Environmental Engineering

Transcription

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2 Environmental Engineering Series Editors: U. Forstner, R.J. Murphy, WH.Rulkens Springer-Verlag Berlin Heidelberg GmbH

3 Mogens Henze is associate Professor at the Institute of Environmental Science and Technology at the Technical University of Denmark. His research area is water and wastewater treatment, with special emphasis on biological nutrient removal processes, wastewater characterization and modelling. He is chairman of the IAWQ Nutrient Removal Specialist Group and the IAWQ Task Group on Modelling of Activated Sludge Processes. Poul Harremoes is department head and Professor at the Department of Environmental Engineering at the Technical University of Denmark. His research and teaching interests are mainly water quality and water pollution with an emphasis on the fundamental understanding rather than empirical rules for design. Professor Harremoes is past president and honorary menber of the International Association for Water Quality (IAWQ), chairman of the board of the Water Quality Institute which is affiliated to the Danish Academy of Technical Sciences, and director of PH-Consult ApS. Jes Ia Cour Jansen is consulting ingeneer concentrating on nutrient removal and treatment of industrial wastewater in activated sludge and biofilm systems. He received his Ph.D. from the Technical University of Denmark in biofilm kinetics. He has been engaged in education, research, development and practical aspects of wastewater treatment at the university, in engineering companies, at a research institute and as manager of Research Department at one of the major Danish wastewater treatment plants. Eric Arvin is associate Professor at the Institute of Environmental Sciences and Engineering at the Technical University of Denmark. His research has covered chemical and biological phosphorus removal, but it is now mainly focused on biological degradation of organic chemical pollutants in groundwater, industrial wastewater and waste gases. Biological transformation in biofilm systems are of major interest. He is a member of the board of the IAWQ Specialist Group on Biofilm Systems.

4 Mogens Henze. Poul Harremoes J es la Cour J ansen. Erik Arvin Wastewater Treatment Biological and Chemical Processes Second Edition With 190 Figures, Springer

5 Series Editors Prof. Dr. U. Forstner Prof. Robert J. Murphy Prof. Dr. ir. W.H. Rulkens Arbeitsbereich Umweltschutztechnik Technische Universitat Hamburg-Harburg Eillendorfer StraBe 40 D Hamburg, Germany Dept. of Civil Engineering and Mechanics College of Engineering University of South Florida 4202 East FowlerAvenue, ENG 118 Tampa, Fl ,USA Wageningen Agricultural University Dept. of EnvironmentalTechnology Bomenweg 2, P.O. Box 8129 NL-6700 WV Wageningen, The Netherlands Authors Prof. Mogens Henze Prof. Poul Harremoes and Prof. Erik Arvin Dr. Jes la Cour Jansen Technical University of Denmark Department of Environmental Science and Engineering BuildingllS, DK-2800 Lyngby, Denmark Trudeslundl, DK-3460 Birkemd, Denmark. ISBN Catalogin-in-Publication Data applied for Wastewater treatment : biological and chemical processes I Mogens Henze ed. (Environmental engineering) ISBN ISBN (ebook) DOI / This work is subject to copyright. All rights are reserved, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilm or in other ways, and storage in data banks. Duplication of this publication or parts thereof is permitted only under the provisions of the German Copyright Law of September 9, 1965, in its current version, and permission for use must always be obtained from Springer-Verlag Berlin Heidelberg. Violations are liable for prosecution act under German Copyright Law. Springer-Verlag Berlin Heidelberg 1997 Originally published by Springer-Verlag Berlin Heidelberg New York in 1997 Softcover reprint of the hardcover 2nd edition 1997 The use of general descriptive names, registered names, trademarks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. '!YPesetting: Dedicated PrePress, Lyngby, Denmark SPIN: / o- Printed on acid-free paper

6 Preface 'Art is about guessing the correct solution. Science is about producing tables in which we can find the correct solution, and engineering is about consulting the tables'. Poul Henningsen (Danish architect and writer) This book has been written for engineers who wish to familiarize themselves with the tables and part of the science behind the tables. You won't learn to build wastewater treatment plants by reading this book; the idea is to create a scientifically based platform from which to work. The book has been written for M.Sc. and Ph.D. students, consulting engineers and process engineers at wastewater treatment plants. Drawings have been produced by Birte Brejl and Torben Dolin. Translation of the 2nd Danish edition by Nancy M. Andersen was made possible by a grant from the CowiConsult Foundation. Thank you. Lyngby, Spring 1995 Mogens Henze Preface to 2nd edition The 2nd edition has been slightly revised. The book can be used together with the 1st edition as figures and equations have kept their numbering. Lyngby, Autumn 1996 Mogens Henze 5

7 Contents 1. Wastewater, Volumes and Composition The volumes of wastewater Measurements Statistics Estimates Population Equivalent Prognoses Wastewater components Domestic wastewater I municipal wastewater Variations Characterization of Wastewaters and Sludges Suspended solids Settleable solids Organic matter Nitrogen Phosphorus Alkalinity (TAL) Sludge volume index etc Respiration rate of sludge Basic Biological Processes The biology in biological treatment plants The organisms Selection Conversions in biological treatment plants Biological growth Hydrolysis Decay Aerobic heterotrophic conversion of organic matter Reactions, aerobic conversions Yield constant, aerobic heterotrophic conversions Nutrients, aerobic heterotrophic conversions Kinetics, aerobic heterotrophic conversions Heterotrophic micro-organisms, aerobic conversions The influence of the environmental factors, aerobic heterotrophic conversions Nitrification Reactions by nitrification Alkalinity 79 6

8 Contents Kinetics, nitrification The influence of the environmental factors on nitrification Denitrification Reactions by denitrification Yield constant by denitrification Nutrients, denitrification Alkalinity Kinetics, denitrification The influence of the environmental factors, denitrification Biological phosphorus removal Reactions, biological phosphorus removal Yield constant, biological phosphorus removal Alkalinity Kinetics, biological phosphorus removal Environmental factors, biological phosphorus removal Anaerobic processes Reactions, anaerobic processes Yield constants, anaerobic processes Nutrients, anaerobic processes Alkalinity, anaerobic processes Kinetics, anaerobic processes Gas production The influence of the environmental factors, anaerobic processes Activated Sludge Treatment Plants 4.1. Mass balances, activated sludge plants "Activated sludge" plant without recycle Activated sludge plant with recycle 4.2. Concepts and definitions of the activated sludge process 4.3. Types of plants, activated sludge plants Activated sludge with recycle Single tank activated sludge plants Biofilters 5.1. Biofilm kinetics Contact stabilization plants Biosorption plants Design of activated sludge processes Design by means of volumetric loading Design by means of sludge loading or sludge age Computer-aided plant design 5.2. Biofilm kinetic parameters

9 Contents 5.3. Hydraulic film diffusion Two-component diffusion Filter kinetics Mass balances for biofilters Biofilters without recycle Biofilters with recycle Concepts and definitions Types of plants Trickling filters Submerged filters Rotating discs Design of biofilters Design of trickling filters Design of discs Rules for other types of filter Design of biofilters for dissolved organic matter Technical conditions concerning biofilters Aeration in biofilters Growth and sloughing off of the biofilm Removal of particulate organic matter Detailed model Treament Plants for Nitrification Mass balances, nitrifying plants Separate nitrifying plants Combined removal of organic matter and ammonium Types of plants for nitrification Nitrification plants with separate sludge Single sludge nitrification plants Nitrification in two sludge treatment systems Nitrification plants with separate sludge in filters Two sludge nitrification plants in filters Combined biofilters and activated sludge treatment plants for nitrification Design of nitrifying plants Design of activated sludge treatment plants for nitrification Optimizing operation of nitrifying plants Design of biofilters for nitrification Treatment Plants for Denitrification Mass balances, denitrifying treatment plants Separate denitrifying plant Combined nitrification and denitrification Types of plants for denitrification 241 8

10 Contents Denitrification plants with separate sludge Denitrification plants with combined sludge Biofilters for denitrification Design of denitrifying plants C/Nratio Stirring/ oxygen Nitrogen gas in settling tanks and biofilters Oxygen consumption Alkalinity Design of activated sludge plants with denitrification Computerized process design Design of biofilters for denitrification Redox-zones in the biomass Plants for Biological Phosphorus-Removal Mass balances, biological phosphorus removal plants with activated sludge Plant types, biological phosphorus removal Biological phosphorus removahw.itli nitrification-denitrification and\an internal carbon source Biological phosphorus removahwith nitrificationdenitrification and an external carbon source Biological phosphorus removal with internally produced easily degradable organic matter Biological phosphorus removal without nitrificationdenitrification Design of biological phosphorus removal Easily degradable organic matter Design of tanks for biological phosphorus removal Optimization of plant operation; biological phosphorus removal Anaerobic Wastewater Treatment Mass balances, anaerobic plants ' Plant types, anaerobic processes, Pretreatment of wastewater, anaerobic plants Plants with suspended sludge Anaerobic filter processes Layout of an anaerobic treatment plant Design of anaerobic plants Design of plants with suspended sludge Design of anaerobic filter plants Gas production, anaerobic processes Optimization, anaerobic plants 304 9

11 Contents Start-up, anaerobic plants Disturbances, anaerobic plants 10. Treatment Plants for Phosphorus Removal from Wastewater Mass balances for phosphorus removal processes Mechanisms for chemical/physical phosphorus removal Precipitation Coagulation Flocculation Phosphorus binding in soil Treatment plants for phosphorus removal Precipitants Treatment processes Design of plants for phosphorus removal Chemical precipitation Phosphorus binding in soil Operation of plants for phosphorus removal List of Symbols Index

12 1. Wastewater, Volumes and Composition by Mogens Henze 1.1. The volumes of wastewater Wastewater flows are not steady or uniform, but vary from one hour to another, from day to day, from month to month and from year to year. When building a treatment plant, it is important to know the volumes of wastewater and their variations, now as well as in future. Based on the knowledge of the wastewater, the design of the treatment plant can be determined, taking into account the wastewater to be treated. In this connection measurements are useful; if such measurements do not exist, an estimate should be made. In respect of the volume of future wastewater, the development should of course be taken into account, i.e. a prognosis should be made Measurements Measurements of the volume of wastewater will be either in the form of curves or in the form of figures (metering). Fig 1.1 shows a diurnal variation for wastewater in the influent entering a treatment plant. The curve is the sum of domestic, industrial and public institution wastewater, infiltration and exfiltration. There is no reason to consider the size of the individual contributions as the curve shows what reaches the treatment plant. In case of a projection of the volumes of wastewater and their variations, however, it is recommended to analyze the curve and the catchment area for the purpose of splitting up the sub-contributions as it will be easier to project these separately. This is briefly dealt with in Sections 1.2 and 1.5. Sampling and measurements at treatment plants are difficult. Watch out for flows of return water (such as supernatant) which are often mixed into the raw wastewater before reaching bar screen and grit chamber, hence making correct measurement on the raw wastewater difficult. The curve shown in Fig 1.1 can be used to find the maximum hourly flow (190 m 3 /h) and the average hourly flow (78 m 3 /h) on the day in question. If a sufficient number of diurnal measurements are available, two important quantities can be calculated which form part of the design of the treatment plant, i.e. Qh,max Oh,av the average of the maximum hourly flow rate of the individual days (m 3 /h) the average hourly flow rate for many days (m 3 /h) 11

13 The volumes of wastewater Influent to treatment plant m 3 /h Maximum 244 % of average soo Fig 1.1 Influent to Tuelso wastewater treatment plant (Denmark, July 10-11, 1980) /1/. The maximum hourly flow rate, Qh,maXt can be calculated on the basis of a number of maximum hourly flows rates. The average maximum hourly flow rate, Oh,ma» is, among other things, used as a basis for the hydraulic design of sewers and ponds. The average hourly volume of water, Oh,aw or the diurnal volume of water, Qd,av' is for example used for the calculation of operating expenses. Hour Statistics By processing the data statistically a more detailed picture of wastewater variations is obtained. The different volumes of water (volume, maximum hour, maximum second, etc. over a 24-hour period) will often be normally distributed or log-normally distributed. Data sets for wastewater are never ideal as there will be irregularities which may, if they are too excessive, result in a special treatment of the data. Fractile diagrams can be an important tool in the design of treatment plants. Fig 1.2 gives an example of such a diagram. The 60 per cent fractile is frequently used as an average load and a fractile of per cent as a maximum load. A number of irregularities in wastewater data can be revealed visually by listing the collected data in order of time (a time series). Hence irregularities such as -jumps - trend (increasing or decreasing) -variation (for example weekly or seasonal variations) 12