Development of a High-Throughput Fiber-Optic-Based Closed Bottle System for Evaluating the Ready Biodegradability of Water-Soluble Polymers

Water-soluble polymers are widely used in various applications. However, a large portion of them may end up in natural environments after use and may pose a risk if they do not decompose naturally, especially through biodegradation. Existing methods for evaluating the ready biodegradability of water-soluble polymers are generally costly, low throughput, and labor-intensive. To overcome such limitations, this study developed a high-throughput method using a fiber-optic dissolved oxygen measurement approach based on a modified OECD 301D method. The new method was first compared with traditional methods and showed similar biodegradation results. PolySeed was then evaluated as an alternative inoculum to secondary effluent, and a strong correlation was observed between the inoculum types, especially for highly biodegradable substances (>60% of degradation). The investigation on the effect of inoculum dosage suggested little difference among the three dosage levels (0.05, 0.5, and 5 mL/L) within the recommended range by OECD 301D. Compared to smaller reactors (20 and 40 mL), only reactors with volumes of 300 mL resulted in reasonable biodegradation. The further evaluation of this new method on over 40 natural, synthetic, and graft polymers indicated that it could be reliably applied for testing the ready biodegradability of diverse water-soluble polymers.