Josue Ntimugura, top photo, uses a power washer Thursday to clean a wall treated with potassium hydroxide, a solution used for removing graffiti.

Ntimugura and Amanda Fielder, shown in bottom photo applying the solution to the wall on Moody Street in Portland’s Munjoy Hill neighborhood, are involved with LearningWorks, which contracts with the city for graffiti removal.

This week marks the start of the annual Graffiti Busters program. Last year, 189 participants cleared about 30,000 square feet of graffiti.