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.

Field validation of a physically-based model for bioretention systems

Monitoring the hydrochemical efficiency of urban stormwater treatment devices is not straightforward as the traditional, automated, In urban areas, efficient drainage of impervious surfaces means that polluted stormwater is frequently delivered to streams. Commonly, catchment urbanization can increase runoff frequency by a factor of 10 or more, as the effective imperviousness - the proportion of the catchment that consists of impervious surfaces drained to streams - is increased. This causes a decline in stream health.
 To decrease runoff frequency, effective imperviousness must be reduced. This requires urban drainage systems to be redesigned, using techniques such as infiltration and rainwater harvesting, so that stormwater from small rain events is not piped directly to streams but instead is infiltrated, reused or retained. We have developed scenarios that explore alternative urban drainage systems appropriate for a small partly urbanised catchment in Melbourne’s east. These scenarios incorporate, biofiltration basins, swales and dual purpose rainwater tanks that supply water for householders. Our results suggested that sufficient reductions in effective imperviousness and runoff frequency are possible to achieve improvements in stream health.

Scenarios for redesigning an urban drainage system to reduce runoff frequency and restore stream ecological condition

Stormwater Biofiltration Systems - Adoption Guidelines

Economics of rainwater tanks in multi-storied complexes in three cities of New South Wales, Australia

The CRC for Catchment Hydrology's Model for Urban Stormwater Improvement Conceptualisation (MUSIC) can predict removal of total suspended solids, TSS, by grass swales. It uses a first-order kinetic decay equation that contains two calibration parameters k (decay rate constant) and C* (background concentration). The aim of this project was to verify and improve MUSIC using a detailed deterministic model of sediment behaviour in flow over grassed surfaces, known as TRAVA. Firstly, TRAVA was successfully verified using TSS field data from an experimental swale in Brisbane. Subsequently, TRAVA was run for different soil and grass conditions, and these results were used to calibrate MUSIC for each of the studied cases. It was concluded that for TSS removal: (1) parameters k and C* depend on flow rate; (2) the soil-type of the swale has a negligible effect on k and C; and (3) an increase in grass density causes a decrease in k and an increase in C. On average, k = 8500, 6900, and 5200 m/year and C=3, 7, and 17 mg/L for low, medium and high grass density, respectively. These values could be used as calibration values for MUSIC.

Tim D. Fletcher

Papers

Field validation of a physically-based model for bioretention systems

Scenarios for redesigning an urban drainage system to reduce runoff frequency and restore stream ecological condition

Stormwater Biofiltration Systems - Adoption Guidelines

Economics of rainwater tanks in multi-storied complexes in three cities of New South Wales, Australia

Modelling performance of stormwater grass swales - application of simple and complex models