External heating units upgrade wastewater plant

Prince of Wales Bay Sewage Treatment Plant upgrade

This article contains paid for content produced in collaboration with HRS Heat Exchangers.

A new sludge heater supplied by HRS Heat Exchangers has formed part of an upgrade to one of Tasmania’s most important wastewater treatment plants.

TasWater is the water and sewage utility for the island state of Tasmania in Australia. It is responsible for providing drinking water and collecting and treating sewage across the state.

In 2020, TasWater and main contractor Aquatec Maxcon undertook a multimillion-dollar upgrade of the Prince of Wales Bay Sewage Treatment Plant in Hobart to give it operational suitability until 2060.

The upgrade included a new roof for the main digester, new control system, new biogas waste flares, and an improved heating system, supplied by HRS Heat Exchangers. HRS supplied Aquatec Maxcon with a corrugated tube heat exchanger to warm the recirculating sludge and maintain optimum operating temperatures in the main digester.

Jim Foley of Aquatec Maxcon said: “There were a number of heat exchanger suppliers that we could have chosen, but one of the issues we faced was a limit of the space available for the heat exchanger, and the HRS unit had slightly smaller dimensions than some others for the same thermal performance. HRS provided me a with a reference, and after that and a performance test, we were happy to go with the HRS product.”

The supplied unit consists of a six-module HRS DTI Series heat exchanger to raise the sludge temperature from 33°C to 36°C, with a capacity to process 72,000 litres of sludge every hour using hot water supplied by a separate boiler. To facilitate routine maintenance and cleaning, the heating unit has been installed outside the digester; a design which is rapidly becoming the norm for biogas plants due to the benefits it provides over internal designs.

The heat exchanger was delivered well ahead of the required installation date. Since operation, the unit has performed according to specification, dealing with a range of feedstocks and sludges, including sewerage sludge and as fats and oils from trade wastes.