Module 2 Flashcards
Define: Dipole
A molecule with two poles, one positive and one negative
Hydrogen bonding
strong type of intermolecular dipole-dipole attraction. Occurs between hydrogen and F, O or N (molecules with lone pair electrons)
Describe the molecular structure and size of water
Bond angles of 105 degrees with an electronegative side on the oxygen and an electropositive side on the hydrogens
Key properties of water
Dipolar- facilitating interactions with other dipoles or charges molecules (ions);
Hydrogen bonding- leading to high density (1 g /mL, highest density at 4 degrees), cohesiveness, high boiling point and surface tension (water clusters together);
transparent to visible and UV light- allows light for photosynthesis to penetrate water bodies to considerable depth;
very polar- allowing for the ability to hydrate ions, a good solvent for ions, most important / abundant solvent on earth;
High heat capacity- cp = 4.1855 Jg^-1K^-1, temperature stabilization of organisms / geographical regions, water used for AC chillers, nuclear power plants, etc;
High surface tension- ~73 mN/m (organic solvents 18-33 mN/m)
Define: Water (aqueous) chemistry
the study of chemical reactions and processes affecting the distribution and circulation of chemical species in natural waters
What can water dissolve?
Inorganic molecules- Salts that dissociate to anions and cations (ie. CO3(2-), Ca(2+), Cl(-), Mg(2+)
Organic molecules- Natural organic matter (ie. decaying leaves), pollutants (ie. pesticides, PAHs, estrogen disruptors)
Dissolved gases- Oxygen and Carbon dioxide
Biological Microorganisms- Bacteria and viruses
How is water distributed on earth?
Polar Ice Caps: 1.7%
Oceans: 97.5%
Fresh Water: 0.77%
Describe the water cycle
Global pools include oceans, ice, groundwater, lakes and rivers and clouds. The water circulates between pools through condensation, precipitation and evaporation. Water is also impacted by the anthrosphere through municipal and industrial use.
What molecule has a significant effect on water pH?
Increase in sulfate causes a significant decrease in pH
What size of molecules are considered to be POC domain? DOC domain?
POC = greater than 1 microm (contains bacteria, protozoa, phytoplankton, zooplankton)
DOC = less than 1 microm (contains viruses, humic acids, etc.)
When did water usage stabalize in the US?
1985
What is the primary use of water in terms of anthropogenic use?
Electric power generation
Define Point sources of pollution
Sources which emanate from a single point (wastewater treatement plant, industry)
Define: nonpoint sources of pollution
land areas such as fields roads and parking lots that generate surface runoff containing various types of contaminants
Describe the physical characteristics of water
- Temperate - pH, density, dissolved gases
- Turbidity - measure of water clarity. Affected by suspended solids and coloured material
- Colour - due to dissolved substances
- Taste and odor - organic (bacterial degredation, of algae and algal waste products) and inorganic compounds in water (ferrous, manganous and sulfide ions and chlorine)
- Solids content - Total solides refer to material left in a dish after a water sample is evaporated and dried
Describe the different types of solids in water
- Dissolved solids - refer to material that pass through a standard glass-fibre filter
- Suspended solids - refer to material retained by a standard glass-fibre filter
- Volatile solids - refer to material lost when dried solids are burnt organic material -> CO2
- Fixed solids - Refer to material retained when dried solids are burnt
How do you calculate total solids?
mg/L total solids = (mg of dried residue)/ (L of sample)
Describe the chemical characteristics of water
- Salinity (dissolved solids) - measure of salts in water usually expressed in ppm (mg/L). A result of the polarity of H2O, increasing the ability to hydrate ions, and a good solvent of ions. Many rocks weather and disolve, changing the salinity of the water
- Hardness - Hardness index = ([Ca(2+)]+[Mg(2+)]) * MW (CaCO3)
- Dissolved gases (oxygen and CO2) - critical for living species in water (esp. O2 and CO2). The amount that a gas dissolved in water is calculated by Henry’s Law. Stratification has a significant effect on the system
- Biochemical Oxygen Demand (BOD) - the amount of oxygen required by microorganism to oxidize dissolved organic matter in water samples. Calculated by letting water sit for an extended amount of time, where a big change in DO indicates a large BOD
- Chemical Oxygen Demand (COD) - The amount of ocygen consumed as a result of oxidation (by dichromate, a powerful oxidizing agent) of dissolved organic matter (and other oxidizable components) in the water
- Total organic carbon (TOC) - calculated from non-filtered samples, while dissolved organic carbon calculates from filtered samples. Measured through a TOC analyzer. An Important parameter for both drinking water and wastewater treatment. Also includes dissolved oxygen carbon which is removed through filtered samples
- Alkalinity
- pH
Describe the implications of lake stratification in chemistry
Epilimnion has a realatively high dissolved O3, chemical specieas in oxidized forms as photosynthesis > than respiration
Hypolimnion has relatively low dissolved O2, chemical species in reduced form, there is exchange of chemical species with sediments
What factors affect dissolved oxygen (DO)
- Temperature - solubility of gases in water decreases with increasing temperature
- dissolved O2 is consumed by the degredation of organic matter in water
- Overturn causes the chemicals in lakes to mix, changing the
- Photosynthesis and respiration in aquatic organism
What are the conditions of aerobic water?
describe the molecules present and the electron activity
CO2, SO4-, H2CO3, HCO3-, NO3-, Fe(OH)3 are present with a high pE value; oxidizing environment
What are the conditions of anaerobic water?
CH4, H2S, NH3, NH4+, Fe(2+) are present; low pE values and a reducing environment
Define pE
The degree to which a water is oxidizing or reducing depending on the solute species present, reflecting the activity of the electron, e-
describes the availability of electrons in solution
is analogous to teh concept of pH
Describe carbon chemical transformations in the hydrosphere
Photosynthesis: CO2 + H2O + hv -> {CH2O} +O2 (g)
Biochemical oxidation of biomass, {CH2O}:
{CH2O} + O2 -> CO2 + H2O
Describe the Nitrogen chemical transformations in the hydrosphere
Nitrogen fixation: 3{CH2O} + 2 N2 + 3 H2O + 4H+ -> 3 CO2 + 4 NH4+
Nitrification: 2 O2 + NH4+ -> NO3- + 2 H+ + H2O
Denitrification: 4 NO3- + 5{CH2O} + 4 H+ -> 2 N2 + 5 CO2 + 7 H2O
Describe the Sulfate chemical transformation in the hydrosphere
Sulfate reduction: SO4(2-) + 2 {CH2O} + 2 H+ -> H2S + 2 CO2 + 2 H2O
Sulfate Oxidation: H2S +2 O2 -> 2 H+ + SO4(2-)
What are the biological characteristic of water?
- Biological Microorgamisms- Pathogenic (including bacteria, protozoa, viruses, helminths); Non-pathogenic (including algae and fungi, non-pathogenic bacteria)
What are the potential consequences of pathogenic microorganisms in water?
Infectious disease: Fecal-oral route, disease passed from feces of a hot to the mouth of another; usually indirect route via contaminated water and food; can be from viruses, bacteria and / or protozoa. We need a different amount of each virus / bacteria / protozoa for it to be infectious
Describe pathogen testing and why it can be challenging
Challenges:
1. Present in low numbers,
2. limited survival time
3. numerous pathogens to analyze
4. time and cost prohibitive
Pathogens are normally monitered based on indicator organisms, which help us better understand if there are pathogens in the water
Describe the Ideal characteristics of an indicator organism
- present when pathogens are in the water
- absent in non-contaminated water
- present in higher numbers than pathogens in contaminated water
- easy to analyze
ie. coliform bacteria as an indicator of E. Coli
How does pH work in water?
Water auto-ionizes with dissociation constant @ 25 degrees: 2 H2O <-> H3O+ + OH-
Kw = 1.008 x 10^(-14) = [H3O+] x [OH-]
[H3O+] = [OH-] = 1.0 x 10^(-7) mol x L ^(-1)
pH = -log [H3O+]
pH = 7.0
Kw changes with temperature (all equillbrium constants are affected by temperature)
The neutral pH changes for different temperatures
Neutral pH at 15 degrees C is 7.18 not 7.0
What are the major components of the carbon cycle?
Photosynthesis - Atmospheric CO2 is tranferred to biosphere (plants) by photosynthesis and covnert it to biomass
Biodegradation - Plants and living organisms die and becom humic carbon in dirt and soil
Respiration - Animals also produce CO2 to the atmosphere by respiration
Atmospheric CO2 - absorbed to surface water and oceans to form bicarbonate and carbonate
Minerals and Rocks - carbonates in water in the presence of Ca2+ can precipitate to for CaCO3 (limestone) and other rocks. Limeston can also dissolve to form carbonates in water
Fossil Fuels - Human economic activities (burning of carbon-containing fuels) also contribute ot the release of CO2 to the atmosphere
What chemical equation describes photosynthesis
CO2 + H2O + hv -> {CH2O} + O2
What chemical equation describes biodegradation?
5 {CH2O} + 4 H3O+ + 4 NO3- -> 2 N2 + 5 CO2 + 11 H2O
2 {CH2O} + H3O+ + SO4(2-) -> HS- + 2 CO2 + 3 H2O
2 {CH2O} -> CH4 + CO2
What chemical equation describes respiration
{CH2O} +O2(g) -> CO2 + H2O
What chemical equations describe atmospheric carbon absorption?
H2CO3 <-> HCO3- + H+; K2 = 4.3x10^(-7)
HCO3- <-> CO3(2-) + H+; K3 = 4.7x10^(-11)
What chemical equation describes the interactions of minerals and rocks with water?
CaCO3 +CO2 + H2O -> CO2 + H2O
Describe the interactions of carbonate species in water, air and rock, soil and sediments
CO2(g) <-> H2CO3; as per Henry’s Law btwn air and water
CaCO3(s) <-> Ca 2+ + CO3 (2-); as per Ksp btwn rocks and water
CO3(2-) + H2O <-> OH- + HCO3-; acid base reaction in aq
H2CO3 <-> H+ + HCO3-; acid base reaction in aq
The carbonate species in water are CO3(2-), HCO3- and H2CO3
What is the rate of dissolution of carbon dioxide?
CO2(g) <-> CO2(aq) H = 3.4x10^(-2) Atm^(-1)
H2CO3 <-> HCO3- + H+ Ka1 = 4.3 x 10^(-7) M
HCO3- <-> CO3(2-) + H+ Ka2 = 4,7 x 10^(-11) M
How does carbonate species present reflect the pH
< pKa 1 (pH = 6.3); [H2CO3] > [HCO3-]
pka = 1 (pH = 6.3); [H2CO3] = [HCO3-]
between pKa 1 - 2 (pH 6.3 - 10.6); [H2CO3] < [HCO3-] < [CO3(2-)]
pKa = 2 (pH =10.6); HCO3- = CO3(2-)
> pKa2 (pH > 10.6); [CO3(2-)] > [HCO3-]
Why is the ocean pH <8.7
- Temperature gradients and stratification
- Deposition of acidic compounds (south america, saudi arabia)
- Presemce of other “buffers” (ie. silica, CaSO4)
- non-equilibrium: ocean not wel mixed
Define Alkalinity
a measure of the capacity of water to neutralize a strong acid. In natural waters: HCO3-, CO3(2-), OH; borates, ammonia, phosphates, organic bases, organic matter (in low concentration)
Define Total Alkalinity
the number of H+ equivalents required to ritrate a water sample to pH ~4
The most common indicator for endpoint is methyl orange, which changes colour at pH~4)
What are the units of Alkalinity (as CaCO3)
Alkalinity is expressed as mg/L of CaCO3
What are the environmental issues with water and soils with no carbonate?
Watersheds with no limestone have a much lower pH bc there is no CaCO3(s) to react with as a buffer when acidic properties are added to the lake
What is the ideal alkalinity in treated water?
A good stability in the distribution system is ~100-120 mg/L as CaCO3
Too little -> wide changes in pH, which is not good for the distribution system; corrosive environment (acidic conditions); depletion of oxidants (protect against pahtogens)
Too much -> may contribute to scaling
Why should you not drink directly from the Bow River / Lake Louise?
- Pathogens- viruses, bacteria, protozoa
- Debris & Runoff- minterals, ions, sand
- Organic matter- decaying leaves
How has water sanitation impacted death rate for infectious disease?
More chlorine / sanitation = fewer deaths
What is regulated when it comes to drinking water sanitation?
- Physical characteristics: Total solids, colour, turbidity, tast & odor
- Chemical characeteristics: pH, alkalinity, hardness (minerals), total dissolved solids, total organic carbon, biological oxygen demant, chemical oxygen demant
- Biological characteristics: pathogens
What are the different levels of water purification?
- Drinking water: removal of pathogens, turbidity, colour, taste and odor, organic mattter and other contaminants (safe for human consumption)
- Wastewater: removal of BOD and COD, pathogens, nutrients, organic matter, contaminants (Safe to return to rivers & lakes (does not affect wildlife and minimizes ecological impacts))
What are the sources of raw water?
- Freshwater (conventional treatment) - surface waters (rivers, lakes); groundwater (wells)
- Alternative sources of water (advanced treatment) - Ocean water; saline groundwaters (ie. Texas); wastewater
In what order does the conventional drinking water treatment take place in?
- Screens
- Flocculation / Coagulation
- Sedimentation
- Filtration
- Disinfection
- Distribution
Describe screens in water treatment
Keep out fish, mussels and large particles from coming into the facility
Describe floculation in water treatment (including mechanism)
- Floculation: coagulants (+) are added which bind and neutralize particles and organize matter (-) to create “flocs”
- Coagulants may be polymers and aluminum or iron based chemicals (aluminum sulfate and ferric chloride)
- Particles are negativel charges and attract positive ions around it (Stern layer) which will then surround itself by negatively charged ions (double layer)
- coagulants are added to increase th ions dissolved in solution (ionic strength) which will compress the electrical double layer
- this compression will reduce the repulsion forces
- Particles will attract each other (van der Waals) and form small flocs
Describe Sedimentation in water treatment
Large flocs are allowed to settle at the bottom of tanks. clear water is collected at the top of the tank
Describe Filtration in water treatment
- small particles and pathogens are filtered out
- filter media can be sand anthracite, or activated carbon
- filters need to be cleaned every ~60 hr of operation
Describe Disinfection in water treatment
- chemical disinfectants and UV light are applied to water to inactivate pathogens (bacteria, viruses, protozoa)
- Common chemical disinfectants include: Chlorine (HOCl); combined chlorine (ammonia + chlorine = NH2Cl & NHCl2); Chlorine dioxide (ClO2); Ozone (O3)
- After chemical disinfectants are added, water is sent to a storage tank to allow disinfectants to react and inactivate pathogens (disinfectant + pathogens -> (at rate k) inactivated pathogen)
- Inactivation goal = 99.9% protozoa, 99.99% viruses
- pathogen inactivation is dependent on disinfectant concentration and contact time with the pathogen
Describe Distribution in water treatment
- Water may travel through the distribution system up to 5 days
- North America: typical disinfectands are chlorine or combined chlorine ~ 1-4 mg/L as Cl2 known as chlorine residual
- Chlorine residual & sustained water pressure protects treated water against recontamination in the distribution system
What is activated carbon?
- Activated carbon absorbs organic compounds and are typically used to remove organic matter and trace contaminants (pesticides, taste and odor compounds)
- can be used as filter media (instead of anthracits) or as a finishing step after filtration
What are the strengths of different disinfectants?
- Ozone: 2.87 V (O3 +2H+ +2e- –> O2 +H2O)
- Chlorine Dioxide: 1.71 V (CLO2 + 2 H2O + 5e- –> Cl- + 4 OH-)
- Hypochlorous acid: 1.49 V (HOCl + H+ + 2e- —> 2 Cl-)
- Monochloramine (combined chlorine): 0.75 V (NH2Cl + 2 H2O + 4e- –> 2 Cl- + NH3 + 2 OH-)
Describe the process of Chlorine in disinfection
- HOCl is an acid (pKa = 7.5)
- HOCl is stronger oxidant than OCl-, however ineffective agains cryptosporidium parvum (protozoa)
- Chlorine is not stable at high concentrations so it has to be produced on site by Cl2 + H2O <-> HOCl + H+ + Cl-
Descibe the process of combined chlorine in disinfection
- series of reactions between chlorine and ammonia:
NH3 +HOCl <-> NH2Cl + H2O
NH2Cl + HOCl <-> NHCl2 + H2O
NHCl2 + HOCl <-> NCl3 + H2O
- Mostly used as residual disinfectant for the distribution system
Descibe the process of UV Light in disinfection
- UV Light can disinfect water
- 200-400 nm
- Light disrupts DNA in microorganisms and prevent from replicating
- Lamps centered on UV-C (254 nm) needs about 10 s
- Other compounds can also absorb light
- Effective against crytosporidium parvum (protozoa)
What are disinfection by products?
- They are by products as a result of disinfection
- They are always in your drinking water (usually at mu g/L levels)
What are the Canadian guidelines for disinfection byproducts (DBPs)?
- Chlorine DBPs: Trihalomethanes (100 mu g/L), Haloacetic acids (80 mu g/L)
- Ozone DBP: Bromate (BrO3-, 10 mu g/L)
- Chlorine Dioxide DBP: Chlorite (ClO2-, 1 mg/L)
- Combined chlorine DBP: Nitrosodimethylamine (40ng/L)
Describe DBP health risks
- an epidemiologic study relating the consumption of chlorinated surface water and cancer suggest: increased risk in the incidence of bladder cancer and DBP exposure
- Another study found associations between DBPs and adverse reproductive outcomes including: low birth weight and preterm delivery
What are the trade offs with disinfection treatment
- Acute risks: pathogens that cause waterborne diseases
- Chronic risks: long term exposure to low level concentrations of DBPs
What are the reasons to use ocean / saline waters, and what are the cons?
- Limited access to freshwater
- Close to the ocean or groundwater with high salt content
- desalination is energy-intensive, therefore, expensive
- common in singapore, saugi arabia, USA (San Diego), Spain (Barcelona), Kuwait, Australia
What is the desalination treatment process
- Screens
- Microfiltration
- Reverse Osmosis
- Disinfection
- Distribution
Describe membrane technology
- water can be purified by passing or forcing it through a membrane with small pores (individuals holes) uniform and microscopic size
- components that are rejected go to the waste stream
- permeable components (which can pass through membrane) go to the product stream (water and other components)
- Membranes need significant amount of pressure (and therefore, energy) to drive the water across the membrane ($$)
Describe the drawbacks of membrane filtration
- membranes can foul, that means it can no longer filter water (they need to be cleaned with disinfectants)
- membranes can also react with disinfectants and may degrade
- reverse osmosis is energy-intensive and very expensive
- about 1/3 of water is wasted, brine disposal (some times back to the ocean, but we don’t know what type of consequences that could have)
- Neutral small compounds can pass through the membrane (disinfection byproducts)
What are the different pore sizes in membrane filtration?
- microfiltration 0.1 microm (remove particles, sediment, algae, protozoa, bacteria)
- ultrafiltration 0.01 microm (removes small colloids, viruses)
- nanofiltration 0.001 microm (dissolved organic matter, divalent ions Ca2+, Mg2+)
- Reverse osmosis, nonporous (monovalent species (Na+, Cl-)
What is important to know about wastewater effluent treatment?
- various degrees of reuse: agriculture, potable water, industrial
- public acceptance is a baig issue: education is a big component
- Wastewater reuse is also an option to desalination: singapore, orange county (disneyland)
- wastewater reuse praciced in places that are in-land (no access to ocean): Mexico City is used for agriculture outside the city
How can we use alternative water sources to accomodate water shortages?
- using alternatives help augment water resources through desalination and wastewater reuse
Describe defacto wastewater reuse
- source waters (rivers and lakes) have a percent volune that is composed from treated wastewater effluents
- defacto wastewater reuse is the unintentional use of treated wastewater found in rivers and lakes for drinking water
- A study in the USA: 17 of 25 cities analyzed, defacto reuse increased by 68% (1980-2008) - 4 larges cities have a de facto reuse of 8% or higher
What is the wastewater reuse treatment process
- wastewater treatment
- microfiltration
- reverse osmosis
- advanced oxidation
Describe advanced oxidation processes (AOPs)
- Combination of two processes: UV light and an oxidant (ie. H2O2, O3); many configurations are also used
- AOPs generate OH radicals that can react with organic contaminants to break them down to CO2 (not often the case)
- OH radicals are highly reactive and are non-selective (can react with everything)
- AOPs are used when pharmacueticals and personal care products are a concern
Describe the wastewater treatment process steps
- Influent enters system
- Pre-treatment
- Primary settling (produces primary sludge)
- Biological treatment (produces return sludge)
- Secondary settling (produces return sludge, effluent)
Return sludge (aka excess sludge) goes through thickener, then enters a anaerobic digester which becomes stabalised slidge and biogas. Stabalized sludge goes into storage where it then goes through a dewatering process and is disposed of. The biogas enters a gas tank which goes through a generator, producing electricity
Describe the pre-treatment purpose and objectives in wastewater treatment
purposes:
- protect wastewater treatment plant
- low effect on BOD
Objectives:
- removes debris, grit and oily scum
- minimizes shock loadings
- condition the wastewater for subsequent treatment processes
Describe Primary treatment in wastewater treatment process
- physically seperates solids from wastewater
- remove settleable solids that settle
- does not remove soluble solides
- about 30% of BOD is removed
Describe the secondary / biological treatment in wastewater treatment process
Purpose:
- reduce BOD, COD
- additional removal of total suspended solids
Objectives:
- secondary treatment may remove N, P, heavy metels, but often requires tertiary treatment (nitrification/denitrification)
- pathogens are reduced
- biological degredation of soluble organic matter (by oxidation)
- about 30% sludge is returned from the secondary clarifier to the biological reactor
Describe the chemical equation in seconday / biological treatment of wastewater
organics ——> (aerobic, microorgamism) CO2 + H2O + Energy
in activated sludge aeration tank
Describe the aeration tank mechanism
- air is injected into the tank to accelerate biological degredation of organic matter
- High treatment efficiency
- High operational cost
Describe tertiary treatmetn in wastewater treatment
- processes after secondary treatment to remove contaminants/nutrients to lower concentration levels (Nitrogen and phosphorus)
- Wastewater potable reuse
Describe disinfection processes used in wastewater treatment
- UV light (widely used in Canada)
- Ozone
- Chlorination (cannot discharge chlorinated waters to rivers and lakes bc fish die; dechlorination is applied with thiosulfate or sulfite-based reducers)
What is sludge? Where does it come from?
Sludge: residue collected from wastewater treatment in hte form of liquid or semisolid
comes from primary clarifier, secondary clarifier
How is sludge treated?
- volume reduction
- safe disposal
- resource and reuse
How does sludge digestion work?
Aerobic digestion (with oxygen): Oxidation of sludge, high energy requirements for aeration
Anaerobic digestion (without oxygen): decomposition of sludge in the absence of oxygen. It reduces mass of sludge and destroys pathogens. Offers attractive energy saving and energy source. Used by most large treatment plants
How does anaerobic digestion work for sludge disposal?
- Hydrolysis: complex organic matter (carbohydrates, proteins, fats) becomes soluble organic molecules (sugars, amino acids, fatty acids)
- fermentation: soluble organic molecules becomes volatile fatty acids, acetic acid and H2, CO2
- Acetogenesis: formation of soluble organic compounds and short-chain organic acids (where volatile fatty acids become acedic acid and H2, CO2)
- Methanogenesis: The bacterial conversion of organic acids into methan and CO2
How is sludge disposed of?
- Land application (as a fertilizer)
- Landfilling
- Incineration (most common use in big urban centres)
What does the nitrogen cycle involve?
Atmosphere, geosphere, hydrosphere, biosphere, anthrosphere
Describe the importance of Nitrogen
essential nutrient for all living organisms; a very important element as it is a part of both proteins (present in the composition of the amino acids) as well as nucleic acids, such as DNA and RNA (present in nitrogenous bases)
What types of nitrogen exist in the different parts of the world system?
Atmosphere:
Gas: N2, N2O, NO, NO2, HNO3
aerosol: NH4NO3, NH4NO3
Hydrosphere: NO3-, NO2-, NH4+
Geosphere: NO3-, NH4+
Anthrosphere: NH3, HNO3, NO, NO2, inorganic nitrates, organonitrogen
Define Aerosol
suspension of fine solid paricles or liquid droplets
Describe nitrogen fixation
Stable nitrogen gas is converted into “fixed” forms of nitrogen (ammonia and NO3-)
Natural fixation of N2:
- microorganisms capable to convert N2 to NH3, and NH4+ (marine organisms known as blue-green algae, bacteria that live on plant’s roots)
- In the atmosphere radiation or lightnigh discharges on N2 may form NOx
Human fixation of N2:
- Industrial nitrogen fixation: production of NH3 fertiliser N2 +3 H2 -> 2 NH3
- Combustion can lead to fixation of N2 anf N2O and NOx
- Legume cultivation (microogranisms to fix N2), increases nitrogen in soil and good for crop cultivation (ie. crop rotation between corn/soybeans)
Describe Ammonification
Organic matter decomposition into inorganic nitrogen
2 CH3NHCOOH + 3 O2 + 2 H2O –> 2 NH4+ + 4 CO2 + 4 H2O
Describe Nitrification
Ammonium ion is oxidized to NO2- and NO3- by microbial action in two steps:
- 2 NH4+ + 3 O2 –> 2 NO2- + 4 H+ + 2 H2O
- 2 NO2- + O2 –> 2 NO3-
Overall: 2 O2 + NH4+ –> NO3- + 2 H+ + H2O
Describe Denitrification
Nitrate ion (NO3-) is tranformed to N2 under anoxid conditions (ansence of oxygen by microbial action:
4 NO3- + 5{CH2O} + 4 H+ –> 2 N2 + 5 CO2 + 7 H2O
in the presence of small amounts of oxygen:
2 NO3- + 2{CH2O} + 2 H+ –> 2 N2O + 2 CO2 + 5 H2O
How is nitrification and denitrification used ot treate wastewater
Used to transform ammonia from wastewater to N2
What impacts have humans had on the nitrogen cycle?
Land and water:
- increase rate of nitrogen input (N2) into the terrestrial nitrogen (NH3) cycle
- increased transfer of nitrogen (eg. fertilizers) into the rivers and coastals oceans
atmospheric:
- increased concentration of the potent greenhouse gas N2O globally
- increased concentrations of other oxides of nitrogen (NOx) that drive the formation of photochemical smog over large regions of earth
What are the effects of Eutrophication?
Gulf of Mexico:
- Excess fertilizer has clogged water with algae -> fish and other marine life suffocate
Fresh water:
- NO3- boots the growth of one or two plant species which dominate the lake (more nitrate -> fewer species)
Erie lake and Ohio River:
- 2014 algae bloom
- shut down drinking water plank in Toledo, OH and left many without water
Nitrogen research is a “developing area of science” and global nitrogen pollution “is the third major threat to our planet after biodiversity loss and climate change” ~2005 (John Lawton was a previous CEO of Natural Environment Research Council)
What does the Phosphorus cycle include?
Geosphere, hydrosphere, biosphere, anthrosphere (minimum participation in the atmopshere)
What is the importance of phosphorus?
Essential nutrient for all living organisms; a very important element as it si a part of DNA, ATP, and ADP (energy transfer between organisms)
What is the source of excess phosphorus in water and what are the consequences of it?
Municipal wastewater is a source of phosphates primarily from detergens and soaps (ie. sodium tripolyphosphate, can complex with calcium, or react with water to release phosphate ions)
Excess phosphorus in water can stimulate grown including plant and algae; promotes algae blooms that can also lead to eutrophication
- 1970s - Lake Erie’s eutrophication problem was primarily from excess phosphate in water
- 1972 - US and Canada signed the great lakes water quality agreement. 8 billion dollars were spent on wastewater facilities were built ot remove phosphorus. Ontario restricted level of phosphates in laundry detergents
Describe the process by which phosphorus is removed from watewater
Influent goes through anaerobic reactor, then aerobic reactor, to a clarifier, where the phsororous is removed from the sludge. Activated sludge is returned to the influent where it goes through the same process
In anaerobic conditions, the influent is processed through organic carbon and PO4(3-) is released
Under aerobic conditions, PO4(3-) enters the system
What is the relationship between phosphorus type and pH
low pH = H2PO4-
higher pH = HPO4 (2-)
