Waterborne Sanitation Design Guide - WRC

1 WaterborneSanitation Design GuideSJ van Vuuren & M van DijkTT 481/11TT 481/11 Waterborne Sanitation Design Guide Waterborne Sanitation Design Guide Report to the WATER RESEARCH COMMISSION By S J van Vuuren and M van Dijk University of Pretoria WRC REPORT NO. TT 481/11 MARCH 2011 Obtainable from: Water Research Commission Private Bag X03 Gezina 0031 The publication of this report emanates from a project entitled: Development of a South African Guide for the Design and Operation of Waterborne Sewerage Systems (WRC Project No. K5/1744) DISCLAIMER This report has been reviewed by the Water Research Commission (WRC) and approved for publication. Approval does not signify that the contents necessarily reflect the views and policies of the WRC, nor does mention of trade names or commercial products constitute endorsement or recommendation for use.

2 ISBN 978-1-4312-0078-8 Set no 978-1-4312-0080-1 Printed in the Republic of South Africa Waterborne Sanitation Design Guide i Executive Summary The general health of the population improves when people have access to basic clean water supply and Sanitation . The safe disposal of human excreta and greywater is vitally important in the control of infectious and other communicable diseases and the Design and construction of appropriate Sanitation systems is of paramount importance in contributing to the safe disposal of human excreta. However, on its own, the proper planning and construction of Sanitation systems does not provide a guarantee that the general health of the population will improve. A holistic approach to health care is required, with the provision of suitable Sanitation being just one of the necessary components thereof.

3 A three-pronged approach was followed to source the information required to produce this Guide . At the outset, the authors collaborated with a number of local authorities in South Africa and gathered information regarding the Design and operation of their sewer systems. The main concerns raised by the managers of the various sewer networks in South Africa were also noted and were addressed in compiling this report. Secondly, the standards and guidelines used in practice in the Design and operation of Waterborne Sanitation systems were reviewed. Thirdly, many sources of information were consulted and a synthesis of the material was tailored to South African conditions to produce a comprehensive Guide on Waterborne Sanitation systems. In particular, the following documents were heavily relied on: Guidelines for the Provision of Engineering Services and Amenities in Residential Township Development (CSIR, 2003); Alternative Sewer Systems (WEF Manual of Practice, 2008); the USEPA (1991) manual entitled Gravity Sanitary Sewer Design and Construction; and the Sewer Design Manual (ASCE, 1982).

4 This report summarizes the available knowledge, information and advancements of all Waterborne Sanitation systems used in South Africa. The objective of the report is to provide a concise Guide for the analysis and Design of Waterborne Sanitation systems. In order to streamline the planning and Design process in South Africa a three-tier philosophy is proposed for sewage collection system planning and Design . As described by Jacobs and Van Dijk (2009) the philosophy used originates from the field of transport engineering where three different solution levels for Design procedures are documented in the South African Code of Practice for the Design of Highway Bridges and Culverts (Department of Transport, TMH 7). Adopting this concept for the planning and Design of sewage collection systems leads to three technical tiers.

5 This three-tiered philosophy could be used as a basis to derive a best management practice for sewer system planning and Design . General information Detailed Design Specialized/Advanced Design Throughout this Guide the information provided is partitioned into these three tiers. Waterborne Sanitation Design Guide ii The four main Waterborne Sanitation systems which are described in this Guide are: Conventional gravity sewer Vacuum sewer systems Small-bore sewer Simplified sewerage A summary description with advantages and disadvantages of these systems is provided. A technical Design criterion for designing each of these systems is given with a worked example guiding the designer through the process to be followed. To provide further classification and background information photos, videos, software and additional literature were included on the accompanying DVD.

6 Where this icon is shown in this report movie clips, photos, additional literature or software are available in the SewerAid DVD to visually enhance the understanding of the specific concept. Waterborne Sanitation Design Guide iii ACKNOWLEDGEMENTS The research presented in this report/ Guide emanated from a study funded by the Water Research Commission (WRC), whose support is acknowledged with gratitude. The Reference Group made an important contribution in steering and guiding this study to obtain the format and results reflected in this report. The support of the Chairman and Manager of this study, Mr Jay Bhagwan, as well as the staff of WRC, is greatly appreciated. The members of the Reference Group and Project Team are: Mr JN Bhagwan Ms C Dladla Mr NS Ireland Mr CS Crawford Mr M Ristic Dr HE Jacobs Prof NP Armitage Mr JL Harrison Mr K Moodley Prof SJ van Vuuren Mr M van Dijk Mr A Otterman : : : : : : : : : : : : Water Research Commission Chairman Water Research Commission Project co-ordinator City of Cape Town DWAF SRK University of Stellenbosch University of Cape Town eThekwini Water and Sanitation PD Naidoo and Associates University of Pretoria (Project leader) University of Pretoria PULA We also acknowledge with thanks the inputs made by a number of students from the University of Pretoria, who conducted some of the personal interviews and assisted in compiling this report.

7 They are: Messrs A Oosthuizen, A Beck, JP Velloen and GL Coetzee, as well as Miss M Peens. Waterborne Sanitation Design Guide iv Waterborne Sanitation Design Guide Table of Contents Page Executive Summary Acknowledgements Table of Contents List of Tables List of Figures Appendices Glossary of Terms List of Symbols Abbreviations 1. INTRODUCTION 2. PLANNING CONSIDERATIONS AND POLICIES 3. Waterborne Sanitation SYSTEMS Introduction Classification of Sanitation systems History of Design standards and criteria Conventional gravity sewer system General description Technical Design criteria Construction Advantages and disadvantages Vacuum sewer systems General description Technical Design criteria Construction Advantages and disadvantages Small-bore sewer General description Technical Design criteria Construction Advantages and disadvantages Simplified sewerage / shallow sewerage / condominial sewerage Background and general description Technical Design criteria Construction Advantages and disadvantages Other systems Conservancy tank system General description Technical Design criteria Advantages/disadvantages Septic tanks Background i iii iv

8 Ix x xii xiii xix xx 1 4 9 9 10 11 13 13 15 20 22 24 24 25 30 31 33 33 35 37 40 41 41 41 45 46 48 48 48 48 50 51 51 Waterborne Sanitation Design Guide v General description Technical Design criteria Advantages and disadvantages Anaerobic digester Aqua-privies Summary 4. COSTING OF Waterborne Sanitation SYSTEMS 5. Design GUIDELINES FOR CONVENTIONAL GRAVITY SEWER Sewer system planning Gravity sewer system Design (reticulation, link and main) General Design of sewers Design criteria Design -flow calculations Extraneous flows Hydraulics of sewers Pipe material Alignment of sewers Pipe cover Loading conditions Bedding and backfill Corrosion Maintenance holes and transitions Manhole location and spacing Shape and dimensions Construction material Fall through manhole Terminal cleanouts Erf connections Field testing and inspection Sewer pump station Design criteria General requirements facility capacity and hydraulic Design criteria System Design and pump selection Piping and appurtenances Sumps Net positive suction head Electrical, controls.

9 And instrumentation Ancillary equipment Wet and dry well installations Rising/ force main Pump-station building and site Siphon Design Silt trap Standard drawings and schedule of quantities House connection pipe Step-by-step Design procedure (house connection pipe) 51 52 56 56 56 57 58 61 61 62 62 62 62 63 66 70 76 78 81 82 84 86 87 87 88 90 92 93 94 95 96 97 98 100 105 107 109 109 111 113 115 117 117 118 118 118 118 Waterborne Sanitation Design Guide vi Worked Example #1: House connection pipe Design hints and tips (house connection pipe Design ) Main sewer line Step-by-step Design procedure (conventional main sewer Design ) Worked Example #2: Conventional gravity sewer line Design Design hints and tips (conventional sewer Design ) 6. Design GUIDELINE FOR VACUUM SEWERS Vacuum sewer system planning Design criteria General requirements Vacuum collection system Vacuum-valve pit Vacuum valve Buffer tank Vacuum station Vacuum collection system and vacuum station Design Step-by-step Design procedure (vacuum collection system) Worked Example #1 7.

10 Design GUIDELINE FOR SMALL-BORE SYSTEMS System components Building sewers/house connections Interceptor tanks Pumps and controls Service laterals Collector mains Cleanouts Valves and vents Design criteria Hydraulic Design Design -flow estimates Flow velocities Hydraulic analysis Collector mains Layout Alignment and grade Pipe diameter Depth Pipe materials Service laterals Interceptor tanks Manholes and cleanouts Valves Odours and corrosion House connector to interceptor tank Interceptor tank Step-by-step Design procedure (interceptor/septic tank: Method 1 middle to upper income groups) 126 128 129 129 135 140 141 142 142 142 143 146 148 149 151 156 156 158 164 165 165 166 166 167 167 167 168 168 168 168 169 170 170 170 171 171 171 172 172 172 174 175 176 176 176 176 Waterborne Sanitation Design Guide vii Step-by-step Design procedure (interceptor/septic tank: Method 2 lower income groups) Worked Example #1 Interceptor/septic tank Design Design hints and tips (Interceptor tank Design ) Main sewer line (small-bore) Step-by-step Design procedure (small-bore gravity sewer) Worked Example #2 Small-bore main sewer line Design Design hints and tips (small-bore sewer Design ) 8.