Myrtleford Sawmill operator Carter Holt Harvey has introduced the boiler ash water recycling project. The company has adapted water treatment industry technology to achieve a 90 percent reduction in its onsite potable water consumption.
The mill’s boiler ash water recycling project, funded through the Smart Water Fund, reduced the amount of potable water used to cool hot ash waste from its boilers from 38 million litres a year to 4 million litres.
The Myrtleford Sawmill operator Carter Holt Harvey had been using town water to quench the ash in our boilers, but the boiler ash water recycling project put in a settling system that gets the ash out of the water and it has been found that the water can be reused up to 10 times.
The Boiler ash water recycling project works under the principle, when a stream of water containing suspended solids can be reduced to a very low speed, the solids will drop out of suspension and the project uses settling tanks to reduce the speed of the ash-contaminated quench water.
The quench water flows across an existing separation screen, removing approximately 90 percent of the suspended ash, and into the tanks formed by modifying existing concrete bunds. As the water flows from one tank to the next, it becomes progressively cleaner and is able to be reused.
Installed in October 2006, the mill has completed a six-month trial of the process, which also shows CHH is on track to reduce its trade waste discharge by 90 percent, saving the business up to $60,000 in yearly charges.
Prior to the project’s installation, approximately 35 million litres of ash-contaminated water was disposed of as trade waste. Now, about 10% of the quench water is bled off to trade waste in order to prevent its pH rising to an unacceptable level and the remaining sediment, cold ash (carbon), is sold as a soil conditioner.
The water recycling concept was adapted for the sawmill by a CHH engineer and constructed by local firm Nicoll Engineering.
With results confirming the efficiency of the water recycling process, CHH will examine using the technology across its sawmills in Australia and New Zealand.
Carter Holt Harvey processes plantation timber predominantly for housing construction.