Vorlesung 2

Question 1

What does solubility depends on?

Answer 1

Solubility depends on the value of lattice energy and hydration energy
→ Dissolution may result in exo- or endothermal process

Question 2

What indicates the ionic content?

Answer 2

The electrical conductivity of water indicates its total ionic content

Question 3

How do the water molecules orbitals form?

Answer 3

A single oxygen molecuel forms a cross-like form. In combination with two hydrogen atoms the binding orbitals are greater than the free electron pairs

Question 4

What form does a water molecuel form?

Answer 4

Tethraedar

Question 5

Do salts have a low or high solbility?

Answer 5

high solubility

Question 6

Welche “Art” Wasser hat die höchste Leitfähigkeit?

Answer 6

Meerwasser mit 50.000 mykroSIemens pro Zenitimeter

Question 7

What’s the dissociation constant for water at 25°C?

Answer 7

10^-14

Question 8

What is pH?

Answer 8

pH is the negative logarithm of the hydrogen-ion concentration

Question 9

How do you define acid?

Answer 9

substance, dissociating in water forming hydrogen ions as only cation e.g. hydrochloric acid

Question 10

How do you define base (alkali)?

Answer 10

substance, dissociating in water forming hydroxyl ion as only anion
e.g. sodium hydroxide

Question 11

What is a monoprotic acid?

Answer 11

Yields one proton

Question 12

What is a diprotic acid?

Answer 12

Yields two protons

Question 13

What is activity?

Answer 13

Effective concentration
-> Non-ideal behavior due to electrostatic interactions

Question 14

What is the difference between Kw and Kw*?

Answer 14

Kw depends on activity (non-ideal behavior)
Kw* depends on H+ and OH- concentration (ideal behavior)

Question 15

What is the differnce between pH and pH*?

Answer 15

pH: Describes ideal behaviour (depends on 𝑯+ concentration)

pH*: Describes non-ideal behavior (depends on activity)

Question 16

What is alkalinity?

Answer 16

Ability of water to neutralize acids

Question 17

What is acidicity?

Answer 17

Ability of water to neutralize bases

Question 18

What are the concequences of calcium carbonat and carbon acid?

Answer 18

corrosion and scaling

Question 19

What are DWD and TrinkwV? What do they contain?

Answer 19

• Drinking Water Directive
• German Drinking Water decree (TrinkwV, 2001)

-> 48 parameter limits:
● Microbiological parameters ➔ Indicator organisms
● Chemical parameters ➔ Carbon, Nitrogen, Phosphorus
● Organoleptic parameters ➔ color, odour, taste

Question 20

What is UWWTD?

Answer 20

Urban Wastewater Treatment Directive (UWWTD):
● Minimum effluent quality (suspended solids, organic material, nutrients)
● Requirements dependant on treatment plant capacity

Question 21

Name physical parameters.

Answer 21

Temperature, flow rate, total dissolved solids (TDS), total suspended solids (TSS),
turbidity etc.

Question 22

Name organoleptic parameters.

Answer 22

Taste, odour, etc.

Question 23

Name general chemical parameters.

Answer 23

pH, dissolved oxygen (DO), nitrogen, phoshorous etc.

Question 24

Name organic chemical parameters.

Answer 24

Biochemical oxygen demand (BOD), total organic carbon (TOC),
adsorbable organic halogens (AOX) etc.

Question 25

Name microbiological parameters.

Answer 25

Bacteria count, viruses, protozoa, algae

Question 26

Name biological effect-parameters.

Answer 26

Toxicity on bacteria, daphnia, fish etc.

Question 27

What is COD?

Answer 27

COD = chemical oxygen demand ►Total quantity of oxygen required for oxidation to CO2 and water * all organic compounds can be oxidized by strong oxidizing agent under acidic condition * organic matter is oxidized regardless of biodegradability

Question 28

What is a classical methode to measure the COD?

Answer 28

Potassium dichromate is used to measure COD in classical method:

Question 29

What rule is usual for natural waters?

Answer 29

COD = 3*TOC

Question 30

What is BOD5? Name two methods to measure it.

Answer 30

BOD5 = Biochemical oxygen demand ►Direct method: * Direct measurement of oxygen before and after 5 days of incubation at 20°C * When a bacterial seed is not added to the dilution water, calculate the BOD as follows: 𝐵𝑂𝐷5 [𝑚𝑔/𝐿] = (𝐷1 – 𝐷2) ÷ 𝑃 ►Dilution method: * When a bacterial seed is added to the dilution water, calculate the BOD as follows: 𝐵𝑂𝐷5[𝑚𝑔/𝐿] = ((𝐷1 – 𝐷2) – (𝐵1 – 𝐵2) × 𝑓) ÷ P

Question 31

Name the different ratio of biodegradability from COD/BOD5.

Answer 31

Biodegradabiliy from COD/ BOD5 ratio * < 1.7: practically complete * 1.7-10: incomplete and/or presence of toxic compounds * > 10: practically not and/or complete inhibition

Question 32

How do you measure DOC and TOC?

Answer 32

Method: ● Inorganic carbon is stripped under acidic conditions ● Remaining organic carbon is oxidized and detected as CO2 ● In many natural waters: 𝐷𝑂𝐶 ≈ 𝑇𝑂C

Question 33

Where is phosphate used and what does it cause?

Answer 33

►Phosphate in surface water is used as fertilizer together with N ►Causes eutrophication – explosive growth of phytoplankton (algae bloom) ►Domestic wastewater is rich in phosphorus compounds (3 – 5 mg/L)

Question 34

How does the Bacterial quantification using flow cytometry work?

Answer 34

1. water sample contains bacteria whos DNA is markes with one or two fluorescent dyes 2. hydrodnamic focussing 3. laser points at bacteria which emits green or red fluorescens (1000 cells/sec)

Question 35

Can chlorination cause negativ effects?

Answer 35

- Addition of ClO2 can cause an increase of HNA - germination potential increased