National greenhouse waste-water recycling project (VG09073)

This was a final research report from Hort Innovation’s historical archives. Please note that as these reports may date back as far as the 1990s, the content and recommendations within them may be superseded by more recent research.

What was it all about?

The national greenhouse waste-water recirculation project was designed to deliver necessary skills to greenhouse vegetable growers in converting their free-drainage (open) systems to full recycling (closed) as per the following:

• Collect the technical knowledge and information required to enable growers to efficiently convert their greenhouse waste-water systems.
• Investigate any potential pathology issues related to recycling waste-water including assessing the efficacy of various sterilisation systems.
• Knowledge gained was delivered to key Australian growing areas by a series of theoretical & practical workshops.
• A literature review was conducted to assess the information available at the time about converting systems, waste-water sterilisation options and recycling nutrients. This review ensured global world’s best-practice was included in project and knowledge gaps were identified and research commissioned to address issues.
• A training package containing information and course details was developed for delivery to industry.
• It was identified that waste-water products from hydroponic systems were potentially harmful to the environment and should be managed on farm.
• Additionally, greenhouse growers could substantially reduce their cost of production through average savings of 40 per cent water and 60 per cent fertilizer and further reduce their impact on the natural environment. (resulting in an average annual saving for every 4,000m2 greenhouse system of ±$15,000)
• This project identified from the hundreds of workshop attendees that the average drain per cent was ±40 per cent (to maintain a suitable root-zone condition) and 60 per cent fertiliser savings calculated Pre EC (drain EC x drain per cent e.g. 3.7 x 40 per cent = 1.5 Pre EC, feed EC = 2.6, 1.5 / 2.6 = ±60 per cent fertiliser savings)
• Municipality’s reluctance to issue new (or extend existing) permits for greenhouse production based on perceived environmental impacts was minimised
• Growers gained skills to safely recirculate nutrient rich waste-water, sterilise and neutralise disease pathogens and rebalance nutrient inputs and outputs.

The investment was relatively low with high returns on the cost of production and for the natural environment as this project had the capacity to deliver an annual benefit to industry of $25million and divert around 5,000 mega-litres of nutrient-rich water from impacting on the natural environment.