Lecture 2+3: EPANET (Fresh water supply)

Question 1

Water supply is a complicated topic because it relates to several different aspects. Which?

Answer 1

Governance, Finance, Social, Political, Health, Infrastructures, Engineering

Question 2

Mention the governance and finance authorities related to water supply.

Answer 2

EU, Danish EPA, Danish Competition and Consumer Authority, Municipality, Danish Business Authority

Question 3

What are the social and political aspects of water supply?

Answer 3

o Water resources vs. public awareness
o Human rights vs. paying water bills
o Public vs. private service
o Climate changes vs. efficiency improvement
o Export and international aids
 SDG 6.1 Safe and affordable drinking water
 SDG 6.a Expand water and sanitation support to developing countries

Question 4

Mention the health authorities related to water supply

Answer 4

Danish Patient Safety Authority
Danish Health Authority
Region

Question 5

What are the overall infrastructure of water supply (4 steps)?

Answer 5

1) Water abstraction
2) Water treatment
3) Water distribution
4) Water consumption

Question 6

Engineering is related to three main areas. Which?

Answer 6

1) Water production
2) Water distribution
3) Water consumption

Question 7

Within the water production area we are operating with three different water sources. Which?

Answer 7

• Surface water –> demands before use:
  o coagulation/flocculation, sedimentation, filtration and disinfection
• Sea water –> demands before use:
  o desalination (reverse osmosis), disinfection
• Groundwater –> demands before use:
  o abstraction (finding water through geographical surveys  collecting the water by making a borehole station), aeration and filtration

Question 8

The treatment of water before consumption includes?

Answer 8

• Water softening –> pellets or ion exchange
• Removal of pesticide residues:
  o 2,6-dichlorobenzamide (BAM)
  o N,N-dimethylsulfamide (DMS)
  o Desphenyl Chloridazon (DPC)

Question 9

When water is transported from treatment plant to consumers two major factors have to be tracked. Which?

Answer 9

Supply pressures
Water quality

Question 10

What is Non-Revenue Water?

Answer 10

• Water that is not creating revenue –> unbilled consumption (free drinking fountains), leakage, meter inaccuracies etc.

Question 11

The Infrastructure Leakage Index (ILI) is expressed by the formula: ILI = CARL/UARL. What is CARL and UARL?

Answer 11

• CARL: Current Annual Real Losses, equal to real losses over one year
• UARL: Unavoidable Annual Real Losses, a certain volume of real losses that is unavoidable.

Question 12

Explain Top-Down assessment and Bottom-Up assessment.

Answer 12

Top-down assessment: Inspect existing systems and collect available data to complete a Water balance Analysis

Bottom-up assessment: Field inspections and field testing to validate the results from the top-down assessment and reduce or eliminate inaccurracies and uncertainties in the Water Balance Analysis

Question 13

What are the methods for reduction of Non-Revenue Water?

Answer 13

o Pressure Management
o Speed and quality of repairs
o Active leakage control
o Strategic planning

Question 14

Explain the three types of active leakage control.

Answer 14

 None: Leak Detection activities are only performed based on reported leaks by staff or customers.

 Scheduled: Leak Detection activities are conducted cyclically at regular intervals for each area.

 Event driven: Leak Detection activities are conducted based on performance indicators, events and alarms.

Question 15

In strategic planning we are operating with the term; District Metered Area (DMA). Explain this term.

Answer 15

• Size of DMA (generally between 1,000 and 2,500 connections)
• Meet the special requirements from special consumption types, e.g. hospitals, food productions, fire sprinklers etc.
• Best with unified water consumer types.
• Limited number of valves that must be closed to isolate the DMA –> needs to be possible to isolate the DMA in case of disease spread, leakage or other issues.
• Limited number of flow meters to measure inflows and outflows
• Limited ground-level variations
• Avoid crossing of major water bodies, railways, highways etc.
• Allow simple division into sub-zones with few valve opening and closing.
• Sectioning the network in DMS allows for monitoring the level of water loss.
• It is one of the most cost-effective ways to spot leaks and thereby reduce non-revenue water

Question 16

What are the basic pipeline hydraulic equations used for calculating pressure drops?

Answer 16

• Darcy-Weisbach Equation
• Colebrook-White Equation
• Hazen-Williams Equation

Question 17

Explain what Renolds number is.

Answer 17

Gives information about the risk of turbulences – Velocity, Diameter, Density and Viscosity (turbulent: Re is above 4000)

Reynolds number is expressed by: (density * velocity * length)/viscosity

Question 18

What are the advantage and the disadvantage of the Hazen-Williams equation?

Answer 18

Advantage: Reynolds number not involved.

Disadvantage: Can only be used for water.

Question 19

What is EPANET?

Answer 19

EPANET is a water distribution system modelling software package developed by the US Environmental Protection Agency (US EPA).

Question 20

What can EPANET be used for?

Answer 20

• EPANET can be used for modeling existing Water Supply Networks, supporting the design of extensions or even the design of new water supply systems.
• EPANET allows both hydraulic and water quality simulations.

Question 21

Which types of elements are we operating with in EPANET?

Answer 21

• Nodes
  o Junction nodes
  o Reservoir nodes
  o Tank nodes
• Links - defined between two nodes.
  o Pipes
  o Pump
  o Valves (different types)

Question 22

Explain what assignment 2 is about.

Answer 22

In the EPANET assignment the distribution of freshwater is analysed for a specific area over a period of 168 hours. The distribution network contains different nodes with different pressures. In the assignment we are investigating how the pressure is altered under different scenarios. These scenarios could be leakage of one pipe. In a scenario of a leakage the pressure will fall downstream the leakage but the pressure will remain constant before the leakage. In a scenario with low pressure we are able to use a pump for increasing the pressure.
In a event where we are closing the pipes due to reparations nothing will happen to the upstream pressure and flow.

Question 23

Explain head loss

Answer 23

Head loss is a measure of the reduction in the total head (sum of elevation head, velocity head and pressure head) of the fluid as it moves through a fluid system.

Question 24

What is head loss dependent on

Answer 24

The head loss that occurs in pipes is dependent on the flow velocity, pipe length and diameter, and a friction factor based on the roughness of the pipe and the Reynolds number of the flow.

Question 25

Hydrologic models fall into one of two categories. Which two catagories?

Answer 25

Continous and event based

Question 26

Explain continous based hydrologic models.

Answer 26

Continuous time models typically are used for long-term simulations covering many days/months/years maintaining a continuous balance of the hydrologic process. Therefore, even in the absence of precipitation, the model continues to update the water balance.

Question 27

Explain event based hydrological models.

Answer 27

Event-based models are usually short duration, covering only a single cycle of variables, such as storms and responses to such events. These models are also classified as lumped and distributed model based on the model parameters as a function of space and time and deterministic and stochastic models based on the output criteria.