Hydraulic conductivity and impact on retrofit stormwater biofiltration - case study of the design, assessment and function of retrofit raingardens using different filter media in Sydney

This paper presents a case study of the design and performance of various biofiltration systems using different filter media and different methods to measure hydraulic conductivity. Modelling undertaken as part of this study indicated that for small systems a high hydraulic conductivity will result in a better overall performance. Assessment of the hydraulic performance of four biofiltration systems was carried out using two different methods, both using a single ring infiltrometer but using different formulas to calculate the hydraulic conductivity. The results showed that biofiltration using sandy loam reported significantly lower hydraulic conductivity using both methods than that previously reported in laboratory tests. In all testing there was great variability in the results suggesting the need for caution to rely on any single test or method to accurately report the hydraulic conductivity. From a design and operational perspective this study supports the use of sand over sandy loam as a filter media particularly where there is insufficient space to size the biofiltration system according to best practice guidelines.10 page(s

Biofiltration design - a case study of biofiltration systems in residential areas using different filer media

14 page(s

The Effect of the in-transport process on urban water chemistry : an examination of the contribution of concrete pipes and gutters on urban water quality

The objective of this study was to test the impact of concrete pipes on the chemistry of water and how this may be a factor that influences water quality in urban streams. While contemporary urban water management is increasing its understanding of the impacts of urban catchment development on the environment, little research has been undertaken on in-transport processes associated with the stormwater drainage network. Stormwater systems are designed primarily to manage the impacts of flooding and overland flow. Robust and hydraulically efficient materials, such as concrete pipes, have been the favoured to achieve these outcomes. An investigation of water quality in the northern suburbs of Sydney showed pH and bicarbonate levels were statistically higher in the developed catchments compared to the undeveloped or bushland catchments. This prompted the researchers to investigate if concrete, being the dominate material of the stormwater drainage system, may be contributing to this difference. Rainwater collected from the catchment was passed through various concrete pipes over a period of 120 minutes and measured for a range of analytes. The results reported that irrespective of the age of the concrete pipe there was a significant change in water chemistry when compared with the flows through a plastic stormwater pipe (used as a control). Newer pipes reported the greatest degree of change. The principal cause was the dissolution of cement products into the water. These findings are particularly relevant where the buffering of naturally acidic rain, primarily achieved through the dissolution of calcium from concrete drainage structures, alters the chemistry of natural water bodies. These ecosystems are naturally acidic and sensitive to changes in alkalinity and bicarbonate levels.10 page(s

Impact of concrete and PVC pipes on urban water chemistry

Waterways contain a chemical signature of catchment land use, climate and geology. This is increasingly being influenced by the urban landscape and particularly the composition of materials and activities that occur on impervious surfaces. This paper examines the degree and extent of two types of drainage materials, concrete and PVC, on urban water chemistry. This study found that water collected from a zinc and slate/tile roof and stored in a plastic rain tank (roof water) was acidic (pH 4.79) and had low bicarbonate concentrations (0.5 mg/l), water from an undeveloped catchment (reference creek) was mildly acidic (pH 5.5) with bicarbonate concentrations of 1.7 mg/l while water from a stream draining a residential catchment (urban creek) was mildly alkaline (pH 7.35) with bicarbonate concentrations of 36.3mg/l. The three types of water were then circulated through a concrete pipe or PVC pipe for 100 min and measured for a range of water chemical attributes. Roof water and water from the reference creek reported a significant increase across a range of analytes, most notably bicarbonate and calcium levels when passed through the concrete pipe, while water from the urban creek changed a lesser amount. When passed through the PVC pipe the changes in water chemistry were significantly less for roof water and urban creek water. The data suggests that in-transport processes from concrete drainage systems are having a significant influence on water chemistry, particularly where inflow is acidic. The major factor identified in this study could be attributed to the dissolution of calcium, bicarbonate and potassium ions from the concrete pipe. This could impact on receiving environments that are naturally acidic and low in bicarbonate, such as those in northern Sydney. The implications of this study point towards a need to consider the type of materials used in urban drainage networks if water chemistry and stream ecosystem health is to be protected

Geochemical contamination of urban water by concrete stormwater infrastructure : applying an epoxy resin coating as a control treatment

Urban drainage systems that use concrete gutters, pits and pipes have been adopted worldwide by drainage engineers. This study tested the hypothesis that treating a concrete pipe with a coating of epoxy resin is an effective method to reduce the concrete mineral leaching and associated contamination of water carried within the pipe. Four 20 litre samples of rainwater were individually circulated through the untreated and epoxy treated portions of the pipe for 100 minutes. After recirculation through the untreated portion of the pipe pH increased by almost two units, electrical conductivity doubled and there were significant increases in bicarbonate, calcium and other ions. In contrast, rainwater circulated through the epoxy treated portion of the pipe showed a minimal pH increase (0.32 pH units) but no other significant increases in any other water chemistry attributes. The epoxy resin greatly reduced mineral contamination of recirculated water, supporting the hypothesis

Extracting base flow to substitute for potable water use – how much is too much for urban stream health?

Stormwater harvesting is becoming an accepted strategy to provide water for sustainable urban irrigation. Base flow from either the constructed stormwater system or a stream can provide an important contribution to the water supply of a stormwater harvesting system. This can be beneficial as it can reduce the storage size (and thus cost) and improve reliability of supply. However, removing base flows can impact on other management objectives such as maintaining environmental flows for ecosystem health. The volume and origin of base flows in urban stormwater systems and streams can reflect land use changes and anthropogenic sources such as leaking water mains or sewers. In order to assess the origin of urban base flows, a study was undertaken in 2010 that monitored the concentration of fluoride in the water. This was used to indicate the contribution of potable water (including that contained in sewage). Eleven urban and two reference (bushland) streams were assessed across northern Sydney. Four urban streams reported more than 20% of their base flow as potable in origin with one of these urban streams reporting 89% of base flow as potable. Reference streams reported zero to very low concentrations of fluoride. This paper discusses the impact of urbanization on base flows and the potential impacts of removing these flows from urban streams for stormwater harvesting.8 page(s

Impact of urban development on aquatic macroinvertebrates in south eastern Australia : degradation of in-stream habitats and comparison with non-urban streams

Internationally, waterways within urban areas are subject to broad-scale environmental impairment from urban land uses. In this study, we used in-stream macroinvertebrates as surrogates to measure the aquatic health of urban streams in the established suburbs of northern Sydney, in temperate south eastern Australia. We compared these with samples collected from streams flowing in adjacent naturally vegetated catchments. Macroinvertebrates were collected over a 30-month period from riffle, edge and pool rock habitats and were identified to the family level. Macroinvertebrate assemblages were assessed against the influence of imperviousness and other catchment and water quality variables. The study revealed that urban streams were significantly impaired compared with those that flowed through naturally vegetated non-urban catchments. Urban streams had consistently lower family richness, and sensitive guilds were rare or missing. We found that variation in community assemblages among the in-stream habitats (pool edges, riffles and pool rocks) were more pronounced within streams in naturally vegetated catchments than in urban waterways

Estrogen-progestin use and breast cancer characteristics in lean and overweight postmenopausal women.

To access publisher's full text version of this article click on the hyperlink belowBreast cancer associated with estrogen-progestin (EP) therapy may have more favorable characteristics than cancer in never users, but results are conflicting. It is not well known either whether Body Mass Index (BMI) modifies this association. We investigated breast cancer characteristics in EP users for lean (BMI < 25 kg/m(2)) and overweight women (BMI ≥ 25 kg/m(2)).The Icelandic Cancer Detection Clinic cohort, with information on breast cancer risk factors for 90% of Icelandic women, was linked with the population-based Icelandic Cancer Registry. A total of 781 women with invasive breast cancer diagnosed 51 years or older were matched with 7761 controls from the cohort. Conditional logistic regression was used for estimating adjusted odds ratios (OR) and 95% confidence intervals (CI) according to tumor characteristics, stratified by BMI. Polytomous logistic regression was applied in a case-only analysis for testing whether the risk associated with EP use differed according to tumor characteristics.Ever EP users had a twofold higher risk of breast cancer compared with never users (OR 2.05, 95% CI 1.71-2.45). In lean women, EP use was significantly less likely to be associated with grade 2 or 3 tumors than grade 1 tumors, contrary to overweight women for whom risk was increased irrespective of grade. EP use in overweight women was associated with a higher risk of lobular than ductal cancer (OR 2.75, 95% CI 1.29-5.87).Among lean EP users, tumor characteristics were more favorable than among never users. This effect was not observed for overweight women.Icelandic Cancer Societ