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Water Harvesting and Recycling
A Nursery Traders project

In 1992 we constructed our current Nursery Traders Pty Ltd premises, incorporating infrastructure for a water recycling system.

Building on this investment—and in line with our business strategy to Conduct our business with integrity, employing sound business and environmental management practises—Nursery Traders began implementing a series of innovative sustainable water saving and recycling projects. The projects focused on collecting, storing and reusing rainwater run-off from building roofs and car parks.

An ecoBiz member, Nursery Traders takes immense pride in distributing hundreds of thousands of plants into the environment each year—all of them grown sustainably. Matching our environmental goals, we are committed to continuous improvement in all aspects of our business. Delivering on that commitment, we commissioned the water recycling infrastructure projects in five stages—in 1992, 1999, 2002, and 2008 and again in 2010.

Stages 1 and 2 focused on establishing and then expanding water capture recycling and filtration infrastructure.

Stage 3 further extended these methods with water capture and treatment strategies, and included a demonstration project to showcase to industry the potential of recycled water use.

Stage 4 focused on further increasing our water harvesting methods and infrastructure.

Stage 5 focused on installing an on-site weather station to monitor rainfall, humidity, solar radiation, evapotranspiration and wind speed each hour, along with upgrading our water processing and treatment.

Each of these stages required intensive research and analysis on Nursery Traders’ behalf. The new industry ground we were travelling meant that we were continually selecting, refining and adapting available technologies to work in nursery environments.

As a result of these projects, we now capture and use rainwater from building roofs, stormwater run-off and nursery run-off from irrigation to supply more than 80 per cent of our water needs. In addition, we use our on-site weather station to monitor rainfall, humidity temperature, solar radiation, evapotranspiration, and wind speed hourly. Monitoring environmental conditions allows us to automatically adjust the irrigation cycle to ensure we irrigate correctly.

Today Nursery Traders has a proven record of investment in water recycling—demonstrating the pay-offs of a proactive commitment of time, energy and capital with savings of more than 40 000 000 litres per annum since 1999.

This represents a 96 per cent reduction in potable water use per hectare from 29 937 kilolitres per hectare in 1999/2000 to 1232 kilolitres in 2008/2009. Our best achievement to date was in August and September 2008 when only 11 litres of potable water were used to irrigate the nursery—an area of over 12,000 m2.

Nursery Traders operates well beyond industry best practice and has achieved significant and on-going potable water savings since 1999 (see Table 1)—with further savings being achieved every day.


Table 1

Stage 11992 Stage 1 – Water Recycling

In July 1992, Nursery Traders opened its purpose-built facility—incorporating water recycling infrastructure into the design. The site included a 1,000 m2 display shed for indoor plants and associated landscape lines, and approximately 2,500 m2 of open and shade-covered plant displays.

We began recycling water using a 2,000 litre underground concrete tank (which is still in use today) to capture nursery run-off. After capture, the water would be treated, filtered and stored in an above ground 22,000 litre tank for subsequent use in irrigating the nursery.

1999 Stage 2 – Water Recycling

Stage 2After two expansions of the outdoor nursery areas in 1993 and 1997 (to an area approximately 8,990 m2) we installed sand filtration and replaced the original 22,000 litre fibreglass tank with four 35,000 litre poly tanks. We also redirected downpipes from 334 m2 of roof area directly into these tanks.

As a result, our water quality for irrigation improved and the on-site storage of capture run-off, rain and stormwater increased from 24,000 litres to 142,000 litres.

2002 Stage 3 – Water Recycling

Stage 3In 2002, Nursery Traders developed a Queensland Water Recycling Strategy – Demonstration Project. The project incorporated systems to capture, filter, treat and re-use nursery run-off waste water, as well as rainwater from building roofs and stormwater from car parks.

The project had the following objectives:

  1. Reducing our dependence on town water
  2. Gaining the nursery industry’s acceptance of the potential of reusing recycled water
  3. Showcasing a demonstration project for the nursery industry
  4. Providing an environmental and economic solution to the need to supply high quality irrigation water for use on nursery crops

Stage 3Commissioned in May 2002, the final design included:

  • constructing and installing two in-ground collection tanks totalling a capacity of 50,000 litres
  • installing an additional 35,000 litre above-ground poly tank (taking the total to five on-site)
  • installing a chamber to divert stormwater from buildings and car parks
  • fitting filtration, tank level sensors and control units, removable silt bins, grass swales, and various other modifications

By this time, the total nursery area had expanded by approximately thirty per cent from 8,990 m2 to 11,700 m2. Consequently, we increased the on-site storage of captured run-off, rain and stormwater by some 60 per cent from 142,000 litres to 227,000 litres. This step yielded significant water savings—with an 88 per cent reduction in potable water used per hectare compared against our base-line for the 2000 Financial Year.

Together with the major capital expenditure, we implemented the following simple measures and practices:

  1. Grouping products by similar water use
  2. Installing Nelson R2000 sprinklers which increased the water droplet size—making irrigated water less prone to mist away in the wind
  3. Operating sprinklers at the optimal water pressure
  4. Installing drip irrigation where appropriate
  5. Installing capillary matting where appropriate
  6. Monitoring water use daily
  7. Constructing new display areas with underground water drainage for collection and re-use
  8. Most importantly, creating a workplace culture that is focused on maximising the amount of water we recycle

A full description of Stage 3...

2008 Stage 4 – Water Recycling and Stormwater capture and Storage

Stage 4Monitoring the performance of Stage 3 over six years convinced us that additional water harvesting and recycling was achievable. We decided to optimise our existing catchment infrastructure—using our 3,200 m2 of roof area, over 4,200 m2 of concrete pathways, and 3,500 m2 of roadways and parking.

In Catchment 1, our Stage 3 treatment and storage rate was approximately 90 litres of water per minute. Importantly, in storm events we measured up to approximately 1,000 litres a minute in catchment one and 1,500 to 2,000 litres a minute of stormwater in Catchment 2. We therefore determined that we were not harvesting the majority of these larger flows for treatment and re-use.

Stage 4 made further use of our catchment and existing recycling infrastructure to optimise the harvest and increase the amount of stormwater collected and recycled on the site. We achieved this by investing in four above-ground steel tanks (three 93,600 litres and one 192,000 litres), along with pumping, piping and switching equipment.

Stage 4 has enabled us to divert rainwater from the Nursery Traders distribution shed—a 1,400 m2 building—directly into a 93,000 litre above-ground tank. Significantly, during rain events we direct stormwater to the existing underground tanks built in Stage 3 and then pump it at a rate of approximately 1000 litres a minute from Catchment 1 (nursery displays) and at approximately 1,500 litres a minute from Catchment 2 (roadways, parking, gardens and undeveloped areas). We then store it above ground in two 93,000 litre and one 192,000 litre above-ground tanks. When we require water to irrigate the nursery, the stored water is automatically gravity-fed back to an underground tank for filtration, treatment and storage prior to use.

We largely decommissioned the existing control function and replaced it with water-level sensors and switches in all tanks. Wherever possible, we use gravity to transfer water between tanks, minimising total power used. Although we had installed three new large capacity pumps, with the other power savings made we had paid for the additional power used within two weeks of commissioning the system.

A full description of Stage 4...

2010 Stage 5 – Weather Station, Upgrade of Water Processing and Chlorine Injection

Although we had decreased our water use by 96 per cent per hectare, in late 2009 we reviewed the water recycling infrastructure and performance to determine if further improvements could be made. As a result we decided to commence Stage 5 of our water recycling project, which entailed installing an on-site weather station together with an integrated irrigation controller, and upgrading both the filtration and treatment of water.

In December 2009 we commissioned an on-site weather station that records rainfall, humidity temperature, solar radiation, evapotranspiration, and wind speed hourly—then automatically adjusts the irrigation cycle to ensure we apply the correct amount of irrigation.

Stage 5Previously we had used a rain switch that would turn off the irrigation cycle once we had received 12 mm of rain. As a result of Stage 5, all weather conditions are recorded and automatically taken into account in determining the amount of water applied in each irrigation cycle. So, if we have 2.5 mm of rain, the system reduces the amount of time the irrigation will run, thus saving both water and power.

In February 2010 we commissioned a new chlorine storage and injection system. Chlorine is used to disinfest the water from pathogens. Previously, it was applied at a preset rate per minute regardless of the flow of the water. This caused overdosing when the filters began to clog, and under-dosing when the filter loads were low. As a result it was very difficult to maintain optimum residual chlorine levels.

Now, we can match chlorine injection to the flow rate of the water so that we apply the exact amount required per litre of water recycled. So the potential for overdosing is all but eliminated. All chlorine components—from storage to pumping and injection—are applied over a bunded area, with triple emergency spill redundancy vastly reducing spill risks and improving safety to personnel in the event of any unforeseen equipment failure.

The existing sand filters installed in 1999 and associated plumbing were creating a bottleneck in our processing of captured water. Restrictions in the plumbing and sand filters were limiting us to a maximum treatment rate that equalled 26 per cent of the capacity of the transfer pump. Consequently, the sand filters required back-flushing frequently and based on time elapsed rather than load demands.

Therefore, we decommissioned the existing hydrocyclone and associated plumbing, control equipment, header tank and plumbing installed in 2002, along with the sand filters installed in 1999. We then installed three low-rate sand filters. The large surface area of these filters means they are better suited to operating with the high volume of water now captured on-site.

The reduced impediment to water flow and the automatic independent flushing of filters (one at a time) mean that the filters are always operating and are cleaned on demand—ensuring a high capacity of flows through the filters. We have tripled our rate of treatment and storage of water from an average of 150 litres a minute to a consistent 450 litres a minute—with an 85 per cent decrease in back flushing and an estimated 80 per cent reduction in energy consumption.

In addition, the above initiatives now allow us to measure the volume of water captured and treated for re-use, the total amount of water used in irrigation and the amount of town water input into the system for irrigation. From January 2010 we have published this data monthly on our website.

Since March 2010, with the commissioning of the solar power generation systems, we are generating our own green power to operate the system during the day.