A simpler approach to quality water assessment

While there is no shortage of water quality modelling software available to utilities, one company has developed a back-to-basics modelling approach to help gain insight to discharge impacts fast.

Presenting at Ozwater’18 on simple water quality modelling of wastewater discharges to waterways, Jacobs Environmental Chemist Dr Bonnie Bonneville said taking a simple approach to water quality assessment can help utilities move through decision making quickly.

“A lot of the water quality models that are around at the moment are really time consuming and complex and a lot of people put them in the too-hard basket,” Bonneville said.

“By returning to first principles – looking at simple processes like dilution and concentration and first order decay rates – we developed a simple model that can be tailored to each individual situation.

“We wanted to help our clients answer some questions about whether or not it’s worthwhile investing millions of dollars upgrading treatment plants to protect receiving waterways. We work with whatever data is available. The models are developed specifically for the catchment in question, and the questions that the client has.”

Bonneville said one of the benefits of employing simple water quality modelling is that it enables fast scenario building, without having to invest time and money into more complicated modelling software.

“For a lot of the questions we are dealing with at the moment, this simple approach works for 90% of the time. When you get into complex simulations, you need to go down the path of current modelling methods,” she said.

“But these models are user friendly, they only take a day or two to set up and calibrate, and then you are ready to go. This is a first cut you can do, and if it's not giving you the answers you want, you haven't wasted much time or energy.”

Bonneville said another bonus was the ability to compare and contrast different scenarios, which is huge help for utilities when it comes to planning and decision making around discharge management and treatment qualities.

“We use any background water quality and flow data that is available for the waterway that the discharge is going into and any effluent quality and flow data that is available currently, or any future upgrade specifications too,” she said.

“Each model is set up to run all the parameters of interest to utilities, such as nutrients, enterococci, metals, chlorine, estrogens and basic chemistry.

“This is a helpful way of assessing whether water quality objectives can be achieved in the waterways under proposed upgrades, and if not, what treatment specifications are needed to protect the environment – so that utilities can develop adaptively.”

The success of this type of water quality modelling has been tested out at Jacksons Creek in Melbourne, Bonneville said, with the information supplied helping the utility build a business case around treatment plant upgrades in response to urbanisation.

“Jacksons Creek receives treated water from three treatment plants. We simulated water quality right along the creek. We looked at where all the treatment plants discharge and how it impacts on water quality all along the river,” she said.

“The question was then: if urbanisation creates higher volumes of sewage, but we upgrade the plants and manage the discharges, how would that change the water quality and flows in the river?

“We simulated a few different scenarios of release regimes of treated water into the river to see what effect that would have on environmental values downstream.

“That information was really useful to feed back into a business case for upgrading the treatment plant. The real strength in this type of modelling is you can compare scenarios really easily to help make decisions.”

Register for Ozwater’18 to hear more from Dr Bonnie Bonneville about how simplified water quality modelling can help utilities make decisions.