Alternative Water Resources for Rural Residential Development in Western Australia

Rainwater collected from residential roofs and greywater generated from domestic uses except toilets are viewed as possible substitutes for high grade water sources which supply nonpotable indoor uses and irrigation in Australia. This paper searches for alternatives by adopting roofwater and greywater in residential envelope as per Australian water standards. A water balance model Aquacycle was applied to determine storage capacities and to evaluate the percentage reduction in water supplying, stormwater run-off and wastewater disposal, as well as volume of rainwater use and greywater reuse. This study provides the results of greywater recycling, which contributes to the greater saving of mains water supply than rainwater use, and which reduces more than half of the wastewater to receiving waters in the rural township of Cranbrook, Western Australia. The results of this study provide greywater usage (maximum reduction 32.5%) more significantly reduces scheme water supply than rainwater harvesting (maximum reduction 25.1%). Use of greywater on individual residential lots has the dramatic effect for drainage system by reduction approximately 54.1% or 88.1 m³/lot/year. The results of rainwater use analysis show explicitly that rainwater tanks are much more effective in intercepting roof runoff, with the maximum stormwater reduction 48.1% or 68.3 m³/lot/year. This research endeavours to offer a typical paradigm for an integrated water system in the rural residential sectors.     

The effect of selection of time steps and average assumptions on the continuous simulation of rainwater harvesting strategies.

The use of domestic rainwater tanks with back up from mains water supplies in urban areas can produce considerable reductions in mains water demands and stormwater runoff. It is commonplace to analyse the performance of rainwater tanks using continuous simulation with daily time steps and average water use assumptions. This paper compares this simplistic analysis to more detailed analysis that employs 6 minute time steps and climate dependent water demand. The use of daily time steps produced considerable under-estimation of annual rainwater yields that were dependent on tank size, rain depth, seasonal distribution of rainfall, water demand and tank configuration. It is shown that analysis of the performance of rainwater tanks is critically dependent on detailed inputs.     

Analysis and Modelling of Stormwater Volume Control Performance of Rainwater Harvesting Systems in Four Climatic Zones of China

Rainwater harvesting has been widely used to alleviate urban water scarcity and waterlogging problems. In this study, a water balance model is developed to continuously simulate the long-term (57 to 65 years) stormwater capture efficiency of rainwater harvesting systems for three water demand scenarios at four cities across four climatic zones of China. The impacts of the “yield after spillage” (YAS) and “yield before spillage” (YBS) operating algorithms, climatic conditions, and storage and demand fractions on stormwater capture efficiency of rainwater harvesting systems are analyzed. The YAS algorithm, compared with the YBS, results in more conservative estimations of stormwater capture efficiency of rainwater harvesting systems with relatively small storage tanks (e.g., ≤50 m³). The difference between stormwater capture efficiency calculated using the YBS and YAS algorithms can be remedied by increasing storage capacity and reduced by decreasing water demand rates. Higher stormwater capture efficiency can be achieved for rainwater harvesting systems with higher storage and demand fractions and located in regions with less rainfall. However, the lager variations in annual rainfall in arid zones may lead to unstable stormwater management performance of rainwater harvesting systems. The impacts of storage and demand fractions on stormwater capture efficiency of rainwater harvesting systems are interactive and dependent on climatic conditions. Based on the relationships among storage capacity, contributing area, water demand, and stormwater capture efficiency of rainwater harvesting systems, easy-to-use equations are proposed for the hydrologic design of rainwater harvesting systems to meet specific stormwater control requirements at the four cities.     

水景社区的雨水收集与综合利用设计

为研究城市雨水收集与综合利用,以上海郊区一生态水景社区为例,进行水量平衡计算。结果表明,该社区年均雨水可收集量约45 678 m3,占一年总降雨量的62%左右,不但满足社区每年的绿化浇灌、硬地冲洗以及水面蒸发等消耗量,而且富余雨水经过处理后可用作景观湖的补充水源及其他用水。雨水收集利用系统设计以景观湖为中心,屋面雨水通过2个总容积为675 m3的地下集蓄池来收集,集蓄水量可达1.83万m3/a;绝大部分绿地、道路广场以及极少数屋面的雨水径流通过长1 km的植草浅沟和500 m长的碎石沟渠收集,并汇入2个总面积为800 m2的暴雨塘系统内暂时储存。户外小停车场和小广场的雨水通过砂床过滤系统收集。     

Effectiveness of Rainwater Harvesting in Runoff Volume Reduction in a Planned Industrial Park,China

It is urgent to effectively mitigate flood disasters in humid mountainous areas in southeastern China for the increasing flood risk under urbanization and industrialization. In this study, a rural district with an area of 13.39 km² that planning to build an industrial park covering an area of 7.98 km² in Changting was selected to estimate the potential of collectable rainwater and the extent to which runoff volume can potentially be mitigated by rainwater harvesting. In addition, the optimum cistern capacity of a rainwater harvesting system in the planned industrial park was evaluated using daily water balance simulation and cost-efficiency analysis. The results showed that rainwater harvesting in the planned industrial park has great potential. The annually collectable rainwater is approximately 9.8?×?10⁶ m³ and the optimum cistern capacity is determined to be 0.9?×?10⁶ m³. With the optimum cistern capacity, the annual rainwater usage rate is 0.99, showing neither financial savings nor deficits. Rainwater harvesting can reduce 100 % of runoff volume in the cases of critical rainfall storm (50 mm) and annual average maximum daily rainfall (111.2 mm), and 58 % of runoff volume in the case of maximum daily rainfall (233.6 mm), respectively. All surface runoff can be collected and stored in the cisterns when rainfall amount is less than 135.5 mm in a rainstorm event.     

城市雨水利用工程设计中的若干关键技术

随着我国城市化进程的加快,城市不透水面积增加导致雨水排泄负担加重,城市内涝更为严峻和频繁。城市雨水利用作为缓解这些问题的一项重要措施在我国逐步受到重视。由于缺乏系统、完善的工程设计方法,该项技术推广应用的速度、范围和效果受到限制。依据北京10年来的研究成果和工程设计与建设经验,探讨了雨水利用工程设计中的设计降雨、雨水池容积、溢流堰标高、调控排放调蓄池容积、绿地下渗设施规模、透水地面结构等技术关键的计算、设计方法和技术要点;提出了通过时间频率曲线推求较短历时设计降雨过程的方法;将雨水池的容积分成回用容积和调蓄容积,应用逐日调节计算法和数值模拟法分别进行计算;提出了调控排放系统调蓄容积的水量平衡估算法;建立了透水砖地面的设计流程。成果可为指导城市雨水利用工程建设、促进城市雨水利用技术的推广提供技术支撑。     

A Desktop Analysis of Potable Water Savings from Internally Plumbed Rainwater Tanks in South-East Queensland,Australia

A methodology for the estimation of household potable water saving due to internally plumbed rainwater tanks (IPT) is presented in this paper. The methodology is based on a pairwise comparison of household water billing data between homes with IPT and without rainwater tanks (No Tank). These savings were compared with estimations using measured end use data and rainwater demand predictions using the Rainwater TANK model. The paper describes the application of this methodology to a case study in the south-east Queensland (SEQ) region of Australia. There was a significant reduction in mains water consumption for IPT properties in all regions studied in SEQ. Water reductions from mains supplies varied markedly across regions with mean values ranging from 20 to 95 kL/hh/y with an average mean of 50 kL/hh/y. Median water consumption values, ranged in mains water reductions from 28 to 52 kL/hh/y, with an average median of 40 kL/hh/y. Considering both measures an average water saving between 40 and 50 kL/hh/y can be expected from internally plumbed rainwater tanks. Water restrictions appear to have a strong influence on estimated reductions in mains water use. In regions where water restrictions were severe, water consumption was less varied between No Tank and IPT homes with a consequent reduction in estimated savings observed. Recommendations for further work include a survey to capture confounding factors that could not be fully controlled in the desktop study and a controlled pairwise experiment to monitor water consumption from raintanks.     

Performance Analysis of a Communal Residential Rainwater System for Potable Supply: A Case Study in Brisbane, Australia

Cities in developed countries have increasingly adopted rainwater tanks as an alternative water source over the last 15 years. The rapid uptake of rainwater tanks has been driven by the need to reduce demand for centralised water services that are under pressure to adapt to population growth and climate change impacts. Rainwater tanks are part of integrated urban water management approach that considers the whole water cycle to provide water services on a fit for purpose basis that minimises the impact on the local environment and receiving waters. Rainwater tanks are typically applied at the household scale for non-potable water source uses such as toilet flushing and garden irrigation. However, this paper reports on a communal approach to rainwater harvesting, where the water is treated for potable use. A communal approach to rainwater harvesting can offer benefits, such as: economies of scale for capital costs, reduced land footprint, centralised disinfection and flexibility in matching supply and demand for different households. The analysis showed that the communal approach could provide a reliable potable water source to a small urban development. However, there was an energy penalty associated with this water source compared to centralised systems that could be addressed through more appropriate pump sizing. The outputs from this monitoring and modelling study demonstrated rainwater harvesting can be expanded beyond the current mainstream practices of household systems for non-potable use in certain development contexts. The analysis contained in this paper can be used for the improved planning and design of communal approaches to rainwater harvesting.     

Microbial challenge-testing of treatment processes for quantifying stormwater recycling risks and management.

Pathogenic microorganisms have been identified as the main human health risks associated with the reuse of treated urban stormwater (runoff from paved and unpaved urban areas). As part of the Smart Water initiative (Victorian Government, Australia), a collaborative evaluation of three existing integrated stormwater recycling systems, and the risks involved in non-potable reuse of treated urban stormwater is being undertaken. Three stormwater recycling systems were selected at urban locations to provide a range of barriers including biofiltration, storage tanks, UV disinfection, a constructed wetland, and retention ponds. Recycled water from each of the systems is used for open space irrigation. In order to adequately undertake exposure assessments, it was necessary to quantify the efficacy of key barriers in each exposure pathway. Given that none of the selected treatment systems had previously been evaluated for their treatment efficiency, experimental work was carried out comprising dry and wet weather monitoring of each system (for a period of 12 months), as well as challenging the barriers with model microbes (for viruses, bacteria and parasitic protozoa) to provide input data for use in Quantitative Microbial Risk Assessment.     

城镇雨水收集利用储存池优化规模的探讨

区域性雨水利用系统的雨水利用量应以改善区域的水循环系统和生态环境为基本目标,宜以接近自然状态地表径流排放量为雨水利用总量的控制标准。根据研究给出典型城市雨水收集储存池规模的合理设计参数;雨水可收集量小于日需水量时,储存池规模按日降雨量计算,各城市设计雨量重现期不宜超过0.3年,或设计雨量上限不超过50mm,或直接采用水质控制体积(WQV)的设计雨量;雨水收集量大于日需水量时,储存池规模可按5日需水量计算;对于储存能力较大的人工水体,其所需规模除考虑景观设计要求外,需要通过年水量平衡分析来确定。     

雨水回用对城市水循环和下游生态环境的影响

基于水量平衡理论和城市径流污染控制理论,从水量和水质2个方面探讨城市雨水回用对地表水和地下水原有自然径流以及对下游生态环境的影响。结果表明:雨水回用不仅不会减少雨水入渗量,还可以控制雨水径流污染,削减汛期江河下游区域的洪峰流量,是改善下游区域生态环境的有效途径。最后对城市雨水回用的合理规划提出了建议。     

下凹式绿地和蓄水池对城市型洪水的影响

以北京市奥林匹克公园为研究区,采用美国环保局开发的SWMM(Storm Water Management Model),对研究区内下凹式绿地和蓄水池两种措施条件下排水管道主要断面洪峰流量的变化进行了计算分析.计算结果表明,下凹式绿地和蓄水池可以有效地削减洪峰,推迟峰现时刻,减小径流系数,从而增加雨洪资源利用量.     

SSUIS - a research model for predicting suspended solids loads in stormwater runoff from urban impervious surfaces

Suspended solids from urban impervious surfaces (SSUIS) is a spreadsheet-based model that predicts the mass loading of suspended solids (SS) in stormwater runoff generated from impervious urban surfaces. The model is intended to be a research tool and incorporates several particle accumulation and washoff processes. Development of SSUIS is based on interpretation of storm event data obtained from a galvanised iron roof, a concrete car park and a bitumen road located in Toowoomba, Australia. SSUIS is a source area model that tracks the particle mass balance on the impervious surface and within its lateral drain to a point of discharge. Particles are separated into two groups: free and detained, depending on the rainfall energy required for surface washoff. Calibration and verification of SSUIS against the Toowoomba SS data yielded R(2) values ranging from 0.60 to 0.98. Parameter sensitivity analysis and an example of how SSUIS can be applied to predict the treatment efficiency of a grass swale are also provided.     

基于人工神经网络和粒子群优化的初期雨水调蓄池设计方法研究

城市地表径流所产生的非点源污染是城市水系水质恶化的主要原因,设置初期雨水调蓄池是缓解地表径流污染最经济有效的手段之一。目前,初期雨水调蓄池一般采用经验方法设计,没有考虑汇水区污染物累计特性、污水处理厂处理规模、可用征地等客观条件,初期雨水调蓄池的截污效果有限。本文利用SWMM模型模拟分析了地表径流污染物累积特性,利用人工神经网络得到各调蓄池不同截污率与对应总截污量之间的高精度非线性数学模型;结合该模型,以调蓄池总截污量最大为优化目标,以污水处理厂处理规模和可用征地为约束条件,采用粒子群优化算法得出各调蓄池的优化截污率;结合各调蓄池截污率与径流量累积量之间的关系,得出各调蓄池的设计容积,并与国内常用的设计方法进行对比。分析表明,本文提出方法可在满足约束条件下实现截污效果最大化,采用本文提出方法设计的调蓄池在土地使用率和截污效果上均优于规范设计法。该方法合理、高效和适用范围广,可为城市初期雨水调蓄池设计提供技术支撑。     

Restoration of stormwater retention capacity at the allotment-scale through a novel economic instrument

Urbanisation results in changes to runoff behaviour which, if not addressed, inevitably degrade receiving waters. To date, most stormwater management has focussed on the streetscape and public open space. Given that much of the catchment imperviousness is located on private land, we developed and tested a novel economic instrument (a uniform price auction) for encouraging allotment-scale stormwater retention. We evaluated bids using an integrated environmental benefit index (EBI), based on the ability of the proposed works to reduce runoff frequency, pollutant loads and to reduce potable water demand. The uniform price auction resulted in 1.4 ha of impervious areas being effectively 'disconnected' from the stormwater system. The EBI provided an objective and transparent method of comparing bids, which varied in the type of works proposed (e.g. rainwater tank, rain-garden), the cost and the resulting environmental benefit. Whilst the pilot auction was a success, the public subsidy of works undertaken was around 85%, meaning that property owners a relatively small private benefit in the works. Future auction rounds will be revised to (i) test an EBI which is more focussed on the protection of streams (assessing changes to runoff frequency, baseflow volumes and water quality) and (ii) provide an auction process which is simpler to understand, and provides greater practical support for landholders who wish to undertake works.     

海绵型公园雨水控制分析计算方法——以成都市活水公园为例

海绵城市建设中,为了实现对雨水控制的定量计算,若采用模型模拟需要详实的数据基础,推广起来存在诸多问题。本文以径流系数为主要分析手段,运用较为简便的方法对成都市活水公园进行海绵型公园改造前后的雨水控制各项指标做了定量计算,利用芝加哥雨型进行雨量分配,对改造前后公园外排水流量进行对比分析,结果表明进行海绵型公园改造后,5年一遇降雨外排水流量削峰率达74%,峰现时间延后25min。外排水流量径流系数为0.278,年径流总量控制率大于85%。对3年和5年重现期的雨水控制效果均较好。此计算方法可用于面积不大的海绵城市试点区域或海绵型公园的雨水控制计算,所需数据量小,操作性强,具有可重复性和实用价值。可对海绵城市建设中的雨水控制指标计算提供一定参考。     

An investigation of rainwater tanks quality and sediment dynamics.

Rainwater tanks are being introduced into urban areas in Australia to supplement centralised potable supply systems. A pilot scale tank study and a full-scale field tank study found that heavy metal concentrations in water samples taken from the tank's supply point can, in some cases, exceed levels recommended by guidelines. Both studies also found very high concentrations of heavy metals in the sediments accumulated at the base of rainwater tanks. Laboratory experiments are underway to investigate sediment transport processes within a full-scale tank. Preliminary results demonstrate the effect of sediment resuspension on the quality of water released from the tank outlet. Improved tank designs that reduce sediment resuspension and mitigate impacts on water quality are the focus of future work.     

城市雨水调蓄利用及效益分析——以南京大学仙林校区为例

随着城市化发展,水资源短缺、水环境污染和城市内涝等问题日益突出,雨水调蓄利用成为缓解以上问题的重要手段。以南京大学仙林校区为研究区,进行可集雨量与室外用水需求的水量平衡计算,结合雨水利用措施分析,开展雨水调蓄利用的方案设计及综合效益分析。结果表明:雨水调蓄利用后,研究区综合径流系数下降为0. 532,重现期2、5、10 a对应的屋面集雨量均能满足室外用水需求,对应的单位面积雨水利用年综合效益分别为8 475. 6、10 506. 3、11 786. 4元/hm2。城市雨水调蓄利用可产生显著的生态、经济和社会效益,在城市新区开发和旧城改造过程中应当得到足够的重视。     

Water balance modelling of alternate water sources at the household scale

Alternate water sources are being implemented in urban areas to augment scheme water supplied by a water utility to homes. These sources include residential wells, rainwater tanks and greywater systems. Greater water efficiency can be achieved when these systems are designed to match a water source to a given demand based on both water quantity and quality parameters. In this way the use of an alternate water source can be maximised and the use of the high quality scheme water minimised. This paper examines the use of multiple alternate water sources sequentially to supply the same demand point potentially optimising the use of all available water sources. It also allows correct sizing of such water systems and their components to reduce scheme water demand. A decision support tool based on water balance modelling was developed that considers such water options at the household scale. Application of this tool to eight scenarios for both large and small house lots shows that using alternate water sources individually can result in significant scheme water savings. However by integrating these sources additional scheme water saving can be made.