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Sustainable Class A water is used in Mount Hotham's snow making

Sustainable Class A water is used in Mount Hotham's snow making

Mount Hotham snowmaking is a complex process that takes the resort’s biowaste in its most organic form and turns it into purified Class A water to be used to make snow.

The resort’s biowaste goes through countless processes to eliminate pathogens, phosphorus, ammonia, nitrates and other microorganisms that can be harmful to humans.

The UF Plant was commissioned on the government’s belief of the need for Alpine Resorts to diversify, in consideration of climate change and shorter snow seasons.

Initially, the idea was to invest in the expansion of snowmaking which led to the knowledge of recycling water and making Mount Hotham more water sustainable. This was also combined with prior years of draught and the desalination plant at Wonthaggi which had just come out of the draught.

The waste water process operates as follows:

  1. Inlet Works

The inlet works is the first stage of the process and is the “nastiest” part of the station. Inside the inlet is a large pipe that has a orgascreen which pulls out bigger materials (like toilet paper and plastics) which is bagged and sent off to landfill. The rest of the remaining material goes up the orgascreen and into the compacter.

  1. Bioreactor Tanks

It then leaves the inlet works and finds its way to the five bioreactor tanks, which is where the incoming sewerage and water is mixed with the biology to promote a reaction. This process is called a biological nutrient removal where anything carbon based gets eaten by the biology and the ammonia (urine) turns into nitrate which then changes to nitrate gas and leaves the system.

Urine is high in ammonia which is toxic for waterways and is acted on biologically. Alum is then added which helps flock and trap the phosphorous creating a sludge which is wasted from the system over time.

In summer, only two bioreactor tanks operate due to lower levels of sewerage from the resort. In winter, all five tanks operate which allows for 24 hours of detention time under full flow, to give more time for the biology to act longer on the water that is coming through.

       3. Clarifier Tank

The clarifier tank is where the clear water and the biology separate (Class C water). The quality of the Class C water has a certain licence attached to it and is treated to a level that can be released into the environment, but there are rules around its proximity to humans. A certain amount of treatment is done and then a log reduction is attached to it and informs of the number of microorganisms and pathogens it contains.

A log reduction is the number of microorganisms that are getting eradicated via the various process, whereby the quality of water is not so much in terms of clarity but the chance of the water causing illness in humans.

When it goes through the processes and becomes Class A, it still has a different set of rules and regulations on what it can be used for but you can have more contact with humans.

Once in the clarifier, the water has two exit pathways: the holding tank which is the feedwater tank for the ultra-filtration plant (UF Plant), and the UV disinfection (Dargo UV) where the water is treated and then released back into the environment.

  1. Feed Water Tank to the Membranes

From the clarifier tanks and through the feedwater tank, the water then gets pumped up through the membranes which each have 10,0000 small straws. These straws have micro pores along them which filter the water as it gets forced through the membranes. This process eliminates bacteria and viruses down to two microns, with only the smallest viruses remaining present.

Over time, the pores get clogged by everything that’s coming through – from microorganisms to plastics, to bits of paper product and carbon. Chemicals like citric acid and sodium chloride are used to back-flush them and clear the pores.

The membranes get challenged annually with a virus challenge test by putting a virus on one side and seeing what the detection on the other side is.

  1. UV Unit and Chlorine Contact Tank

Following the membrane filter process, the water has had everything stripped out and runs clearer than potable drinking water. However, some pathogens may remain in the water so it must go through the UV unit, which produces the power of a small house.

The UV sterilises the pathogens and then the water goes through a chlorine contact tank which acts on microorganisms by oxidising them and breaking them up.

The UV unit and the chlorine contact tank is a multibarrier approach, a back-up in case of broken fibres in the membranes, which would allow some pathogens and microorganisms to get through.

Prior to the installation of the UF Plant, water taken out of Swindlers catchment was released into Dargo catchment.

Waste Water Manager Orme Kewish said that since the operation of the UF Plant, a combination of Class A and Swindlers catchment water is now taken from Loch Dam, used in the snowmaking system, and then returned to the Swindlers catchment.

“In my mind its slightly less disruptive to that water cycle and environment if you are returning the water to the same catchment area it came from, otherwise you’re basically stealing from one catchment and putting it into another,” Mr Kewish said.

“Climate change was a driving force for the snowmaking to go ahead, to try and ensure that we were going to have a more reliable water supply for snow.

“Realistically, the environmental streamflow for snowmaking is a far larger portion of the water. Having said that, every year we get more efficient with how much water we put back out there,” he said.

16 May 2017