The training equipment

The EDS® – Water Management is a modular training equipment which simulates

the core processes of water and wastewater treatment plants.

The EDS Wastewater Transport System

Wastewater transport

EDS® – Water

Management

Festo Didactic

11/2013

Wastewater transport

Introduction to the learning module “Wastewater transport”

Wastewater is produced from the use – and contamination – of water in households, commerce, industry

and agriculture. It is supplemented by runoff from roads, roofs and other paved areas following rain.

It is transported to wastewater treatment plants by gravity and, if necessary, by powerful pumps. Rainwater

is often transported to the wastewater treatment plant with other wastewater in a “combined rainwater and

sanitary sewage system” (short: combined sewer). Runoff from rainfall regularly multiplies the flow in the

combined sewer, it reaches ma multiple of the dry weather flow.

Flooding of a lane near a pumping station in the countryside. Cover plates of manholes in the lane were lifted off by the submerging

water, front left side. (Source: Peter Maurer, ISWA, University of Stuttgart, Germany)

Private households generate between 50 l and 400 l of wastewater per person per day, depending on the

region. Where wastewater treatment data are not available, the quantity of wastewater from households is

determined based on drinking water consumption. For example: In 2010, all municipal wastewater in the

German state of Baden-Württemberg was treated in central wastewater treatment plants. The Baden-

Württemberg State Bureau of Statistics stated an average volume of 147 l per resident per day.

Depending on its origin, wastewater can contain many dissolved and suspended contaminants: highly

degradable organic materials, persistent organic materials, salts, heavy-metal compounds, and fertilizers.

Some of these materials are harmful to humans, animals or water organisms, some may endanger the

quality of surface water, and some are corrosive. Solid material tends to settle. Sewer systems have to

provide transport, prevent blockage of pipes and support a stormwater overflow into the rivers as clean as

possible. This learning module focuses on the topics of hydraulic capacity of pipes, transport of solids and

control of overflow basins.

2 © Festo Didactic GmbH & Co. KG

Wastewater transport

Exercise: Transport of solids in sewers with varying flow rates

Problem description

Different flow rates occur particularly in combined rainwater and sanitary sewage systems. The EDS Water

Management has a transparent pipe or “gravity sewer” simulating the wastewater discharge with plastic

granules. Thus, the behaviour of solids in a sewer system with different flow rates can be tested and

observed directly.

Dosage of solids with screw feeder

Layout

In the EDS® – Water Management training equipment, solids in the wastewater are represented by coloured

plastic granules. These granules can be dosed into the storage tank of the Wastewater Transport System

(B303) by a metering screw. The granules behave similarly to solids in wastewater.

Learning outcomes

When you have successfully completed the following exercises you can:

• Describe sedimentation in a combined sewer during dry-weather periods.

• Name the basic mechanisms that lead to a first flush.

• Explain the impact of blockage of a combined sewer by solids.

© Festo Didactic GmbH & Co. KG 3

Wastewater transport

Tasks

1. Simulating dry water flow

Switch on the pump with a flow of 0.5 l/min or less. The flow rate through gravity sewers is now equivalent

to dry-weather flow. Add a dose of granules into the sewer by turning the dosage of solids (screw feeder

M351) about 3 to 5 times.

a) What happens in the transparent pipe or gravity sewer?

Like solids in the real world, the plastic granules settle in the pipe.

2. Simulating runoff during rain

The pump continues to deliver the dry-weather flow. Now simulate a runoff during rain by pouring water

manually into the system.

a) What happens to the plastic granules that settled in the pipes during the dry-weather period?

The plastic granules are flushed by the significantly greater flow in the pipe. The concentration of

granules is high, especially in the beginning of the flush.

b) What is this effect called in reality?

This effect is called “first flush” and occurs at the beginning of a rain event. As in the exercise solids

concentration is very high then.

The transparent gravity sewer with plastic granules

4 © Festo Didactic GmbH & Co. KG

Wastewater transport

3. Varying the amount of solids

The pump continues to deliver the dry-weather flow. Now, add a considerably higher quantity of the

granules, as compared to the previous exercise.

a) What effect does the large quantity of granules have?

The plastic granules settle. The large quantity results in obstructions in the pipe.

b) What effect does this have on the hydraulic capacity of the pipes?

Large quantities of settled plastic granules decrease the hydraulic capacity of the pipes up to

blockage. Impounding results, when the hydraulic capacity is exceeded.

c) See whether impounding or even blockage can be caused in the model!

In the real world this is called blockage. In extreme situations this can result in unplanned

submergence.

d) Increase the flow rate simulating a rain event, as in the previous task initiating a first flush.

© Festo Didactic GmbH & Co. KG 5

Festo Didactic GmbH & Co. KG

Rechbergstraße 3

73770 Denkendorf

Germany

Internet: www.festo-didactic.com

E-mail: did@de.festo.com