Capturing the potential of stormwater
Management of the urban water cycle in Australia has changed significantly over the past few decades. As we lived through a series of droughts and floods, we adapted our water systems to cope with our ever changing environment. Australia's variable climate means that droughts and floods are inevitable - we just don't know when they will next occur, or how severe they will be. Today, we know much more about our water cycle than ever before and we have markedly improved our knowledge about water system management.
The water cycle includes all forms of water - recycled water, rainwater, stormwater, wastewater, groundwater, potable water and water contained in our rivers and bays. The notion of the whole-of-water-cycle management and planning (also known as Integrated Water Cycle Management IWCM) has become an accepted fact and the common practice amongst water experts and within the various levels of government and general public.
Living in the dry country we need to value and use the rain that falls on our land and the stormwater runoff generated by that rainfall.
Stormwater management philosophy in most developed countries has evolved over the last decades from the conventional, but still important, flood mitigation paradigm, to the current runoff quality control approach. It is now progressing towards the harvesting and reuse concept whilst retaining the previous two targets.
Urban Stormwater Harvesting (SWH) is one of the essential components of Integrated Water Cycle Management (IWCM) that offers multiple solutions to urban water systems such as mains water demand reduction, water quality improvement and in many cases creek ecosystem health protection. A number of SWH projects have been implemented in Australia to date and the number of SWH schemes is expected to grow with wider uptake of the IWCM encouraged by the State's and Federal Government.
In this paper the author presents the key observations gained through his involvement in the planning, design, construction and operation of the stormwater harvesting schemes and the practitioner's view on some of the key issues that need to be addressed.
Urban Stormwater Harvesting and its major components
Urban Stormwater Harvesting can be defined as the collection, treatment, storage and use of stormwater run-off from urban areas.
Stormwater harvesting requires a number of physical facilities. These include infrastructure for capture, storage, appropriate treatment, maintenance and supply to end users in cost effective ways. Sufficient runoff must be available and sufficient space be available to permit storage or retention, depending on whether the aim is water supply or to manage stormwater quantity and quality.
Typical urban stormwater harvesting schemes include all or a combination of the following components (Figure 1):
- Catchment providing the run off volume
- Diversion structure (DS)
- Primary screening device
- Buffer storage
- Transfer facilities from buffer storage (e.g. pump and rising main)
- Treatment facilities
- Transfer facilities to the clear water storage
- Clear water storage
- Distribution pumps
- Disinfection and supply rising main
- End use
Figure 1Functional Diagram - Stormwater Harvesting System components
Typical mode of operation for Stormwater harvesting scheme (Figure 1):
Designated volume of run off from the catchment (1) is diverted by the diversion structure (2) installed on the existing drainage system
The diverted run off is screened to remove gross pollutants and coarse sediment (3)
Screened run off gravitates into the buffer storage (4); the aim of the buffer storage is to level out the
variance in the incoming flows and optimize the operational parameters of the pump that supplies water to
the treatment component
Water from the buffer tank is transferred/pumped (5) into the treatment component e.g. wetland/bio
retention (6) were the required quality of product water is achieved
Treated water is transferred to the clear water storage typically via a pump (7)
The treated water is stored in the Clear Water storage (8)for intended use; in many of the schemes
involving irrigational use of product water a relatively large storage is required due to the temporal
difference between the rainfall (collection) and irrigation (usage)
Product water is distributed to the end users via a system of pump(s) and lilac pipes (9)
Distribution process typically includes the disinfection of product water (10) e.g. with the on line UV system
Fit for purpose water is delivered to the end users (11)
Planning, Design, Construction and Operational Considerations
While it is beyond the scope of this article to discuss the particular detail of stormwater harvesting schemes, a few general comments based on practical experience should prove useful for stakeholders contemplating a stormwater harvesting scheme.
The tasks/disciplines required for the successful delivery of a stormwater harvesting scheme are diverse and would typically include the following:
- Flora & Fauna
- Heritage & Cultural
- LCA (Land Capability assessment)
- Environmental Risks Assessment
- Statutory & land acquisition, planning zone, dam permit
- Diversion and water use licenses from water authorities
- Other utilities (e.g. electricity, communication )
4.0 Site Investigations
- Services and Surveying
- Water quality sampling and flow monitoring
5.0 Detail Design of Stormwater harvesting scheme
- Diversion works incl. primary screens
- Raw water transfer infrastructure
- In line detention
- Raw water storage (open dam or underground tanks)
- Water treatment
- Clear water storage
- Distribution infrastructure
- Hydraulics design (diversion rates, detention and storage volumes, intake/outlet structures, pipes, pumps)
- Mechanical (pipes, pumps, tanks)
- Structural engineering (soil mechanics/retaining structures, dams, concrete structures, pits, pump stations)
- Civil structures (open storages, access roads, drainage, waste disposal)
- Electrical engineering (extension of services, switchboards)
- Process treatment part 1 - natural systems (e.g. wetlands, bio filtration) Process treatment part 2 - conventional (e.g. media filtration, UV) Instrumentation & Controls (e.g. SCADA)
6.0 Landscape architecture (some projects)
7.0 Irrigation design (some projects)
8.0 Estimation of Construction Costs/QS
9.0 Project management, reporting and QA
10.0 Construction Management
11.0 Commissioning and scheme validation
12.0 Post Commissioning scheme performance assessment, audit and reporting
13.0 Operation & Maintenance
Development of stormwater harvesting practice
The robust engineering basis for the planning, design, construction, operation and maintenance of urban stormwater harvesting is yet to be developed. This is because it is a relatively new engineering concept, despite being used in some form or another in various places around the world for centuries.
In the absence of the established design basis for stormwater harvesting - designers of these schemes frequently resort to the approaches borrowed from the more traditional disciplines such as municipal drainage and water sensitive urban design (WSUD). A number of leading Australian stormwater professional have commented on this issue e.g. Hatt, Deletic, Fletcher wrote in their article ‘Integrated treatment and recycling of stormwater: a review of Australian practice' Journal of Environmental Management, vol.79, issue 1, April 2006:
Existing stormwater recycling practice is far ahead of research, in that there are no technologies designed specifically for stormwater recycling. Instead, technologies designed for general stormwater pollution control are frequently utilized, which do not guarantee the necessary reliability of treatment. Performance modelling for evaluation purposes also needs further research, so that industry can objectively assess alternative approaches. "
However, as the practice of stormwater harvesting is continued and more projects are commissioned in the years to come, the design paradigm for stormwater harvesting should be further developed and validated.
Stormwater Harvesting guidelines
One of the major barriers to the wider uptake of SWH particularly by Local Government is the absence of comprehensive SWH guidelines. Such a guideline would allow the proponents of the schemes (Councils, regulators, consultants, contractors and other stakeholders' groups) to have a uniform reference document outlining current best practice including legislative framework, design / functionality, construction, operation and maintenance.
This document, once developed could offer comprehensive guidelines for implementation of storm water harvesting schemes in Australia as part of an Integrated Water Cycle Management (IWCM) approach, based on current legislation, best available engineering science and practical lessons learnt during planning, design, construction and operation of existing SWH schemes.
The SWH Guidelines will provide the clear path for implementation of the best practice stormwater management related to SWH and re-use in Australia, contributing to:
- bettermanagementof storm water (balancing the harvesting to maximum aquatic and terrestrial benefits)
- improved water quantity and quality management
- reducedloca lflooding
- maximising the sustainable utilisation of storm water as a resource
- greater uptake of storm waterharvesting
- improved green space in urban areascontributing to livability
- improve allocation and harvesting of stormwater and integration with water sensitive urban design
- better landscapes and parkland managed with available stormwater
- informed strategic directions and policies for stormwater management and integrated water managementacross communities, councils and catchments
By providing the knowledge and confidence to implement sustainable well designed SWH projects the Guidelines will set the bench-mark for best practice SWH and provide the know-how to achieve it, overcoming many concerns and lack of knowledge currently associated with stormwater harvesting. The SWH guidelines will also assist in de- mystifying operational concerns and build confidence in managing "Harvesting Storm-water".
The development of SWH Guidelines is a complex and multidiscipline project requiring good coordination, adequate resources, extensive stakeholder's consultation and sufficient time and funding.
The resultant document should be based on "four pillar" (Figure 2):
Current regulation & legislation
Best engineering practice
Consideration of operation & maintenance issues
Case studies and practical examples
Fig 2:Stormwater Harvesting Guidelines development - major components
More detail flowchart on topics and structure of the guidelines is presented in Figure 3.
Stormwater Harvesting Guidelines- detailed components (Figure 3)
Also, an indicative Table of contents (TOC) for the SWH Guidelines is presented in Table: 1
Performance assessment for stormwater treatment devices
Selecting the right treatment train to meet the water quality objectives is essential for the successful and sustainable operation of SWH systems.
At present, there are no standard methods or guidelines for the testing, validation and performance assessment of stormwater treatment devices in Australia. The wider uptake of IWCM and WSUD and growing number of stormwater treatment devices pose a need for the consistent and verifiable performance database to inform the fair and technically robust assessment and selection processes for treatment of stormwater. As the market for stormwater treatment devices' expands - the lack of published data on their performance becomes more apparent (Victorian Stormwater Committee 1999), while detailed field monitoring is also very scarce (Wong et al. 2000). The combination of a large number of devices, a lack of reporting protocols and standard methods and only a small number of detailed monitoring studies has resulted in a large uncertainty in stormwater treatment devices selection. Local government, which is largely responsible for the implementation and management of stormwater infrastructure in Australia, is dependent on in-house expertise and manufacturer's advice in selecting appropriate stormwater treatment strategies. Independent discussions with local government, water authorities and stormwater industry professionals have revealed interest in the documentation and development of guidelines and frameworks to assist in the system design, product selection and evaluation to ensure adequate stormwater treatment and management.
Development of the protocols on the performance assessment for stormwater treatment devices will greatly assist in the adoption and utilization of Integrated Water Cycle Management (IWCM) approach in Australian towns and cities via the:
- increased certainty in the performance of stormwater treatment devices and resultant water quality delivered by IWCM projects
- Consistent and structured approach to the selection of stormwater treatment devices with the direct benefit to the proponents (e.g. councils/developers), designers, asset owners and other stakeholders of a stormwater projects
- Sharing the legacy of knowledge in storm water treatment with theindustry
In recognition of this industry need a number of research projects have been commissioned by various organizations with a view to assess the options available for independent verification of stormwater treatment devices in Australia, both at the state and federal level.
In this article I'd like to acknowledge the initiatives and support of Melbourne Water Corporation (MWC) and Stormwater Australia (SIA) and their respective work in this area that resulted in two reports produced and now displayed for public consultation via the SIA website, namely:
1.0 Independent Verification Scheme for Stormwater Treatment Devices - Road Map Discussion Paper
2.0 Literature Review on Performance Testing Approaches of Gross Pollutant Traps
Practicing in the area of integrated water cycle management and seeing through the delivery of both waste water and stormwater projects I have noticed some significant differences between those two groups affecting the choice of its delivery mechanism, namely:
- Stricter and more defined regulations in the wastewater market including treatment standards, roles and responsibilities of various stakeholders, approval processes etc.
- Wider adoption of the Design and Construct and Design, Built and Operate contract types as a waste water project delivery mechanism, generally with the Performance Guarantee provided by the Contractor
- Established practice of performance validation and verification in the waste water market
Given the current interest in the uptake of stormwater as a resource (stormwater harvesting) and the on-going commitment to control and treat the run off prior to its discharge into the natural environment by application of WSUD - the Australian stormwater market is likely to grow in the years to come.
The pace that the stormwater market in Australia grows will, to a large degree, depend on the certainty that it can offer to the public, the clients and the government in delivering the stated objectives. Which requires, amongst other things, the clear path on how to achieve the stated objectives (i.e. Stormwater Harvesting Guidelines) and the means to verify that it actually works (i.e. validation and verification protocols).
The increased certainty in the requirements for and the performance of the stormwater treatment components delivered by these guidelines and protocols should allow the market to offer/request a guarantee of performance. This guarantee should open more opportunities for funding, delivery, operation and maintenance of stormwater projects, leading to the greater uptake of stormwater treatment and utilization as a resource.
- Melbourne Water Corporation
- Stormwater Australia (SIA)
- CSIRO Land and Water
- Institute of Public Works Engineering (IPWEA) VIC Claudio Cullino, MECC Consulting Pty Ltd
- Dr Daryl Stevens, Atura Pty Ltd
- Michelle Philp, Joseph McMahon, Sonja Heyenga, Oswald Marinoni, Graham Jenkins, Shiroma Maheepala, Margaret Greenway - "Review of Stormwater Harvesting Practices" CSIRO Publishing, 2008
- Hatt B.E., Deletic A., Fletcher T.D. - ‘Integrated treatment and recycling of stormwater: a review of Australian practice' article published in the Journal of Environmental Management, vol.79, issue 1, April 2006"
- " Institutional and Regulatory Models for Integrated Urban Water Cycle Management - Issues and Scoping Paper" Australian Government, National Water Commission, February 2007
- I.Brodie "Stormwater Harvesting and Water Sensitive Urban Design Detention: A Compatibility Analysis" 12nd International Conference on Urban Drainage, Porto Alegre/Brazil, 10-15 September 2011
About Author: Iouri Vaisman, MD Iouriv Water Solutions (IVS).
Iouri is a civil - construction engineer with over 20 years extensive professional experience in the water idustry both in Australia and internationally. His experience encompasses planning, design, project management and operation of water reuse and recycling schemes including stormwater harvesting, sewer mining, grey water and effluent reuse, stormwater management strategies and hydraulics studies, drainage and Water Sensitive Urban Design.
Iouri is a well-respected member of many professional bodies such as Stormwater Industry Association, AWA, IEAUS and has been actively involved in the training and professional development of the industry on the issues of stormwater harvesting, testing and validation of WSUD components, Integrated Urban Water Management, etc.
Iouri designed and project managed eight currently operational water reuse schemes in Australia including stormwater harvesting, sewer mining, grey water and effluent reuse schemes.
Iouri's other blogs can be read here