Bailonggang Sludge Treatment Plant in Shanghai has 8 ellipsoidal digestion tanks, each having a height of 45m, a maximum diameter of 25m, and at present is the largest sludge digestion works of its kind with the largest group of digestion tanks and the largest single volume in China. The arc outer shells of the tanks with variable thickness were constructed by large formwork and support system with self-owned intellectual property right.