Activated Sludge Separation Problems

Theory, Control Measures, Practical Experiences

Simona Rossetti, Valter Tandoi, Jiri Wanner

• Publisher: IWA Publishing
• Year: 2017
• eBook ISBN: 9781780408859
• Edition: 2
• Topic: Biological Sciences
• Subtopic: Applied Sciences
• Index: Biological Sciences

Activated Sludge Separation Problems: Theory, Control Measures, Practical Experiences, Second Edition, describes the most common activated sludge separation problems and explains the main reasons for the growth of the different filamentous microorganisms in activated sludge. The book summarizes the identification techniques for important groups of activated sludge microorganisms both based on conventional microscopic analysis and using the biological molecular tools available today (FISH and PCR). This new edition, with 70% new and updated material, also provides explanation of basic activated sludge process principles and of parameters necessary for process control and operation. The theory of secondary clarifies is described to the extent necessary for understanding the construction and operation of secondary clarifiers. The activated sludge reactor and secondary clarifies are treated as one system and the interactions are explained. The wide range of experiences around the world is documented and the methods to avoid the proliferation of these organisms are presented and critically reviewed. Activated Sludge Separation Problems consists of six chapters, presenting up-to-date technical and scientific aspects of these processes. The new edition also features an extended list of literature references for further reading. The book will be a valuable help for students of environmental engineering, wastewater specialists, plant operators and designers of activated sludge plants. It is also useful for specialists in wastewater operation laboratories, especially for those studying activated sludge separation properties.

© IWA Publishing 2017. Activated Sludge Separation Problems:

Theory, Control Measures, Practical Experiences

Simona Rossetti, Valter Tandoi and Jiri Wanner

doi: 10.2166/9781780408644_001

Chapter 1

Wastewater characterization

M. C. Tomei and D. Mosca Angelucci

1.1 INTRODUCTION

At the beginning of wastewater treatment ‘history’, wastewater characterization data were limited to BOD5 and COD, suspended solids and ammonia concentrations. In recent decades model development has required wastewater characterization in order to better describe complex biological process systems such as activated sludge.

The first simple models, based on Monod kinetics which considered one carbonaceous substrate and one biomass as homogeneous substances, were inadequate to explain the bacterial selection mechanisms, which determine the equilibrium conditions in the reactors and the plant response under dynamic conditions; consequently it was necessary to introduce a more detailed substrate characterization. The first model including the distinction between soluble and suspended carbonaceous substrate (COD) was the Clifft and Andrews model (1981); subsequent models (Dold et al. 1980; Henze et al. 1987) recognized the importance of evaluating the COD and nitrogen substrate fractions in the influent not only in terms of the physical state but also in terms of biodegradability. This approach, in fact, allows us to better take into account the role of the colloidal fraction that includes readily and slowly biodegradable components. The COD characterization, as a function of biodegradability, is also the most effective in relation to the bulking phenomena, the kinetic competition between floc-forming and filamentous bacteria for readily biodegradable COD being one of the most important selection mechanisms causing the predominance of one of the two species in the sludge biocenosis (Kappeler & Gujer, 1994).

A detailed and structured knowledge of wastewater composition is also necessary for understanding the bulking and foaming problems and for finding proper control measures.

In the following paragraphs, the different approaches to wastewater characterization will be presented.

1.2 GROSS PARAMETERS

Sewage is a complex mixture of inorganic and organic substances. The chemical and physical nature of municipal wastewater varies significantly both in terms of place and time, furthermore it can depend on variable industrial contributions.

Average wastewater characteristics are difficult to determine because of their temporal variability. The simplest method of characterizing municipal wastewater is the determination of ‘gross parameters’ such as BOD, COD, TSS, TKN and TP concentrations. An overview of the values of these parameters is reported in Tables 1.1–1.3. Table 1.1 shows annual pollution loads for different countries, Table 1.2 the pollutant concentration data for settled and raw municipal wastewater, while the typical composition of raw domestic/municipal wastewater is given in Table 1.3 for different concentration/dilution conditions.

Table 1.1 Pollution load (referred to persons) in various countries (from Henze et al. 2002).

Table 1.2 Typical pollutant concentration of settled and raw (for USA and UK) municipal wastewater in different countries (Al-Salem, 1987; Henze et al. 1987; Ekama & Marais, 1984; Gray, 2004). Data for Italy are referring to Regione Emilia Romagna (Regione Emilia Romagna ARPA E.R., 2002).

Table 1.3 Typical composition of raw municipal w...

Table of contents

• Cover
• Half Title
• Title Page
• Copyright Page
• Dedication
• Contents
• Abbreviations
• List of Contributors
• Preface
• Chapter 1: Wastewater characterization
• Chapter 2: The microbiology of the activated sludge process
• Chapter 3: Activated sludge separation problems
• Chapter 4: Aeration tank and secondary clarifier as one system
• Chapter 5: Bulking and foaming control methods
• Chapter 6: Experiences in various countries
• Index