Objective In this lesson we will answer the following questions:

•What is a water and wastewater

•Why we characterize water and wastewater

•What are the common characteristic of water and wastewater

•Description of the significance water and wastewater quality parameters

CHARACTERIZATIOPN OF WATER AND WASTEWATER

Difference of water and wastewater • Water =surface water and groundwater

• Wastewater=sewage, domestic and industrial discharge

Why characterize the water and wastewater • To determine it’s properties-physical, chemical

and biological

• To design the suitable treatment techniques

Common quality parameters for water and wastewater

Water Wastewater

pH pH

Color Suspended solids (SS)

Dissolved oxygen Dissolved oxygen

Total solids (TS) Volatile suspended solids (VSS)

Total dissolved solids (TDS) Chemical oxygen demand (COD)

Alkalinity Biochemical oxygen demand

Anions (SO42-, NO3+ Cl-) Oil and grease

Cations (Ca2+, Fe3+, Mg2+) Heavy metals (Ni, Fe, Cr etc)

Pesticides Total kjeldahl nitrogen (TKN)

Coliform bacteria Ammonia, phosphate, nitrate and etc

Some of the significance water and wastewater quality parameters

PHYSICAL PARAMETERS

usually associated with the general appearance of the water.

• Odor and Taste most common observation in water quality.

• sources :

– organic compounds , i.e : degradation of organic matters or petroleum,

– inorganic compounds, i.e: minerals, metals, salts which gives the taste.

– Others: certain types of algae, i.e the blue-green algae, can also impact foul tastes and odors.

• The significant effect:

– our health and feeling aesthetic.

•

• Color • Sources:

– Yellow due to tannins, humic acid and hunates from plant material

– Iron oxides-reddish – MnO2 –cause brown or blackish – Color originated from industrial activities: textile, paper, pulp etc

• The significant effect:

– Aesthetically unpleasant – Some are carcinogenic

• pH Term used to indicate the alkalinity or acidity of a substance

ranked on a scale from 1.0 to 14.0. indicator of the existence of biological life most of them thrive in a quite narrow and critical pH range.

• Factors affecting pH:

– The concentration of CO2 in the water – Respiration of aquatic organisms – Geology and Soils of the watershed

• Releasing of acidic and alkaline compounds from different types of rock and soil.

i.e Releasing of carbonates (HCO3, CO3-2) due to

present of calcite (CaCO3) will increasing the alkalinity of the water

– Air Pollution

• Air pollution from car exhaust and power plant emissions increases the concentrations of nitrogen oxides (NO2, NO3) and sulfur dioxide (SO2) in the air.

• End up in water via rain/precipitation

– Industrial discharge

• Turbidity Amount of particulate matter that is suspended in water /cloudiness

• Normally measured in Nephelometric Turbidity Units (NTU) or Formazin Turbidity Units (FTU).

• Sources:

– organic compounds. i.e plant fiber, human waste, etc. – inorganic compounds. i.e clay or sand.

• The significant effect: – feeling aesthetic – effect upon health – Effect microorganism.

• Temperature Temperature of the water

• Sources:

– changes of weather or heat

– industrial activities such as cooling tower operation, boiler etc

• The significant effect:

– the ability of water to hold oxygen

• Cold water hold more oxygen

– the rate of photosynthesis by aquatic plants

• water temperature rises, the rate of photosynthesis increases

– the metabolic rates of aquatic organisms • Water temperature rise, metabolic rate increase (for cold-blooded

aquatic life)

• Total solids suspended or dissolved matter in water or wastewater related to both specific conductance and turbidity • Total Solids includes both:

– Total suspended solids (TSS), • the portion of total solids retained by a filter

– Total dissolved solids (TDS) , • the portion that passes through a filter.

• *TSS is a physical parameter • *TDS is a chemical parameter Will be further discussed

CHEMICAL PARAMETERS normally monitor for a variety of inorganic and organic components. Alkalinity

• the quantity of ions in water which responsible in neutralizing the acid • It is not a pollutant • The main constituents are bicarbonate (HCO3

-), carbonate (CO32-), and

hydroxide (OH-) ions. • Sources:

– mineral dissolved in water and air – human activities such as detergent (in wastewater), fertilizers,

pesticide etc • Effects:

– would caused non pleasant taste – reaction between alkaline constituent and cation (positive ion),

produces precipitation in pipe.

Hardness Measure of multi-valent cations in water such as Ca2+, Mg2+, Fe2+, Mn3+. Ca2+ and Mg2+

• very important and usually present in water.

• Source:

– Natural mineral from Earth

• effects of hardness

– would be excessive usage of soap

– precipitate form on hardware and in pipelines which increased temperature and pH

*Will be further discussed in the next chapter-water treatment

• Nutrients crucial elements needed by living things especially animals and plants to live and survive.

• Important elements are carbon, nitrogen, and phosphorus.

• Sources: – Carbon from carbon dioxide (CO2) – nitrogen from for protein, chlorophyll and biological

compounds. – Phosphorus exists in a form of orthophosphate, condensed

phosphate, and organic phosphate and

• Effect: – Excessive amount cause uncontrollable growth of algae

Total Dissolved Solid (TDS)

consist of inorganic salts and dissolved materials. • solid left in water after it was filtered and dried. • sources

– organic compounds( i.e from degradation of organic matters or gas) – inorganic compounds i.e minerals, metals and gases.

• Effect: – cause the taste, color, and odor problems – water would becomes corrosive

• Note: It measured in either mg/L for organic and inorganic or mS/m for conductivity measurement.

*Will be further discussed

Food For Thought

BIOLOGICAL PARAMETERS

• Microbiological test is to detect the level of pollutions caused by living thing especially human who live or work in the area especially upstream of the site.

• These tests are based on coliform bacteria as the indicator organism.

• The typical indicators used are the coliform groups:

• -Fecal coliforms (E-coli) • -Total coliforms (Fecal coliforms and any others).

Water and wastewater parameters

• Objective

• In this lesson we will discuss the following items:

• Variant of organic carbon in water/wastewater and its significance

• What is BOD

– Variant of BOD

• What is COD

– Variant of COD

• Measurement of carbon contents in water:

-Biochemical Oxygen Demand (BOD)

-Chemical Oxygen Demand (COD)

-Total Organic Carbon (TOC)

Why measure:

Organic carbon pollutant in water among other depleted the oxygen concentration in water

BOD

• BOD is a measure of the oxygen used by microorganisms to decompose biodegradable organic waste.

• The most common BOD test takes 5 days to complete. Hence called BOD5

• Typically divided into two parts-

- carbonaceous oxygen demand (CBOD)

- nitrogenous oxygen demand (NBOD)

• CBOD is the result of the breakdown of organic molecules such a cellulose and sugars into carbon dioxide and water. – Could be obtained by applied inhibitory agent that inhibited the

oxidation of nitrogen

– Eg of Inhibitor are methylene blue, thiourea, allylthiourea

• NBOD is the result of the breakdown of proteins usually to ammonia then to nitrate.

– Usually applicable after 6 to 10 days of incubation

• Ultimate BOD (UBOD) is the total amount of oxygen consumed when the biochemical reaction is allowed to proceed to completion

• The BOD5 test procedure

The BOD test is carried out by diluting the sample with dilution water in the BOD bottle.

The initial dissolved oxygen then measured (DOi) before BOD bottle was sealed

The sample is incubated for 5 days at 20 °C in the dark/or wrapped with aluminium foil to prevent photosynthesis.

After 5 days incubation, DO is then measured again (DOf)

BOD for sample is: (DOi-DOf)w

• Blank sample of consist only the dilution water are conducted as a correction for the loss of the DO due to the other factor.

• Exactly the same procedure as the sample is applied

• BOD for blank is: (DOi-DOf)bl

BOD5 can be calculated by:

• BOD5 = BOD sample-BOD blank x Dilution effect x Dilution Factor

• = (DOi-DOf)w-(DOi-DOf)bl x df x Dilution Factor

• df = dilution effect = 1

• To measure carbonaceous BOD(cBOD), a nitrification inhibitor

is added after the dilution water has been added to the sample.

• In this lesson we will discuss the following items:

• The significance of Dilution water in BOD test

• Ultimate BOD

• What is?

• calculation

• Limitation of BOD test

Introduction to Chemical Oxygen Demand (COD)

• Dilution water is the water that has been saturated with Dissolved oxygen

• DO in saturated water at 30 C , 1 atm 8.0 mg/L

• Dilution water consist of: FeCl3, CaCl2, MgSO4, seeding microbe, phosphate buffer-nutrients for microbes

• Why adding dilution water: – To dilute the sample (for concentrated/high strength sample)

– Provide seeding microorganism

– Provide nutrients

– Provide oxygen (as the water has been saturated with dissolved oxygen)

• To accurately measure the BOD, following condition must be checked:

– DO depletion for sample (DOi-DOf)w must be greater than 2 mg/L

– DO residual reading for sample (DOf) must be greater than 1 mg/L

UBOD

• Ultimate or total BOD

• Can be measure using below equation derived from kinetic experiments

• Lo = Ultimate or total BOD

• BODt = BOD at day t

• Kinetic reaction constant(k)

• K10 (base 10)

• K (base e)

Simple compounds(i.e sugars, starches), easily utilized by m/organism- high K rate

Complex compounds(i.e phenols,cellulose), difficult to utilized by m/organism- low K rate

• From literature, typical K (base 10) value at 20 C

• Note: This is K10 value

Water Type K10

Tap water 0.04

Surface water 0.04-0.1

Raw sewage 0.15-0.30

Well treated sewage 0.05-0.10

• Limitations of BOD test

-seed bacteria must be acclimatized

-only measure the biodegradable organics.

( Not applicable to non biodegradable organics such as tannic, lignic acids, cellulose, humus etc)

-The test does not work when toxic chemicals present

-Inconsistent number of microbe in each testing

-Time consuming took 5 days for the result

• Example:

Calculate 1) BOD5 and 2) ultimate BOD using below data:

-Initial DO of blank 7.90 mg/L

-Final DO of blank after 5 days 7.85 mg/L

-Final DO of sample 5.00 mg/L

-wastewater sample used 2.0 ml

-BOD kinetic reaction constant (K) 0.23 /d

BOD bottles of 300 mL have been used for the measurement

Comments on below BOD data:

Situation 1

-Initial DO of blank 7.90 mg/L

-Final DO of blank after 5 days 7.85 mg/L

-Final DO of sample 6.50 mg/L

Are this info valid for the calculation?

Situation 2

-Initial DO of blank 7.90 mg/L

-Final DO of blank after 5 days 7.85 mg/L

-Final DO of sample 0.80 mg/L

Are this info valid for the calculation?

• Example of:

• BOD calculation

• Ultimate BOD calculation

Men’s best successes come after their disappointments

Henry Ward Beecher

• Why determine the properties of the water/wastewater?

• What difference between a) water and b) wastewater treatment

• Why the fresh water supply is at alarming state (across the world)

• Public always sceptical on the color wastewater, any suggestion why??

• Why need to measure the organic content level in water/wastewater

• Why COD level always higher then BOD

• What the function of:

Bacteria in BOD test

Oxidation agent in COD test

• Question a) • Calculate the ultimate BOD if:

– Volume of sample added to the 300 ml BOD bottle is 4 mL – Initial DO for blank: 8.0 mg/L – DO for blank after 5 days : 7.8 mg/L – Initial DO for sample: 8.0 mg/L – DO for sample after 5 days : 5.0 mg/L – Assume biodegradability constant (K)= 0.23/d

• b) For BOD calculation, Initial DO for blank and sample

usually identical. Why?

In this lesson we will discuss the following items: • Introduction to COD •Test procedure •COD calculation •Interference during measurement •Advantage/disadvantage of COD •BOD/COD ratio •Work ed example

• Chemical Oxygen Demand (COD) • Measures the carbon contents of soluble organic

matter in water that can be oxidised by strong oxidation agent (i.e Cr2O7

2/H+ and KMnO4/H+ ) in an acidic condition

• Why Measure COD?

• COD is often measured as a rapid indicator of organic pollutant in water.

Ag2SO4

• 3[C] + 2 Cr2O72- + 16 H+ ---- 4 Cr3+ + 3CO2 + 8H2O

Orange green

• potassium dichromate (Cr2O72-) is reduced to Cr3+.

• The amount of Cr3+ is determined after oxidization is complete

• (used as an indirect measure of the organic contents of the water sample).

• Test procedure in brief

• Blank sample

• To ensure no outside organic material be accidently added

• created by adding all reagents (e.g. acid and oxidizing agent) to a volume of distilled water

• COD is measured for both the water sample and blank samples, and the two are compared.

• result for the water sample later subtracted with blank (to ensure a true measurement of organic matter).

• Measurement of excess/unreacted dichromate • To completely oxidized organic matter, an excess amount of

potassium dichromate must be used • Once (oxidation) completed, amount of unreacted(excess)

potassium dichromate then measured • Measurement was done by titrating with ferrous

ammonium sulfate (FAS) until all of the excess/unreacted oxidizing agent has been reduced to Cr3+

• The amount of FAS added = the amount of excess

potassium dichromate added to the original sample • For all organic matter to be completely oxidized, an excess

amount of potassium dichromate was needed

• Back titration against FAS

• 6Fe2+ + Cr2O72- + 14 H+ ---- 2Cr3+ + 6 Fe3+ + 7H2O

FAS unreacted green

• Calculation

• COD (mg/L) =

• A= volume of FAS for blank titration, VFAS with blank (mL)

• B= volume of FAS for sample titration VFAS with sample (mL)

• C = Molarity of FAS used in titration, MFAS ( mol/L)

• V = volume of sample used (mL)

Inorganic interference • Some samples of water contain high levels of oxidizable

inorganic materials • This may interfere with the determination of COD.

i.e of inorganic interference: chlorine Overcome Add HgSO4 - To eliminate Cl- which may react with Cr2O7

2-

Low molecular fatty acids add Ag2SO4 - catalyst for low molecular weight fatty acids

• Advantages of COD

• Disadvantages of COD

• Significance of BOD/COD ratio

Type of wastewater BOD/COD ratio

Untreated 0.3 – 0.8

After primary settling 0.4 – 0.6

Final effluent 0.1 – 0.3

BOD/COD ≥ 0.5, wastewater easily treated by biological means BOD/COD < 0.3, Difficult to treated biologically

-Waste may be toxic or -microorganism need acclimatization

• Work example 1:

From the below data, determine the COD

-FAS titration for:

blank: 12.5 mL

sample : 10.3 mL

-volume of sample used: 1.5 mL

-FAS molarity: 0.09 M (answ: 1056 mg/L)

• Work example 2

The FAS used to titrate against the blank and sample for COD determination where the FAS needed was 13.50 and 11.30 mL respectively. If the sample volume used is 2.0 mL, calculate the COD

(prior experiment to standardise the FAS, found that 26.0 mL of FAS needed to titrate 10 mL 0.04M potassium dichromate)

6Fe2+ + Cr2O72- + 14 H+ ---- 2Cr3+ + 6 Fe3+ + 7H2O

Hint:

Calculate the molarity of FAS used