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With respect to the drainage method, i.e. the “way of draining sewage” [DIN4045:2016], it is, for example, distinguished between: (Image: Combined system according to Girnau) Combined drainage method/ combined system: "drain and sewer system designed to carry both foul wastewater and surface water in the same pipeline(s)" [EN16323:2014]. (Image: Separate system according to Girnau) Separate drainage method/ separate system: "drain and sewer system, usually … |
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(Image: Schematic depiction of drainage in combined sewer systems - illustration of combined wasterwater overflow for peak flows) Drain and sewer system designed to carry both wastewater and surface water in the same pipeline- or sewer system. A discharge from a combined sewer system, referred to as a combined sewer overflow (CSO), occurs in response to rainfall and/or snowmelt because the carrying capacity of the combined sewer system is exceeded. … |
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(Image: Pros and cons) (Image: Drainage of wastewater and surface water in combined systems) Advantages combined system
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(Image: Schematic depiction of drainage in seperate systems) Drain and sewer system, usually composed of two pipe-or sewer systems for the separate drainage of wastewater and surface water. The wastewater is led into the treatment works to be treated there. Depending on its level of pollution, the surface water is discharged into the receiving water either with or without prior treatment. |
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(Image: Pros and cons) (Image: Drainage of wastewater and surface water in separate system) Advantages separate system
Disadvantages separate system
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Both for the combined and separate system, there are options that allow for a separate discharge of the precipitation water. These are summarised under the term of modified combined system or modified separate system. Modified combined system (Image: Modified combined system) Modified separate system (Image: Modified separate system) |
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Modified combined system: Drain and sewer system to discharge both wastewater and precipitation water in the same pipe- or sewer system, whereas the precipitation water is categorised according to its level of pollution. The target is to avoid the discharge of the precipitation water in the sewer network as far as possible. Precipitation water that does not require any prior treatment is discharged separately in bodies of water of the vicinity, drained … |
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Modified separate system: Drain and sewer system that is usually composed of two pipe networks- or sewer systems for the separate discharge of wastewater and precipitation water. The target is to keep the precipitation water away from the surface water sewer as far as possible and to discharge it decentrally, semi-centrally or centrally into a seepage system or to store it intermediately in situ to be used at a later point in time. (Image: Modified … |
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New concepts of drainage systems are not restricted to separation and collection of rainwater, but enable a comprehensive separation and collection of waste water streams. This results in pipelines for:
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In the scenario "municipal water cycle" parts of the sewage streams are handled separately to allow more efficient and more competitive wastewater cleaning processes and the closing of nutrient cycles. (Image: Scenario "municipal water cycle") |
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The scenario "small-scale cycles of matter“ leaves the responsibility for their supply and discharge with the private households and thus defines the realization of the cost-by-cause principle. A prerequisite for the wide autarchy is the building up of circuitry within the single houses or quarters. (Image: Local recycling scenario) |
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Congratulations! You have successfully finished this lesson. Next you will have the opportunity to review the newly acquired knowledge with an interactive questionnaire. You can of course still navigate back to any point in the lessons if you wish to review a specific point or subject. Stay curious! |
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Aug 10, 2015 Drain and sewer systems are used for the collection and discharge of wastewater. The module provides basic knowledge about the objectives, functional requirements, design and operation, modes of operation, and drainage methods of drain and sewer systems. This module focuses exclusively on drain and sewer systems that are operated as gravity systems. After completing this module, you will have knowledge regarding:
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Aug 11, 2015 How to differentiate the cross-sectional dimensions of a pipe? Sewers with widely varying cross sections and dimensions have been used since the beginning of modern sewage technology, and some are still in use in their original form to this day. The differentiation of cross-sectional dimensions takes place via the abbreviation for nominal size (internal diameter) "ID“`and the abbreviation for the nominal diameter of the outer diameter “OD”. Definition … |
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Aug 12, 2015 What aspects have an influence on the shape and dimensions of the pipe cross-section? The dimension of the pipe cross-section is derived from the hydraulic dimensioning. This is particularly the case combined sewer systems where the shape of the pipe cross section has to match to the strongly fluctuating flows. Further influence on the shape and dimensions are:
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Aug 12, 2015 What are the main cross-sectional shapes? The most common cross sectional shapes, also called sewer profiles, are the circular, the standard ovoid and the standard arch cross sections. They are summarised under the term standard shapes (Image: Standardised sewers cross sections with geometrical values at full filling according to DIN 4263 (06.2011)) |
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Aug 12, 2015 The circular cross section has been and still is preferred in use because of its structural and hydraulic advantages in the nominal size range 100 ≤ DN/ID ≤ 500. Since the development of reinforced- and prestressed concrete technology and, consequently, a continuous improvement of the pipeline manufacturing and pipeline construction/engineering methods, pre-fabricated pipes with a circular cross section up to DN 4000 are also used for main collectors. |
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Aug 12, 2015 The ovoid cross section has been used for the first time in London in 1846 and arrived in Germany about 1870 [Frühl10]. Hydraulically, the ovoid cross section has particular advantages in the drainage of larger, erratic drain flows, as e.g. in combined sewers with small dry weather flows Qt/Qv =0.22. Additionally, this special shape allows great cleansing effect and high flow velocity even with low water level in the pipeline. Just like the arch cross … |
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Aug 12, 2015 Arch cross sections offer advantages for large flows and a restricted construction height. Although the hydraulic efficiency for partial filling is poor, yet the shape is structurally advantageous because it approximates the course of the pressure line. In the past, two more cross sectional shapes have been in use that have been derived from the standard arch cross section, namely the “extended arch cross section” and the “squashed arch cross section”. |
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Aug 12, 2015 In particular cases, e.g. in the construction of stormwater sewers, stormwater retention tanks or for defined location collecting points, rectangular cross sections have been and are still used. DIN 4263 in its edition of 1991 recommended about 800 mm as the smallest clear axial dimensions. The invert has a cross-slope to the low point at the centre of the cross-section. [DIN4263:2011] (Image: Rectangular cross section - profile) (Image: Reinforced … |
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Aug 12, 2015 In addition to these standard cross sections there are numerous other cross sectional shapes and -sizes, that, partly, have also been standardised in the past and that are still used today in individual cases. Examples for non-standardised cross sections in practice: (Image: Non-standardised sewer cross section - Parabolic cross section made of masonry) (Image: Non-standardised sewer cross section - Channel cross section made of masonry) (Image: Non-… |
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Aug 12, 2015 Are there any minimum nominal sizes that need to be adhered to? The nominal sizes of drains and sewers must have a sufficient capacity to discharge the designed/calculated rates of inflow. In this context it is very important to properly define the minimum nominal sizes within sewer systems. Criteria for these definitions could be a guaranteed disposal also of coarser and more bulky materials within the flow, (thus reducing the risk of blockages), … |
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Definition: According to DIN EN 1610, depth of cover (formerly also called depth position) is defined as “the vertical distance from the top of the pipe barrel to the surface." [EN1610:2015] The lowest level of cellars/basements to be drained normally defines the minimum depth of cover of combined water and wastewater sewers. Another aspect which may influence the minimum depth is the position of the receiving water body. (Image: Depth of cover- vertical … |
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