The demands on wastewater treatment technology are particularly high in the industrial-wastewater treatment sector. In order to keep the maintenance works as low as possible, it is important that the employed materials should be resistant to aggressive components of wastewater. In case of aeration technologies, the membrane is sensitive. Poor quality or unsuitable plastic leads to faster membrane wear-out.
As a consequence AQUACONSULT invests continually in research and development. The Austrian company has made aeration technology its field of expertise and manufactures all AEROSTRIP fine bubble diffusers in a facility near Vienna in Traiskirchen. These diffusers are in use in more than 100 industrial-wastewater treatment plants around the world. They are characterised by maximal energy efficiency and above average service life, which was scientifically proved in 2012 in a study from California, USA. The oxygen transfer efficiency reaches up to 60%, and the oxygen yield ranges 3 to 6 kg O2/kWh. Owing to the energy savings and therefore the lower operating costs, the investment of the aeration technology can be paid off in one to three years.
This technology is particularly relevant for the paper and textile industry, as well as the chemical and petrochemical industry.
The AEROSTRIP fine bubble diffusers have been in use since 1996 in wastewater treatment plants in various petrochemical industries from countries like Germany, Slovakia, Romania and Kazakhstan.
“Our polyurethane membrane have really proved their value in this sector”, says Gerald Glaninger, sales manager at AQUACONSULT. “This material shows above-average durability towards petroleum and is more resistant than ethylene propylene diene monomer rubber (EPDM rubber).”
Experience with existing plants shows that the service life of the polyurethane membrane is around 10 years. Of course, the system can continue to be used once the membrane has been renewed. One reference plant in Australia received the “Prime Minister’s Water Wise Award” in 2011 for its optimal resource efficiency.
In the field of industrial wastewater treatment, there are particular challenges with fine-bubble diffusers: the high bicarbonate concentrations in the wastewater lead to carbonate deposits on the membrane, which causes the pores to block.
For this reason, the company has developed a maintenance procedure with de-scaling and acid dosing that largely prevents this pore blocking. Automation of the de-scaling process is recommended, having it ran three or four times a day. This allows the pressure in the piping system to sink so far that the membrane can relax. Afterwards the normal operation may load the diffusers again. This causes variations in membrane elongation, which effectively loosens sediments from the surface. Fresh deposits are prevented. Monitoring and logging the system pressure is very important. Once the plant operator noticed that the pressure was above the threshold value, dosing of acetic acid shall be performed in the air stream, which cleans the pores and lowers the pressure loss.
With these simple but highly efficient maintenance measures that cost less time and money, the diffuser lifespan — until the membrane needs to be changed — is around ten years, even in industrial wastewater treatment.
With particularly aggressive wastewaters or with water temperatures above 35 °C, it is recommended to use special membranes such as those made of silicone. These have almost the same oxygen transfer rates as membranes made of polyurethane. Depending on the material, the operation life of these membranes is between five and eight years.
It is important to adapt the aeration technology exactly to the individual conditions on site.