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.

1 Waterway Ecosystem Research Group, School of Ecosystem and Forest Sciences, The University of Melbourne, Victoria, Australia 3121 2 Grace Detailed-GIS Services, 7 Arcadia Close, Taylors Lakes, Victoria, Australia 3038 Moroka Pty Ltd 4 Water Technology, 15 Business Park Drive, Notting Hill, Victoria, Australia 3168 Word Limit of the Paper should not be more than 3000 Words = 7/8 Pages) Abstract: Currently climate models exist as a desktop exercise in various formats and in a dis-integrated way. Any city with wide range of natural and cultural assets which make a major contribution to its liveability benefit greatly if various models and data can be accessed in an integrated way at any time using the Web to inform strategic response to climate change and variability, including: flood risk, river rise, sea level rise, extreme temperatures during heat waves, drought and subsequent reductions in soil moisture, and decline in tree health. There is a need to develop a decision support system that is spatially explicit and integrates various climate models into one visualisation environment to enable multi-criteria analysis to identify vulnerable areas and then to model possible interventions.

A Web-GIS Based Integrated Climate Adaptation Model

Three large bioretention cells (each 955m2) were analysed for their removal of TSS, TN and TP. Two of the cells consisted of standard filter media, whereas the third incorporated a saturated zone intended to enhance TN removal via denitrification. The concentrations of total suspended solids (TSS), total nitrogen (TN) and total phosphorus (TP) measured in the runoff at the inlet to the bioretention cells were markedly lower than those typically recorded in urban catchments. Nevertheless, all cells performed well in terms of TSS removal, with significant reductions in outflow relative to inflow concentrations (p<0.05, muin=29.6 mg/L, muout=16.4 mg/L). In terms of TN, the two standard cells acted as sources (given the very low inflow concentrations) while the cell with the saturated zone significantly reduced concentrations (muin=0.98 mg/L, muout=1.05 mg/L). All cells significantly reduced TP concentrations (muin=0.087 mg/L, muout =0.059 mg/L), with the saturated cell performing the best. Given the difficulty in removing nitrogen, designers should focus on careful selection of filter media, plants and the possible use of a saturated zone with carbon, to enhance nitrogen removal processes. Even at this large-scale, a saturated zone effectively improves TN removal; these findings are consistent with those previously demonstrated by small-scale laboratory studies. Importantly, phosphorus leaching from the saturated zone does not appear to be an issue here. Large-scale trials in areas with inflows that have higher pollutant concentrations need to be investigated. A study that analyses event mean concentrations (EMC) as opposed to discrete concentrations is also required, as are investigations into the influence of vegetation type and composition on performance at this large-scale.

Bioretention saturated zones: Do they work at the large-scale?

https://hal.archives-ouvertes.fr/hal-01722327/document

Understanding the challenges of managing SUDS to maintain or improve their performance over time

The frequent direct delivery of water and pollutants from impervious surfaces to streams has a detrimental effect on stream health. Where there is opportunity for attenuation of these inputs, that is, where the link between impervious surfaces and streams is less direct, the damage to stream health is mitigated. This suggests that improving stream health, in areas subject to urbanisation, involves finding ways to decrease the efficiency of water delivery from impervious surfaces. We have undertaken a feasibility study to examine options to reduce the area of impervious surfaces that are directly connected to waterways. These options include: rainwater tanks where the captured water is used to replace a portion of the mains supply; permeable pavements that reduce runoff from roads; and swale drains and bioretention systems along roads rather than piped drainage direct to streams. Models of the relationship between effective imperviousness and a range of ecological indicators are used to assess the likely effect of these options on stream health. A large-scale experiment is now proposed to test this new approach to urban stream restoration.

Tim D. Fletcher

Papers

A Web-GIS Based Integrated Climate Adaptation Model

Bioretention saturated zones: Do they work at the large-scale?

Understanding the challenges of managing SUDS to maintain or improve their performance over time

Improving stream health by reducing the connection between impervious surfaces and waterways

Effect of retrofitting a submerged zone on the performance of biofiltration for heavy metal removal - preliminary results of a laboratory study