Foreword

1.1 NECESSITY OF THE MANUAL

The creation of the manual 'Hydraulic design and management of wastewater transport systems' arose from the research project CAPWAT (CAPacity loss in wasteWATer pressure pipelines), which researched the mechanisms for the creation, stagnation and discharge of gas bubbles in wastewater pressure pipelines. During this six-year research programme, it was recognised that there is no hydraulic manual/guideline that focuses on the entire wastewater pressure pipeline system, the processes it includes, and the interaction between the pressure pipeline and the pumping station.

Processes that hardly or never occur in clean water transport systems (such as cooling water, drinking water) must be taken into account when designing a wastewater transport system. In case of wastewater, we have to deal with discontinuous supply. The type of sewer system (combined, separated, improved separated) determines the distribution of supply flow during both dry and wet weather.

The characteristics of the wastewater (such as surface tension and turbidity) vary in time and per location, as well as the waste load (floating and non-floating parts).

Usually, the designers and managers are used to thinking in terms of stationary processes. A wastewater pressure pipeline does not operate according to a stationary process, certainly not in dry weather conditions. Knowledge about the dynamic processes (variation in time) that occur in a wastewater transport system is necessary in order to determine the design and management guidelines.

Two important processes that the designer/manager deals with are:

• The process of the creation, stagnation and transportation of gas bubbles, and

• The water hammer phenomenon.

Another aspect is that the wastewater transport system is becoming more complex. Due to building larger sewage water treatment plants, wastewater is being transported over greater distances and increasingly more (and smaller) pipelines connect to the main sewers. The operation of the pumping stations is largely determined by how the entire system behaves. Insight into this operation is, therefore, crucial for proper design and management.

The manual 'Hydraulic design and management of wastewater transport systems' provides an overview of all the aspects and interrelatedness that are crucial for the hydraulic design and management of a wastewater transport system. A wastewater transportation system is understood to mean the pressure pipeline and/or the pressure pipeline system, including the pumping station and the receiving basin.

The central point of the design is to create an independent and safe system with the necessary transport capacity at minimum societal costs. Predominantly, the management aspect focuses on guidelines to maintain the design principles regarding capacity and required energy.

1.2 SCOPE OF THE MANUAL

The purpose of this manual is to create a compilation of all the hydraulic knowledge that is necessary for designing a wastewater transport system and to manage it operationally. The wastewater transport system is the link between the collection and treatment of the wastewater. The collection system includes, among others, the gravity flow sewage system from the house (or consumer) and service connection through street and main sewers up to the suction basins. The transport system, for which this manual was written, includes the suction basin, the sewage pumping station and the pressure pipelines.

In the Netherlands, municipalities and district water boards are the organisations responsible for the wastewater transport systems, as shown in Table 1.1.

This is a supplement to the existing and generally accessible information such as the Dutch Sewage Guideline. Modules B2000, B2100 and B2200 focus on the hydraulic design of the gravity flow system and provide designed flow rates for sewage pumping stations. Module C6000, pumping station management, mostly focuses on the design of the pumping station, as well as on management and maintenance organisation. This manual is also a supplement to existing standards, especially the Dutch standards NEN-EN 752:2008 Drain and sewer systems outside buildings – mostly about gravity flow sewerage – and NEN-EN 1671: Pressurized sewerage systems outside buildings – about pressure sewerage. This manual completely focuses on the hydraulic aspects of the design and management of wastewater transport systems.

In addition, many organisations have manuals about the design and management of pumping stations. These manuals mostly describe civil engineering, mechanical and electro-technical issues.

For now, this manual 'Hydraulic design and management of wastewater transport systems' should not be viewed as a replacement of such manuals, but as a supplement.

The following stages are recognised in the life cycle of a pipeline system (see also the Dutch standard NEN-EN 3650 'Requirements for Pipeline Systems'):

- Design

- Construction and testing

- Usage stage (operational management)

Before the design, the development stage takes place, also known as the preliminary design. The preliminary design is mostly determined by the usage requirements (functional requirements) and planning aspects. The design stage can be divided into the basic design stage and the detailed design stage. In the basic design stage, the definite points of departure (schedule of requirements) for the design are determined. In the detailed design stage, the calculations, drawings and specifications are established for the realisation and operational management stage. There is no fine distinction between the two design stages and, in this manual, it is summarised as 'design'.

The flow chart in Figure 1.1 describes the scope and interconnectivity of this manual. The starting point is that the preliminary design is available, although some points of attention are still mentioned. Therefore, this flow-chart emphasises the design of the transport system, followed by a chapter about the delivery of the installation, which describes how to test whether the built installation complies with the hydraulic design criteria. The construction of the installation is a stage that takes place between the design stage and delivery. In this stage, there are no specific hydraulic focal points and, therefore, this manual does not include a separate chapter about the building stage of the transport system.

During the utilisation stage, the purpose of this manual is to maintain the desired capacity at minimal societal costs.

1.3 AUTHORS AND EDITORIAL STAFF

In 2010, the first version of this manual was drafted by Michiel Tukker (B.Eng), Kees Kooij...