Chemistry of the Environment - Water Chemistry PDF

MODULE 3 ENG 201 CHEMISTRY of the ENVIRONMENT 3.1 Water Chemistry FACULTY OF ENGINEERING U N I V E R S I T Y O F S A N TO TO M A S MANILA, PHILIPPINES Intended Learning Outcomes - ILOs Explain the key physica...

MODULE 3 ENG 201 CHEMISTRY of the ENVIRONMENT 3.1 Water Chemistry FACULTY OF ENGINEERING U N I V E R S I T Y O F S A N TO TO M A S MANILA, PHILIPPINES Intended Learning Outcomes - ILOs Explain the key physical and chemical properties of water. Discuss key water quality parameters. Discuss water contaminants and pollutants and the consequences. UST FACULTY OF ENGINEERING  3.1.1 WATER § One of the most important substances on Earth. § Can dissolve many different substances. § A polar molecule because of its unequal charge distribution. 3 Hydrogen Bonds Unusually strong type of dipole force § Strong hydrogen bonds occurs among polar covalent molecules containing H and one of the three small, highly electronegative elements, F, N,O § H from one molecule can associate itself with the negative end of the dipole of another § Dipole arises from the difference in the electronegativity between H and N, O, or F § Small size of H allows the unshared pair from the negative end of the dipole to approach the H closely § HF, H2O, and NH3 - Unusually high boiling points as a result of hydrogen bonding 4 Water Hydrogen bonding in water accounts for: §High specific heat §High boiling point §Higher density of the liquid phase relative to the solid 5  Intermolecular Forces in H2O Water: One molecule can participate in four hydrogen bonds with other molecules. Because of the hydrogen bond, water has a boiling point 100oC higher than if the bond were not present. 6  Intermolecular Forces in H2O Permanent dipole-dipole interactions occur between polar covalent molecules because of the attraction of the d+ atoms of one molecule to the d- atoms of another molecule. 7 Water Cycle Not in the photo is infiltration and percolation UST FACULTY OF ENGINEERING 8 3.1.2. Water Quality Parameters ü Water Hardness ü pH ü Phosphates (PO43-) ü Nitrites and Nitrates (NO2-, NO3-) ü Ammonium (NH4+) ü Dissolved Oxygen ü Turbidity UST FACULTY OF ENGINEERING 9  Water Hardness Water Hardness — Is the amount of dissolved calcium and magnesium in the water — is caused by divalent ions, especially Ca2+ and Mg2+ Concerns ◦ Scaling ◦ Cleaning ◦ Public Health UST FACULTY OF ENGINEERING 10 UST FACULTY OF ENGINEERING 11 Water Hardness Water Hardness Rating mg/L as CaCO3 Degree of Hardness 0-60 Soft water 61-120 Moderately hard water 121-180 Hard water >180 Very hard water From USGS UST FACULTY OF ENGINEERING 12 UST FACULTY OF ENGINEERING 13 pH pH is criteria of acidity and basicity of water. pH = -log [H30+] [H30+] > 10-7 => pH < 7 (acid) [H30+] = 10-7 => pH = 7 (neutral) [H30+] < 10-7 => pH > 7 (base) FACTORS THAT AFFECT pH in WATER. algal blooms, bacterial activity, water turbulence, chemicals flowing into the water body, sewage overflows, pollution. UST FACULTY OF ENGINEERING 14 Algal Bloom UST FACULTY OF ENGINEERING 15 Sewage Overflow UST FACULTY OF ENGINEERING 16 pH of natural waters Sea water due to humic acid Limestone, marble, CO3 rich Pure rain, snow Modified from www.waterwatch.org http://www.vic.waterwatch.org.au/fortheteacher/manual/sect4f.htm UST FACULTY OF ENGINEERING 17 Estuary Modified from www.waterwatch.org http://www.vic.waterwatch.org.au/fortheteacher/manual/sect4f.htm UST FACULTY OF ENGINEERING 18 UST FACULTY OF ENGINEERING 19 Phosphates (PO43-) Natural unpolluted water contains less than 0.1mg/L of all the PO43- (higher concentrations are caused by human pollution). Sources of pollution: ◦ phosphoric manures ◦ laundry detergents ◦ sewage ◦ synthetic fertilizers Blue green algae UST FACULTY OF ENGINEERING 20  Nitrites and Nitrates (NO2 , NO3 ) - - Nitrates (NO3-) are the major polluters of ground water and also of many effluent and influent waters. Sources of pollution: ◦ fertilizers ◦ manures ◦ intensive livestock breeding ◦ poor urban infrastructure (domestic sewage) Can lead to: eutrophication of natural water systems (overproduction of vegetation) UST FACULTY OF ENGINEERING 21 UST FACULTY OF ENGINEERING 22 Ammonium (NH4+) The presence of ammonium in water shows that the water was in contact with rotting organic materials, fecals, food wastes, etc. High ammonium contents in surface water and shallow groundwater are typically attributed to anthropogenic sources such as sewage from industrial emission or leakage of manure and fertilizers from agricultural activities (Du et al., 2017). UST FACULTY OF ENGINEERING 23 Dissolved Oxygen §DO is the measurement of oxygen dissolved in water and available for fish and other aquatic life. §Indicates health of an aquatic system. §Can range from 0-18 ppm. §Most natural water systems require 5-6 ppm to support a diverse population. UST FACULTY OF ENGINEERING 24 Dissolved Oxygen Increase in organic waste Increase in algae/plant vegetation Decrease in DO available to organisms Leads to changes in ecosystem as organisms needing lots of DO are replaced by organisms needing little. UST FACULTY OF ENGINEERING 25 Dissolved Oxygen Potential Causes of Low Dissolved oxygen Natural increased sunlight or other climate factors increased nutrient availability Changes in ocean properties Changes in river input (e.g.: drought) Changes in weather conditions Artificial human loading of nutrients or organic material Changes in river input (eg: diversion) UST FACULTY OF ENGINEERING 26 UST FACULTY OF ENGINEERING 27 Turbidity ØMeasures how “murky” the water is Estimates: ØMineral fraction ØOrganics ØInorganics ØSoluble organic compounds ØPlankton ØMicroscopic organisms UST FACULTY OF ENGINEERING 28 Turbidity Measuring Turbidity §Nephelometric Turbidity Unit (NTU) The WHO (World Health Organization), establishes that the turbidity of drinking water should not be more than 5 NTU, and should ideally be below 1 NTU. https://www.lenntech.com/turbidity.htm#:~ :text=The%20WHO%20(World%20Health %20Organization,ideally%20be%20below %201%20NTU. UST FACULTY OF ENGINEERING 29 UST FACULTY OF ENGINEERING 30 Causes of High Turbidity Effects of Highly Turbid Water In open waters, phytoplankton Modify light penetration Closer to shore, particulates re- Increase sedimentation rate suspended bottom sediments Settling clay particles can (wind) suffocate newly-hatched larvae Organic detritus from stream Fine particulate material also and/or wastewater discharges. can damage sensitive gill Dredging operations structures Floods Decrease organism resistance to disease Too many bottom-feeding fish (such as carp) Prevent proper egg and larval development Reduced photosynthesis can lead to lower daytime release of oxygen UST FACULTY OF ENGINEERING 31 3.1.3 Water Pollution Water pollution occurs when harmful substances are released into the water in large quantities which cause damage to people, wildlife, or habitat or indirectly into water bodies without proper treatment to remove harmful compounds. UST FACULTY OF ENGINEERING 32  Source: https://www.linkedin.com/pulse/what-difference-between- pollutant-contaminant-mohammad-hadi-bazrkar UST FACULTY OF ENGINEERING 33 Contaminants in Water Inorganic water pollutants include: 1. Acidity caused by industrial discharges (especially sulfur dioxide from power plants) 2. Ammonia from food processing waste 3. Chemical waste as industrial by-products 4. Fertilizers containing nutrients - nitrates and phosphates - which are found in storm water run off from agriculture, as well as commercial and residential use 5. Heavy metals from motor vehicles (via urban storm water runoff) and acid mine drainage 6. Silt (sediment) in runoff from construction sites, logging, slash and burn practices or land clearing sites. UST FACULTY OF ENGINEERING 34 Consequences of Water Pollution Eutrophication is characterized by excessive plant and algal growth due to the increased availability of one or more limiting growth factors needed for photosynthesis such as sunlight, carbon dioxide, and nutrient fertilizers. The consequence is the creation of dense blooms of noxious, foul-smelling phytoplankton that reduce water clarity and harm water quality. Water without oxygen is called anoxic UST FACULTY OF ENGINEERING 35 Consequences of Water Pollution Eutrophication in a body of water… UST FACULTY OF ENGINEERING 36 Consequences of Water Pollution Eutrophication in a body of water… UST FACULTY OF ENGINEERING 37 Consequences of Water Pollution Bioaccumulation and Biomagnification Bioaccumulation is the intake of a chemical and its concentration in the organism by all possible means, including contact, respiration and ingestion. Biomagnification occurs when the chemical is passed up the food chain to higher trophic levels, such that in predators it exceeds the concentration to be expected where equilibrium prevails between an organism and its environment UST FACULTY OF ENGINEERING 38 Consequences of Water Pollution Bioaccumulation and Biomagnification UST FACULTY OF ENGINEERING 39 Consequences of Water Pollution “Minamata is a small Japanese fishing town living in the shadow of the chemical factory of the Chisso Corporation. When the factory began dumping large amounts of mercury in the bay in 1956 thousands of people began to develop symptoms of mercury poisoning. Almost all the towns cats went insane... Birds fell out of the sky. Panic gripped the city. In time, thousands of people would die from the poisoning.” UST FACULTY OF ENGINEERING 40 UST FACULTY OF ENGINEERING 41 Minamata, Japan UST FACULTY OF ENGINEERING 42  Minamata, Japan The financial compensation was too little too late for the thousands of victims In a tremendous “loss of face”, corporate official were forced to apologize in public UST FACULTY OF ENGINEERING 43 Additional readings: Water Properties https://www.usgs.gov/special-topics/water-science-school/science/water- properties Water Quality Monitoring Manual Volume 1 https://water.emb.gov.ph/wp-content/uploads/2017/09/Water-Quality- Monitoring-Manual-Vol.-1-ambient_14aug08.pdf What is Water Pollution? https://education.nationalgeographic.org/resource/what-water-pollution/ UST FACULTY OF ENGINEERING 44  MODULE 3 ENG 201 CHEMISTRY of the ENVIRONMENT 3.1 Water Chemistry FACULTY OF ENGINEERING U N I V E R S I T Y O F S A N TO TO M A S MANILA, PHILIPPINES