01:460:202 Lecture Notes - Lecture 13: Toxic Heavy Metal, Sewage Treatment, Leachate
30 Jul 2018
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• What is water? Potable water? Hard water? How do you treat for hard water?
o Water- a dipolar molecule and an excellent solvent- interacts with many
substances
o Potable water- drinking water
▪ Allowable concentrations of particular dissolved substances in natural
water
o Hard water- high concentrations of dissolved ions (calcium and magnesium)
▪ Problems:
• Prevents soap lathering
• Mineral deposits in appliances
▪ Solution:
• Water softeners remove hardness by ion exchange (e.g. sodium
→ calcium)
• Groundwater contamination (definition, types, causes).
o Any degradation of ground-water quality resulting from human activity
o Organic chemicals- pesticides, oils, solvents
o Metals- arsenic, lead, mercury
o Cleaning up contaminated aquifers- expensive and time consuming
• Point vs. non-point source pollution
o Point- specific source
▪ Factories, sewage treatment, mine drainage
▪ Discrete, confines, and readily identifiable
▪ Easier to deal with: identify sources, on-site treatment and mitigation,
prevention
o Non-point- diffuse
▪ Agriculture runoff, roads
▪ Regional, intermittent, and hard to identify
• Pollution by organic chemicals- DDT case study
o DDT= insecticide
▪ Insects develop resistance requiring higher applications of DDT
▪ Toxic and persistent- build up in fat tissues- toxicity in fish
▪ Impaired calcium metabolism
• Devastated bird populations due to thin eggshells
o EPS banned DDT- 1972
• Pollution by metals- arsenic pollution and case studies (India and NJ)
o Arsenic- 0.05 ppm (nervous system toxicity)
▪ Cancer, coronary heart disease, diabetes, skin lesions, reproductive,
respiratory diseases, hepatoxicity, neurologic
o India- groundwater arsenic contamination
▪ Water wells drilled into pyrite-coated sediments of Ganges river delta for
municipal and agricultural use
• Skin lesions, other diseases began to appear
▪ 20,000 wells analyzed
