WaMa 2 Water Purification

Department of Hydro Sciences, Institute for Urban Water Management

UNEP Course CIPSEM Dresden, September 2014

Water Management and Climate Change Adaptation

2 Water extraction and purification

Peter Krebs

UNEP Water and Climate 2 Water extraction and purification PK, 2014 page 2


2.1 Concept, overview

2.2 Raw water composition

2.3 Water extraction

2.4 Gas exchange

2.5 Removal of particles

2.6 Removal of particles and colloids

2.7 Chemical stabilisation

2.8 Disinfection and network protection


Peter Krebs






2.4 Gas exchange






Peter Krebs


Sufficient Drinking Water of good Quality at any Time

Political decision making

sufficient how much, how long during dry periods ?

good quality hygiene, to be drunk, for toilet flushing, how long ?

any time extreme drought, contaminated water spring

Task of water supply


Implementation via guidelines, threshold values

DIN 2000

Drinking water should be appetizing and tempting, colourless, clear, cold, odourless, and perfectly fresh with regard to taste.

Drinking water quality


Ground water

Storage

Industry

Settlement

Lake, dam

Water protection

Tight construction

Protection zone

Pressure

Saftey barriers

Spring intake

Protection zone

Purification

Water distribution

Structure of a water supply system


Regional water supply systems in Germany


Type of water supply Typical consumption

l/(Cad)

Rangel/(Cad)

Communal water pointdistance > 1000 m distance 250 1000 m

712

5 1010 15

Village well distance < 250 m 20 15 25

Communal standpipe distance < 250 m 30 20 50

Yard connection 40 20 80

House connection single tapmultiple tap

50150

30 6070 250

System dependent water consumption


Drinking water consumption in Germany

116

133

112

98

127133

123

100

128135

118 116

8590

133

90

122

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20

40

60

80

100

120

140

160

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28%

34%

12%

6%6%

6% 4% 2%2%

28% WC34% bathing/shower12% washing cloths6% personal hygiene6% wash dishes6% cleaning4% watering2% cooking/drinking2% cleaning cars

Drinking water consumption of private households


Qd average daily consumption over a year

Qh average hours consumption at average day

Qd,max maximum daily consumption of a year

Qh,max maximum hours consumption at maximums day

fd Peak days factor

fh Peak hours factor

Parameters to characterise consumption (i)


Parameter Decisive for

Maximum daily water needQd,max = fd Qd

Purification, reservoir

Average hourly need at average day Qh = Qd / 24

Maximum hours need at maximum day Qh,max = fh Qd / 24

Distribution system

Parameters to characterise consumption (ii)


Drinking water prices for centralised systems

2,18

1,761,65 1,63

1,261,16

1,000,94

0,81 0,76 0,750,68 0,67

0,52

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0,50

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1,50

2,00

2,50

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Drinking water prices in Germany

1,81

1,27

2,29

1,51

1,98

1,52

1,93

1,55

1,19

1,59 1,55

1,81,93

1,57

1,3

2,04

1,6

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2.4 Gas exchange






Peter Krebs


pH-value:

Ferric (Fe):

Manganese (Mn):

5 6,5

1 10 mg/l

0,2 1 mg/l

Oxygen (O2): < 1 mg/l

Typical ranges:

Additional anthropogenic loads:

Agriculture: Nitrate (NO3-), pesticides

Industry (Air and wastewater):

Organic compounds, ammonia, acid rain dissolution of metals (e.g. aluminium)

Characteristics of groundwater


Geology LocationpH O2 Fe Mn KB 8,2

Hard-ness KS 4,3

mg/l mg/l mg/l mol/m3 dH mol/m3

Crystalline Gotteszell 6,0 10,8 0,3 0,6 0,1

Sandstone Heldmann-berg 7,3 0,5 0,3 0,04 1,2 18,9 6,3

Pleistozene

Tettau 5,7...7,1 n.n.152

50,10,

8 1,0... 2,56,0...12

,10,15...1,25

Spremberg 5,3 0,02 7,5 0,15 1,6 5,1 0,14

Engelsdorf 2 (Leipzig) 7,2 1,0 7,6 0,54 0,88 42,9 4,48

Lommatzsch 7,2 < 0,5 7,5 0,5 1,61 36,6 8,21

Gravel Munich 7,2 10,5 0,01 0,43 14,3 4,4

Ground and spring water


Parameter Unit Wahnbach (Siegelsknippen)

Klingenberg (Coschtz)

Muldenberg(Muldenberg)

Temperature C 3,86,7 4,014,5 0,712,8

pH-value 6,8...7,1 6,6...7,7 4,3...4,9

Oxygen mg/l 5,9...11,1 7,8...12,3 5,8...12,9

DOC mg/l 0,48...1,27 2,2...2,6 2,0

SAC 436 nm m-1 0,06...0,08 0,14...0,46 < 0,1...0,4

Turbidity TE/F 0,48...1,27 0,3...1,8 0,43...2,5

AOX mg/l < 0,01 < 0,01...0,018 < 0,0015

KS 4,3 mol/m 0,43...0,50 0,15...0,4 0,01...0,03

Hardness mol/m 0,7...0,8 0,5...0,7 0,17...0,19

Aluminium mg/l 0,02...0,27 < 0,02...0,16 0,62...0,96

Nitrate mg/l 16...17 12...19 2,0...3,6

Ferric, total mg/l < 0,01...0,03 < 0,05...0,12 < 0,17...0,60

Manganese mg/l 0,01...0,19 0,024...0,14 0,48...0,59

Arsenic g/l < 0,5 1,0...2,9 < 1,0

Colonies no. at 20 C ml-1 22...1490 0... > 1000 0...528

Coliformes 1/100 ml 0...12 0 0

Water of a dam


Parameter Unit Elbe(Hosterwitz)

Donau at LeipheimMean 2001

Temperature C 0,622,5 10,4

pH-value 7,3...8,6 8,12

Oxygen mg/l 4,4...11,8 10,51

DOC mg/l 4,6...6,6 2,85

SAC 436 nm m-1 0,65...1,9 n.b.

Turbidity TE/F 34...140 8,48

AOX mg/l 0,022...0,199 0,012

KS 4,3 mol/m 1,2...2,15 4,27

Hardness mol/m 1,4...2,1 2,5

Aluminium mg/l 0,025...0,82 0,04

Nitrate mg/l 16...30 13,7

Ferric mg/l 0,25...4,4 0,02

Manganese mg/l < 0,02...0,51 < 0,0050

Arsenic g/l 2,5...3,3 0,00014

Colonies no. at 20 C ml-1 1000... > 168 000 5651

Coliforms 1/100 ml > 2400 13393

River water


Parameter Unit Lake of Constance (60 m depth)Mean 2000

Temperature C 5,1

pH-value 8,05

Oxygen mg/l 10,6

DOC mg/l 1,3

SAC 254 nm m-1 3,1

SAC 436 nm m-1 Not detectable

Turbidity FNU 0,51

AOX mg/l 0,006

KS 4,3 mol/m 2,52

KB 8,2 mol/m 0,03

Hardness dH 8,97

Aluminium mg/l 0,0085

Nitrate mg/l 4,5

Ferric mg/l 0,010

Manganese mg/l 0,0009

Arsenic mg/l 0,0013

Lake water


Parameter River water Bank filtrate

Coliforms < 29.000 < 640 (per 100 ml)

E. Coli < 2.000 < 4 (pro 100 ml)

Temperature 3,5 23,4 9,7 16,5 (C)

O2 10,1 5,2 (g/m3)

CO2 2,3 6,5 (g/m3)

NH4+-N < 0,055 < 0,016 (g/m3)

Biomass < 7 < 0,02 (g/m3)

River bank filtrate

typical values from Zurich






2.4 Gas exchange






Peter Krebs


Often good quality and relatively simple purification

Aquifer is a large storage unit and levels out variations in extraction

Supporting filter layers against wash-out of sand from neighbouring ground

The smaller the wells diameter, the more serious is the danger silting up

Maintenance against clogging

Characteristics of groundwater


Undisturbed GW-level

QW

concentric flow

Rain

Impervious ground

Water extraction: filter well


Natural ground

Steel filter pipe Supporting sand- and gravel layers

Filter pipe with supporting layers


Horizontal intake

QW

Undisturbed GW-table

Horizontal filter well


Infiltration Collection shaft

Overflow Aquifer

Spring water abstraction

Spring water extraction


Buchbrunnenquelle (Foto von Steinmetz, M.)

Spring water intake


Dam with multiple intake


Intake with Fish screen30 - 60 m deep10 m above ground

Raw waterpumping station

Sediments,Partly loose

Rock

Lake water intake






2.4 Gas exchange






Peter Krebs


Export of CO2, for de-acidification

Export (purging) of volatile substances, such as H2S, CH4

Stripping of volatile organic compounds

Import of oxygen for oxidation of dissolved compounds (e.g. ferric substances, manganese, ammonia) and to improve taste and development of protection layers

Introduction of ozone

Goals of gas transfer


HENRY-DALTON law cS = cGcS Gas saturation concentration in water cG Gas concentration in air Solubility coefficient = f (t, pG)

Import flux

ccDF Sin Export flux

ccDF Sex ccS ccS

Transfer process description


( Aquadosil)

Aeration with free surface






2.4 Gas exchange






Peter Krebs


Turbid raw water

Pre-treated water

Drinking water

Removal of particles

Enhanced treatment, stabilisation, disinfection

Two major steps of water purification


Rack only with surface waters wide and narrow slots

Micro sieves Steel or textile grid size < 0,1 mm, continuous back rinsing

Raw water Clear water tank Effluent Micro sieve Rotating cylinder Rinsing Driver, controlled

Removal of coarse particles

UNEP Water and Climate 2 Water extraction and purification PK, 2014 page 38Source: Bodenseewasserversorgung

Micro sieve


0.1

10

1000

10-5 10-3 10-1 10

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Particle size (mm)

Flocculation

Filtration

Sedimentation

Sieves

Rack

Viruses Bacteria Algae

Processes to remove particles


Mixing Flocculation Separation

Sludge Treatment

Flocculant

De-stabilisation, generation of micro-flocs

Aggregation and generation of macro-flocs

Sedimentation, flotation, filtration

Enhanced treatment

Filtration

ev. flocculation aid

Flocculation


Q Q

Inlet region Effluent region Sediments Sedimentation region

Length of tank

Sedimentation Length LS

Sedimentation


often layered (two or more layers) top: coarse, light material (e.g. pumice stone 1,4 2,5 mm)bottom: fine, heavy material (e.g. sand, 0,71 1,25 mm)

hydraulic load 4 30 m/h

Pressure head 2 5 m

Quick increase of resistance an pressure head decrease; clogging of fine material is faster,

Back rinsing with water, air, and water/air

Pressure filtration for smaller filter areas

Fast filtration


Open fast filter


Filtrate concentration Filter resistance

Threshold values pcr (hF,cr)

critical filtrate conc. ccr

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Filter operation time tt1 t2

Filtration effect and resistance


Back rinsing


Removal of particlesmicrobial loadbio-degradable substances

Sieve effect Adsorptive effect over entire filter depth Mud cover, a few cm, biologically active

Organic compounds are degraded Ammonia is nitrified

Prerequisite O2-concentration is sufficient small TSS-concentration

Surface overflow rate 0,1 0,2 m/h, pressure head ca. 1 m 3 24 months removal of mud cover large area necessary

Slow filtration (i)


Raw waterFiltration

Mud layer, bio-active !

Sand filter, 0.6 mm, H > 0.5 m

Drainage bottom

Sand filter, layered with increasing diameter towards bottom

Slow filtration (ii)






2.4 Gas exchange






Peter Krebs


Fe2+ Fe3+

Contact with O2

High solubility

Low solubility

Rusty precipitation

Filtration

Manganese

Similar to ferric substances, Oxidation through micro-organisms or catalytic reaction

Removal of Ferric and Manganese


Removal of dissolved organic compounds

microscopic pores through glowing of coal at 650C, as a significant part is oxidised and volatilised as CO2

huge internal surface: 1000 2000 (m2/g active carbon)

active carbon is sensitive on mechanical stress

rinsing as seldom as possible via pre-treatment and separation of particles before the activated carbon process

Micro-organisms on the surface bio-degradation of organic compounds

Activated carbon adsorption






2.4 Gas exchange






Peter Krebs


CO2 CaCO3

Drinking water treatment Neutralisation

Acid Lime, calcium carbonate

Aggressive, corrosive

Aeration Filtration through lime Adding hydroxides, soda

Precipitation, encrusting

Precipitation Reduction of solubility

Ion exchange

De-acidification


KS4,3 KB8,2

Lime carbonic acid system






2.4 Gas exchange






Peter Krebs


Inactivation of pathogenic germs

Chemical oxidation

UV-radiation

O3 fast decay, no by-products, Oxidation

Cl2 cheap, Network safety, reactive

ClO2 Network protection, local production

In 1 cm layer, for some seconds

No by-products

No network protection

Only for small plants, expensive

possibly production of by-products

Disinfection


Oxidation Disinfection long term effect

Chlorine Satisfactory good good

Chlorine dioxide Bad satisfactory satisfactory

Ozone Good good negative

UV-Radiation Bad satisfactory negative

Effect of disinfection means

Documents

WaMa 2 Water Purification