Summer bacterial bloom prompts changes for island water district

Water District 19, the largest drinking water supplier on Vashon Island, encountered a crisis this summer when a cyanobacteria bloom developed in its treatment center's recycling ponds. While the bloom did not threaten drinking water quality, it disrupted operations and triggered a nearly two-month state of emergency. The bloom, marked by visible discoloration and worsened by a heat wave, significantly decreased the treatment plant's efficiency. In consultation with the Washington State Department of Health, the district conducted water testing that revealed cyanobacteria levels exceeding safe thresholds, although no harmful cyanotoxins were detected. As a precaution, the treatment plant was temporarily shut down.

To address this issue, WD 19 is implementing strategies such as installing pond covers to block sunlight, using potassium permanganate for chemical treatment, and enhancing infrastructure for contaminated wastewater management. With climate change impacting local ecosystems, the district anticipates more frequent microorganism challenges and is committed to maintaining safe water quality for its customers through proactive measures.