The patent was filed in the US on December 22, 1887. The patented method treated sewage and other impure Water by’ electrolytic action in such manner as both to precipitate the solid matter and to oxidize (or disinfect) the organic impurities in the water.
For further reading, check this list of waste-water treatment technologies – https://en.wikipedia.org/wiki/List_of_waste-water_treatment_technologies
Patent Information
Publication number: US398101 A
Patent Title: William webster
Publication type: Grant
Publication date: 19 Feb 1889
Filing date: 22 Dec 1887
Inventors: William Webster