On December 16, Véolia, the company that manages the Saint-Omer wastewater treatment plant and partnered up with CAPSO for the study on sludge optimization, showed the partners around the site. The visit ended at the modified installation for sludge treatment, where a lime mixer and three conveyor screws now replace the feeder pump and its discharge.
Here, to come to the best solution to reach the applicable quality standards for the sludge (and its handling), Véolia and CAPSO have done a range of experiments with different lime types and mixing ratios. From this study, they concluded that it is the combination of 35% of Q90SR-type lime mixed into the sludge and a better mixing thanks to the new conveyor screws that leads to the best results.
Reuse on local farmlands
In short, the modifications resulted in a more stable sludge, with better heap and the required 30% dryness, making it eligible for reuse on the nearby farmlands. As Lucas Lacombe from CAPSO pointed out, this means that local farmers can now come and pick up the dried sludge and use it on their fields as fertilizer, thus cutting back on the need to buy extra products.
Interest from press and students
While the visit to the wastewater treatment plant took place as part of the biannual NEREUS partner meeting, it wasn’t just the partners who were introduced to the demonstration. Students from the wastewater treatment section of the Lycée Blaise Pascal Longuenesse were also given a tour of the site, as was the press. In response, local newspaper L’indépendant du Pas-de-Calais featured a short article on NEREUS and the sludge treatment in Saint-Omer, while Delta FM did a radio coverage of the visit.