Bypass solution for wastewater treatment plant

To upgrade an aeration tank at a major wastewater treatment plant in Toulouse, France, the plant required a bypass solution that could efficiently reroute 10,000 cubic meters of water per hour. The local water utility, Eau de Toulouse Métropole, partnered with Xylem's rental team to install a customized bypass solution that not only operated without fail but also saved energy.

The Ginestous-Garonne treatment plant treats wastewater for 76% of the Toulouse metropolitan area, with a capacity for 950,000 inhabitants, equivalent to around 160,000 cubic meters per day. The plant is managed by SUEZ, on behalf of Eau de Toulouse Métropole, through the company ASTEO.

In the summer of 2023, the treatment plant needed to replace the air diffuser membranes in an aeration tank as part of an upgrade. Xylem's rental team was commissioned to deliver a tailor-made bypass solution for the tank in just six weeks without disrupting the plant's day-to-day operations or the work of its teams.

Delivering a bypass solution that saved energy

To reduce the environmental footprint of the bypass, Xylem's team designed a pumping system that did not require a new generator. Instead, they repurposed the electrical power of the aeration tank's two turbo-compressors, which were shut down during the upgrade. The pumping system was connected directly to the compressors and required no additional power supply, thanks to the high efficiency of Xylem's Flygt pumps, which resulted in significant energy savings.

"Xylem's solution appealed to us because of its extremely advanced technical features," says Yoan Beaujon, Operations Manager, Ginestous-Garonne Wastewater Treatment Plant. "Their structured approach, including on-call teams and guaranteed continuity of service while respecting the budget, was also reassuring, and a key factor in the decision-making process."

Designing two bypasses for the aeration tank

When designing the bypass solution for the aeration tank, Xylem and the technical team from the wastewater treatment plant installed two bypasses, each rated at 5,000 m3/hour. The first bypass on the inlet channel to the aeration tank included five dry-installed Flygt pumps, providing a total installed power of 260 kW. The second bypass for the recirculation zone, used to convey sludge from the clarifier tanks, included another five pumps, delivering 185 kW of total installed power.

To achieve an output of 10,000 cubic meters of rerouted water per hour, the bypass system required the installation of large-diameter suction and discharge pipes. The size of the models used (DN 400 and 600 for suction and DN 800 for discharge) reduced potential head losses.

To further increase efficiency, the pumping system uses a monitoring and control system of sensors to match the pumps' operation to actual demand, enabling one or several pumps to be activated when needed. This also enabled both bypass zones to maintain a consistent level of wastewater.

Providing 24/7 on-call service during bypass operations

The bypass solution was installed on time and put into operation at the start of August 2023.

"The bypass project presented several technical challenges, which we successfully overcame," says Vincent Buerba, Business Development Manager, Service and Rental, Xylem. "Once the equipment was installed, we launched the commissioning phase with the SUEZ ASTEO team, to see if our pumping solution met their expectations, in terms of both efficiency and the process. Next, we set up a 24/7 on-call service, so Xylem would always be available to manage alarms and provide repairs if necessary. The system worked perfectly, and we're proud to have contributed to its collective success."

"We worked in close collaboration with Xylem and included them in our weekly site meetings," says Aurélien Alirol, Water and Sanitation Project Manager, SUEZ. "Frequent meetings with the on-call teams in charge of minor pump maintenance enabled us to exchange ideas and optimize the pump station settings. There were no breakdowns during the operation of the bypass project, which meant there were no spills into the surrounding environment."

By partnering with Xylem's rental solutions, the Toulouse metropolitan area successfully completed the wastewater treatment plant upgrades with no service interruptions. Over the four-month period, both bypasses operated seamlessly, ensuring the community's needs were met without any additional greenhouse gas emissions - a significant advantage over other proposed solutions.

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