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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)


All processes prior to the first flocculation (ex: screening, presedimentation, microstraining, aeration, and chlorination, flow measurement)


Protect pumps and mixing equipment from large object


-Removes 50-95% of algae in incoming water

-Constructed from woven stainless steel fabric in a rotating hollow drum that radiates the flow outward

Algae Pretretment

-Algaecide with Copper Sulfate


Traditionally employed

-Not used as much anymore because it can form trihalomethanes (THMs)


Remove easily settled sand and grit

(Trash racks can be used to debris and leaves)

Flow Measurement

Measures flow with:

-Parshall Fume (choked neck for flow)

-venturi meters

-orifice plates

-modern passive devices (magnetic and ultrasound)


-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]


Sedimination Tank or Sedimination Basin

-settle particles, with an incoming flow

-usually have scrappers to remove accumulated sediment


Chemicals used to remove fine solids

Two Types:

-Ionic Polymers:

-Hydrolyzing Metal Ions: alum[(Al2(SO4)3nH2O], copperas[FeSO4 7H2O], and chlorinated coppeas


Where coagulants and water treatment chemicals

(known as flocculator if added at downstream)

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)

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)


When colloids stick to each other to form floc and settle easier. Done by gentle agitation

Tapered Flocculation: when agitation decreases overtime (tapered energy)


Combines mixing, flocculation, and sedimentation into a single tank.

(aka solid contact tanks or aka upflow tanks)


Water waste that carries off the settled floc and the water softening precipitates


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)

Sand Filter Backwashing

When pores in filter particles clog up

Aka Clean Bed

Bed Expansion

The depth of the fluidized bed media increases during backwashing.

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


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

What happens when absorbent reaches saturation

it not longer can remove the solute from the effluent

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


Done with chlorination (liquid or gas form)

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,

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)