Water Pollution Case Studies

WATER POLLUTION CASE STUDIESChesapeake Bay and Bangladesh

CHESAPEAKE BAY

Largest estuary in US 64,000 sq.-mi watershed,

with human population of 15 million

Important for fisheries, recreation, shipping

NUTRIENTS IN THE BAY: MAJOR POLLUTION PROBLEM

Nitrogen (primarily sewage and atmospheric deposition)

Phosphorus (primarily sewage) Oxygen-demanding wastes

Organic matter that is a substrate for aerobic decomposition

Sources are both point sources and non-point sources.

All these add to the eutrophication of the Bay, and the ultimate result: decreased oxygen Eutrophication: ecosystem change due to increased

nutrients; can be cultural or natural

NITROGEN TRENDS

OXYGEN

SEDIMENTS IN THE BAY

Top water pollutant in terms of weight. Problems caused by sediment:

Smother benthic (bottom-dwelling) organisms Decrease light transmission therefore reduce

benthic photosynthesis Carry toxins and nutrients

SEDIMENT TRENDS

TOXIC CONTAMINANTS (METALS, SYNTHETIC ORGANIC COMPOUNDS)

Solid red: region of concern; probable adverse impactDashed red: area of emphasis, potential adverse impact Dashed lines: low probablity of impactDotted: little information

From: http://www.mdsg.umd.edu/CB/toxics/map.html

Toxic Impacts

From: http://www.mdsg.umd.edu/CB/toxics/map.html

Toxic Impacts: Potomac

Solid red: region of concern; probable adverse impactDashed red: area of emphasis, potential adverse impact Dashed lines: low probablity of impactDotted: little information

SUSQUEHANNA: PREVENTION OF A PROBLEM

Cooling towers move heat to the air rather than to the River and Bay

BANGLADESH

Surface water unsafe to drink; large amount mortality from of waterborne disease.

1970s: UN Health and Development Agencies dropped 10 million deep tube wells to provide ‘safe’ drinking water.

Now 35-77 million Bangladeshis (up to half the population) drink water contaminated with arsenic at concentrations greater than 50 ug/l

WHO standards: 10 ug/lArsensic causes: skin lesions (early signs of

poisoning) skin cancer, bladder, kidney, lung cancer… (takes 7-10 years to appear)

ARSENIC POISONING: THE VISIBLE EFFECTS

Lesions on hands, feet, chest or head

Lesions can become cancerous:

ARSENIC MITIGATION Monitoring wells: which are safe?

ARSENIC MITIGATION Boy pumps

from well marked with green paint: “safe to drink”

Arsenic filter is possible on contaminated wells: $1500 per well.