Water Pollution and Treatment Chapter outlines: Water Quality, Water Pollution, BOD, Waterborne Diseases, Nutrients, Sediments,　Eutrophication, Oil Spills,　Groundwater pollution, Wastewater Treatment and Reuse. Lec 12

Global Water Supplies Globally, more than 99%of the Planetary Water Supply is unusable. –97% Saline; 2% Frozen –of the 1% remaining, extremely uneven distribution. –Thus, (fresh) Water Conservation is the major issue. •80% of the water we use is surface, not underground Lec 11_RDg

Water Quality The term water quality is used to describe the condition of the water, including its - chemical, physical and biological characteristics Chemical- DO, BOD Physical - Turbidity, cloudiness or haziness Biological- levels of coliform bacteria - for a particular purpose (i.e., drinking, swimming or fishing) the desirable quality will be different. Lec 12

Water Pollution Definition –degradation of water quality Considered polluted if it becomes unsuitable for a specific purpose Quality depends on potential use ( drinking water or irrigation water has different quality) EPA ( Environmental Protection Agency in USA) sets limits form concentrations of pollutants in water Lec 12

Biochemical Oxygen Demand (BOD) Amount of O2 needed for bacteria to decompose organic matter in water Natural sources, i.e., runoff, human sewage contribute to increases BOD Increased BOD = decreased dissolved O2 SAFE OXYGEN LIMIT = 5 ppm in water < 5 ppm O2 Many aquatic organisms may die Sudden discharges of organic matter –e.g., raw sewage Lec 12

BOD Lec 12

Waterborne Disease Serious human disease & epidemics result from waterborne pathogens Modern water treatment facilities can’t always guarantee pathogen-free water supplies Fecal coliform bacteria Continual testing is necessary to protect public health Lec 12

Nutrients Excesses, especially N & P, can lead to serious problems Eutrophication Excessive nutrients stimulate growth of aquatic plants, increased decomposition, increased BOD, death of aquatic organisms Natural or cultural ( Agricultural fertilizers of N, P) Lec 12

Sediment By volume, most significant water pollutant –Reduces water quality –Represents losses of soil (erosion) at point of origin –Forest land << agricultural lands – Sediments increase turbidity or haziness turbidity increases by suspended sediments, algae in water reduces light penetration for aquatic photosynthesis Lec 12

Eutrophication or Dying Lake Ecosystem 1. Nutrient addition to lake by runoff of fertilizers, sediments 2. Stimulated growth of aquatic Plants; i.e, algae (green)　 3. High turbidity, Less light penetration for photosynthesis, less oxygen　 4. Death of Fish Lec 12

Died fish in Gulshan lake Lec 12

Oil Spills Add nutrients to water Tanker, offshore drilling accidents, shipping activities In 2010 March, BP= British Petroleum’s Oil rig spill over 205 million gallons of oil were released into the Gulf of Mexico Lec 12

Groundwater pollution: Diagram illustrating leak from a Underground gasoline tank Lec 12

Pesticides and Water pollution Pesticide: chemical substance that kills pests, harmful insects, fungi, weeds, rodents, etc Lecture10_RDg

Chemical Pesticides: DDT Dichlorodiphenyltrichloroethane (DDT) Persist in the environment for many yrs • banned in 1972, still persists Bioaccumulates: concentrates in body tissues (fat)-may remain there for decades Lecture10_RDg

Honeybees Honeybees help flowering process of plant. Honeybees dramatically improve crop yields by increasing the rate of pollenization. Honeybees are threatened by disease and pesticide use. Lecture10_RDg

Biomagnifications occurs within a trophic levels, and is the increase in concentration of a substance in certain tissues of organisms' bodies due to absorption from food and the environment. For example, herring contains mercury at approximately 0.01 ppm and shark contains mercury at greater than 1 ppm (EPA 1997). DDT, PCBs, and the organic forms of Mercury and Arsenic do biomagnify in nature. Suedel et al. (1994) Lecture10_RDg

Biomagnifications: Environmental Step in USA In the United States, the government has an action level for methyl mercury in commercial marine and freshwater fish that is 1.0 parts per million (ppm). It means, 1 microgram in 1 gram we know 1 gram = 1000000 microgram or, 1 million microgram Lecture10_RDg

Have you ever thought of eating fish of Buriganga river and its biomagnifications in food chain? Lec 12