Scientific and Technical Report Series

Mechanism and Design of Sequencing Batch Reactors for Nutrient Removal

Scientific and Technical Report No. 19

Nazik Artan and Derin Orhon Istanbul Technical University, Environmental Engineering Department

Published with the knowledge of the IWA Specialist Group on Nutrient Removal and Recovery

Published by IWA Publishing, Alliance House, 12 Caxton Street, London SW1H 0QS, UK Telephone: +44 (0) 20 7654 5500; Fax: +44 (0) 20 7654 5555; Email: publications@iwap.co.uk Web: www.iwapublishing.com First published 2005 2005 IWA Publishing Index prepared by Indexing Specialists, Hove, UK. Printed by Lightning Source Apart from any fair dealing for the purposes of research or private study, or criticism or review, as permitted under the UK Copyright, Designs and Patents Act (1998), no part of this publication may be reproduced, stored or transmitted in any form or by any means, without the prior permission in writing of the publisher, or, in the case of photographic reproduction, in accordance with the terms of licences issued by the Copyright Licensing Agency in the UK, or in accordance with the terms of licenses issued by the appropriate reproduction rights organization outside the UK. Enquiries concerning reproduction outside the terms stated here should be sent to IWA Publishing at the address printed above. The publisher makes no representation, express or implied, with regard to the accuracy of the information contained in this book and cannot accept any legal responsibility or liability for errors or omissions that may be made.

Disclaimer

The information provided and the opinions given in this publication are not necessarily those of IWA or of the IWA Specialist Group on Nutrient Removal and Recovery, and should not be acted upon without independent consideration and professional advice. IWA and the authors will not accept responsibility for any loss or damage suffered by any person acting or refraining from acting upon any material contained in this publication.

British Library Cataloguing in Publication Data A CIP catalogue record for this book is available from the British Library

Library of Congress Cataloging- in-Publication Data A catalog record for this book is available from the Library of Congress ISBN 1843390825

Contents

Preface vii

The Authors ix Nomenclature x

1 Introduction 1 1.1 Historical perspective 1 1.2 Current experience 3

1.2.1 Basic and applied research 3 1.2.2 Full-scale application 5

1.3 Need for modeling and a unified basis for design 5 1.3.1 The concept of process stoichiometry and modelling 6 1.3.2 Objective and scope 7

2 Process description 9

2.1 General description 9 2.1.1 Cycle frequency (m) 10 2.1.2 Nominal Hydraulic Retention Time (HRT) 10 2.1.3 Duration of phases in a cycle 11 2.1.4 Duration of periods in a process phase 11 2.1.5 Number of tanks 12 2.1.6 Sludge Retention Time (SRT) 12

2.2 Reactor hydraulics 13 2.3 Process options 16

2.3.1 Carbon removal and nitrification 16 2.3.2 Nutrient removal 17

2.4 Effects of filling and aeration patterns on population dynamics 22

3 Process design for carbon removal 23 3.1 Basic principles 23 3.2 Selection of SRT 25

3.2.1 Effluent quality 26

vi Mechanism and Design of SBRs

3.2.2 Excess sludge production and reactor biomass 26 3.3 Single tank design principles 27 3.4 Aeration system design principles 30 3.5 Process design 33

3.5.1 Design procedure 33 3.5.2 SBR equipment and the practical aspects of SBR design 36 3.5.3 Design example 41

4 Process design for nutrient removal 46

4.1 Basic principles for nitrogen removal 46 4.1.1 Nitrogen mass balances 47 4.1.2 Carbon and nitrate limitations 49 4.1.3 Selection of process option 50

4.2 Unified design procedure for nitrogen removal 51 4.2.1 SBR design for pre-denitrification 53 4.2.2 SBR design for step feeding 57 4.2.3 SBR design for intermittent aeration 59

4.3 Design considerations for phosphorus removal 60 4.3.1 Mechanism of Biological Phosphorus Removal 61 4.3.2 Factors affecting EBPR 61 4.3.3 EBPR without nitrogen removal 63 4.3.4 Simultaneous nitrogen and phosphorus removal 64

4.4 Retrofit of existing SBR plants 66

5 Performance evaluation by simulation models 69 5.1 Need for simulation models 69 5.2 Performance evaluation for COD removal 71

5.2.1 Effect of filling on effluent soluble COD 73 5.2.2 Effect of filling on dissolved oxygen profile 75

5.3 Performance evaluation for nitrogen removal 76 5.3.1 Evaluation of simulation results 77 5.3.2 Comparison of process options 81

5.4 Performance evaluation for phosphorus removal 82 5.4.1 Effect of system parameters 82 5.4.2 Effect of wastewater composition 85

5.5 Evaluation of simultaneous nitrogen and phosphorus removal performances

88

5.6 Evaluations of dynamic conditions 89

6 Concluding Remarks 92 References 94 Index 97

Preface

This report is prepared to provide the basic understanding and description of a unified basis of design for suspended-growth sequencing batch reactors. It is hoped that it will be useful as a complement to an earlier volume of the IWAs Scientific and Technology Report Series, mainly covering practical aspects of sequencing batch reactor technology, but also emphasizing the need for appropriate design guidelines.

The proposed basis for design is elaborated in a stepwise approach for both organic carbon removal and nutrient control. Nutrient removal from wastewaters presents a vital importance for the protection of sensitive water bodies from eutrophication. Greater concern for the water quality has been the major incentive for the implementation of stringent effluent regulations. The increasigly stricter nitrogen and phosphorus limits on wastewater discharges have stimulated studies on improving the activated sludge process and developing single sludge biological nutrient removal process configurations. Accumulated experience indicate that SBR also incorporates all the necessary attributes to qualify as a viable and competitive alternative to continuous-flow systems for nutrient removal. With their intrinsic flexibility of operation, SBR systems can be engineered in a simple way, to provide the most feasible process options for different nitrogen and phosphorus removal schemes. The striking feature of various SBR configurations for nutrient removal is that they can all be interpreted with a unified design approach, provided that the specific operating functions are fully understood and interpreted in terms of related mass balance equations.

The main message of the report is that SBR systems with different modes of filling and operation should not be viewed and interpreted as different generic SBR groups. The unified design procedure, when properly understood and applied, will provide all the necessary tools for the selection of the most appropriate cyclic operation scheme, the sequence of necessary phases and filling patterns for the particular application. Support of model simulation and evaluation as an integral component of system design is also emphasized.

The report has greatly benefited from the accumulated scientific work so far conducted at Istanbul Technical University on microbial kinetics and especially, on the mechanistic evaluation of different activated sludge configurations.

viii Mechanism and Design of SBRs

We gratefully acknowledge the contribution of Reha Artan on practical aspects of SBR operation. We would also like to express our gratitude to our colleagues, Gl Insel and Nevin zgr Yac for their valuable time and effort in the preparation of various parts of the manuscript.

Nazik Artan

Derin Orhon