The ranking covers 19 assignees across 62 records, and it is led by a single assignee with 13 records, well ahead of fifth place at 4. The top 5 assignees together hold 58.1% of all 62 records, and the top 10 hold 82.3%, so filing activity is concentrated rather than evenly spread. Anyone assessing this space should treat that leading group as the primary prior-art risk rather than assuming the field is fragmented.

Filing peaked at 7 records in 2018 and has since declined, with a -100% change recorded between 2021 and 2024. However, publication typically lags filing by around 18 months, so the most recent one to two years in any dataset will always understate true filing activity. The honest read is that the field has cooled from its 2018 high, not that it has stopped — later years need time to finish publishing before a firm conclusion is possible.

Based on IPC classification of the 62 records, 71.0% carry C02F (water and wastewater treatment) codes and 29.0% carry E03F (sewerage) codes, meaning treatment technology is claimed far more often than sewer infrastructure itself. Smaller shares cover digital data processing (19.4%), control and regulating systems (14.5%), and biocide-related treatment (12.9%). Because records can carry multiple classes, these figures describe overlapping technical content rather than a clean split of the field.

US20060108294A1, filed by Ebara Corporation, covers a sewer system designed to rapidly disinfect combined sewer overflow, separated sewer rainwater overflow and separated sanitary sewer overflow before discharge to a public water body, without routing that flow through a full sewage treatment plant. One disclosed embodiment sends sewage to treatment when inflow stays within the plant's capacity, and diverts to a disinfection pathway once that capacity is exceeded. For anyone designing an overflow-disinfection route that triggers on capacity exceedance, this filing is a reference point worth checking against directly.

The classification data suggests control-and-regulating-systems claims (G05B, 14.5% of records) and digital-processing claims (G06F, 19.4%) are thinner than the dominant treatment-chemistry and hardware claims sitting in C02F (71.0%). That gap points toward real-time control algorithms, automated hydraulic model calibration, and receiving-water impact monitoring as comparatively under-claimed branches. A first claim there would likely need to tie a specific sensor input or model output directly to a control action, rather than claiming the treatment or diversion hardware alone.