Innovation and Integration of Water Systems in a Public Building: The Grove
‘The Grove’ is an innovative public building project, jointly undertaken by the Towns of Cottesloe and Mosman Park and the Shire of Peppermint Grove. The facility consists of a library, community learning centre and administration offices and incorporates a broad range of environmentally sensitive design (ESD) features including climate-sensitive building design, energy and water-efficient fixtures and fittings, renewable energy systems, rainwater harvesting, as well as the onsite treatment and reuse of wastewater and stormwater, and waterwise gardens and irrigation.
While all of these features are ideal, it wasn’t an easy task to bring everything together. The difficulty was that this project was the first public building in the Perth metropolitan area to have rainwater supply for internal potable uses (in a mains water serviced area) and onsite treatment of wastewater (in a sewered area).
It is also the first in Australia to have yellow water diversion for nutrient recovery via onsite fertigation. The water systems design aims to reduce reliance on both mains water and bore water, as well as to utilise nutrients within the landscape through appropriate plant selection and irrigation system design.
Pics above: Rainwater tank installations. 210,000 L external concrete tanks (6) and 44,000 L internal steel tanks (11). Wastewater systems installations.
Clever landscaping and garden design continues the building’s integration with the environment, including fruit trees, insect-attracting plants and recycled timber features. Waterwise drip irrigation is used throughout the grounds and soil moisture sensors contribute to control the watering regime of plants, and the balance of wastewater and bore water used for irrigation purposes.
Internal water consumption is reduced through the use of approved limited flow water fixtures and fittings, including the use of waterless urinals. Rainwater will meet 100% of internal water demand, saving an estimated 730,000L of mains water each year. The rainwater harvesting system includes a range of above and below ground storage tanks to the capacity of 258 kL, symphonic guttering, automatic first flush diverters, micro filtration and UV disinfection for potable water and mains water backup. The smaller, steel aquaplate tanks (total 40 kL) in the basement will be drawn down last due to their dual duty and contribution as part a thermal mass cooling of the building.
The design recognises that a public facility such as this one will have widely varying usage patterns subject to events, seasons, and public and school holidays. However applying medium daily occupancy and based on the water-efficient fixtures that have been specified for the buildings, it is estimated that mains water savings would increase to approximately 905 kL under a business-as-usual scenario where ‘standard’ water fixtures were being used in the buildings. An automated back-up via scheme water is provided should collected rainwater be insufficient and not meet demand.
Wastewater is separated by stream (grey, brown and yellow) at the source to enable fit for purpose treatment based on the intended reuse. Greywater from the handbasins and showers is used to irrigate plantings in the children’s sensory garden via substrata dripline after sedimentation, filtration and disinfection with ozone. Brown water (toilets and kitchen sink sullage) is treated to a secondary standard through biological processes and applied to turf areas via subsurface drip irrigation. Yellow water is collected from the male urinals (and from future urine collecting toilet bowls) and stored for use as fertiliser via controlled dosing of the irrigation lines or wastewater pump out tanks.
Pic: Wastewater stream was separated at source – brown water treated in three Biolytix tanks, greywater treated in a GRS WaterClear system with ozone disinfection and yellow water (urine) collected and stored for use as fertilise as required.
The injection of fertiliser into the flowing water of an irrigation system is termed ‘fertigation’. By controlling the dosing rate of urine injection into the different pump tank systems, the amount of fertiliser/nutrients given to specific plant groups can be regulated. Bore water is used to irrigate native planting areas and to supplement wastewater volumes based on building occupancy and seasonal plant water demands. It’s estimated that the wastewater system will reduce the draw on groundwater that would be used for irrigation by approximately 700,000L each year.
Stormwater collects on site from a 20 hectare catchment. A constructed reed bed and wetland system has been created to treat low and normal flows as well as first-flush peak stormwater flows to improve stormwater water quality prior to infiltration into the aquifer by reducing hydrocarbons and nutrients. The stormwater treatment system has been designed to create an aesthetically pleasing, functional and educational landscape feature that reflects the seasonality of the Swan Coastal Plain.
Control and monitoring of the water systems will be carried out by a building monitoring system that can provides real time reporting on water availability and usage by source, soil moisture levels and on-site rainfall, along with information on other parameters of the performance of the building. A dedicated computer monitors and runs all the integrated systems so designers can identify improvements and the public will be able to see the building’s energy and water use at a reception display. The implementation of ESD features has been a remarkable success, and already the building and surrounds are seen as a benchmark for future green buildings and climate-sensitive and climate-responsive landscapes and irrigation.
For example, irrigation specialists often suggest that plants should get about 25 to 35 mm each week, but this has to be fine-tuned after consideration of both local climate, considering evaporation rates and air temperature, as well as the water demand by the vegetation. i.e. crop factor. Irrigation demand can be calculated by considering all of these factors because clearly water demand by turf in summer in Perth is far greater than native plants during winter. Using these types of calculations, a thorough and meticulous watering plan was developed. The Grove landscape also has plants grouped with similar water demand and the irrigation schedule adjusted to reflect seasonal change. To ensure over-watering doesn’t occur an electronic rain gauge is used to stop bore use during rainy periods, and even this can be adjusted to delay irrigation for one to seven days.
The turf (lawn) area was spilt into for subzones of about 90-100 m2 to enable best practice watering to occur. Frequent, but under-watering lawn may translate to plants being shallow-rooted and weak, and not well-established. In fact, shallow, frequent irrigation also encourages irrigation “dependency”, poor drought tolerance, fungal disease, increased evaporative losses and salt accumulation at the surface. The optimum water regime for plants is at least a 10 mm application at any one time, and this practice was followed when determining the run times for stations. In a similar way, greywater use for exotics is split into four zones, each approximately 60 m2. Making irrigations as deep and infrequent as possible will maximise rooting depth and plant use efficiency (evapotranspiration). There have been many other lessons learnt in this project. It is essential to collect reliable data to ensure optimum water regimes, and how often to use the bore to top-up the brown and greywater systems.
Maintenance is another key issue. The regular cleaning and checking of pumps, filters, flush valves, tank systems, ozone generation, UV filtration, and the desludging of tanks and first flush devices would seem overwhelming to some, but extremely necessary to prevent malfunction of complex systems. In addition to servicing, replacement of some components is also necessary. Every year UV lamps, ozone lamps and tech filters need replacing, and if, for some reason, pumps failed then their replacement adds further costs which need to be factored whenever these types of projects are instigated. Furthermore, to validate system function regular monitoring and testing of water quality is crucial. Indeed, thousands of dollars must be spent each year on water testing to ensure public safety. Regulatory compliance can be frustrating. Out-dated regulations about rainwater use, wastewater recycling, and the rigorous regime of testing and reporting that is required prohibit many more schemes being adopted.
In order to achieve maximum water efficiency and water conservation on this site it is necessary to maximise the use of alternative water supplies, namely rainwater and recycled water. This has led to the preparation of both an Alternative Water Quality Management Plan (AWQMP) and a Recycled Water Quality Management Plan (RWQMP) with an emphasis on urine separation and use for fertigation. In the meantime, a vigorous and thorough sampling program will establish benchmarks until such time as consistency of satisfactory performance is achieved and demonstrated. The integration of this suite of innovative water systems within one building represents a first in Western Australia and compliment the many other sustainable environmental technologies that have been incorporated within this groundbreaking project.