The biennial International Gothenburg Symposia on Chemical Water and Waste water Treatment have proven to be a unique platform for the exchange of ideas and experiences between administrators, engineers and scientists active in the fields of water supply, wastewater disposal and pollution control. The First Symposium (Gothenburg, 1984) provided a long needed survey over theory and application of chemical water and wastewater treatment. The Second Symposium (Berlin, 1986) was devoted to aspects of recycling in chemical water and wastewater technology. The Third Symposium (Gothenburg, 1988) recognised the growing need and the potentials of pretreatment. These proceedings of the 4th Symposium focus on technology transfer from chemical treatment theory to practical treatment of drinking water and industrial or domestic wastewater. The contributions are devoted to questions of floc for mation and floc separation as well as problems and practical solutions associated with chemicals and dosing control. Special attention is given to the combination of chemical and biological processes for nutrient removal from wastewater. It is the editors' privilege to acknowledge the invaluable help from the authors of this book. It is the editors' hope that they might convey the significance and potential of chemical treatment in solving the challenging problems water purification, wastewater disposal and pollution control.

With joy and pride parents observe the coming of age of their children, confer. , ence conveners the acceptance of their programmes, and editors the demand for their volumes. The scientific advisory board of the Gothenburg . . Symposia, the Springer publishing house of the proceedings and the editors are more than pleased with the fact that the demand for these books far exceeds the supply. The themes vocalized by the Gothenburg Symposia reHect research and development needs for the environment more than envisioned at the concep tion of the conferences. An environment-oriented analysis of the situation, not confined to the European community, furnishes the following results: (1) Due to the very high population density in many areas environmental quality is endangered; this has become apparent at the very moment in particular in the aqueous habitat and is corroborated by corresponding regulation proposals from the European Council. (2) Pollution control concepts and measures are developed to a varying degree in many countries of the world, reHecting in most instances the need for environmental protection and the closely related devel opment of (judicial and technical) measures. In most instances these controlling and protective measures need to be intensified. (3) Thus, nearly all countries face the problem of developing and/or improving pollution control strategies, i. e. building new treatment plants, upgrading overloaded or outdated instal lations and designing new operating and controlling strategies for improved plant performance.

The International Gothenburg Symposia on Chemical Treatment have proven to be a unique platform for the exchange of ideas between theory and practice. They bring together administrators, engineers and scientists, who are concerned with water purification and wastewater treatment through precipitation, coagulation and subsequent solid/liquid separation. This volume contains the proceedings of the 3rd Symposium, focussing on Pretreatment. Pretreatment is understood as the scene total of all measures taken at the pollutant source to protect water supply, the sewerage system, the central treatment plant, and the aqueous environment. It is, where applicable, the most efficient measure in ecological and economic respects. The contributions of this third volume address questions of surveillance, automation and remote control of installations as well as the principles of legal, administrative and economic measures for regulations within the context of pretreatment. Special attention is given to the possibilities and limits of pretreatment of industrial discharges. Again it is the editors'privilege to acknowledge the invaluable help from the authors of this book. It is the editors' hope that they might convey the significance and potential of pretreatment in water supply, in industrial waste management and in municipal wastewater treatment and sludge handling.

Exactly ten years ago an experiment was started that proved to be extremely successful: the First Gothenburg Symposium. Its intent was to further the under standing of all processes pertaining to Chemical Water and Wastewater Treatment, and to bring together specialists working in basic research as well as in devel opment and administration. Now, the Proceedings of the Sixth Symposium are about to be published, clearly proving that there is a need for this forum. They dramatically illustrate the significance and the dynamic development of the topics of these symposia. It is fascinating to witness that in this time of reduced economic growth or even standstill, the environmental drive has not come to a halt, as many anticipated or feared. It is accepted more and more that the protection of the environment, a constant theme in all the Gothenburg Symposia, is not only a topic to be dealt with in times of affluence; it is now also seen as an instrument for cutting ex penditure, saving energy, and husbanding resources. The ever growing interest in these Gothenburg Symposia, documented by the large number of contributions the scientific panel received and the large demand for the books of this series that always exceeds the supply, testify to this commitment."

It was intended to return with the International Gothenburg Symposia every other time to the birthplace of these events, Gothenburg in Sweden. But instead the 8th symposium has been invited to be organized and held in Prague, i. e. in the midst of Central and Eastern Europe a region now keen on intensified environmental control. This attests that the symposia have attained such standing in the interna tional world of operators, designers, officers and researchers in water treatment technology that their presence in various parts of the world has been requested. And this ever growing significance, in short the success of this conference series, stems form the fact that the symposia offer a unique platform for the exchange of ideas and experiences on all aspects of water and wastewater treatment between administrators, engineers and scientists. The content of this book, i. e. the schedule of the symposium lectures, results for the most part from a vast response to an international call for papers. Many excellent contributions are included in this volume but at the same time many outstanding ones could not be included for lack of time and space. The total sum of these contributions document again the development in the field, both in terms of new technological (and other) developments as well as public and administrative acceptance and approval of solutions offered."

This seventh symposium in the series of biennial Gothenburg Symposia, taking place in Edingburgh 1996 continues to bring together research scientists, designing and operating engineers and funding and supervising administrators. It also has enlarged the scope of its platform by bringing together concerned specialists from Western countries and Central and Eastern Europe and furthermore attempts to bridge the gap between developing and industrialized countries. The traditionally presented topics, such as treatment of potable water and wastwater predominantly by chemical means are of utmost importance for those that need immediate action at reasonable costs. It is particularly noteworthy that an increasing number of contributions address these problems of the emerging need for environmental protection. And more and more presentations are delivered by experts from Central and Eastern Europe and from developing countries. Again the proceedings of this seventh symposium indicate and demonstrate new developments that advance the field of water and wastewater treatment. Be sides the ever present topics there is now a whole section on automation and control, a highly significant topic for water technology that so far has not received too much attention in symposia of this kind addressing theoreticians and prac titioners at the same time."

For the ninth Gothenburg Symposium time design and operation engineers as well as supervising and funding administrators in chemical water and waste water treatment, have come together to exchange ideas, experiences and personal views on issues of water and waste water management. While the main thrust of past symposia was in the description of the technological know-how of existing chemical unit-operations in water technology this ninth symposium focuses in addition on aspects of overall energy and mass flux analyses, the strive for more and more sustainable solutions (not only in technological turns) and public private partnership in all areas of water management. As the symposium in its effort to address also different geographical areas and therefore different water problems moved to Istanbul in Turkey a special effort was made in developing a platform for industrial water management.

Fallung, Flockung und die dazugehorige Abtrennung sind "Arbeitspferde' der Wasseraufbereitung, ebenso wie die mechanisch-biologische Behandlung das wichtigste Grundverfahren der Abwasserreinigung ist. Mit zunehmender In- tensivierung der Wassernutzung und der sich ergebenden Verkiirzung des natiirlichen Wasserkreislaufes verlieren sich die Unterschiede zwischen Wasser- aufbereitung und Wasserreinigung mehr und mehr. Und die Dosierung fallungs- und flockungswirksamer Chemikalien wird zu einem haufiger eingesetzten Ver- fahren in der intensivierten Abwasserreinigung. Es ist also zweifelsohne an der Zeit, diese ProzeBschritte allgemein als wichtige wassertechnologische Verfah- ren darzustellen und im Hinblick auf Grundlagen, Anwendungsbereiche und Leistungsfahigkeit zu analysieren. Das Hauptanliegen dieses Buches ist, den Ingenieur der Wassergiitewirt- schaft und des Siedlungswasserbaus - Studenten und in der Praxis Stehende gleichermaBen - mit den Moglichkeiten und Grenzen von" Fallung, Flockung, Abtrennung" in der Wassertechnologie vertraut zu machen. Dabei liegt in den mehr anwendungsorientierten Kapiteln das Schwergewicht der Darstellung bei der Erorterung der Moglichkeiten in der Abwasserreinigung in Ubereinstim- mung mit der eingangs beschriebenen Entwicklungstendenz. Mit den einleitenden Bemerkungen wird versucht, die Wechselwirkung und auch die Verwandtschaft zwischen Wasseraufbereitung und Abwasserreinigung vor dem Hintergrund der Nutzungsvielfalt der Wasserresourcen darzustellen.