Keeping Drinking Water Safe | Hopkins Bloomberg Public Health Magazine

Climate change drives the water cycle to its extremes. It looks like melting glaciers and rising, churning seas—and also like tiles of desiccated soil and cracked lake beds. And one of the things it endangers is water itself: Public drinking water systems were built for previous generations’ weather.

That’s why Natalie Exum, PhD ’16, MS, an assistant scientist in Environmental Health and Engineering, is working to understand climate-related threats to Baltimore’s water infrastructure. With funding from a Bloomberg American Health Initiative Spark Award, she and Kellogg Schwab, PhD, MSPH, Abel Wolman Professor in Water and Public Health, are measuring tap water quality following extreme rainstorms. Understanding the effects of today’s storms can predict future vulnerabilities—and inform a plan for infrastructure resilience that can withstand extreme events for generations to come.

Protections on Tap

Thirsty Baltimoreans can thank Abel Wolman for their safe public drinking water. Wolman, chair of Sanitary Engineering in the schools of Engineering and Public Health from 1937 to 1962, co-developed the standard method of chlorinating municipal water supplies. He also planned the regional system that leads from protected watersheds to reservoirs that provide source water for Baltimore. Most U.S. cities don’t have this system, leaving their water supplies more susceptible to contamination following extreme weather events.

Cityscape illustrating the effects of droughts and deluges on urban drinking water resources

Shrinking reserves

If reservoirs’ levels decrease significantly, treatment facilities may need to draw water from rivers instead. These may contain pollutants the facility is not equipped to address.

Sudden Rush

Parched soil causes more runoff when rain comes. This means a greater volume and increased turbidity (murkiness caused by suspended solids) of water flowing to treatment plants.

First Flush

Without regular rainfall, pollutants such as pesticides, automobile fluids, and fertilizers accumulate on the ground. A post-drought storm flushes those contaminants in high concentrations into the source water.

Diluted effect

Treatment systems add residual disinfectant to keep water safe as it travels through pipes to the tap. The disinfectant may be reduced if extreme storms cause pipe breaks or other disruptions to the pressurized pipes.

Muddying the Waters

Prolonged heavy rains stir up sediment and other solids in source water, making it hard for treatment systems to adequately filter or disinfect water.

Slow Flow

Extreme rains can cause power outages that affect either pressure or flow in the pipes. If water sits longer in old pipes, contaminants have more opportunities to enter the drinking water.

Banked on Danger

Often located near rivers, water treatment plants are vulnerable to damage when extreme precipitation causes rivers to flood.

Crack in the Shield

Flooding can cause direct damage to pipes, creating leaks or breaks that allow contaminants from sewer overflows to enter the distribution system.

Watch

Researchers Exum and Schwab describe their work in Baltimore and how they hope it will translate to global water quality research.