Water Supply Treatment And Distribution

Front 1

Water Demand

Back 1

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)

Front 2

Pretreatment

Back 2

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

Front 3

Screening

Back 3

Protect pumps and mixing equipment from large object

Front 4

Microstraining

Back 4

-Removes 50-95% of algae in incoming water

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

Front 5

Algae Pretretment

Back 5

-Algaecide with Copper Sulfate

Front 6

PreChlorination

Back 6

Traditionally employed

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

Front 7

PreSedimintation

Back 7

Remove easily settled sand and grit

(Trash racks can be used to debris and leaves)

Front 8

Flow Measurement

Back 8

Measures flow with:

-Parshall Fume (choked neck for flow)

-venturi meters

-orifice plates

-modern passive devices (magnetic and ultrasound)

Front 9

Aeration

Back 9

-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]

Front 10

Clarifier

Back 10

Sedimination Tank or Sedimination Basin

-settle particles, with an incoming flow

-usually have scrappers to remove accumulated sediment

Front 11

Coagulants

Back 11

Chemicals used to remove fine solids

Two Types:

-Ionic Polymers:

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

Front 12

Mixers

Back 12

Where coagulants and water treatment chemicals

(known as flocculator if added at downstream)

Front 13

Two basic models for mixing

Back 13

---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)

Front 14

Types of Rotating Impellers

Back 14

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)

Front 15

Flocculation

Back 15

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

Tapered Flocculation: when agitation decreases overtime (tapered energy)

Front 16

Flocculator-clarifier

Back 16

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

(aka solid contact tanks or aka upflow tanks)

Front 17

Sludge

Back 17

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

Front 18

Filtration

Back 18

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)

Front 19

Sand Filter Backwashing

Back 19

When pores in filter particles clog up

Aka Clean Bed

Front 20

Bed Expansion

Back 20

The depth of the fluidized bed media increases during backwashing.

Front 21

Types of Filtration

Back 21

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

Front 22

Adsorption

Back 22

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

Front 23

What happens when absorbent reaches saturation

Back 23

it not longer can remove the solute from the effluent

Front 24

Precipitation Softening

Back 24

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

Front 25

Disinfection

Back 25

Done with chlorination (liquid or gas form)

Front 26

Demineralization and Desalination

Back 26

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,

Front 27

Air Strippers

Back 27

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)