NORRES offers its customers and partners from the range of the environment solutions in its 125th year anniversary further new innovative products: The PRO₂AIR Pre-PUR^? membrane tube diffuser with the lowest pressure can also be used in small sewage treatment plants now. This high quality product, which is absolutely free from softeners and has permanent elasticity, can also save plants for the treatment of sewage with a value of four to 50 population equivalent (EP) therefore providing much lower energy costs.