Not surprisingly, one of the largest expenses of operating a wastewater treatment system is electricity. Most wastewater treatment systems require aeration for unit processes starting at the beginning (equalization, grit handling), middle (biological treatment), side (sludge handling) and end (post aeration) of the plant. It is a well known fact that aeration systems and the power to operate them typically represent more than 40% of the electrical costs of a wastewater treatment plant.
Fine bubble diffused aeration is one of the most efficient forms of aeration when utilized for the main unit processes of a treatment system to reduce power consumption. However, there are a number of additional factors to consider when designing and operating a diffused aeration system to help manage its energy costs. Here’s what you need to know:
System design
When designing a diffused aeration system, proper sizing of equipment is imperative. A reputable supplier should ask many questions to determine what is required for your wastewater treatment plant to operate at peak efficiency.
Some plant owners accept nothing less than maximum efficiency and weigh the first cost of the system, which may include additional diffusers to reduce overall energy costs. Others opt for less diffusers, which use more energy and cost more to operate and maintain.
Those who select their aeration systems based on best life cycle costs benefit from reduced energy and lowest cost of ownership.
What are the differences between these two schools of thought?
Blowers
Blower sizing is very important to the success of a diffused aeration system. The blowers must be large enough for the system to be turned up to full capacity without over-gassing the diffusers. Flexing the diffusers by increasing the airflow rate is required periodically for routing cleaning. However, too much air flow can damage the diffusers and piping system.
There are several types of blowers; each has a specific efficiency, and energy requirement. Consult with your aeration system provider to select the best type for your needs. If you’re retrofitting an existing system, let them know your current operating conditions and system efficiency.
Diffusers
Diffuser designs can also affect the energy cost of the system. For best results, the design selected should be based on the system’s operating pressure and the wastewater constituents. For example, certain chemicals can cause EPDM diffusers to deteriorate. Aquarius’ EPDM-based membrane is specially formulated to offer a longer service life at a higher level of efficiency than competing membranes. It contains 15% less extractable oil than other membranes. This makes it more chemically stable, which results in a longer life.
In new diffused aeration system installations, where designers are specifying all of the equipment, they can optimize it to perform at maximum energy efficiency. Aquarius Technology’s membrane diffuser offers a high density of perforations per unit area, resulting in smaller bubbles and higher oxygen transfer efficiencies. They have been independently verified to provide a 5+% advantage in energy consumption compared to other manufacturers’ new diffusers.
In retrofit applications, designers typically must integrate with existing aeration tanks and piping as well as blowers. One or more of these needs may dictate the type of diffusers used and the optimum efficiency that can be achieved.
There are a number of ways Aquarius products can help increase the efficiency of existing aeration systems:
- Replace aging membrane disc diffusers with advanced performance Aquarius membrane disc diffusers.
- Adding air distributors and diffusers to systems that are struggling to manage increased loads
- Updating mechanical or coarse bubble systems to fine bubble.
To maintain the efficiency of your diffusers, operate your fine bubble aeration system according to the manufacturer’s guidelines. Treat the diffusers like the critical part of your wastewater treatment process that they actually are.
For example, EPDM diffusers are designed to flex; that’s how they create fine bubbles. Aquarius recommends exercising your diffusers by increasing air flow periodically to remove calcium deposits and other obstructions from the pores of the diffusers and enable better fine bubble formation. It also helps prevent the EPDM from adopting a permanent set.
In addition, follow your manufacturer’s recommendations for draining and cleaning the tanks, and for making routine inspections of your aeration system. Identifying any potential issues early can help you save money on repairs and replacements.
When it comes to the energy efficiency of diffused aeration systems, a bit of preventive maintenance can really pay off in the long run.
