By injecting ultra-high-pressure water, most blockages are eliminated.
Literal
Ultra-high-pressure water [possessive-の] injection [by-により], most blockages [subject-が] eliminated.
超高圧水 'ultra-high-pressure water.' 噴射 'injection, jetting.' により 'by means of' is the formal instrumental particle. 排除される is passive — 'are eliminated.' Technical/industrial language about hydro-jetting.