Ownership in this field is concentrated: the leading assignee alone holds 48 of the 112 records in scope, and the top five assignees combined account for 78.6% of all records. That share rises to 90.2% across the top ten. Beyond that, the ranking includes 24 companies in total, most holding only a handful of filings each, so due diligence should focus first on the handful of large portfolios rather than the long tail.

Ion exchange resin chemistry is the strongest single thread, anchored by decades-old filings such as US3966489A, which remains the most-cited record in this dataset at 108 citations. Activated carbon treatment and lime carbonatation or phosphatation also appear throughout the corpus. IPC data confirms this: sugar production and refining (C13B) and chemical or physical treatment processes (B01J) each tag more than half of all 112 records.

The filing trend peaked at 9 records in 2019 without a clear sustained growth pattern before or after that year, and the leading named assignees show zero filings in the most recent year captured. This should not be read as the field going dormant, however, because publication typically lags filing by around 18 months, meaning recent-year filings are undercounted in any dataset with a fixed cutoff. A meaningful growth rate cannot be computed from fewer than four complete post-lag years, so no such figure is claimed here.