Following a prolonged drought and pressure from a growing population demanding potable water, State Governments around Australia have sought industry and community input to reduce potable water consumption.

The Government of Victoria, in conjunction with Melbourne’s water companies, established and jointly operate the Smart Water Fund.

The aim of the fund is to encourage and support innovative development of water, biosolids recycling and water-saving projects.

Cleaning the carrots

As is the case on the fringe of most cities, market gardens supply many of the fresh vegetable needs of residents.

Due to their city proximity, many market gardens access the mains water supply. In Melbourne, a capital city with a population of 3.5 million, residents have been on water restrictions for three years, and farmers must also help to ease the water crisis.

Rick Butler is a fourth-generation farmer and was advised by provider South East Water that his farm was one of the top 1000 users of potable water.

“We were using a lot of water to wash our vegetables in preparation for supermarket sale,” Butler says.

“Our daily use was about 80,000L (21,000 gallons). The water came straight from the mains and, once used, went into a holding dam. Although we were able to make secondary use of the water for crop watering, the run-off was lost.”

The farm’s vegetable washing machine, installed in 1991, was ready to be supplemented and eventually replaced by a more efficient model. The Smart Water fund allowed Butler to design a water-saving solution.

He feels particularly proud of the new soft-vegetable washing machine installed with the help of the Smart Water Fund grant, because he designed it himself.

“The idea for the machine had always been in my head. But the Smart Water grant allowed me to pursue and develop a machine for commercial use that would treat and recycle water as it washed the vegetables.”

The concept for the new equipment was developed in consultation with a local company, Tripax Engineering, which then built and installed the final product.

The new machine saves about 90% of the water the farm used to consume for processing, bringing the daily use down to about 5,000L (1,300 gallons).

The machine’s ability to wash soft vegetables which are hard to handle – for example, lettuces and Asian greens – made it unique and secured the grant.

Presentation of the produce is very important to Butler and his major customers, which demand ISO accreditation to ensure quality for supermarket shelves.

So how does it work? The machine has three tanks, containing water of varying degrees of freshness.

One tank is filled with fresh water for a fine spray – from above and below – over vegetables traveling along a conveyor belt.
“Some vegetables are difficult to wash,” Rick says. “The spray aims at the vegetables with precision, so there is minimum wastage.”

Excess water is caught in a tray and channeled to another holding tank via a series of increasingly fine filters that sift out soil and sand, which collects at the bottom of specially designed V-shaped tanks. Recycled water is then treated with an electronically controlled dose of biocide to remove bacteria.

“We were using chlorine for sterilization purposes, but chlorine is in the past,” Butler says.

“We wanted to move to a safer, biologically based product, not only to improve the quality of the vegetables but also for the health and safety of our staff. We now use a biocide that is integrated into the recycling process and automated by the machine. There are several on the market to chose from.”

The automatic system ensures that precise doses of biocide are released into the recycled water. At specific levels, the biocide effectively kills bacteria. The system also monitors biocide levels in the water in parts per million.

“The product is completely biodegradable and turns into a vinegar-like substance that goes safely into the holding dam,” Rick says.

The message is that plumbing engineers and contractors can take this water-saving idea to farmers in their own cities rather than wait for them to ask for assistance, as they probably don’t realize the savings that can be made.

We have included a copy of the equipment plan which can be easily replicated locally.

Butler and Tripax Engineering are keen to see others pick up on their design ideas and save water in market garden processing sheds the world over.