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27 Cards in this Set
- Front
- Back
Water Demand |
AADF (average annual daily flow): average amount used per day over the course of the year Units : gpcd (gallons per capita day): gallons used per person per day (typically planned at 165 L/d) |
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Pretreatment |
All processes prior to the first flocculation (ex: screening, presedimentation, microstraining, aeration, and chlorination, flow measurement) |
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Screening |
Protect pumps and mixing equipment from large object |
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Microstraining |
-Removes 50-95% of algae in incoming water -Constructed from woven stainless steel fabric in a rotating hollow drum that radiates the flow outward |
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Algae Pretretment |
-Algaecide with Copper Sulfate |
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PreChlorination |
Traditionally employed -Not used as much anymore because it can form trihalomethanes (THMs) |
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PreSedimintation |
Remove easily settled sand and grit (Trash racks can be used to debris and leaves) |
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Flow Measurement |
Measures flow with: -Parshall Fume (choked neck for flow) -venturi meters -orifice plates -modern passive devices (magnetic and ultrasound) |
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Aeration |
-reduces taste and odor causing compounds -decrease CO2, Fe, -increase O2 -Best if air-water contact area is large -Force draft air injection is commonly used (depending on Q and depth of injection)[typically 10-25ft] -Diffused air systems (pressurized compressed air) [at 5-10psi, 0.2-0.3 ft3/gal, 5-10ft depth] |
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Clarifier |
Sedimination Tank or Sedimination Basin -settle particles, with an incoming flow -usually have scrappers to remove accumulated sediment |
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Coagulants |
Chemicals used to remove fine solids Two Types: -Ionic Polymers: -Hydrolyzing Metal Ions: alum[(Al2(SO4)3nH2O], copperas[FeSO4 7H2O], and chlorinated coppeas |
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Mixers |
Where coagulants and water treatment chemicals (known as flocculator if added at downstream) |
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Two basic models for mixing |
---Complete Mixing: via impellers and paddles, detention time depend on mixing rate constant (flash mixers[made out of square concrete tanks] are for smaller basin volumes and shorter mixing time) ---Plug Flow Mixing: for long narrow chamber, with only addition of chemicals (no mechanical action) |
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Types of Rotating Impellers |
Radial Flow Impellers: paddle type, turbine impellers (blades are parallel to drive shaft) Axial Flow Impellers: blades are inclined (better at keeping particle in suspension) |
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Flocculation |
When colloids stick to each other to form floc and settle easier. Done by gentle agitation Tapered Flocculation: when agitation decreases overtime (tapered energy) |
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Flocculator-clarifier |
Combines mixing, flocculation, and sedimentation into a single tank. (aka solid contact tanks or aka upflow tanks) |
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Sludge |
Water waste that carries off the settled floc and the water softening precipitates |
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Filtration |
Removal of nonsettled floc, algae, suspended- precipitates from softening, and metallic iopns (Sand filters are most common) Discharges into clearwell reservoir (Hydraulic head is the distance between the filter water surface and the clearwell) (Influent: feed) (Effluent: filtrate) |
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Sand Filter Backwashing |
When pores in filter particles clog up Aka Clean Bed |
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Bed Expansion |
The depth of the fluidized bed media increases during backwashing. |
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Types of Filtration |
Sand filters: beds of gravel, sand, granules... backwashing, bed expansion Pressure filters: sand filter but pressures up to 25ft gage Biofilm Filters: use microbes to remove some contaminants Slow Sand Filters: larger surface area and slowers Ultrafilters: membranes as sieves |
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Adsorption |
When contaiminants(solute) get attached to surface of medium (aka adsorbent, typically an Activated Carbon) Activated Carbon (Include GAC[granular] and PAC[powdered]) is produced by closed combustion of coal and organic materials (for recovery of gas and reuse) -Used for removing heavy metals and organics from water |
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What happens when absorbent reaches saturation |
it not longer can remove the solute from the effluent |
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Precipitation Softening |
Using lime-soda ash process to remove Ca and Mg Lime (CaO) Soda Ash (Na2CO3) Water recarbonation to lower pH and reduce scale forming potential |
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Disinfection |
Done with chlorination (liquid or gas form) |
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Demineralization and Desalination |
Removal of minerals and salts ---distillation[vaporize water out into, leave salt & minerals behind, then collect water seperately via condensation] ---reverse osmosis [ with thin very small pores] ---nanofiltration [pressure and midly small pores] ---electrodialysis [electrical gradient] ---ion exchange, |
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Air Strippers |
used to remove VOCs (volatile organic compounds), done by inserting contaminated water and fresh air into media.. coming out clean water ---packed towers[synthetic packing media] ---spray towers ---tray towers (redistribution rings prevent channeling down of contaminated water through narrow paths) |