ReWater SUMMER 2010 Water recycling in Australia Reverse osmosis pipe for drip irrigation Page 2 Biogas power Federal funding Recycled Yarra Park water from water for stormwater water key to project plans recycling plant harvesting supply security revealed Page 4 Page 5 Page 6 Page 8 Image: ReWater http://eureka.australianmuseum.net.a CONTENTS FEATURES Reverse osmosis pipe for drip irrigation 2 Biogas power fuelled from water u recycling plant 4 Stormwater harvesting and reuse schemes receive federal funding 5 Rainwater harvesting replenishes cave network 6 Recycled water key to supply security 6 Yarra Park water project plans revealed 8 Hawkesbury river replenished with $209 million recycled water plant 9 Integrated water management vital for US horticulture 10 ROSDI was found to be suitable for cultivating tomato plants on brackish water. REGULARS Events diary dates 3 Good Reads and website links 7Reverse osmosis pipe for News innovations & information 10 drip irrigation “The right to food is not negotiable.” etween now and 2030, the world’s with lower surface water run-off in this area, population is expected to grow by has restricted farmers’ access to surface wa- About ReWater “ B two billion people. Feeding this grow- ter for irrigation. Although brackish ground- ing population and reducing hunger will only water is available, prolonged irrigation with ReWater is a newsletter designed to make information be possible if agricultural yields can be in- 3,500 to 5,000 mg/L TDS water gradually relevant to recycled water use in horticulture more accessible to horticulturalists (growers/farmers), creased significantly – and sustainably. With damages the soil structure. Current technol- primary producers, members of the water industry so much of the Earth’s water being used for ogies used to remove salt from water, such and other interested people. It is part of the service agriculture1, it is clear that an improvement as reverse osmosis, are both capital and provided by the Australian Coordinator for Recycled in the management of agricultural water be- energy intensive and cannot viably be used Water Use in Horticulture, funded by Horticulture Australia Limited. comes key to the achievement of global food in these applications. The research began security.2” with a simple research question; “if a reverse Back issues and instructions for subscribing to receive osmosis membrane could be incorporated ReWater electronically quarterly can be accessed at “Instead of using a high into a drip irrigation line, www.recycledwater.com.au/rewater applied pressure on would the suction in the the saline side of the Water tension on the Your Feedback and Contributions root zone of a plant pro- membrane to “push” soil side “pulls” water We would appreciate your feedback and are always vide sufficient energy to water through the mem- looking for suggestions and contributions. Please through the membrane extract water for plant email [email protected] or contact us on brane, the new system growth while preventing 03 9640 0221. uses a water tension on the soil side of the the movement of salt into the soil?” If so, a www.recycledwater.com.au membrane to “pull” water through the mem- simple irrigation system with these properties brane.” The delivery of research and would allow farmers to use saline water, not development outcomes from In many agricultural precincts there are large only in times of protracted drought, but also this project to the horticultural numbers of existing groundwater bores that as an alternative to increasingly restricted industry is made possible by the Commonwealth Government’s access aquifers containing brackish water fresh water supplies, to produce a crop while 50% investment in all Horticulture containing levels of dissolved salts gener- managing the potentially adverse impacts of Australia’s research and ally in excess of 2000 mg/L total dissolved salt accumulation in the soil. development initiatives. salt (TDS), or 3000 µS/cm when expressed as an electrical conductivity (EC). As a gen- Research DISCLAIMER: Every attempt is made to ensure the accuracy eral rule, groundwater bores with salinity in Experiments performed by Greg Leslie of the of all statements and claims made in ReWater. However, excess of 2000 mg/L are unsafe to use for due to the nature of the industry it is impossible for us to University of New South Wales and Bruce sustained irrigation3. A Reverse Osmosis know your precise circumstances. Therefore we disclaim any Sutton of the University of Sydney demon- capable Sub-surface Drip Irrigation (ROSDI) responsibility for any action you take as a result of reading strated that a subsurface drip irrigation line ReWater. issn1449-9800 was developed to allow farmers to use this manufactured from a commercially available brackish water. Edited & compiled by reverse osmosis membrane is capable of Atura Pty Ltd. The idea providing sufficient water for the cultivation Ph: (03) 9640 0221 of tomato plants on brackish water with an www.atura.com.au The development of ROSDI was originally electrical conductivity of 4000 to 5000 µS/cm, s Designed by Arris Pty Ltd inspired by drought conditions in food pro- while preventing the accumulation of salts Ph: (08) 8303 6706 duction areas of south east Australia, where in the soil. These preliminary experiments rri reduced annual average precipitation, along a www.arris.com.au continued page 3 Summer 2010 2 www.recycledwater.com.au from page 2 demonstrated that brackish and saline water of the plant. This avoids the problem of ex- that would normally be unsuitable for use in cessive abstraction from the water source. irrigation systems (e.g. groundwater or some The residual salts stream is about the same water recycled from sewage effluent) for the EC as highly saline water which can be im- cultivation of food crops, can be used to pounded and used for other applications grow plants, such as tomatoes without allow- such as the inland cultivation of bream and ing the build-up of salts in the soil. In normal brine shrimp. operation, transpiration water loss by plants causes a water suction pressure (properly Leslie & Sutton have successfully filed for a referred to as a low water potential) to ap- patent for this technology and are currently pear at the root surface. This acts to draw conducting research on the use of biode- water from the soil to the root. As the soil gradable cellulosic-based membranes for near the root is dried, it too displays a suction the drip irrigation lines. pressure that draws water from further away. Associate Professor Greg Leslie and Professor Source: Greg Leslie, Associate Professor, UNSW, Deputy Typical values of this pressure are within the Director, UNESCO Centre for Membrane Science and range -0.1 bar (field capacity) to -15 bars Bruce Sutton receiving the Peter Cullen Eureka Technology. All images courtesy of Greg Leslie. Prize for water research and innovation. (permanent wilting point). So, instead of us- ing a high applied pressure on the saline side of the membrane to “push” water through the between 0.25 L/m2/h and 1.5 L/m2/h as the membrane, the ROSDI system uses a water height and leaf count of the plant changes as tension on the soil side part of the plants growth of the membrane to The rate of water movement pattern. Clearly the rate of “pull” water through the across the membrane into the water movement across membrane. Leslie & the membrane into the Breaking news! Sutton also found that root zone varies according to root zone varies accord- The Groundwater Replenishment Trial in by increasing the water ing to the needs of the the needs of the plant Perth is now fully operational and recycled holding properties of plant. Moreover, unlike water was first recharged into groundwater the soil by varying the amount of loam, sand conventional reverse osmosis, the transport on Wednesday 10 November 2010. and clay it was possible to increase the rate of water across the membrane is not driven of transport of water across the membrane. by a high energy pump that produces water The advanced water recycling plant has at a rate of 20 L/m2/h at pressures of 10-15 at- been operational since late 2009 and has Practicalities mospheres but by the matric potential in the been producing water that meets all the soil as governed by the evaporative losses required standards. The WA Department The ROSDI operates at constant low flow at through the plants’ stomata. of Health gave approval for the Water Cor- low pressure (e.g. with a ring-main approach poration to commence recharge in early to reticulation). The researchers have demon- The irrigation tube diameter is sufficiently November 2010. strated that saline water with an EC of 4000 large (2-5 cm) to allow the flow of water with- µS/cm can be drawn across an RO mem- out the usual problems of internal fouling of In addition, the Water Corporation has also brane in soil with a root water potential of the membrane by silts, clays and suspended completed construction of an interactive less than -2 bar at an initial flux of 1.5 L/m2/h solids that are common in conventional RO Visitor Centre at the advanced water recy- with an average salt rejection of 50%. They systems. The losses from the system are cling plant and public tours of the facility have observed that the flux rises and falls only associated with the water requirements will commence early next year. For more information: 1Seventy to eighty percent of the fresh water harvested by humans is used for agriculture, producing about half the world’s food. 2FAO (2009). Water at a glance. The relationship between water, agriculture, food security and poverty.