Ceramic Media Filters Out Metals for Less

Legacy industrial effluent treatment systems typically have been designed to meet lower standards of discharge. As these mandated standards have become more stringent, these systems have fallen behind and are creating issues for their users. Ion exchange and chemical treatments might be more effective; however, they too are expensive, are labor and energy intensive, intolerant of process changes and create secondary sludge and backwash.

One company has developed an answer to this wastewater treatment dilemma. Although not meant to be a replacement for effluent treatment, Serfilco has developed the SerPure filtration system, a low-cost alternative to legacy technologies. The wastewater purification system uses ceramic molecular (CeraMol) media to remove metals and impurities from water to achieve compliance and minimize wastewater discharge.

“An effluent treatment plant investment can cost upwards of $200,000 to $300,000, sometimes more than that,” says Huw Williams, global general manager at Serfilco. “But even then, it doesn't necessarily generate water that's clean enough to meet compliance to put back into the plant or out into the sewer system. Many people are running out of compliance, so they run the risk of having (large) fines and even being shut down.”

However, the company’s newly developed system is not only more effective than legacy wastewater treatment systems, but also costs significantly less – around $25,000 to $30,000. In addition, the unit enables the user to recycle water into the plant so less waste water is discharged. It is also low maintenance, and the media can be recycled or regenerated.

The CeraMol media, which can be targeted to specific metals removal, was the brainchild of a professional in the materials science field. Rob Sawyer, general manager at Serfilco UK, recalls the woman approaching him at a National Association of Surface Finishing exhibition in 2022 with the new filtration media. “She said, ‘Do you think this will work?’ And I haven’t let go since,” Sawyer says. He knew it was exactly what the industry needed: a low-investment, low-tech solution.

The purifying process

Besides offering application-specific media choices to guarantee water purity, CeraMol media is unique in that is provides a huge surface area in a small package – at 300 m² per gram, just 18 g gives you a filter area as large as a football field, according to Williams. He explains that its large chemisorptive surface area makes it significantly more efficient than typical ion exchange resins due to its ability to retain contaminates. Impurity retention capacity for the new filtration ranges typically 0.4-0.6 to 1, but can go as high as 1-1 in certain applications.

As a result, the filtration system can reduce wastewater discharge rates by returning cleaned water back into the plant. Depending upon the specification chosen, this can present opportunities to recycle more than 50% of water previously discharged. “When water is recycled, companies not only pay less to discharge to sewers, but also don’t need to buy as much in – providing significant savings,” Williams adds.

CeraMol media are available in a number of various configurations that are manufactured to target specific molecules and solve specific problems. Each media remove different types of dissolved contaminant including typical metals found in the surface treatment industry, acid, recalcitrant chemical oxygen demand (COD) and organics, aluminum, iron, chrome 3 and 6, sulfate, chloride, phosphate, nitrate, fluoride and other metals such as copper, nickel, zinc, tin, chromium and cadmium. (See Figure 1.)

As much as 26 pounds of CeraMol media is encapsulated within one chamber of the SerPure filtration system. As a customizable system, manufacturers can choose two to four chambers for their unit depending on the contamination that needs to be removed from the water. And, for every 22 pounds of media in a chamber, 11 to 16 pounds of metal or contaminant is removed.

Williams explains that the system is most successful when placed right before the wastewater discharge. Therefore, the water has already been through settlement, coagulation, flocculation and other standard effluent treatments by the time it encounters the media.

The media’s chemisorption process removes contaminants by means of adsorption, absorption and chemical reaction. Metals can be recovered from the wastewater and reused with this system as well. This option is especially useful for companies that provide precious metal electroplating services and want to get money back from the metal they recovered.

Williams says Serfilco works with companies to define their goals as they are customizing a system. “It’s all based on benchmarking where we’re at as a starting point, and then targeting where we need to either meet compliance or reuse water, and sometimes it’s both,” Williams explains.

Equipment setup explained

Designed as a simple unit, the SerPure filtration system’s standard model is compact, making it easy to find space for its placement in a facility or even to add on to an existing effluent plant by bolting it onto the equipment. In fact, Serfilco is targeting effluent plant manufacturers to incorporate this technology as part of their process.

“If you already have a decent effluent plant, this is going to help you run it even more effectively,” Williams explains.

Unlike an effluent plant with a lot of piping and pumps, SerPure has only two to four chambers, one pump, an in-line flow meter and motor starter. The first chamber in the series often works as a pre-filter for particles that overflow from the settlement tank.

“Even after good coagulation, flocculation, you still get carryover of solids,” Williams explains. “So, we remove the solids to start with, which will be the first chamber, and then basically we would add as many chambers as we need, depending on how many different media are necessary. Apart from the anion media, which you can mix and match, the other media needs to be running in isolation to target a specific contaminant.” A backwash system can be built either into the equipment or as a stand-alone device.

A typical system covers a lot of flow rates and is also usable in a rinse tank environment. However, Williams explains that higher removal expectations require larger tanks or more tanks.

But the point of the SerPure system is the compactness to keep it at a low price point. “The system was designed originally for very large processes, big steel mills, big textile processes, with six or seven chambers. But then we’re looking at million-dollar systems, which is not what our industry needs,” Sawyer explains. “So, the challenge is to take a tech that’s been applied in one way and apply it in another and apply it to things it hasn’t been applied to before.”

3 Applications

Serfilco implements its CeraMol media in one of three typical applications based on the user’s needs. Applications include polishing of water post-waste treatment, online treatment of rinses, and selective tank treatment for metal recovery.

• Polishing of water after waste treatment: Ensuring that the user meets Consent to Discharge limits, this application facilitates water recycling to reverse osmosis/deionized rinses for a much lower cost compared with a zero liquid discharge effluent treatment plant. This application necessitates a pre-filter, CeraMol-C and CeraMol-M to remove organics and metals.
• Online treatment of rinses: This enables users to recirculate rinses continually and keeps metals out of the waste stream, which reduces the load on a wastewater treatment plant. It also prevents carryover of contaminants to a plating process. A filter, CeraMol-S, CeraMol-C, CeraMol-M, CeraMol-AN are required to remove acids, organics, metals and resultant anions.
• Selective tank treatment for metal recovery: This tailored solution prevents metal from entering the effluent stream, including precious metal rinses, cadmium, and so on. It is ideal for reclamation of gold, silver, rhodium, palladium, even nickel in some instances.

Regenerate or replace

CeraMol is designed with the ability to regenerate, which removes the contaminants, but is low enough cost that in the right application it would just be replaced. Regeneration, which occurs while soaking in a regeneration solution, releases the contamination from the surface into the regeneration solution and concentrates them. The metals can then be extracted via evaporation or flocculation and filter. 

For users with a low contamination level in their water, CeraMol media will last a significant amount of time between saturation, and in these cases Serfilco recommend clients replace the media rather than add the additional investment in the regeneration systems.

The decision to regenerate or dispose of media is based on use and cost. Where large amounts of metals are present, the media will exhaust quickly. In this case, regeneration is recommended as the most cost-effective solution.