Term
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Definition
| accumulating substances on a surface |
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Term
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Definition
| What is adsorbing (e.g. TCE, PCB, etc) |
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Term
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Definition
| What is adsorbing the material (GAC, PAC) |
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Term
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Definition
| Granular activated carbon |
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Term
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Definition
>0.1 mm in diameter
surface area: 700-1300 m^2/g GAC
pore radius: 16-30 A |
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Term
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Definition
| Powdered activated carbon |
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Term
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Definition
<0.079mm in diameter
Surface area: 800-1800 m^2/g PAC
pore radius: 20-40A |
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Term
| What other types of adsorbents are there besides GAC and PAC? |
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Definition
| silica-based adsorbents and synthetic polymers |
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Term
| How do you make activated carbon? |
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Definition
| Heat organic material to about 700 degrees C w/o O2. "Activate" charred materials by exposing to steam. |
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Term
| How is activated carbon regenerated? |
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Definition
| By repeating production process |
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Term
| What types of contaminants do GAC and PAC remove? |
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Definition
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Term
| What factors affect design of activated carbon systems? |
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Definition
| WW flowrate, contaminant concentration, temperature, carbon characteristics (surface area, pore size, etc.). |
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Term
| What are three AC isotherms and what are they used for? |
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Definition
linear
freundlich
langmuir
used to quantify level of attraction between GAC/PAC and the contaminant |
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Term
| What is the equation for the langmuir isotherm? |
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Definition
This is a theoretical approximation model.
qe = x/m = abCe/(1+bCe)
x = mass of adsorbate (e.g. TCE)
m = mass adsorbent (e.g. GAC)
qe [=] mg TCE/gGAC |
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Term
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Definition
| concentration of adsorbate (e.g. TCE) in the liquid or gas phase of equilibrium with GAC. ~Cfinal |
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Term
| What is the equation for the Freundlich model? |
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Definition
This is an empirical model.
qe = x/m = KfCe^(1/n) |
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Term
| What is the material balance equation for AC? |
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Definition
| QCint - QCet - m(GAC)qe = 0 |
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Term
| What are inorganic constituents common to water treatment? |
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Definition
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Term
| What are some cations of concern in WT? |
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Definition
| calcium, magnesium, iron. Also Mn, K, Na |
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Term
| What are some anions of concern in WT? |
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Definition
| bicarbonate, chloride. Also fluoride, nitrate, sulfate |
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Term
| What sources contain calcium ions? |
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Definition
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Term
| Why is calcium significant? |
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Definition
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Term
| What are sources of calcium? |
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Definition
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Term
| Why is magnesium significant? |
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Definition
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Term
| In what type of source is iron higher? |
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Definition
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Term
| What happens if high-iron-containing GW that is low in O2 and HCO3- is pumped to the surface? |
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Definition
| Forms Fe(OH)3 (red color) |
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Term
| What are concentrations of bicarbonate (HCO3-) in rain, SW, and GW? |
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Definition
Rain: <10 mg/L
SW: <200 mg/L
GW: Can be >1000 mg/L |
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Term
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Definition
| causes methylglobinemia (blue baby syndrome). Treatment goal: <10 mg NO3-/L |
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Term
| What can you use to remove cations and anions from water? |
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Definition
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Term
| What gases are of concern in WT? |
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Definition
| H2S, VOC (volatile organic contaminants) |
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Term
| How big is a suspended particle? |
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Definition
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Term
| How bit is a colloidal particle? |
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Definition
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Term
| Are most particles + or - charged? |
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Definition
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Term
| How can one best settle particles? |
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Definition
| us cationic flocculent to encourage floc formation then settlement |
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Term
| What are some characteristics of GW? |
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Definition
| GW: more minerals, consistent composition, less turbidity, less color, few microbes, low DO, high hardness, H2S |
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Term
| What are some characteristics of SW? |
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Definition
| low minerals, variable composition (seasonal), high turbidity, can have color, more microbes, high DO, low hardness, taste and odor |
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Term
| What are the formulas for lime and soda? |
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Definition
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Term
| What does lime softening do to the pH? |
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Definition
| raises it. Must then do acidification to lower pH. |
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Term
| What is the generic treatment process for hard water? |
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Definition
| lime softening (softening sludge goes out, effluent goes out), CO2 added for pH, media filter, chlorine/O3, clear well |
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Term
| What is the generic treatment process for turbid water? |
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Definition
| screen, pH control, coagulants, rapid mix, flocculation, clarifier, media filter, chlorine/O3 disinfection, clear well |
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Term
| Are G values of rapid-mix high or low? |
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Definition
| high. 1000-4000 s- is typical. |
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Term
| What two types of mixers can be used for rapid mix? |
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Definition
| tank (impellar) or static (in-line) mixers |
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Term
| What is the HRT for rapid mix? |
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Definition
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Term
| What are typical coagulants? |
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Definition
| As particles are typically negative, use cationic coagulants. Like iron and aluminum salts. Organic polymers. |
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Term
| What are G values for flocculators? |
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Definition
HOrizontal: 20-50
Vertical: 10-80 |
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Term
| What are tip speeds for flocculators? |
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Definition
HOrizontal: 1
Vertical: 2-3 |
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Term
| What are the revolutions per minute of flocculators? |
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Definition
Horizontal: 1-5
Vertical: 10-30 |
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Term
| What are typical dimensions of flocculators? |
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Definition
width: Horizontal: 3-6; Vertical: 6-30
length: Horizontal: 3-6; Vertical: 3-5 |
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Term
| What are typical numbers of compartments for flocculators? |
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Definition
Horizontal: 2-6 (3)
Vertical: 4-6 (4) |
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Term
| What is total flocculator HRT? |
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Definition
| 20-30 min for conventional system. Rule of thumb: 20 min. |
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Term
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Definition
| power number (dimensionless) |
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Term
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Definition
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Term
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Definition
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Term
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Definition
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Term
| What is the power equal to? |
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Definition
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Term
| What is D/Te for vertical impellar? |
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Definition
|
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Term
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Definition
| effective area. [4*Aplan/pi]^0.5 |
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Term
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Definition
| using gravity settling to remove flocs formed in a flocculator |
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Term
| When can you use direct filtration? |
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Definition
| if turbidity and floc concentration is low after flocculation |
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Term
| What is typical @ for flocculators? |
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Definition
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Term
| What are the L:W ratios for rectangular flocculators? |
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Definition
| L:W is 5:1. Max depth: 5m |
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Term
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Definition
| The settling velocity Vs must be greater than the overflow velocity Vo |
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Term
| What are the two filtration types? |
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Definition
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Term
| What is the process for conventional filtration? |
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Definition
| coagulate -> floc - > sedi -> filtration |
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Term
| Up until how much turbidity can you use conventional filtration? |
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Definition
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Term
| What is the general process for direct filtration? |
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Definition
| coagulate - flocculate - filter |
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Term
| With how much turbidity can you use direct filtration? |
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Definition
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Term
| What are three types of filter media? |
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Definition
| monomedia, deep-bed media, and dual media |
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Term
| What are the characteristics of a monomedia filter? |
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Definition
| one medium, often sand, 0.6-0.8m deep. Infrequently used in U.S.A. . aka "slow sand filter." |
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Term
| What are the characteristics of a deep bed monomedia? |
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Definition
| material: anthrocite or GAC. 1.5-1.8m depth |
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Term
| What are the characteristics of a dual media filter? |
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Definition
| traditionally 0.45-promonthrocite (GAC)+0.2+0.3m sand |
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Term
| What is the schmutzdecke? |
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Definition
| slime layer that captures particles atop a filter. Little particle removal occurs in bulk sand in this type of filtration (ex. slow sand) |
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Term
| What is depth filtration? |
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Definition
| uses entire volume of filter for partical removal |
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Term
| What are the layers of modern rapid filters? |
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Definition
| backwash catchment system, water, anthrocite, sand, support, underdrain (to filtered water and ripening water) |
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Term
| What are the stages of filtration? |
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Definition
| run 1-4 days. backwash 15 min - 1h. run ripening. run. |
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Term
| What is the typical hydraulic loading for filters? |
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Definition
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Term
| What is the max surface area for filters? |
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Definition
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Term
| what are the typical depths for filters? |
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Definition
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Term
| What is the goal of disinfection? |
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Definition
| decrease pathogen concentration |
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Term
| What are protozoa of concern? |
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Definition
| Ghardia and cryptosporidium (highly resistant to chlorine) |
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Term
| What are bacteria of concern? |
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Definition
| legionella, E. coli, mycobacterium |
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Term
| What are viruses of concern? |
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Definition
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Term
| Name types of disinfection |
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Definition
| Ozone (O3), Chlorine (hypochlorous acid, HOCl/OCl-) /chlorine bleach (sodium hypochlorite, NaOCl), chlorine dioxide (ClO2), UV |
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Term
| What is the typical wavelength of UV treatment? |
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Definition
| 254 nm. <200nm, not germicidal. |
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Term
| How does turbidity affect UV treatment? |
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Definition
| Turbidity hinders UV treatment |
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Term
| What are chlorine disinfection byproducts? |
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Definition
TriHalomethanes (THMs): CHCl3, CHBr3
Haloacetic acids (HAASs): acetic acid: CH3COOH
HAA: CH2ClCOOH |
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Term
| What is NDMA and why do we care? |
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Definition
| N-nitrosodimethyamine. More toxic compound, present at low levels |
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Term
| What voltage is required for ozone generation? |
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Definition
| 6000-20,000 V across two electrodes |
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Term
| What is the range at which you can smell ozone? |
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Definition
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Term
| What is the OSHA standard for ozone exposure? |
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Definition
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Term
| How do you generate ozone? |
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Definition
pass air or O2 through arc. O2 -> O3
If air is used: 1-4% ozone
If O2 is used: 1-10% ozone |
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Term
| Where must ozone be generated? |
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Definition
| on site due to hazards in production and transport |
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Term
| What are the steps for disinfection design? |
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Definition
1. look up Ct value for disinfectant and level of disinfectant
2. determine C (for chlorine/chloramines, C is residual concentration. For ozone, no residual, so C is concentration of ozone water is exposed to)
3. find t = Ct/C
4. Calculate holding volume V = Q*t |
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Term
| What do larger Ct values imply? |
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Definition
| more contact time is required => less "strong" disinfection power, or higher log removal |
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Term
| What happens to Ct values as Temp goes up? |
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Definition
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Term
| List disinfectants from lower to higher Ct |
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Definition
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Term
| What are typical bed volumes for carbon adsorption? |
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Definition
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Term
| What are typical EBCTs for carbon adsorption? |
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Definition
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Term
| What are typical operation lifetimes of AC units? |
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Definition
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