Water Treatment/Compressors A New Compressor Becomes a Fresh Breath for an Water Treatment Old Plant

Author / Editor: Cristina Cavazzini* / Dominik Stephan

Even in water treatment, the make it or break it factor might be in the air supply. And compressors can make the difference — To much of anything can make you sick: Oversized plants are a common problem in water treatment applications. Working hand in hand with technology experts and supplying companies can be the key for an efficient re-design process.

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Keep an eye on air supply - an oversized setup and inefficient compressors should be taken care of.
Keep an eye on air supply - an oversized setup and inefficient compressors should be taken care of.
(Picture: Loris Canovi)

An air production system that's oversized in relation to the treated load cannot be efficient from the cost and energy consumption viewpoint — In that case, reviewing the plant set-up might be the way to go. With that consideration in mind, the Iren Group, a multi-utility energy company, set its sights in the restructuring of its own water treatment system for urban sewage. The goal was the revision of a waste water plant serving the municipalities of Rubiera and Scandiano in Italy with a population of 45,000 – and Iren’s partner of choice were the technology experts Robuschi.

Overdimensioning: A Common Problem With Water Treatment

The water line of the Rubiera system is formed of four parallel lines, each initially supplied by its own compressor for generating process air in the oxidisation/nitrification compartment. The thorough renovation of this part of the system highlighted some discrepancies.

“The original set-up”, explains Loris Canovi, head of waste water treatment in the Emilia area at Ireti, a company of the Iren Group, “was discovered to be oversized for the actual demands for oxygen in the tank, necessary for supplying the respiration process for the biomass and for the oxidation of the organic components and the ammoniac nitrogen.” During the checks, it was observed that there were very large variations in the use of air during the day, in relation to production. This meant high residue and wasted energy. Basically, the line set-up didn't allow the machines to lower their production below a certain threshold and, as a result, the amount of oxygen supplied was excessive for the requests of the lines themselves for long periods of the day.

Step by Step Integration

The Iren Group designed and built a system for controlling air production, combined with Ro­buschi technology that, with an innovative compressor never before installed, made it possible to improve system performance.

“The first step was to change the set-up, linking all the machines together. It was seen, in fact, that it would have been sufficient to use only one compressor for generating the process air during the period of less demand, but that compressor had to be very versatile and offer a wide range of capacity variations.” This was a fundamental condition as, in the Rubiera system, the variations can cover a wide spectrum from 600 m3/h up to 3000 m3/h during the period of maximum demand. This is where Robuschi technology, with the new permanent magnet screw Robox Energy WS 85, came into its own.

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