CEE 370 Environmental Engineering Principles

Transcription

1 Updated: 4 November 2015 Print version CEE 370 Environmental Engineering Principles Lecture #25 Water Quality Management III: Laes & toxic models Reading: Mihelcic & Zimmerman, Chapter 7 Reading: Davis & Cornwall, Chapt 5-4 Reading: Davis & Masten, Chapter 5-6 & 9-4 David Rechow CEE 370 L#25 1 Lae Pollution Percent impaired by pollutant Percent impaired by sources From Masters, section 5.4 David Rechow CEE 370 L#25 2 Lecture #25 Dave Rechow 1

2 Lae life cycle Succession in laes Oligotrophic Mesotrophic Eutrophic Other Dystrophic Hypereutrophic David Rechow CEE 370 L#25 3 Lae Eutrophication As laes age, they become more productive Natural processes: natural Eutrophication Pollutant loading: cultural Eutrophication Limiting nutrient Liebig s law of minimum Redfield Ratio C:N:P in most phytoplanton is 106:16:1 When P<16*N, it limit s growth David Rechow CEE 370 L#25 4 Lecture #25 Dave Rechow 2

3 Nutrient loading and Eutrophication David Rechow CEE 370 L#25 5 Estrogen lae study David Rechow CEE 370 L#25 6 Lecture #25 Dave Rechow 3

4 Concern over drining water Drugs? CEE 370 L#25 David Rechow 7 Organic Compounds: Types? Natural Compounds Fulvics Proteins, carbohydrates, etc Domestic WW Organics Industrial Synthetic Organics Plasticizers: phthalates solvents: tetrachloroethylene waxes: chlorinated parafins others: PCB s Hydrocarbons & oil derivatives includes products of combustion: PAH s Agricultural Chemicals pesticides: DDT, epone, mirex Pharmaceuticals, etc Anti-epileptics Beta-blocers X-ray contrast media antibiotics Home & Personal Care Products triclosan Muss, flame retardants Endocrine Disrupters Steroidal estrogens Natural process byproducts Conjugated pharmaceuticals Engineered process byproducts disinfection byproducts, etc David Rechow CEE 370 L#25 8 Lecture #25 Dave Rechow 4

5 Pollutant loss in laes Photolysis Destruction by solar light energy Biodegradation Metabolism by microorganism Hydrolysis Chemical decomposition Volatilization Loss to the atmosphere Adsorption and settling Loss to particles that end up buried in sediments David Rechow CEE 370 L#25 9 Photolysis Chemical breadown initiated by light energy two types direct photolysis sensitized (or indirect) photolysis Several steps some solar light reaches water surface some of this light penetrates to the solute some of this is absorbed by the solute some of absorbed light is capable of causing a reaction David Rechow CEE 370 L#25 10 Lecture #25 Dave Rechow 5

6 Solar Radiation David Rechow CEE 370 L#25 11 Susceptible bonds? David Rechow CEE 370 L#25 12 Lecture #25 Dave Rechow 6

7 Biotransformation Microbially mediated transformation of organic and inorganic contaminants Biochemical processes: Metabolism: toxicant is used for synthesis or energy Cometabolism: not used, but transformed anyway Chemical Effects: Detoxication: Toxic to Non-toxic mineralization Activation: Non-toxic to Toxic David Rechow CEE 370 L#25 13 Bio inetics Michaelis-Menten equation: µ max = maximum growth rate (yr -1 ) X=microbial biomass (#cells/m 3 ) Y= yield coefficient (cells produced per mass toxicant removed, #cells/µg) s = half-saturation constant (µg/m 3 ) b = rate of biotransformation (yr -1 ) If c<< s, then: Refer to lecture #17 X max Y m m m2 s Y X max s X c David Rechow CEE 370 L#25 14 Lecture #25 Dave Rechow 7

8 Bio inetics (cont.) Wide environmental range phenol: m =4.0 d -1 diazinon: m =0.016 d -1 Temperature correction = C 2 H 5 S O P O O C 2 H 5 OH CH 3 N CH CH 3 N CH 3 T 20 m T m 20 David Rechow CEE 370 L#25 15 Hydrolysis Reaction with water and its constituents H 2 O OH - H + Autodissociation Combining: or: h h h h n OH b a h H K w b ph n a10 10 K w OH H OH H b n ph a David Rechow CEE 370 L#25 16 Lecture #25 Dave Rechow 8

9 Volatilization: The two film theory p g p i c i Interface c David Rechow CEE 370 L#25 17 Two film model Flux from the bul liquid to the interface J K ( c c) l l Flux from the interface ot the bul gas Mass transfer velocities (m/d) J g a And the K s are related to the molecular diffusion coefficients by: K i Kg ( RT p p g i) D l g l Kg z z l g David Rechow CEE 370 L#25 18 D Lecture #25 Dave Rechow 9

10 Whitman s 2 film model (cont.) According to Henry s law: p H c And relating this bac to the bul concentration p H Jl Kl c i e i now solving and equating the fluxes, we get: 1 1 RTa v K HK The net transfer velocity across the airwater interface (m/d) David Rechow CEE 370 L#25 19 i v e l e g Whitman s 2 film model (cont.) Which can be rewritten as: Now, applying it to toxicants p g 0 And converting to the appropriate units: v v K Contaminant specific l H e K H l e RTa K v g Environment specific vv H David Rechow CEE 370 L#25 20 Lecture #25 Dave Rechow 10

11 Volatilization: Parameter estimation Liquid film mass transfer coefficient (d -1 ) K l K l, O 32 2 M Gas film mass transfer coefficient (d -1 ) K g U W M Wind velocity (mps) Compound molecular weight David Rechow CEE 370 L#25 21 Toxics Model: CSTR with sediments Internal Transport Processes (between compartments) dissolved: diffusion particulate: settling, resuspension & burial Expressed as velocities (e.g., m/yr) Diffusion (v d ) Water (1) Settling (v s ) Resuspension (v r) Mixed Sediments (2) Deep Sediments (3) Burial (v b ) David Rechow CEE 370 L#25 22 Lecture #25 Dave Rechow 11

12 Sorption Linear Isotherm c ' d c p M s ad de C K C particulate dissolved Particle s v s K 1 K David Rechow CEE 370 L#25 23 v s Octanol:water partitioning 2 liquid phases in a separatory funnel that don t mix octanol water Add contaminant to flas Shae and allow contaminant to reach equilibrium between the two Measure concentration in each (K ow is the ratio) Correlate to environmental K K fn( K ) ow From Lecture #16 David Rechow CEE 370 L#25 24 Lecture #25 Dave Rechow 12

13 Bioaccumulation From Lecture #16 Mercury in food chain Data from Onondaga Lae Biomass (box size) Concentration (Shading) David Rechow CEE 370 L#25 25 Lab to Field From Lecture #16 Octanol water partition coefficients and bioconcentration factors David Rechow CEE 370 L#25 26 Lecture #25 Dave Rechow 13

14 Completely-mixed lae or CMFR Often useful to assume perfect mixing same concentration throughout system Accumulation loading outflow reaction settling C in Q Loading C reaction V Outflow C Q settling David Rechow CEE 370 L#25 27 Other Terms in the Mass Balance Outflow Reaction Outflow Qc Reaction M Vc Settling Since: Settling va c v H s Vc s V A s H s A s J=vc Sedimentwater interface David Rechow CEE 370 L#25 28 Lecture #25 Dave Rechow 14

15 Combining all terms: V dc dt Wt () QcVcvAc s Units for each term: mass/time Dependent variable: c Independent variable: t Forcing function: W(t), the way in which the external world forces the system Parameters: V, Q,, v, A s David Rechow CEE 370 L#25 29 Steady State Case With Settling mass balance solution V dc dt 0 Wt ( ) QcVcvAc W c or W c QV va s a assimilation factor Where: a Q V va s The assimilation or cleansing factor W s David Rechow CEE 370 L#25 30 Lecture #25 Dave Rechow 15

16 Simple lae model without settling [accumulation] = [loadings] ± [transport] ± [reactions] W(t) Q V dc dt Wt () QcVc n V For a 1st order reaction (n=1): dc dt c Wt V () Where: Q V W Steady State Solution: c Q V David Rechow CEE 370 L#25 31 Lae Model: Steady State Example A lae has the following characteristics: Volume 50, 000 m 3 Mean Depth = 2 m 3 Inflow = Outflow = 7500 m d o Temperature = 25 C The lae receives the input of a pollutant from three sources: a factory discharge of 50 g d -1, a flux from the atmosphere of 0.6 g m -2 d -1, and the inflow stream that has a concentration of 10 mg/l. If the pollutant decays at the rate of 0.25/d at 20 o C a. compute the assimilation factor b. steady state concentration c. show breadown for each term David Rechow CEE 370 L# Lecture #25 Dave Rechow 16

17 Lae Model: Solution First correct the decay rate for temperature Now the assimilation factor (. ) d 23, a Q V (50,000) 3 m d 1 David Rechow CEE 370 L#25 33 Lae Model: Solution (cont.) The surface area of the lae is: V 50, 000 As 25, 000m 2 H 2 The atmospheric and inflow load is then: W JA 0.( 6 25, 000) 15, 000g/ d atmosphere s Winf 7500( 10) 75, 000g/ d low Combining all loads: W W W Winf 50, , , , 000g/ d factory atmosphere low David Rechow CEE 370 L#25 34 Lecture #25 Dave Rechow 17

18 Lae Model: Solution (cont.) And finally, the concentration: W c a 140,000g / d 3 23,454m / d 5.97mg / L David Rechow CEE 370 L#25 35 Dimictic Laes Epilimnion Hypolimnion Thermocline David Rechow CEE 370 L#25 36 Lecture #25 Dave Rechow 18

19 Temperature & Density David Rechow CEE 370 L#25 37 WQ Profiles in Stratified Laes Temperature Dissolved oxygen Epilimnion Manganese Thermocline Hypolimnion Concentration David Rechow CEE 370 L#25 38 Lecture #25 Dave Rechow 19

20 Temp. Profiles in Stratified Laes Winter Fall Spring Summer Epilimnion Thermocline Hypolimnion Temperature David Rechow CEE 370 L#25 39 To next lecture David Rechow CEE 370 L#25 40 Lecture #25 Dave Rechow 20