What happens to a ContrastCatch filter? From captured contrast agents to recovered iodine

Capturing contrast agents before they enter the sewer is only the beginning. What happens when a ContrastCatch filter is full? Its next journey connects reusable filter components, practical insights and data for hospitals and the recovery of valuable iodine.

Two filters, working together

Current ContrastCatch systems contain two filters. The lower filter captures contrast agents first; the upper filter acts as a polishing stage, capturing what passes through the lower one.

Filter saturation is monitored, and the system signals when replacement is needed. The replacement interval depends on use, based on the number of patients. The aim is to make effective use of both filters’ capacity before they are replaced.

The filter housing is designed for repeated reuse. A filter is therefore not simply a disposable product: it currently returns to Zereau for servicing. We open the housing, remove the filter material containing the captured contrast agents, clean the housing and refill it with fresh material.

Every filter tells a story

At Zereau, we label the filter materials so that we can trace the iodine collected back to a particular filter set and hospital location.

During this development phase, that traceability serves two purposes. It allows us to report how much iodine a hospital has captured and helps us identify ways to improve collection.

By comparing the iodine measured on the filters with patient numbers and contrast administration data, we can estimate the average proportion captured per patient. This also helps us understand whether patients are using the toilet at an effective point after their examination. On-site counts and approved monitoring of average waiting times provide additional context, including indications of how often facilities are used by people outside the intended patient group.

Together, these insights help hospitals refine patient information, guidance and workflow to capture as much contrast agent as possible in the first urination—or first few urinations—after administration.

From filter material to reusable iodine

The removed filter material is stored, measured and sampled per filter set. The relatively dry materials coming out of the filters is safely stored in large drums until enough has accumulated for a shipment.

The drums then travel to Bittner in Marbach, near Stuttgart, where iodine-containing materials are processed into reusable iodine salts. Here, Zereau’s material joins streams such as surplus contrast agents, production rejects from pharma companies and iodine-containing residues from other industries.

Our filter material offers a distinct advantage: while most incoming waste streams are liquid and require substantial evaporation before processing, ours consist of solids with very low moisture content. As a result, little to no evaporation is needed, and the high iodine concentration per kilogram makes the material particularly attractive for recovery.

Nevertheless, with only around a dozen systems currently installed, our contribution to the overall impact of Bittner’s iodine recovery operations remains small. However, as our installed base grows, so too will our potential contribution.

Bittner also measures precisely how much iodine Zereau delivers. This provides an independent cross-check against our own analyses, with results to date closely matching our measurements.

How much can we capture?

The answer depends on the hospital’s procedures, department, patient waiting times and communication.

In outpatient radiology, our project experience indicates that around 25–30% of the administered iodine can be collected in the first urination. In departments where procedures differ or patients stay longer, collection could reach up to 90% of the administered amount. These figures reflect different care settings, rather than a single collection rate that applies everywhere.

That is why the system and the patient pathway need to work together.

“The filters capture what reaches them; organisation and patient participation determine how much can be collected.”

A growing recovery loop

Our contribution is still a drop in the ocean. But wider adoption means more iodine collected, more efficient transport and more material available for recovery - while keeping contrast residues out of wastewater and reusing the filter housings.

Today, this recovery route focuses on iodine. We also filter Gadolinium from MRI examinations, but recovery is not yet part of the process; that is the next development phase.

“A used ContrastCatch filter is therefore not the end of a product’s life. It is the start of another cycle.”