Resource Efficiency and Production

Biofouling results in increased energy and chemical costs, loss of water production, and reduced membrane life. Optimal operation of the increasing number of reverse osmosis (RO) membrane plants in Australia is essential to reducing the large quantities of expensive conventional chemical cleaning agents used; chemicals that may also cause environmental issues with their disposal. Stored membranes also incur costs because the standard preservation solution (sodium bisulfite) used to prevent biofilm growth on them is not stable and needs to be frequently replaced.

This project assessed the effectiveness and benefits of free nitrous acid (FNA)—alone or in combination with hydrogen peroxide—as a novel, low cost, non-oxidising cleaning agent for preventing and removing biofouling, as well as for scale control in RO membranes for wastewater recycling and seawater desalination.

WORK UNDERTAKEN AND OUTCOMES

Some important factors impacting the efficiency of FNA as a cleaning agent for RO membranes have been revealed:

  • the stability of FNA solutions is strongly pH dependant, providing an appreciation of optimal cleaning conditions
  • the permeability and salt rejection of membranes are not adversely affected by FNA cleaning
  • FNA is more efficient at killing bacteria than conventional cleaning solutions
  • no improvements were observed by combining FNA with H2O2 compared to FNA alone.

ADOPTION AND IMPACT

The research team commenced discussions with a local membrane manufacturer to collaborate on a trial comparing and benchmarking the use of FNA against others commercial cleaning solutions.
An international partner is considering undertaking a comparison of FNA with DBNPA using chock dosing for biofouling prevention.The pilot plant will be retained by QUU to assist further development of the technology.

 

Once experimentally-derived FNA cleaning regimes for RO membranes are validated and refined they will provide operators of RO-based equipment with a tool for optimising the operation of their plants.

Photo courtesy of The University of Queensland Advanced Water Management Centre

 

PROJECT PARTNERS
Lead organisation: The University of Queensland – Advanced Water Management Centre
Partner organisations: Veolia Water
Seqwater
National Centre of Excellence in Desalination Australia
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