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.

Stream restoration in urban catchments through redesigning stormwater systems: looking to the catchment to save the stream (vol 24, pg 690, 2005)

Stormwater runs off impervious urban surfaces at artificially high rates, and erodes and pollutes local waterways. Raingardens, as biofiltration systems, are garden beds that are designed to capture and filter runoff using sandy soils and resilient plants. For healthier waterways, the construction of raingardens is being actively promoted in many cities, including Melbourne. However, raingardens might have another significant benefit; as sites of food production, using captured stormwater (runoff) for irrigation. The use of stormwater is an increasingly popular practice for overcoming water scarcity issues, which can constrain home vegetable gardening and urban agriculture. Nonetheless, the use of raingardens for food production has not been explored and vegetables represent a significant departure from the types of plants that are conventionally used in these systems. We investigated the potential to produce vegetables in raingardens through a 5-month greenhouse (pot) experiment and a 1.5-year field trial. The results indicate that it is possible to produce adequate yield in raingardens and the function of raingardens in reducing urban runoff (in terms of discharge to waterways) can be retained. An infiltration-type raingarden, sized 7.5% of its catchment area, reduced both the volume and frequency of runoff by > 90%. However, “vegetable raingardens” must be designed and managed effectively. Design issues include the use of sub-irrigation to ensure food safety and limit plant stress, and choosing filter/growing media that sustains vegetable growth while meeting runoff management objectives. Introduction: Water in Australian cities Stormwater runs off the impervious surfaces of Australian cities at artificially high rates, which poses a significant threat to the health of local waterways. For example, large volumes of urban runoff can cause severe channel erosion and lead to a loss of habitat, as well as transporting elevated concentrations of pollutants (Paul & Meyer 2001). Water Sensitive Urban Design (WSUD) is a way of incorporating treatment of this runoff into urban landscapes (Denman, May & Breen 2006; Lloyd, Wong & Porter 2002). It has involved the design and installation of a wide range of technologies, including “biofiltration” or “bioretention” systems (Davis et al. 2009). These technologies improve runoff management by intercepting stormwater flows and restoring the flow regime closer to the pre-developed, natural level (Bratieres et al. 2008; Williams & Wise 2006). In contrast to the large quantities of runoff in the urban landscape, the amount of water available from the traditional supply networks can be limited, particularly in times of drought. The water scarcity issues that affect many Australian cities are primarily caused by below-average runoff into urban water catchments (Edwards 2011). Melbourne, for example, has been affected by substantial decreases in rainfall since 1960 and some exceptionally severe droughts, the most recent lasting from 1997 to 2009 (Barker-Reid, Harper & Hamilton 2010). Water scarcity will become an even greater concern for Melbourne if long-term predictions of drier, hotter weather, as well as increasing consumption, are accurate (Edwards 2011; Howe et al. 2005). Many Australian cities have responded to water scarcity by implementing water restrictions, which require users (particularly households) to avoid or ration some uses of water. Such restrictions were in place in Melbourne for over ten years (Edwards 2011), but were lifted in December 2012 with the possibility of reinstatement during future drought periods. The most severe stage (Stage 4) included a ban on all outside watering, which significantly constrains urban food production. Urban food production is an important practice; traditional home vegetable gardening is often driven by economic motivations and cultural influences (Gaynor 2006), while a recent resurgence of interest in urban agriculture is a response to issues of environmental sustainability and food security (Barker-Reid, Harper & Hamilton 2010; Dixon et al. 2009). The use of stormwater and wastewater, which is not limited by water restrictions, has become an important component of Melbourne’s response to water scarcity (Barker-Reid, Harper & Hamilton 2010; Hatt, Deletic & Fletcher 2007; Misra, Patel & Baxi 2010). There is considerable opportunity for further expansion of stormwater reuse practices in urban food production, and for incorporation of urban food production into WSUD; at least on a small, non-commercial scale, as an extension of traditional home vegetable gardening. For example, green roofs are primarily used for stormwater management and other environmental benefits, but exploratory research has indicated that they could also be used for vegetable production (Whittinghill, Rowe & Cregg 2013). When it rains, such technology can both protect local waterways from the negative effects of stormwater and use this stormwater as a sustainable resource. The “vegetable raingarden”: Opportunities and challenges Raingardens are another prime example of a WSUD technology that has the potential to be used for vegetable production, but this has not yet been tested. Raingardens, as biofiltration systems, are garden beds which are engineered, typically using resilient plants and sandy soils with low-organic content, to capture and treat stormwater that runs off roofs and other impermeable surfaces. The use of vegetables represents a significant departure from the plant species conventionally used in biofiltration systems, which tend to be perennial, native species selected for their capacity to survive the extreme wetting-drying regime in a raingarden, and their ability to remove pollutants from runoff (Read et al. 2008). In comparison to conventional raingarden plants, vegetables are generally much more sensitive to drought and overwatering, both of which can lead to relatively poor growth and yield, and ultimately plant death in severe conditions. Vegetables typically require significant irrigation to supplement rainfall, even in traditional growing systems. Water availability is therefore a critical issue in a vegetable raingarden. In order to adapt raingardens to function effectively as sites of vegetable production, there are several knowledge gaps and design issues that need to be considered. Foremost among them is the method for delivering runoff water to the raingarden. Water usually enters a raingarden at the surface, but it might be preferable to “invert” a vegetable raingarden so that it is subirrigated. The use of sub-irrigation can offer higher water use efficiency than spray and drip irrigation, as demonstrated for tomato production (Ahmed, Cresswell & Haigh 2000; Goodwin et al. 2003; Incrocci et al. 2006; Santamaria et al. 2003). Sub-irrigation might also be beneficial for food safety, whereby pollutants can be filtered out of the runoff water as it moves upwards through the raingarden, before coming into contact with the plants. The choice of soil type is another important issue. Typically, loamy sand or similar is used in a raingarden, primarily to improve the quality of urban runoff (Bratieres et al. 2008; FAWB 2009; Henderson, Greenway & Phillips 2007). However, the relatively low water holding capacity of sandy soil makes it generally not well suited to vegetable production. Finally, there is a risk that modifying a raingarden for vegetable production will compromise its runoff management function. For example, a vegetable raingarden might be less able to capture urban runoff it is watered excessively, or if waterproof lining is required to maintain adequate soil moisture for vegetable production. Lining is also required if the raingarden is constructed close to a permanent structure, or if it is necessary to reduce the ingress of salt into the treated water, which is important in western Sydney and some other areas of Australia. Such lined systems are regarded as having poor hydrologic performance because they inhibit infiltration into underlying soils (Li et al. 2009), and fail to restore the baseflows that are lost following the creation of impervious areas. Research project summary

Uniting Urban Agriculture and Stormwater Management: The example of the 'vegetable raingarden'

Impacts of rainwater tanks on urban hydrology and stormwater quality

The removal of arsenic by horizontal subsurface flow constructed wetlands

Stormwater biofilters are a reliable technology to remove metals from stormwater. A solid carbon source in the filter (combined with a submerged zone) enhances especially Cu removal further; the al ...

Tim D. Fletcher

Papers

Stream restoration in urban catchments through redesigning stormwater systems: looking to the catchment to save the stream (vol 24, pg 690, 2005)

Uniting Urban Agriculture and Stormwater Management: The example of the 'vegetable raingarden'

Impacts of rainwater tanks on urban hydrology and stormwater quality

The removal of arsenic by horizontal subsurface flow constructed wetlands

Laboratory studies on metal treatment efficiency of stormwater biofilters