Biofouling Control

Biofouling control is monitoring the biofouling and to find the unique values to initiate actions, such as replacement of cartridge filters, biocide shots or chemical cleaning of the involved parts of the plant. Biofouling is still poorly understood even when factors that contribute and influence it are well known. In all membrane processes as Reversed Osmosis and Nano filtration it leads to an increase of pressure drop and consequently to higher costs of plant operation. To control biofouling it is necessary to detect it in an early stage.

The Membrane Fouling Simulator

With the Membrane Fouling Simulator (MFS) which has been developed and tested over the last decade by Dr. Hans Vrouwenvelder, early detection of Biofouling is now possible. The MFS can be used to evaluate the biofouling tendencies of different water sources, of dosed chemicals or as an early warning device. In the case of Biofouling Control the effectiveness of the pretreatment, biocide regimes and chemical cleaning can be monitored and used to optimize the performance of the plant.
Global Membrains can help finding these specific critical indicators and develop strategies to optimize the operation of the plant.The adagio: “to prevent is better than to cure” certainly goes for Biofouling control.  It is common practice to prevent biofouling with hypochlorite. Since the free chlorine is known to  damage the membranes this is usually followed by a Bi-sulphite dose right before the feed end of the plant. A little overdose of bi sulphite neutralizes the free chlorine and its oxidation effects. It is Global Membrains experience this strategy however this strategy enhances Biofouling beyond the Bi-sulphite dosing point. This can be explained by the effect of chlorine of oxidizing the bacteria and other organic components into organic debris. This debris is easy edible by the bacteria that survived (or brought in with the Bi-sulphate) and are situated after the Bi-sulphite dosing point.
We met far better results taking out both chorine and Bi-sulphite dosing. The best strategy to biofouling control has been proven to eliminate essential feed materials from the feed water. For this the pre treatment of the raw water is crucial. These step however can be very costly. To prevent biofouling a biocide treatment can be implemented in certain cases, depending on the circumstances and the purpose of use for the permeate. Dose-rate and –intervals can be determined with the use of the Membrane Fouling Simulator (MFS) and can be different over the seasons in case of surface or re-use water. Global Membrains can help with our worldwide expertise in Biofouling control.