Rainwater and Urban Design 

About: Rainwater and Urban Design is an academic journal. The journal publishes majorly in the area(s): Rainwater harvesting & Stormwater. Over the lifetime, 111 publications have been published receiving 553 citations.

A legionnaires' disease outbreak, a water blaster and roof-collected rainwater systems

Abstract: In February 2006, an outbreak Legionnaires' Disease (LD) was identified in Beachlands, a small, isolated East Auckland suburb. It was investigated using case finding, a case-control study, sampling potential sources of infection, and by molecular typing (using sequence-based typing (SBT) of all Legionella pneumophila serogroup 1 (Lp1) isolates). Four cases were identified. Lp1 was isolated from the respiratory tract of one case, the roof-collected rainwater systems of five households (three associated with cases) and from a water blaster at a nearby marina. All isolates were indistinguishable, exhibiting the same SBT allele pattern. The four LD cases lived close to the water blaster and down wind in prevailing conditions. Another domestic roof-collected rainwater supply contaminated by Lp1 (identical SBT pattern) was incidentally identified in another suburb 4 km east of Beachlands. This is the first outbreak of LD in New Zealand linked to roof-collected rainwater supplies and the first isolation of Legionella from these systems in a temperate climate. Aerosols containing Legionella discharged to air by the marina water blaster may have infected some cases directly and may have seeded Beachland's roof-collected rainwater systems. Cases with Legionella contaminated water supplies may also have been exposed during showering. Roof-collected rainwater systems need appropriate design, careful cleaning and the maintenance of hot water temperatures at a minimum of 60degreesC to reduce the chances of multiplication of Legionella. Further research into the ecology of Legionella in roof-collected rain water systems is indicated.

The microbiological quality of roof-collected rainwater of private dwellings in New Zealand

Abstract: In this 5 - year study we investigated the microbiological quality of roof-collected rainwater samples of 560 private dwellings in New Zealand. At least half of the samples analysed exceeded the minimal acceptable standards for contamination and 41% of the samples showed evidence of heavy faecal contamination. The likely sources of the faecal contamination were faecal material deposited by birds, frogs, rodents and possums, and dead animals and insects, either on the roofs or in the gutters, or in the water tank itself. Many of the roof water supplies surveyed revealed deficiencies in the use of rainwater catchment systems and components. In a significant number of supplies where we found heavy faecal contamination there was evidence of lack of maintenance; inadequate disinfection of the water; poorly designed delivery systems and storage tanks; and failure to adopt physical measures to safeguard the water against microbiological contamination. The results of this study indicate that the information on the safe collection and storage of roof-collected rainwater seems not to be reaching many users in New Zealand. Roof water users need more information pertaining to their roof water supplies but we believe improvements are necessary in the dissemination of this information.

Urban water systems: Drivers of climate change?

Abstract: Urban water systems contribute to climate change both directly through the fugitive greenhouse gas (GHG) emissions associated with water storage reservoirs and wastewater treatment processes, and indirectly through significant energy and materials consumption. This paper presents the findings of an investigation of the GHG emissions associated with operating a case study urban water system in Melbourne, Australia. It was revealed that the appliances associated with the residential end uses of water were responsible for significantly more GHG emissions than all upstream and downstream operations. These findings led to the conclusions that any project seeking to minimise the energy consumption and GHG emissions associated with urban water systems should: (a) consider the whole system, including the end uses of water, in a holistic application of life cycle thinking, and (b) focus on reducing the energy and water consumption associated with the end uses of water, since this will yield multiple benefits upstream, downstream and at the point of use.

The effect of various intermittent dry-wet cycles on nitrogen removal capacity in biofilters systems

Abstract: Stormwater biofilter systems have the potential to remove nutrients from urban runoff. These systems operate in unique intermittent dry-wet cycles that may affect their performance. Current consensus suggests that sediment drying promotes the release of potentially significant amounts of bio-available nitrogen and phosphorus upon re-wetting. We sought to investigate the impact of drying/wetting cycles on biofilter performance. Eighteen columns were planted with Carex appressa which reached maturity after eight months. The recovery of biofilter systems was tested in a range of drying periods from one to eight weeks with and without a Submerged Anoxic Zone (SAZ) and carbon supplement in the filter media. In all experiments, moisture content, adjacent soil and ambient temperature were logged in parallel to record the drawdown profile behaviour. A freely drained biofilter configuration was used as a control. The results indicated that having a submerged anoxic zone is critical for nitrogen removal at dry periods greater than two weeks. In addition, the anoxic zone was able to enhance biofilter nitrogen removal recovery and make it less dependent on drying/wetting.

Treatment efficiency of biofilters; results of a large-scale column study

Abstract: In order to evaluate the optimal design of biofilters for treatment of sediment, nitrogen and phosphorus, 140 biofilter columns were constructed, using different plant species, different depths and types of filter media, along with different storm volumes and input concentrations. All biofilters tested were found to be highly effective for removal of TSS, reducing inflow concentrations by an average of 98%. Total phosphorus was reduced by an average of 80%, whilst nitrogen removal was much more variable, including some configurations which yielded a net increase in nitrogen concentration. However, careful selection of plants and media type was able to achieve a simultaneous reduction of 50-70% of nitrogen and 90% of phosphorus. Carex appressa and to a lesser extent Melaleuca ericifolia performed very well in nutrient removal, whilst Dianella revoluta, Leucophyta brownii and Microlaena stipoides did not, within the nine months of testing, effective in facilitating nitrogen removal. Appropriate sizing of biofilters relative to their catchment area, as well as careful selection of plants for climate condition may be critical for biofilter performance. Further research will be undertaken to determine whether relatively poorly performing biofilter designs can be improved by retrofitting a saturated anaerobic zone, to promote denitrification and enhance drought tolerance.