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Biological Wastewater Treatment TextBook – Water Recycling Systems

Biological Wastewater Treatment TextBook – Water Recycling Systems

Fundamentals of Biological Wastewater Treatment

Author : Udo Wiesmann, In Su Choi, Eva-Maria Dombrowski

Clean water is an essential nutrient for humans, animals and plants. Because of its limited resources, especially in countries with low rainfall, little surface water, deep ground water levels and relatively high temperatures, careful use and frequent reuse after appropriate treatment are requirements for healthy life. This awareness is relatively new, because it was not until the late 19th century that the population of larger industrialized cities learned that wastewater must be treated to prevent disease. The reuse of treated water is still a topic of controversial discussions.

However, the authors of this book are convinced both that we must learn to develop and continue to promote water recycling systems and also that biological wastewater treatment processes play a highly important role. The modern concept of industrial wastewater treatment is moving away from the classic “end-of-pipe” technology towards “decentralized effluent treatment processes”, “process integrated water management” and ultimately in a number of cases being as close as possible to “fresh water-free processes”. The central concept is to save water. In the classic concept, the groups producing intermediate or finished products are relatively isolated from the group which treats the wastewater, frequently treating several different effluents mixed together.

This situation characterizes the first period of industrial wastewater treatment. After sampling, the water quality is determined and compared with regulations and the treated water is discharged into surface water. In all but a few exceptional cases, municipal wastewater treatment is performed in this same manner. Frequently, it is more favorable and economical to treat some industrial effluents by using specialized processes (“decentralized effluent treatment”), giving a water quality which makes it possible to reuse one or more water streams and to save fresh water. The next phase of development is to combine production processes and wastewater treatment, often called “process-integrated water management” (sustainable water use, industrial water use, cleaner production, etc.).

Typically, the improvement comes about through a complete change of the production process paradigm to reduce water and energy consumption, as well as waste production. Here, productional and environmental engineers need to cooperate and build one team. In this book, the fundamentals are discussed which are needed to better understand the processes taking place in “end-of-pipe” and “decentralized effluent treatment” plants. In the last chapter, examples of “processintegrated water management” and “decentralized treatment” are presented.

Two different wastewater treatment concepts can be followed: either the separation of impurities from water, or the partial or complete mineralization of impurities. Separation processes are based on fluid mechanics (sedimentation, centrifugation, filtration and flotation) or on synthetic membranes (micro-, ultra- and nanofiltration, as well as reverse osmosis). Additionally, physical–chemical processes can be used – like adsorption and coagulation – to separate dissolved or emulsified compounds from water. Impurities can be mineralized by biological and chemical processes (advanced oxidation with ozone, H2O2, UV, etc.). We want to concentrate our attention on biological processes. Other ones, such as sedimentation or membranes, will be discussed in connection with the activated sludge process and membrane bioreactors.

The main advantages of biological processes in comparison with chemical oxidation are: no need to separate colloids and dispersed solid particles before treatment, lower energy consumption, the use of open reactors, resulting in lower costs, and no need for waste gas treatment.

The advantages of chemical oxidation over biological processes are: no sludge production, mineralization of non-biodegradable compounds and smaller reactor volumes. If it is necessary to remove very large amounts of organics, both processes should be coupled if possible, first the biological step and then the chemical step. We will concentrate our discussion on the fundamentals of biodegradation.

Because of the early development of wastewater technology in industrialized countries, we frequently find “end-of-pipe” treatment plants in industry which simultaneously treat municipal wastewater and vice versa. “Decentralized effluent treatment” plants are initiated only if a large plant would be overloaded or the process would be negatively influenced by hazardous compounds. The main aim is then to optimize the treatment process by using process controls and thereby to reduce the cost of aeration and pumping.

In countries with rapidly growing industries and no municipal treatment plants, the construction and operation of a “decentralized effluent treatment” plant frequently has to be tested for each factory and realized as necessary. An appropriate treatment method should be applied rigorously to enable water reuse in regions with water scarceness or high water prices, for irrigation in agriculture, or as cooling water for power stations or industry. In addition, it is often very important to protect natural water systems used for drinking water supplies, recreation and conservation.

Compared with “end-of-pipe” treatment, “decentralized treatment” is often the more economical process. A better understanding is needed of the biological, physical, ecological, social and economical interactions surrounding water and wastewater. We cannot consider all these aspects, but this book provides important information about the fundamentals and engineering aspects of biological wastewater treatment. The methods used to describe and solve the problems presented are those used by biochemical engineers developing models based on mass balances which are valid for specific systems. The authors made every effort to present mathematical derivations so comprehensively that at least graduate students can follow. The target group also includes all engineers, biologists and chemists working in the field of wastewater treatment who are interested in learning more about its fundamentals.

After a survey of the historical development of microbiology and wastewater treatment, we give a brief introduction to wastewater characteristics and relevant legislation as well as microbial metabolism and stoichiometry, which is of fundamental importance for mass balances with biological reactions. Gas/liquid oxygen transfer is discussed in detail because of its high importance for all aerobic processes in wastewater treatment. Anaerobic substrate degradation is discussed afterwards as a very interesting alternative for the treatment of high-load effluents.

Persistent, industrially produced compounds are not easily treated in biological processes. Therefore, the results of several recent studies are summarized and discussed here. The great significance of nitrogen and phosphorus removal has led us to report about their stoichiometric and kinetic backgrounds individually. In the past two decades, discussions about modelling of the activated sludge process have increased. To gain a better understanding of activated sludge model number 1 (ASM 1) and its description of nitrogen removal, we give detailed explanations. We have dealt with the use of membranes in place of secondary clarifiers to emphasize that new possibilities exist for reusing and recycling water in the future. Therefore, they may be suitable in tandem with the topic of the previous chapters which discuss production-integrated water management and decentralized effluent treatment.

Over the past 25 years, many new processes have been tested successfully, a lot of them have gone into operation and a great number of papers have been published in this field. We hope that this book will help provide a better understanding and orientation in the important and interesting field of “Biological Wastewater Treatment”.

Product Details
* Format: Adobe Reader (PDF)
* Printable: Yes. This title is printable
* ElviraTigress Category: Cleansing/Balancing
* Mac OS Compatible: OS 9.x or later
* Windows Compatible: Yes
* Handheld Compatible: Yes. Adobe Reader is available for PalmOS, Pocket PC, and Symbian OS.
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Fundamentals of Biological Wastewater Treatment [PDF]

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