Describe the water supply system

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

incident
Module 2 Describe the water supply system
Revise WSP
following incident
(Module 11)
Assemble team
(Module 1)
Describe the water
supply system
(Module 2)
Plan & carry out
periodic WSP review
(Module 10)
Identify the hazards
& assess the risks
(Module 3)
Develop supporting
programmes
(Module 9)
Prepare
management
procedures
(Module 8)
System Assessment
Operational monitoring
Management & communication
Feedback
Verify the
effectiveness of the
WSP (Module 7)
Determine & validate
control measures,
reassess & prioritise
risks (Module 4)
Develop, implement
& maintain an
improvement plan
(Module 5)
Define monitoring of
control measures
(Module 6)
4

Module 2 Describe the water supply system
System components
Catchment
Water supply and quality
Land use
Abstraction method and location
Treatment
Distribution
User
Filtration
Coagulation
Clarification
Chlorination
Networks
Service reservoirs
Tankers
General public
Potable
5

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
• Familiarisation with existing documents relating to the supply
• Etc.
6

Tropical
forest
River
catchment
1
pH
Turbidity
UV254
Coagulant
& pH
adjustment
pH
Supply flow diagram
pH
pH
Turbidity
UV254
pH
Turbidity
UV254
Run-off
Private
connection
RAPID MIX FLOCCULATOR CLARIFICATION FILTRATION
Abstraction
from river
Raw water
transfer
Output 1
Water
treatment
Distribution
system
Users
City 1
Refer to C1 description
7

Example: System mapping
Dennery and Mabouya Valley WSS, St. Lucia

Example: System mapping
Dennery and Mabouya Valley WSS, St. Lucia

Example: catchment description
Dennery & Mabouya Valley WSS, St. Lucia

Example: System description
Dennery and Mabouya Valley WSS, St. Lucia

Module 2 Describe the water supply system
Output 2 – understanding of current water quality
Regulatory limit
Nitrate concentration leaving works
12

Example: water supply quality description
Dennery & Mabouya Valley WSS, St. Lucia

Example: water supply quality description
Dennery & Mabouya Valley WSS, St. Lucia

Example: water supply quality description –
sample point monitoring mapping
Dennery & Mabouya Valley WSS, St. Lucia

Example: water supply quality description –
sample point monitoring
Dennery & Mabouya Valley WSS, St. Lucia

Module 2 Describe the water supply system
Outputs 3 Identification of users and uses
Intended use
The water supplied is intended for
general consumption by ingestion.
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)
Foodstuffs may be prepared from the
water.
Intended users
The organization provides water to the
general population.
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.
17

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
18

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
19

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
• 35 minutes
20