Water and Wastewater treatment L2

Question 1

List some current statistics about water and world health

Answer 1

80% of sickness in world cause by inadequate water supply or sanitation
40% of the world population does not hae access to safe drinking water
Estimated 25,000 people die from water borne diseases everyday
Water borne diseases are leading cause of death in many populated areas of the world

Question 2

Sources of drinking water

Answer 2

Groundwater -shallow wells
-deep wells
Surfacewater -rivers
-lakes
-reservoirs

Question 3

Primary objectives of water treatment

Answer 3

1. Remove suspended material (turbidity) and colour
2. Eliminate pathogenic organisms
3. Remove hardness and other minerals

Question 4

Unit Processes in Water Treatment

Answer 4

1. Screening
2. Chemical Mixing (coagulation) and flocculation
3. Flotation/Sedimentation
4. Filtration
5. Softening
6. Disinfection
7. Pumped to community

Question 5

List Groundwater Properties

Answer 5

constant composition
high mineral content
low turbidity
low colour
low or no D.O.
high hardness
high Fe, Mn

Question 6

List Surface water Properties

Answer 6

variable composition
low mineral content
high turbidity
coloured
D.O. present
low hardness
taste and odor

Question 7

What is a Jar Test

Answer 7

A laboratory procedure to determine the optimum pH and the optimum coagulant dose. A jar test simulates the coagulation and flocculation processes

Question 8

Describe Dissolved air flotation (DAF)

Answer 8

Producing flotation by dissolving air in the water under pressure. When the pressure is released the water becomes supersaturated with air as millions of small bubbles form. These bubbles attach to any particles in the water causing their density to become less that than of water. The particles then rapidly float to the surface for collection and removal, leaving the clarified water behind.

Question 9

What are the boundaries for soft, moderate, hard and very hard water

Answer 9

Soft <50mg/L
Moderate =50-150mg/l
Hard=150-300 mg/l
Very Hard >300mg/l

Question 10

Definition of disinfectant and ideal properties

Answer 10

Operations aimed at killing or inactivating pathogenic microorganisms.
Toxic to pathogens, non toxic to humans, fast rate of kill, residual protection, economical

Question 11

Disinfection Methods

Answer 11

Chlorine- chlorine gas (poisonous- risk of gas leak)
-sodium hypochlorite (bleach)
Ozone
Irradiation with UV light
Sonification
Electric Current 
Gamma ray irradiation