Did you know it’s possible to clean water with shells? Crustacean shells are an abundant byproduct of the seafood industry. But they needn’t be dumped in the ocean en masse, where they cause environmental problems, or landfilled. Chitosan, a polymer extracted from chitin in crustacean shells, has a number of properties that make it good at removing pollutants from  water, including stormwater, wastewater, and drinking water.

Chitosan acts as both a coagulant and a flocculant. NEBRA Member Tidal Vision, which focuses on chitosan-based water treatment solutions, gave a “Lunch and Learn” webinar for NEBRA in August of 2022. Jenn Wood, who is Global Key Account Manager at Tidal Vision, said in the webinar, “We call it a flocc-builder or flocc-booster. It actually works really well in concert with metal coagulants that are a little bit better at kicking off the reaction and then chitosan is really good at floccing those elements.”

Chitosan can displace non-biodegradable flocculants and coagulants in a water-treatment process. “Today, when you coagulate with metal coagulants, you end up with metals in your biosolids,” wrote Alex Gaynor, another representative of Tidal Vision in a May 2023 email. He  continued, “When you coagulate with [the company’s] next generation chitosan coagulants and floc with a small amount of anionic polymer, you end up with food for microbes in your biosolids.” What’s more, chitosan is a plant-elicitor, meaning it helps plants amplify their natural defenses, so it is valuable in fertilizer. An article by F. Renault and others in the European Polymer Journal describes additional characteristics of chitosan:

Chitosan considerably increases the density of the sludge and facilitates its drying compared to the sludge produced with metal salts; in addition, as biopolymers are biodegradable the sludge can be efficiently degraded by micro-organisms; two studies reported that the sludge produced from the treatment of milk processing plant wastewater [Chi and Cheng 2006] and kaolinite suspensions [Divakaran 2001] was non-toxic and could be used to stimulate growth in plants; chitosan does not add much to the salinity of the treated water and is useable at alkaline pH.

Wood explained that the “upcycled” nature of chitosan from seafood waste is central to the company’s mission. One of Tidal Vision’s founders is from Alaska and worked on fishing boats starting in his teens. The experience led him to “[recognize] the extent of the negative impacts that that industry can have,” Wood said. 

The Washington State-based company extracts chitin from crab shells that it gets from sustainable fisheries. The company’s acetylation process “maintains the natural and biocompatible nature” of the polymer, Wood said. Tidal Vision sells the liquid chitosan solution in several different water treatment products, all of which are biodegradable. The company turns the parts of the shells that it doesn’t use into fertilizer, which it also sells.

In a May 2023 phone conversation, Tidal Vision’s Water Sales Team Leader Chris Tabler said the company frequently sees its products used as part of stormwater treatment, but the technology hasn’t been as readily adopted for drinking water or wastewater treatment. Why not? Metal-based salts have been used for so long, he said, and municipal facilities are often limited to products that have undergone certain government-regulated testing. But Wood noted in her NEBRA Lunch & Learn presentation that, “After independent scientific review in 2020, the EPA added chitosan to the Safer Chemical Ingredient List as a Green Circle – the highest rating for human and environmental safety.”

Wood also described how chitosan’s properties can decrease long-term costs of water treatment. For example, it doesn’t retain water, which could lead to decreased hauling costs. Other potential cost savings are related to not needing to use pH adjusters and the fact that chitosan is biodegradable and so doesn’t add to total dissolved solids.

Now Tidal Vision is on the lookout for more wastewater and drinking-water facilities to run trials with its chitosan products as part of regular jar testing. “We are happy to provide samples and cover shipping to the plants and/or water treatment providers to do jar testing,” Tabler wrote in a follow-up email. “Typical sample volumes are 3 oz or 8 oz. In some high impact applications, we may even provide material for a larger trial study. If they are willing to allow us to engage with the planning, testing and have access to the data that is collected it is a best-case scenario for us.”

For more information on Chitosan, check out the Lunch & Learn recording on the NEBRA YouTube Station (https://www.youtube.com/channel/UCpEHEEQAvXvxqMvUGhQh5pQ/). Contact the NEBRA office (info@nebiosolids.org) if you are interested in connecting with Tidal Vision.