Device for filtering contaminated water with means to monitor residual contamination

Apparatus for filtration of water which is contaminated by oil or oil containing substances and may contain air bubbles, comprising:

• a filter zone with an inlet and an outlet enabling contaminated water to flow though the filter zone, the filter zone having an absorption capacity for retaining oil contaminants by adsorption , the filter zone thereby preventing a substantial passage of the oil contaminants from the inlet to the outlet until the adsorption capacity has been reached;
• an inlet line through which the contaminated water is provided to the inlet of the filter zone;
• a circulation line connected between the outlet and the inlet of the filter zone;
• a discharge line connectable to the outlet of the filter zone;
• a circulation valve between the outlet of the filter zone and the discharge line and the circulation line, said circulation valve being switchable between a throughflow position in which the outlet of the filter zone is connected to the discharge line, and a circulating position in which the outlet of the filter zone is connected to the circulation line;
• a pump having a suction side and a pressure side, the suction side being connected to the inlet line and the circulation line, the pressure side being connected to the inlet of the filter zone, said pump feeding water from the inlet line to the inlet of the filter zone in a throughflow operation or from the outlet of the filter zone to the inlet thereof in a circulatory operation in dependence on the position of the circulation valve;
• and
• means for monitoring the contamination of the water, the means for monitoring including a light emitter arranged to pass a light beam through the water at the outlet of the filter zone, and a light sensor adapted for activation by the light beam and generating an output signal having a signal level dependent on light intensities incident on the light sensor, said light intensities being a measure of light scattering caused by light scattering particles including oil particles and air bubbles in the water, the signal level changing as a function of both the quantity of oil particles and the quantity of air bubbles;
• means for determining an exceeding of a threshold value of the light scattering and a lowering of the light scattering below the threshold value based on the output signal;
• means, responsive to the determining means, for changing the circulation valve from the throughflow position to the circulation position upon the exceeding of the threshold value of the light scattering, and for changing the circulation valve back to the throughflow position upon the lowering of the light scattering beneath the threshold value;
• means for monitoring a reduction in the light scattering occurring when the valve is in the circulation position to a substantial reduction of the light scattering indicative of air bubbles, and a negligible reduction of the light scattering indicating that the adsorption capacity of the filter zone has been reached and substantial quantities of the oil particles are passing the filter zone and that a renewal or regeneration of the filter zone is necessary.