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A case study of the wastewater purification process in the city of Bordeaux
At least 60% of the energy consumption on a wastewater treatment site is consumed by the air blowers used in the different aeration applications. The energy efficiency of an air blower unit is thus one of the most important factors when it comes to creating a greener and cleaner way of purifying our tab water. By replacing several lobe blowers with a more energy-efficient alternative, the city of Bordeaux is well on its way to create a greener wastewater treatment process and save up to X% on operational costs.
That the blower system in the aeration process consume at least 60% of the total energy use on a wastewater treatment site, is no secret within the wastewater treatment industry. The costs of having clean water are rising as clean water is becoming increasingly scarce resource worldwide. So getting the energy usage of the compressed air installation down, means getting costs down. Municipalities are looking for ways to decrease the costs of the wastewater treatment process and creating a greener and more sustainable purification process along the way. And so is SABOM, a sub-company of Veolia managing the wastewater treatment sites for the municipality of Bordeaux.
“With a population of 800.000 and counting, the City of Bordeaux processes more than 112 million liters of wastewater every day,” says … . “The amount of tab water used varies during the day, with peaks in the morning and evening. This means the amount of wastewater and thus the need for compressed air also varies throughout the day. The municipal wastewater treatment amenities of the city of Bordeaux are divided into different sites. Some are situated near the city center, right between houses and apartment blocks.”
"We have a responsibility towards the City of Bordeaux, our stakeholders, and the public to make the wastewater treatment process more sustainable from an environmental, economic and social point of view", says... "In order to decrease the operational costs on two of our wastewater treatment sites, the existing lobe blower units, had to be replaced with a greener and more energy-efficient solutions.” By replacing rotary lobe blowers with screw or centrifugal blowers, the city of Bordeaux can save up to 30% on energy usage.
SABOM partnered with Atlas Copco, choosing —depending on the needs at the site— ZS screw blowers and ZB VSD+ centrifugal blowers as an energy-efficient replacement for the existing lobe blowers. Choosing a unit where everything is built-in and ready for installation upon arrival (plug & play unit), has many advantages.
A unit with a built-in variable speed drive is the most energy-efficient option as it automatically adjusts the power of the unit to the flow demand of the application. VSD technology ensures the units always runs in the most energy-efficient way. Replacing an existing installation can be tricky as you are limited to the available space occupied by the previous units. Luckily, our plug and play units are compact and fit easily into the existing blower rooms. In the end, they took up even less space than the previous units.
Our built-in monitoring system, the Elektronikon, was an additional benefit as the previous units didn’t have a visual or remote control. The Elektronikon monitors the running conditions of each unit and makes it easier to prevent breakdowns. It increases reliability, helping to simplify the management of the aeration process altogether. Another benefit of our units is the low noise emission level. As the two sites are located near houses and communities, noise pollution needs to be reduced to the minimum.
Atlas Copco’s compressed air experts helped us design the best solution for our site. Not only did they take into account the energy efficiency, but they also provided us with turn-key units for immediate installation and operation upon arrival at the site.