1 pollutants in wastewater microorganisms (pathogens) nutrients metals other inorganic substances...

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POLLUTANTS IN WASTEWATERPOLLUTANTS IN WASTEWATER

•Microorganisms (pathogens)•Nutrients •Metals •Other inorganic substances•Radioactive substances•Biologically degradable organic substances•Other organic substances•Odor and taste matters•Heat

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• Chemical characterisation

Individual components:

Sewage – impossible

Industrial wastewaters – sometimes there is a possibility

Municipal wastewater - impossible

CHARACTERISATION OF POLLUTANTSCHARACTERISATION OF POLLUTANTS

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• Group characterisation

Carbon

Chemical Oxygen Demand (CODMn, CODCr)

Biochemical Oxygen Demand (BOD5, BOD7, BOD20)

Total Organic Carbon (TOC)

Dissolved Organic Carbon (DOC)

Volatile Organic Carbon (VOC)

Nitrogen

Phosphorus

Suspended solids

Extractable matters

Detergents

CHARACTERISATION OF POLLUTANTSCHARACTERISATION OF POLLUTANTS

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MEASURE OF ORGANIC SUBSTANCESMEASURE OF ORGANIC SUBSTANCES

CHEMICAL OXYGEN DEMAND

Quantity of the pollutants in water that can be oxidised by a chemical oxidant

Consumption of oxidant (potassium dichromate - CODCr or potassium permanganate - CODMn) gives the content of organic substances

CODCr = 250 – 900 mg O2/l in raw wastewater

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BIOCHEMICAL OXYGEN DEMAND

Measure of the content of biologically degradable substances

Quantity of oxygen consumed by microorganisms over a period of 5 days (BOD5) or 7 days (BOD7) in decomposing the organic pollutants (carbon)

BOD5 = 120 – 400 mg/l in raw wastewater

BOD7 = 1.15 BOD5

BOD20: including decomposition of organic nitrogen as well


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time

BO

D [

mg/

l]

BIOCHEMICAL OXYGEN DEMANDBIOCHEMICAL OXYGEN DEMAND

CBOD = BOD5, BOD7

NBOD = BOD20

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TOTAL ORGANIC CARBON (TOC)

Quantity of carbon dioxide produced from oxidation (combustion, ultra violet radiation, chemical oxidants) of a sample

CO2 is measured by infrared analyser for example

DISSOLVED ORGANIC CARBON (DOC)

Sample filtered through 0.45 m pore size membrane filter (colloidal matter is included as well)

VOLATILE ORGANIC CARBON (VOC)

Organic compounds with boiling point 100 °C

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THEORETICAL ORGANIC CARBON : ThOC = 100%

can be calculated if we now the chemical formula of the organic matter

TOC - 95%

DOC - 70%

CODCr - 80%

CODMn - 45%

BOD7 - 60%

BOD5 - 50%

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ORGANIC POLLUTANTS

SUBSTANCE PROPORTION OF ORGANIC CARBON [%]

Carbohydrates 11 - 18

Proteins 8 - 10

Free amino acids 0.5 - 1.5

Higher fatty acids 23 - 25

Dissolved organic acids 7 - 9

Esteres fatty acids (fat) 9 - 12

Tensides 4 - 6

Other 25 -28

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INORGANIC SUBSTANCESINORGANIC SUBSTANCES

DISSOLVED SALTS MAINLY

DETERMINED BY THE IONIC COMPOSITION AND SALT CONCENTRATION OF WATER

NORMALLY UNIMPORTANT

WHAT IS IMPORTANT? NITROGEN

PHOSPHORUS

HEAVY METALS

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NITROGENNITROGEN

ORGANICALLY BOUND

INORGANICAMMONIUM (NH4-N)

NITRATE (NO3-N)

NITRITE (NO2-N)

TOTAL KJELDAHL NITROGEN (TKN)

NON-OXIDISED FORMS (NH4-N + orgN)

TOTAL NITROGEN (TN)

30 mg/l

50 mg/l

0.1 mg/l

0.5 mg/l

80 mg/l

20-700 mg/l

No exact values!!!

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NITROGENNITROGEN

NITRIFICATION

NH4+ + 1,5 O2 NO2

- + H2O + 2H+ + energy

Nitrosomonas

NO2- + 0,5 O2 NO3

- + energy

Nitrobacter

necessary:

ammonium-N

aerobic condition (DO)

bacteria – pH, T, toxic matters, operation

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DENITRIFICATION

2 NO3- + org C + 2H+ CO2 + H2O + N2+ energy

NO3- NO2

- NO N2O N2

necessary:

organic carbon (easily degradable)

anoxic condition (DO=0, NO3-, NO2

-)

bacteria – pH, T, toxic matters, operation

NITROGENNITROGEN

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PHOSPHORUSPHOSPHORUS

MAIN SOURCEDETERGENTS (50%)

HUMAN EXCRETA (50%)

ORGANICALLY BOUNDSOLID

INORGANICPOLYPHOSPHATES

ORTHOPHOSPHATES (PO43-)

DISSOLVED

TP

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PHOSPHORUSPHOSPHORUS

• ORGANICALLY BOUND0 - 4 mg/L

• POLYPHOSPHATES0 - 5 mg/L

• ORTHOPHOSPHATES (PO43-)

4 - 14 mg/L

• TOTAL PHOSPHORUS

8 - 14 mg/L

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OTHER POLLUTION PARAMETERSOTHER POLLUTION PARAMETERS

TOTAL SOLIDS (TS)SUM OF PARTICULAR AND DISSOLVED MATTERS (residue remaining after a wastewater sample has been evaporated and dried at 105 ºC)

TOTAL VOLATILE SOLIDS (TVS)Solids that can be volatilised and burned off when TS are ignited (550 ºC)

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TOTAL SUSPENDED SOLIDS (TSS)Portion of the TS reatined on a filter (0.45 ; 1.58 m), measured after drying at 105 ºC)

SETTLEABLE SOLIDSsuspended solids, expressed in mL/L, that will settle out of suspension within 30 min (1 h)

Imhoff cone (1 L)

60% of TSS is settleable

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• EXTRACTABLE MATTERS (fats and oils)• DETERGENTS (surface active matters)• METALS (dissolved or particulate, heavy metals)

–Fe, Hg, Ni, Cd, Zn, Cu, Cr, Pb, Mn, As• pH

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pH OF WATERpH OF WATER

Dissociation of water = self ionisation2H2O = H3O+ + OH-

[H3O +][OH-] = Kw = 10-14 (constant at constant temperature)

pH = parameter describing acidity or basicity pH = - log [H+]range: 0 - 14natural waters: pH = 6.5-9importance: natural processes take place in a certain interval of pH

how can we influence pHaddition of acid/baseaddition of salts

NH4+ + H2O = NH3 + H3O+

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OTHER PARAMETERSOTHER PARAMETERS MEASURED MEASURED AT A WWTPAT A WWTP

anions: Cl-, SO3-, HCO3

-, CO32-, F-

cations: K+, Na+, Ca2+, Mg2+, Fe2+, Fe3+, Mn2+

organic micropollutants

phenols (C6H5OH)

chlorinated hydrocarbons

detergents

pesticides, herbicides, fungicides, etc

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OTHER PARAMETERSOTHER PARAMETERS MEASURED AT WWTP MEASURED AT WWTP

• ALKALINITY (amount of hydrocarbons)– amount of matters in water that can be titrated with acids

caused by hydro-carbons (mainly Ca- and Mg-hydro-carbons)

– analysis with titration

• SALT CONTENT (electric conductivity)

• DRY MATTER CONTENT (dried at 105 ºC)

• TEMPERATURE• WASTEWATER VOLUME• INGINITION LOSS (TVS)• TECHNOLOGICAL PARAMETERS

– Recirculation rate, sludge concentration, sludge age, etc.

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BIOLOGICAL PARAMETERSBIOLOGICAL PARAMETERS

• viruses• bacteria (Total Coliform, Faecal Coliform,

Streptococcus, Salmonella)• Most often indicator parameters

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ESTIMATING POLLUTANT LOAD AND ESTIMATING POLLUTANT LOAD AND CONCENTRATIONCONCENTRATION

BOD5: 60 g/d/person

COD: 120 g/d/person

TSS: 70 g/d/person

TN: 11 g/d/person

TP: 2.5 g/d/person

drinking water consumption: qd = 60-200 l/d/person

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ESTIMATING POLLUTANT CONCENTRATIONESTIMATING POLLUTANT CONCENTRATION

BOD5: 60 g/d/person

TN: 11 g/d/person

TP: 2.5 g/d/person

calculating with 200 l/d/person:

BOD5 concentration: 60/200 = 0.03 g/L = 300 mg/L

TN concentration: 11/200 = 0.055 g/L = 55 mg/L

TP concentration: 2.5/200 = 0.0125 g/L = 12.5 mg/L

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converting industrial pollutant load - expressing it as a municipal load

The population equivalent is a unit of measurement of organic biodegradable pollution representing the average load of that pollution produced by one person in one day; in the EU Directive it is fixed at 60 grams of B0D5 per day.

e.g. industry producing ww of 1000 pe means 60000 g/d BOD5 load

POPULATION EQUIVALENTPOPULATION EQUIVALENT

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REGIONAL STANDARDS

COUNTRY STANDARDS

MAXIMUM ADMISSIBLE MAXIMUM ADMISSIBLE CONCENTRATIONS (MAC)CONCENTRATIONS (MAC)

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COUNCIL DIRECTIVECOUNCIL DIRECTIVEof 21 May 1991of 21 May 1991

concerning urban waste water treatment concerning urban waste water treatment (91/271/EEC)(91/271/EEC)

This Directive concerns the collection, treatment and discharge of urban waste water and the treatment and discharge of waste water from certain industrial sectors.

Member States shall ensure that urban waste water entering collecting systems shall before discharge be subject to secondary treatment or an equivalent treatment

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Parameters ConcentrationMinimum

percentage of reduction

Reference method of measurement

Biochemical oxygen demand (BOD5 at 20

°C) without nitrification

25 mg/L O2 70-90 40 underArticle 4

Homogenized, unfiltered, undecanted sample. Determination of dissolved oxygen before and after five-day incubation at 20 °C ± 1 °C, in complete darkness. Addition of a nitrification inhibitor

Chemical oxygen demand (COD)

125 mg/L O2 75 Homogenized, unfiltered, undecanted sample Potassium dichromate

Total suspended solids

35 mg/L 35 underArticle 4 >10 000 pe)

60 underArticle 4 (2 000-10 000 pe)

90* 90 underArticle 4 (> 10 000 pe) 70 underArticle 4 (2 000-10 000 pe)

Filtering of a representative sample through a 0,45 m filter membrane. Drying at 105 °C and weighing Centrifuging of a representative sample (for at least five min with mean acceleration of 2 800 to 3 200 g), drying at 105 °C and weighing

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Parameters Concentration

Minimum percentage

of reduction

Reference method of measurement

Total phos-phorus

2 mg/L P (10 000 - 100 000 pe) 1 mg/LP (> 100 000 p e)

80 Molecular absorption spectrophotometry

Total nitrogen

15 mg/L N (10 000 - 100 000 pe)10 mg/L N (> 100 000 p e)*

70-80 Molecular absorption spectrophotometry

Requirements for discharges from urban waste water treatment plants to sensitive areas which are subject to eutrophication. One or both parameters may be applied depending on the local situation. The values for concentration or for the percentage of reduction shall apply.

* Alternatively, the daily average must not exceed 20 mg/l N. This requirement refers to a water temperature of 12° C or more during the operation of the biological reactor of the waste water treatment plant. As a substitute for the condition concerning the temperature, it is possible to apply a limited time of operation, which takes into account the regional climatic conditions.

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CONVENTIONAL TREATMENT OF SEWAGECONVENTIONAL TREATMENT OF SEWAGE

• PHYSICAL (MECHANICAL)SEPARATION OF SETTLEABLE and FLOATING SOLIDS

• BIOLOGICALSEPARATION OF SUSPENDED OR DISSOLVED SOLIDS WITH THE USE OF MICROORGANISMS

• CHEMICALPRECIPITATION, COAGULATION, FLOCCULATION

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MECHANICAL TREATMENTMECHANICAL TREATMENT

1. SEPARATION OF COARSE MATERIALS

SCREENING - floating debrish, leaves, nylon sacks, etc.

GRIT (SAND) TRAP - sand (inorganic, inert substances)

2. SETTLING OF OTHER SUBSTANCES

SEDIMENTATION TANK - organics (COD, BOD, TP, TN)

(OR FLOTATION)

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SCREENINGSCREENING

BAR SCREENS

aim: defending the subsequent instruments

retain floating debrish (wood, rags, etc.)

long, narrow metal bars 25 mm (1 in.) apart

in a frame

vertical or tilted

cleaned automatically (75-80°)

or by hands (60°, 1-2 times a day with rake)

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BAR SCREENSBAR SCREENS

increased clogging during winter time (ice)

debrish has to be collected

massive, oversized structures

if mechanical units defense against overload

shearing element

greater treatment plant at least 2 parallel screens

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BAR SCREENSBAR SCREENS

COARSE SCREENS

50-100 mm free gap

20-30 mm

FINE SCREENS

10-50 mm free gap

1.5-15 mm

BOD removal 5%

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DESIGN OF SCREENSDESIGN OF SCREENS

HYDRAULIC HEAD LOSS (damming)

depends on :

size of free gap

velocity

slope of screen

shape of screen

ALLOWED MAXIMUM DAMMING

hmax = 5 – 15 cm

h = vf2 / 2g

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COMMUNITORCOMMUNITOR

MECHANICAL CUTTING DEVICE

SLOTTED CYLINDRICAL SCREEN WITH MOVING CUTTER BLADE

CHOPS SOLIDS THAT PASSED THROUGH THE BAR SCREEN

SHREDDED MATERIAL IS REMOVED BY SEDIMENTATION OR FLOATING

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SEDIMENTATIONSEDIMENTATION

DISCRETE PARTICLES (do not tend to flocculate)

HEAVIER PARTICLES FALL TO THE BOTTOM

v < vcr SETTLING

CRITICAL VELOCITY – KEEPS THE PARTICLE SUSPENDED

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G

F

S = f ()

Stokes’ law

ρ)(ρ18μ

gdω s

2

- settling velocity

- absolute viscosity of the fluid

- mass density of fluid

s - mass density of particle

g - gravitational constant

d – diameter of the particle

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v1 > vs particles retain in a ratio of v1/vs

v1 < vs particles settle

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GRIT TRAP / SAND TRAPGRIT TRAP / SAND TRAP

SAND CAUSES WEAR-AND-TEAR ON PUMPS

HAVE TO BE REMOVED

HEAVIER PARTICLES FALL TO THE BOTTOM

v < 0.3 m/s (1 ft/s) SETTLING

OFTEN COMBINED WITH SOME FORM OF AERATION TO MAINTAIN DO + SEPARATION OF GREASE

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SAND TRAPSAND TRAP

VERTICAL FLOW

AERATED

HORIZONTAL FLOW

TANGENTIAL

good efficiency difficult to place

high flow, uneven load DO oil skimming

like horizontal flow, but inflow from the side

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SAND TRAPSAND TRAP

DESIGNING

MIN 2 BASINS PARALLEL (dry flow and higher flow)

PEAK FLOW

RESIDENCE TIME (10 min)

HYDRAULIC SPECIFIC LOAD (30 m3/h/m2)

SLUDGE RAMOVAL:

MECHANICAL

GRAVITATIONAL

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SEDIMENTATION BASINSEDIMENTATION BASIN

PRETREATMENT (no dissolved substances removed)

AIM: removal of suspended solids smaller than sand

REMOVES 25-35% OF THE ORGANIC MATTER

SPECIFIC LOADING : 1-3 m3/h/m2

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Q = 150 – 2000 m3/d h/l = 1/15 – 1/20

h = 1.5 – 3.0 m w= 4 – 8 m

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D = 30 –40 m

h = 2-4 m

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SECONDARY (BIOLOGICAL)SECONDARY (BIOLOGICAL) TREATMENT TREATMENT

WITH THE USE OF MICROORGANISMS

ORGANIC MATTERmicroorganisms oxidise the organic matter while producing new cell material, CO2 and H2O

NITROGENammonification, nitrification, denitrification

PHPSPHORUSBiological P-removal

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CONVERSIONS IN BIOLOGICAL CONVERSIONS IN BIOLOGICAL WWWWTREATMENTTREATMENT

biological growth

hydrolysis

decay

Slowly degradable material

Easily degradable material

Biomass

Inert material

hydrolysis

biological growth

decay

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activated sludge reactors

• microorganisms are suspended in water (mobilised)

• different conditions at different places

biofilm reactors

• microorganisms are hold on a fixed surface

• different conditions are at the same place but at other time

TYPE OF TYPE OF REACTORSREACTORS

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BIOLOGICAL PARAMETERSBIOLOGICAL PARAMETERS

• Activated sludge processes– Aeration basin systems

– Oxidation ditch

– Aerated sewage lagoons

• Biofilm processes– Trickling filters

– Rotating biological contactors (biological rotors)

– Thin biofilm systems

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Rotating biological contactors

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SECONDARY TREATMENTSECONDARY TREATMENT

• Biological reactor• Secondary settling• Disinfection

1 pollutants in wastewater microorganisms (pathogens) nutrients metals other inorganic substances...

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