Spiral technology transforms power generation efficiency to drive Southern California wastewater treatment plant to circularity success

With water scarcity and rising demand putting pressure on municipal infrastructure, Orange County Sanitation District (OC San) have found a solution that has doubled the efficiency of their power generation, significantly boosting the circularity of their treatment processes.

Not only that, the two Alfa Laval spiral heat exchangers now helping to transform biogas into electricity at the Huntington Beach site are a mere third of the size of the previous cube and cube equipment, and are proving much easier to maintain and clean thanks to their easy-access design.

The technology heats batches of sludge in anaerobic digesters, where it remains for 18-21 days and reaches temperatures of approximately 36°C (97°F). The methane biogas produced is captured, compressed, and used to fuel engine generators that produce electricity – supplying more than 60% of OC San’s overall energy needs.

The plant generates an average of 7.1 kilowatt hours of energy every month, which means there is a net power saving of US$ 6.2 million a year that would otherwise need to be purchased from the power company.

Nikhil Patole, Alfa Laval regional sales manager based in Milwaukee, Wisconsin, says: “This is a fantastic example of the significant benefits of spiral technology in delivering a critical solution to major utilities operations.”

The heat exchangers are carrying out a crucial job in keeping the tanks at a constant temperature and are performing at twice the efficiency that could be achieved by cube and cube technology.

“The sludge makes these tough operating conditions, but the spiral technology is very robust and if the maintenance team have to access the exchangers for any reason then they can do so very simply by just swinging open the cover. Again, this is a significant benefit over a cube and cube solution, which is more complex and can take three to four times longer to clean,” continues Nikhil.

In terms of space, the spiral heat exchangers have a footprint that is a third of the size of a cube and cube counterpart, which in a region such as California, where land is expensive, can offer significant financial benefits.

OC San oversees the collection, treatment, recycling, and disposal of the wastewater generated by 2.6 million people, commercial and industrial sources, from a 1,240 km² area of central and northwest Orange County.

They operate two wastewater plants, one in Fountain Valley and the second in Huntington Beach, which treats 268,219 cubic metres of wastewater every day and where an extensive capital programme of projects to upgrade, improve and build climate resilience has been ongoing for several years. 

“I am acutely aware of the benefits of the technology we are providing because before I joined Alfa Laval, I was offering an alternative solution and it was tough to sell against the spiral heat exchangers!” says Nikhil, who has now been with Alfa Laval for more than four years. He sees the company’s  after-care package as another major advantage over competitors who do not have the same depth of expertise and reach.

“I believe we are the trailblazers in terms of quality and service when it comes to spiral heat exchanger solutions,” he says. “We are a big company but our individual teams work closely with our customers. We tap into their needs, we find solutions and then we stay around to make sure everything is working as it should. In the US we have a big service network, so customers like OC San can be confident that they have support to hand that can step in quickly to resolve any issues.”