Cost effective ceramic membrane pre-treatment

Leader

 

Challenge

Melbourne has a large source of municipal effluent water that can be harnessed to offset the need for potable water from the Western Treatment Plant (WTP). This water however, is currently too saline for many of the potential residential, agricultural and industry applications. Project partner City West Water have already commenced construction of the Salt Reduction Plant which will take Class A water from WTP and desalinate it to provide for up to 20,000 customers. The first stage of the plant will deliver 6 mega litres per day (MLD) of desalinated treated water for reuse, which after blending with Class A water will produce approximately 10MLD of fit-for-purpose water for 9,000 customers.

This specific case is representative of a number of other water treatment plants intending to treat saline effluent. Desalination of secondary effluent is a nationally viable option for increasing water sustainability. In order to reuse these saline wastewaters there is a need for a resilient pre-treatment process capable of handling widely different water qualities prior to desalination.

Investigation

Explore ceramic membrane technology as a pre-treatment process and its tolerance to water quality variations compared to conventional polymeric membranes. Specifically, determine ceramic membrane performance when coupled with coagulation, ozonation and ultraviolet/hydrogen peroxide (UVH) pre-treatment and the effectiveness on downstream fouling of the reverse osmosis membrane.

Outcomes

Testing on saline wastewater found pre-treatment with coagulation with either ozone or UVH led to high ceramic membrane flux potential due to the very low transmembrane pressure rise at 130L/m2/h. Membrane fouling propensity was similar for all pre-treatment combinations, but coagulation either alone or with ozone or UVH showed superior membrane fouling reversibility. However, the use of ozone or UVH increased the biodegradable fraction of the organics suggesting higher biofouling potential.

Cost analysis showed ceramics are 1.6 times more expensive than polymers on a $/m3 water treated basis (capital and operating combined) when operating at fluxes of a typical polymer plant (45L/m2/h). However, ceramics become more viable when fluxes exceed 110L/m2/h, which is possible with coagulation but not ozone pre-treatment. When ozone and coagulation are used, ceramic membrane fluxes of at least 200L/m2/h are expected, leading to 18% lower cost on a $/m3 water treated basis. Despite this saving, the cost penalty for ozone is not offset by the higher ceramic membrane fluxes and would require additional justification. The analysis also showed higher flux performance of ceramic membranes when used in conjunction with ozone and/or coagulation leads to overall cost savings compared to polymer membranes.

Future Direction

A successful pilot trial is needed to the prove technology as it is new to Australia and yet to be tested at the pilot scale with discussions ongoing with City West Water and other interested companies.

Partners


 

Total Value: $515,896 (cash and in-kind contributions)

Principal Investigator: Professor Mikel Duke

Title: Resilient desalination pre-treatment of saline secondary effluent by ceramic membranes

Length: 22 months

Personnel: 10 collaborators contributing 1.4 FTE

Further Information

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