Salmon farm discharge into greater Hobart drinking water catchment causes alarm

https://www.abc.net.au/news/2022-04-30/salmon-farm-discharge-into-river-causes-alarm/101025338

April 4 2022

The environment upstream of the salmon hatchery on Tasmania’s Florentine River is pristine — it’s a sought-after destination for fly fishers.

Downstream, it is a different story.

Tasmania’s salmon industry has long relied on the state’s freshwater rivers to operate its hatcheries, but the worsening presence of sludge, bacterial matting, and nutrients in the Florentine River has some sounding the alarm.

One of those people is local fly fisher Gerard Castles, who has previously been vocal about concerns with the salmon industry’s operations in coastal waters.

Mr Castles contacted the Environment Protection Authority (EPA) after visiting the Florentine River earlier this month.

He has since sworn off fishing near the Salmon Enterprises of Tasmania (SALTAS) hatchery.

“What I found in the water was absolutely disgusting,” he said.

“I found white bacterial mats, I found a riverbed covered in a brown sludge, and I found white filaments floating through the water.”

The EPA is looking into whether hatchery owner SALTAS — an industry and state government-owned joint enterprise — has breached its license.

“Water sampling indicates nutrient loads from the fish farm may be contributing to the algal issues in the river,” a spokeswoman said.

The EPA said it was working with SALTAS on ways to remedy the problem.

The Florentine River feeds into greater Hobart’s primary drinking supply.

“We’re drinking water that’s got these disgusting, white, bacterial mats in it,” Mr Castles said.

The EPA said preliminary testing had not indicated concerns about Hobart’s drinking water supplies, and further testing at the discharge site was done this week.

The hatchery is one of five industry facilities on the Derwent catchment that discharge wastewater back into the system.

Independent water quality scientist Christine Coughanowr said collectively, the discharge of nutrient-filled water from the hatcheries into the water system was similar to “several good-sized sewage treatment plants”.

She said it was crucial to move away from flow-through hatcheries and instead use recirculated systems to protect Hobart’s water.

“The Derwent particularly is a perfect recipe for algal blooms,” she said.

“We have increasing nutrients, we have declining water flows, we have warming water temperatures.

Ms Coughanowr said once established, an algal bloom would be extremely difficult to eradicate, and could create issues with the drinking water supply if it was not properly treated.

TasWater has already committed to spend more than $240 million upgrading the Derwent’s Bryn Estyn water treatment plant, partly to address taste and odour problems posed by algae further up the system.

Greens leader Cassy O’Connor said while taxpayers would fork out for the upgrade, the salmon industry paid very little to use the river water.

“We see that the river downstream from the hatchery is grotesque, what’s growing in there is disgusting, and if people understand that that’s the headwaters of their drinking supply they’ll be very worried,” she said.

The Greens are pushing for a parliamentary inquiry into water.

A SALTAS spokesman said the enterprise valued healthy waterways and “continues to work towards that”.

“All operations are undertaken within the regulatory conditions, including monitoring programs and reporting.”

2017/18 – Hobart (Tasmania) – Chlorine

2017/18: 10.04mg/L (max)

GENERAL DESCRIPTION
Chlorine dissociates in water to form free chlorine, which consists of aqueous molecular chlorine, hypochlorous acid and hypochlorite ion. Chlorine and hypochlorites are toxic to microorganisms and are used extensively as disinfectants for drinking water supplies. Chlorine is also used to disinfect sewage and wastewater, swimming pool water, in-plant supplies, and industrial cooling water.

Chlorine has an odour threshold in drinking water of about 0.6 mg/L, but some people are particularly sensitive and can detect amounts as low as 0.2 mg/L. Water authorities may need to exceed the odour threshold value of 0.6 mg/L in order to maintain an effective disinfectant residual.

In the food industry, chlorine and hypochlorites are used for general sanitation and for odour control. Large amounts of chlorine are used in the production of industrial and domestic disinfectants and bleaches, and it is used in the synthesis of a large range of chemical compounds.

Free chlorine reacts with ammonia and certain nitrogen compounds to form combined chlorine. With ammonia, chlorine forms chloramines (monochloramine, dichloramine and nitrogen trichloride or trichloramine) (APHA 2012). Chloramines are used for disinfection but are weaker oxidising agents than free chlorine.

Free chlorine and combined chlorine may be present simultaneously (APHA 2012). The term totalchlorine refers to the sum of free chlorine and combined chlorine present in a sample.

Chlorine (Free) ADWG Guideline: 5mg/L (Chlorine in chloraminated supplies 4.1mg/L). Chlorine dissociates in water to form free chlorine, which consists of aqueous molecular chlorine, hypochlorous acid and hypochlorite ion.

Chlorine (Total) ADWG Guideline 5mg/L (chloraminated supplies 4.1mg/L): The term total chlorine refers to the sum of free chlorine and combined chlorine present in a sample

Hobart (Tasmania) – Antimony

8/7/20: Hobart (Tasmania) Antimony 0.005mg/L. (exact location not specified in 2020/21 Taswater Drinking Water Quality Report).

Based on health considerations, the concentration of antimony in drinking water should not
exceed the limit of determination of 0.003 mg/L.
GENERAL DESCRIPTION
Antimony, as the trivalent (Sb(III)) or pentavalent (Sb(V)) salts, has occasionally been detected in
natural source waters. Occurrences are more common in areas near lead or copper smelting operations.
Antimony–tin solder is beginning to replace lead solder and hence exposure to antimony in drinking water may increase in the future.
Antimony alloys and compounds are used in semiconductors, batteries, anti-friction compounds, ammunition, cable sheathing, and flame-proofing compounds. Antimony salts are used in glass, and in the manufacture of ceramics and pottery.
Studies overseas have generally found low concentrations in drinking water, typically less than
0.005 mg/L, but higher concentrations have been reported occasionally.
There are few data available on antimony concentrations in food. The United States Agency for Toxic Substances and Disease Registry has suggested that average daily consumption of antimony in food is about 0.018 mg.

2017/18 – Hobart (Tasmania) – Turbidity

2017/18 – Hobart (Tasmania) – Turbidity 10.01NTU (max), 0.54NTU (av)

Chlorine-resistant pathogen reduction: Where filtration alone is used as the water treatment
process to address identified risks from Cryptosporidium and Giardia, it is essential
that filtration is optimised and consequently the target for the turbidity of water leaving
individual filters should be less than 0.2 NTU, and should not exceed 0.5 NTU at any time
Disinfection: A turbidity of less than 1 NTU is desirable at the time of disinfection with
chlorine unless a higher value can be validated in a specific context.

Aesthetic: Based on aesthetic considerations, the turbidity should not exceed 5 NTU at the
consumer’s tap

Hobart (Tasmania) – pH (acidic)

Average pH: 2015 July-2016 June: 6.502 pH units

Based on the need to reduce corrosion and encrustation in pipes and fittings, the pH of
drinking water should be between 6.5 and 8.5.

New concrete tanks and cement-mortar lined pipes can significantly increase pH and
a value up to 9.2 may be tolerated, provided monitoring indicates no deterioration in
microbiological quality.

pH is a measure of the hydrogen ion concentration of water. It is measured on a logarithmic scale from 0 to 14. A pH of 7 is neutral, greater than 7 is alkaline, and less than 7 is acidic.

One of the major objectives in controlling pH is to minimise corrosion and encrustation in pipes and fittings. Corrosion can be reduced by the formation of a protective layer of calcium carbonate on the inside of the pipe or fitting, and the formation of this layer is affected by pH, temperature, the availability of calcium (hardness) and carbon dioxide. If the water is too alkaline (above pH 8.5), the rapid deposition and build-up of calcium carbonate that can result may eventually block the pipe.

2015/18 + 2020/22 – Hobart (Tasmania) – pH, Chlorine, Antimony, Turbidity

Salmon farm discharge into greater Hobart drinking water catchment causes alarm