Department of Chemistry CHEM1020 General Chemistry ***********************************************

Department of Chemistry

CHEM1020 General Chemistry***********************************************

Instructor: Dr. Hong ZhangFoster Hall, Room 221

Tel: 931-6325

Email: [email protected]

CHEM1020/General Chemistry_________________________________________

Chapter 13. (L27)-Chemistry of Water

• Today’s Outline

…Water quality

…Sources of water pollution

…Transport and fate of water pollutants


• Water quality…Water use classification and water standards

A practical evaluation and definition of water quality depends on how the water is used in addition to its chemical composition

The quality of water is not judged by its purity but rather by its suitability for the particular use desired

For example, nitrate (NO3-) of >10 ppm in drinking water is

considered a potential hazard, particularly to children, but on the other hand, nitrate is a nutrient beneficial to plants; so water of > 10 ppm nitrate may be good one for agricultural use

Water use needs to be defined before water quality can be evaluated against


• Water quality

…Common approach to evaluating water quality

-Define the particular purpose of water use

-Set numerical standards for physical and chemical characteristics of the various waters of different usages

-Field-measure the pertinent water parameters to determine if a particular water source would have a satisfied water quality and suitable for use


• Water quality…Typical water use classification-Recreational Class 1. primary contact, surface water that suitable for or intended to become suitable for prolonged and intimate contact with the body, or for recreational activities where the ingestion of small quantities of water is likely to occur, e.g., swimming, rafting, kayaking, water skiing, etc.,

Class 2. secondary contact, surface water that suitable for or intended to become suitable for recreation in or around the water, which are not included in the primary contact subcategory, e.g., shore fishing, motor yachiting, etc.


• Water quality…Typical water use classification

-Aquatic lifeSurface water that suitable for or intended to become suitable for the protection and maintenance of vigorous communities of aquatic organisms and populations of significant aquatic species

a. Class 1. Cold water aquatic life (Tw < 20 ˚C commonly)

b. Class 1. Warm water aquatic life (Tw > 20 ˚C normally)c. Class 2. Cold and warm water aquatic life. These are waters that are not capable of sustaining a wide variety of cold or warm water biota, including sensitive species, due to conditions of physical habitat, water flows and levels, or uncorrectable water quality that results in substantial impairment of the abundance and diversity of species

-AgricultureFor agriculture, not hazardous as drinking water for livestock


• Water quality…Typical water use classification-Domestic water supplySurface water that suitable for or intended to become suitable for portable water supply. After receiving standard treatment, i.e., coagulation, flocculation, sedimentation, filtration, and disinfection with chlorine and its equivalent, these waters will meet the federal and sate drinking water standards

-WetlandsSurface water and groundwater that supply wetlandsWetlands may be defined as areas that are inundated or saturated by surface or groundwater at a frequency and duration sufficient to support, and under normal conditions, do not support, a prevalence of vegetation and organisms typically adapted for life under saturated soil conditions


• Water quality

…Typical water use classification-Groundwater

Subsurface waters in a zone of saturation that are or can be brought to the surface of the ground or to surface waters through wells, springs, seeps, or other discharge areas.

Domestic use

Agriculture use


• Water quality

Each state has its water quality standards, which can be found from the pertinent state government agency

The US EPA sets baseline standards for different use classifications that serve as minimum requirements for the state standards.


• Water quality…Water determinationWater quality is defined in terms of -Chemical composition: concentration of metals, organic compounds, chlorine, nitrates, ammonia, phosphorous, sulfates, etc.-General physical and chemical properties: T, alkalinity, conductivity, pH, DO, hardness, total dissolved solids (TDS),

COD, etc.-Biological characteristics: BOD, fecal coliforms, whole effluent

toxicity, etc.-Radionuclides: radium-226, radium-228, uranium, radon, gross

alpha and gross beta emissions, etc.

Keep updated about the standards


• Sources of water pollution

..Point sources

Example: industrial discharge

..Non-point sources (diffuse sources)

Example: N, P, pesticides, Hg deposition, PCB deposition


• Transport and fate of water pollutants

Emissions

Sedimentation

Food web accumulation

Bound by humic substances

Adsorbed on suspended particles


• Major water pollution and pollutants…Heavy metals

Examples: Hg, Pb, Cd, Cr, As, Co, etc.…Polychlorinated Biphenyls (PCBs) and Dioxins-Both share similar chemical structures and a range of chemical, biological, and environmental properties

-Trade names of PCBs: Aroclor, Chlophen, Kanechlor, Fenclor-Use: plasticizers, ink-PCB, a mixture of chlorinated biphenyls with different number of Cl-Sources of PCBs, electrical equipment, e.g., capacitors, transformers as heat transfer fluidFirst recognized as environment problem in 1966


• Major water pollution and pollutants

Dioxin, or PCDDs, Polychlorinated dibenzo [1,4] dioxins,

-dioxins are unwanted byproducts in chemical processes involving chlorine and combustion (incinerators, coal-burning power plants, vehicle exhaust), pulp and paper mills bleaching (use of Cl)

-widely distributed in the environment, largely associated with particles in the troposphere

TCDD is a highly toxic member of dioxins


• Major water pollution and pollutants…Synthetic polymers (plastics, elastomers, synthetic fibers)

Plastics, Elastomers, Synthetic fibers Applications in plumbing, textiles, paint, floor covering, clothing;

Environmentally resistant

…Petroleum hydrocarbonsLong carbon chain of C and H only, 50-90%

n-alkanes (normal paraffins, found in all crude oil, C1-C40 or >), branched alkanes, cycloalkanes (largest fraction), aromatics (< 20%)non-hydrocarbonsS-containing compounds, in higher boiling fractionsN-containing compounds


• Major water pollution and pollutants…Pesticides

DDT

HerbicidesInsecticidesFungicides

-Chlorohydrocarbons pesticidesToxic to aquatic life and wildlifeNeurotoxins (nervous systems), inducing tremors


• Major water pollution and pollutants…Detergents and soaps

…Organometallic compounds …Pharmaceutical products and derivatives

Solving water pollutionNatural degradation and cyclingCutting the sourcesWaste water treatment prior to dischargeEngineering treatment of aquatic system (e.g.,

cleaning river beds, Hudson River, NY)Treatment using wetland


Quiz TimeTBA

Department of Chemistry CHEM1020 General Chemistry ***********************************************

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Transcript of Department of Chemistry CHEM1020 General Chemistry ***********************************************