. For the financial, social and ecological elements of the assessment, the new CRC guidelines explain how to use a multi criteria analysis procedure as a decision support tool. This procedure incorporates all aspects of the triple-bottom-line and involves a number of steps which are briefly described in this paper. Traditionally in Australian stormwater management, decisions have been made by few people, with little consultation/participation, have been based on limited information (locally or from the literature), and considered only part of the triple-bottom-line (e.g. traditional benefit-cost analyses where 'externalities' were not considered). We have developed guidelines which attempt to improve on this situation, but are practical to use. The new guidelines, supported by the new life-cycle costing module in MUSIC should substantially assist urban stormwater managers to make more systematic, informed, rigorous, participatory, transparent, defendable, socially acceptable, ecologically sustainable and more cost-effective decisions.

Tim D. Fletcher

Papers

Development of the enviss filtration media: preliminary results

The impact of stormwater source-control strategies on the (low) flow regime of urban catchments L'impact des stratégies de contrôle à la source sur le débit d'étiage des bassins versants urbains

Selecting tree species with high transpiration and drought avoidance to optimise runoff reduction in passive irrigation systems.

Stormwater biofiltration-the challenges of inorganic and organic nitrogen removal

Triple-Bottom-Line Assessment of Proposed Urban Stormwater Measures to Improve Waterway Health