1
Module 2 Describe the water supply system
Session structure
• Overview
• System components and description
• Outputs
• Challenges
• Factors to consider
• Exercise
2
Module 2 Describe the water supply system
Overview
• First task of WSP team
• Aim: To enable risks to be assessed and managed
• Involves field investigations and local knowledge
• Each system assessed on its own
• Involves documentation, review and update
3
Module 2 Describe the water supply system
System components
Catchment
Treatment
Distribution
User
Water supply and quality
Land use
Abstraction method and location
Filtration
Coagulation
Clarification
Disinfection
Networks
Service reservoirs
Tankers
General public
Potable
4
Module 2 Describe the water supply system
Description also involves
• Knowing water quality standards
• Assessing the likely changes to source water quality following
changes in weather
• Describing any interconnectivity of source waters (e.g. 2 wells, 1
aquifer)
• Gathering information relating to water storage
• Identifying the operational & managerial staff involved
• Familiarization with existing documents relating to the supply
• Etc.
5
Supply flow diagram
Coagulant
& pH
adjustment
Tropical
forest
pH
Turbidity
UV254
pH
Turbidity
UV254
pH
pH
pH
Turbidity
UV254
River
catchment
1
Run-off
Abstraction
from river
Private
connection
RAPID MIX
FLOCCULATOR
CLARIFICATION
FILTRATION
Output 1
Raw water
transfer
Water
treatment
Distribution
system
Users
City 1
Refer to C1 description
6
Module 2 Describe the water supply system
Output 2 – understanding of current water quality
Regulatory limit
Nitrate concentration leaving works
7
Module 2 Describe the water supply system
Outputs 3 Identification of users and uses
Intended use
Intended users
The water supplied is intended for
general consumption by ingestion.
The organization provides water to the
general population.
The water supplied is also for bathing
and laundry. (Note that these
activities can also result in dermal
exposure and inhalation – through
showering – of waterborne hazards.)
The intended consumers do not
include those that are significantly
immunocompromised or industries
with special water quality needs.
These groups are advised to provide
additional point-of-use treatment.
Foodstuffs may be prepared from the
water.
8
Module 2 Describe the water supply system
Challenges
• Out of date or no maps
• Unknown catchment land use
• Little stakeholder interaction / unknown stakeholders
• Unknown risks
• Limited staff time / resources available
• Out-of-date documentation
9
Module 2 Describe the water supply system
Factors to consider
Options = photographs,
symbols, drawings
Use flow direction arrows
Cross-reference to other
documents
Continually update
e.g. maps, treatment flow diagrams
10
Module 2 Describe the water supply system
Exercise – create a system flow diagram
• In small groups
• Use symbols to describe a supply system known to you
• Describe from catchment to user
• Add star where information is not known
• Add banner to cross-reference to other documentation
• List the most important items to consider
• Plan how to obtain unknown information
• 25 minutes
11