Arenthon Wastewater Treatment Unit Opens

The treatment plant was built on the same site as the existing Arenthon facility, which meant that the work done by the Degrémont-Pugnat-Degrémont Services group and subcontractor Mauro, begun in October 2008, was subject to significant scheduling constraints. Construction of the operations building and renovation of the existing digester could not begin until new facilities had been brought on line and existing ones demolished. Wastewater treatment services were provided continuously during the entire project.

The treatment plant construction requested during peak activity 90 people on site, 16,000 m³ of preloading material to stabilise the ground, 26,000 m³ of excavation, 8,000 m³ or nearly 20,000 metric tons of concrete, 620 metric tons of stainless steel pipes and collectors, 20 km of electrical cable and 2,000 entrances and leads allowing for 160 motor outlets.

Wastewater treatment in the new plant is divided into three distinct pathways:

A water treatment pathway, consisting of

• pre-treatments
• intake and treatment of sewage
• biological processing of fats
• first sedimentation
• biological processing by low-load activated sludge.

A sludge treatment pathway, consisting of

• thickening of sludge from the first sedimentation by gravity
• thickening of biological sludge on dewatering tables
• mesophilic digestion of mixed sludge
• dewatering of sludge digested by centrifugation
• use of the biogas produced by digestion to heat both the sludge in the digesters and the treatment plant’s technical facilities.

A pathway to treat contaminated air, consisting of two lines of three physical and chemical deodorising towers.

To enhance the reliability of the facility, each treatment pathway consists of two identical treatment lines operating in parallel.