Each year in Australia over 85 million tons of biosolids (sludge) are dewatered at municipal Sewage Treatment Plants (STP’s) into around 1.65 million tons of dewatered biosolids, also called wet biosolids, which is trucked offsite for mainly reuse in agriculture and composting.
Dewatering takes place via a variety of methods, with centrifuges being most commonly used at 39%, followed up closely by belt filter presses and drying beds at 24% and 23% respectively.
Biosolids dewatering takes place in most of the 2400 STP’s in Australia.
Regionally there have always been trends in dewatering technology with centrifuges favoured by most large NSW utilities and belt filter presses being favoured in Queensland and Victoria, along with rural NSW.
There is however a new trend emerging and it has become the primary choice of major utilities in Brisbane and Western Australia – dewatering via screw press.
This is an interesting development, as like most of the dewatering technology used, screw presses are not new and in fact may well be one of the oldest technologies. Indeed whilst the first centrifuges were used to separate dairy products around 1860 and belt filter presses were originally used in Europe in the early 1900’s for pulp and paper, screw presses were first used in Roman times for pressing wine.
This new trend is being driven by changes in our economy and concerns over the environment and sustainability as well as a need for municipalities to continually improve their efficiency and operating costs.
Large increases in operational and maintenance labour and power costs as well as the unsustainability of processes that use large quantities of washwater have certainly forced municipalities to look seriously at their current dewatering technology and search for better alternatives. Add odour generation, either around the dewatering process or in the dewatered biomass, noise and other environmental concerns and the reason for the trend away from belt filter presses and centrifuges to screw presses becomes patently obvious.
Add to this the major advances in screw press technology in the last 10 years, enabling screw presses to now successfully dewater Waste Activated Sludge (WAS) and the trend becomes one that is certainly here to stay.
In fact it is safe to say that we can expect that most medium to large municipal dewatering facilities will make the change to screw press based dewatering in the near future.
The original of this article was published on LinkedIn by John Koumoukelis, a Director of Hydroflux Huber Pty Ltd.
About the Hydroflux Group
The Hydroflux Group comprises seven companies based in Australia and the UK, providing design and build, equipment, processes and operational services in water and wastewater treatment. Hydroflux Huber specialises in municipal wastewater and sludge treatment and is the exclusive Australian representative for HUBER Technology, AEROSTRIP, CNP Technologies, Aeromix, Flootech MBBR and Organica Water.
Hydroflux Huber Pty Ltd is a member of the Hydroflux Group.
24 October 2016
Hydroflux Huber Pty Ltd
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