Rethinking the filtration system to support increased production capacity

The company develops and selects microalgae strains that produce molecules of nutritional and/or cosmetic interest. After industrial-scale cultivation, it harvests and extracts these target molecules to produce solid or liquid ingredients ready for use by manufacturers of dietary supplements or cosmetic products. To do so, it produces and uses osmosis water.

The site is equipped with an osmosis water production unit supplying a storage tank and a looped purified water network (flow rate: 5 m³/h), filtered at 0.2 µm using 20-inch filter housings installed in series (though only one is in use due to pressure-drop constraints).

To obtain the natural active ingredients derived from microalgae, the client uses tubular reactors. Each reactor has two inlet points: it is connected both to the purified osmosis water network and to a seawater feed line. Both seawater and purified water are filtered at 0.2 µm bacterial grade upstream of the reactor. This filtration is performed using PES membrane cartridges (16VPB), 10-inch format, installed in plastic housings to avoid oxidation issues.

To increase its production capacity, the client planned to multiply by four the number of reactors. This scale-up was to take place in two phases: a first expansion from 5 reactors to 10 by the end of the first year, followed by a second expansion reaching 20 reactors during the first quarter of the following year.

In the expansion project, the flow rate on the osmosis water network had to be increased to 15 m³/h, and the purified water inlet flow to 2.5 m³/h, with a pressure of 3 bar at the reactor inlets. The client also required that the new installation have the smallest possible footprint while maintaining controlled operating costs.

We recommended that the client redesign its industrial filtration systems and adopt the following configurations:

For loop filtration, we advised installing a 3 × 30-inch multi-cartridge polypropylene (PP) housing, equipped with 30-inch pleated membrane filter cartridges with a 0.2 µm filtration rating.

The sterilizing filtration of purified water upstream of the reactors (on the loop take-off) is now performed by a set of two 10-inch, three-piece PP filter housings installed in series in front of each reactor, each containing hollow-fiber filters (0.2 µm). The hollow-fiber membrane technology was selected over pleated membrane technology due to its superior flow performance.

Indeed, for a given footprint, the hollow-fiber cartridge proposed to the client offers a filtration surface up to three times larger than that of a pleated membrane cartridge. The selected solution therefore made it possible to stay with 10-inch filter housings, whereas using pleated membranes would have required sizing equivalent to 3 to 5 × 10-inch housings.

We also chose a housing designed for easy assembly and disassembly. Its three-piece construction minimizes mechanical stress on the connectors (inlet and outlet) and the piping.

To learn more about endotoxin filtration

Finally, the sterilizing filtration of seawater upstream of the reactors is carried out using a set of two three-piece PP filter housings installed in series in front of each reactor and equipped with 10-inch pleated membrane filters (0.2 µm). The newly deployed installations have fully met our client’s expectations.

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