Standards for the Dimensioning and Design of Stormwater Structures in Combined Sewers

Transcription

1 GERMAN ATV RULES AND STANDARDS W A S T E W A T E R - W A S T E STANDARD ATV - A 128E Standards for the Dimensioning and Design of Stormwater Structures in Combined Sewers April 1992 ABWASSER ABFALL GEWÄSSERSCHUTZ GERMAN ASSOCIATION FOR THE WATER ENVIRONMENT

2 GERMAN ATV RULES AND STANDARDS W A S T E W A T E R - W A S T E STANDARD ATV - A 128E Standards for the Dimensioning and Design of Stormwater Structures in Combined Sewers April 1992 ISBN Distribution: GFA Gesellschaft zur Förderung der Abwassertechnik e.v. Theodor-Heuss-Allee 17 D Hennef P. O. Box D Hennef Tel / Fax: / vertrieb@atv.de Internet:

3 The ATV ad hoc Working Group 1.9.1/1.9.3 in the ATV Specialist Committee 1.9 "Assessment and Treatment of Stormwater Discharge", who prepared this ATV Standard A 128, is made up from the following members: Dr.-Ing. Göttle, Kempten, (Chairman) Prof. Dr.-Ing. Brunner, Karlsruhe Dr.-Ing. Durchschlag, Bochum Dipl.-Ing. Freund, Wiesbaden Prof. Dr.-Ing. Geiger, Essen Dr.-Ing. Gniosdorsch, Frankfurt Dipl.-Ing. Jacobi, Darmstadt Dr.-Ing. Meißner, München Dipl.-Ing. Pawlowski, Berlin Dr.-Ing. Pecher, Erkrath Dipl.-Ing. Schitthelm, Düsseldorf Dr.-Ing. Schmitt, Kaiserslautern Dipl.-Ing. Sperling, Essen Dr.-Ing. Verworn, Hannover Dipl.-Ing. Willems, Essen Prof. Dr.-Ing. Wolf, Kassel The Standard presented here has been prepared within the framework of the ATV committee work, taking into account the ATV Standard A 400 "Principles for the Preparation of Rules and Standards" in the Rules and Standards Wastewater/Wastes, in the January version. With regard to the application of the Rules and Standards, Para. 1 of Point 5 of A 400 includes the following statement "The Rules and Standards are freely available to everyone. An obligation to apply them can result for reasons of legal regulations, contracts or other legal grounds. Whosoever applies them is responsible for the correct application in specific cases. Through the application of the Rules and Standards no one avoids responsibility for his own actions. However, for the user, prima facie evidence shows that he has taken the necessary care. All rights, in particular those of translation into other languages, are reserved. No part of this Standard may be reproduced in any form by photocopy, microfilm or any other process or transferred or translated into a language usable in machines, in particular data processing machines, without the written approval of the publisher. Gesellschaft zur Förderung der Abwassertechnik e.v. (GFA), Sankt Augustin 1992 German 0riginal produced by: Druck Carl Weyler KG., Bonn 2 December 1992

4 Contents 1 Scope of Application and Terms 7 2 Objective of Stormwater Treatment Principles Method of Approach 7 3 Requirements on Stormwater Treatment Technical Requirements for the Normal Case (Normal Requirements) Advanced Requirements Overall Consideration of a Lake or River Common Requirements in the Overall Drainage Area Combined Requirements with Different Surface Waters 10 4 Planning Principles Reduction of the Amount of Wastewater Produced Rainwater Run-off Domestic and Industrial Wastewater Flow Sewer Infiltration Water Flow Measures for Wastewater Treatment in the Combined Wastewater System Intermediate Storage of Combined Wastewater Redistribution of Rainfall Run-offs Wastewater Treatment Measures Structures with Overflow Stormwater Overflows Stormwater Tanks with Overflow Stormwater Tanks Retaining the First Flush of Stormwater Stormwater Tanks with Overflow for Settled Combined Wastewater Composite Tanks Sewers with Storage Capacity and Overflow Main and By-pass Streams Arrangement of Several Stormwater Tanks with Overflow Parallel Stormwater Tanks with Overflow Series Stormwater Tanks with Overflow Stormwater Holding Tanks 20 5 Planning Scope Determination of Actual Status Determination of the Planning Status Planning Periods Standard and Variant Investigations 22 6 Calculation Principles Sizes of Catchment Areas Annual Precipitation h Pr Surface Areas A CA and A is Flow Time t f Mean Terrain slope group SG m 23 December

5 6.2 Discharges Combined Wastewater Discharge to the Sewage Treatment Plant Q cw Dry weather Flow in Daily Average Q dw Hourly Peak Flow with Dry Weather Flow Q dwx Rainwater Run-off from Separate Areas Q rs Rainwater Run-off Q r Critical Rainwater Run-off Q rcrit Critical Combined Water Flow Q crit Mean Rainwater Run-off During Overflow Q ro Discharge Rates Dry Weather Discharge Rate q dw Rainwater Run-off Rate q r Dry Weather Concentration c dwc Mean Mix ratio in Overflow Water m 27 7 Determination of the Necessary Total Storage Volume Determination of the Permissible Overflow Rate Influence of Heavy Polluters a p Influence of Annual Precipitation a h Influence of Sewer Deposits a a Dimensioning Concentration in the Dry Weather Flow c d Theoretical Overflow Concentration c cc Permissible Annual Overflow Rate e o Necessary Total Storage Volumes Accountable Storage Volumes Minimum Storage Volumes 33 8 Dimensioning of Individual Structures with Overflow Simplified Distribution Method Approach Scope of Application Verification Procedures Special Basic Facts Precipitation Loading Registration of the Sewer Network Fictitious Central Tanks Approach Preliminary Calculation to Determine Permissible, Model-Dependent,Overflow Loads Determination of the Rehabilitation Requirement Planning of Measures Further Verification Parameters Requirements on Pollution Load Calculation Methods 38 9 Dimensioning of Individual Structures with Overflow Stormwater Overflow Stormwater Tanks with Overflow 41 4 December 1992

6 9.3 Sewer with Storage Capacity and Overflow Sewer with Storage Capacity with Top-end Overflow Sewer with Storage Capacity with Bottom-end Overflow Stormwater Holding Tanks Construction and Operation of Structures With Overflow Stormwater Overflows General Method of Construction of Stormwater Overflows with Overflow Weirs Method of Construction of Stormwater Overflows with Floor Opening (Spring Overflow) Stormwater Tanks with Overflow Method of Construction of Separation Structures and Overflows Method of Construction of Stormwater Tanks with Overflow Method of Construction of Sewers with Storage Volume Method of Construction for Discharges Maintenance and Operation Maintenance Facilities Cleaning and Flushing Facilities Measurement Facilities Other Records Dimensioning Example Local Situation Necessary Total Storage Volumes Simplified Distribution Procedure Verification Procedure Hydrologic Method Hydrodynamic Method Presentation of Results Dimensioning of Stormwater Overflows Stormwater Overflow SO1 in Commercial Area Stormwater Overflow SO2 in Sub-area Terms References 60 Appendix 1 64 Notes on Advanced Requirements 64 Protection or Management Need 64 Effects 64 Assessment Criteria 66 Measures 67 Further action 67 December

7 Appendix 2 68 Pollution Load Calculation Methods Hydrologic-Empirical Methods Deterministic Models Hydrologic-Deterministic Models Hydrologic-Hydrodynamic Models Characterisation of Pollution Load Calculation Methods 70 Appendix 3 72 Appendix 4 73 Calculation Formulas for Figs. 12 and Appendix 5 Discharge Diagram for the Simplified Dimensioning Procedure (Th. Bettmann) 74 6 December 1992

8 1 Scope of Application and Terms These Standards apply for structures with overflows in the overall system of a combined wastewater sewer system within the catchment area of sewage treatment plants. It replaces the previous ATV Standard A 128 from 1977/1. Structures with overflows in combined systems are structures with an overflow into a lake or river such as, for example, stormwater overflows (SO), stormwater tanks with overflows (STO) and sewers with storage capacity and overflow (SSCO). Stormwater holding tanks (SHT) are dealt with in ATV Standard A 117. Stormwater sedimentation tanks (SST) serve for the treatment of stormwater with separate systems. They are also not dealt with here. Information is given in the ATV Working Report in "Korrespondenz Abwasser" (1980), Vol Objective of Stormwater Treatment For water management and cost reasons the priority task of the planning of measures for wastewater collection and stormwater treatment is the avoidance of stormwater overflow into the sewer system wherever this is possible. For the remaining discharges, for technical water management and economic reasons, stormwater structures with overflow are located in combined wastewater sewers. With precipitation run-off, high pollutant loads can occur which, with discharge into lakes and rivers, could load these heavily. Although the loadings appear only temporarily these can exceed those from the effluents of sewage treatment plants several times over during rainfall run-off. The task of stormwater treatment is so to limit the rainfall run-off into the sewage treatment plants that there the desired effluent values are maintained and, at the same time, the surge-type loadings of the lakes and rivers remain within acceptable limits. The aim of stormwater treatment must be the best possible reduction of the total emissions from stormwater overflows and sewage treatment plants within the scope of water management requirements. An effective protection of lakes and rivers and of sewage treatment plants from excessive loadings is to be expected if the necessary stormwater treatment takes place according to the criteria of these Standards. 2.1 Principles The objective can be achieved with various formulations - from discharge avoidance to substance retention. Stormwater overflows are fundamentally to be assessed together with the sewage treatment plant for interrelated catchment areas of a section of a lake or river. Requirements on the sewage treatment plant runoffs and on the stormwater overflow installations should be matched in their effectiveness for the lake or river. The regional and network specific quantities precipitation, flow time, gradients, sewage storage capacity, heavy pollutants and areas drained with a separate system have a considerable influence on the overflow quantity and concentration. These are therefore taken into account. 2.2 Method of Approach Having taken into account the given possibilities of discharge reduction or discharge avoidance, both prerelieved and non-prerelieved overflow structures are to be dimensioned for the remaining discharges. The effectiveness of a stormwater treatment here depends not only on the available storage volume but also particularly on the arrangement, design and operation of the installations (Chaps. 4 and 5). Basically, there two procedures available for the dimensioning and verification of the objective of the stormwater treatment: - simplified dimensioning procedure using diagrams (Chap. 8.1), - verification procedure using pollutant load lculations (Chap. 8.2). December