Great beaches, fresh trade winds, big surf and a fascinating culture make Hawaii a very special place. In turn, the popularity of the islands, its climate and geology create special issues for wastewater collections.

In the City and County of Honolulu — now home to more than 1 million people — urban density, aging sewer lines and heavy rainfalls have led to wet weather sewer overflows and spills, some of which have closed the area’s popular beaches. Hurricanes and other...