Reverse Osmosis with additional brine stage

PW-System-Konzentratstufe ©Werner GmbH 2015

In most sectors of the pharmaceutical industry, pharmaceutical water (PW or HPW) is required in different amounts. The daily requirement varies depending on company size, production capacity and process controls from a few liters 100 liters to 100,000 and more. Modern pharmaceutical water systems are based solely on the membrane separation process of reverse osmosis. Here the solvent water is withdrawn through the semi-permeable membrane of the pre-treated potable water. This process results in up to a 10-fold concentration of all substances in the water before the RO membrane. With a lack of pretreatment (usually softening and filtration <5 µm) this concentration leads to a blocking of the membrane by “scaling”.

For this reason the reverse osmosis systems have been operated with a maximum recovery of 75 %  (ratio of permeate: concentrate) for many years.

With the most potable water sources in Germany the recovery can also be increased to 80 or even 85%. If the life cycle of a pharmaceutical water system in terms of operating costs examined more closely, it turns out quickly that the running cost per cubic meter of purified water are largely formed by the fed potable water (in many cases up to 70% per m³ Purified Water).

By this reason, Werner GmbH designs after a detailed cost analysis already in the budgeting phase an additional brine stage (downstream membrane separation process) in order to increase the recovery of the reverse osmosis depending on the quality of drinking water to 90 or even 95%.

In a recent realized project (6 m³/h Purified Water), taking into account the additional investment costs with an amortization period of the total investment of 10 years over the life cycle at a current water price of 4.20 EUR / m³ nearly 80,000 EUR have been saved.