E-Book, Englisch, Band 5, 710 Seiten, eBook
Volume 5
E-Book, Englisch, Band 5, 710 Seiten, eBook
Reihe: Handbook of Environmental Engineering
ISBN: 978-1-59745-173-4
Verlag: Humana Press
Format: PDF
Kopierschutz: 1 - PDF Watermark
Zielgruppe
Research
Autoren/Hrsg.
Weitere Infos & Material
Pressurized Ozonation.- Electrochemical Wastewater Treatment Processes.- Irradiation.- Nonthermal Plasma Technology.- Thermal Distillation and Electrodialysis Technologies for Desalination.- Reverse Osmosis Technology for Desalination.- Emerging Biosorption, Adsorption, Ion Exchange, and Membrane Technologies.- Fine Pore Aeration of Water and Wastewater.- Emerging Flotation Technologies.- Endocrine Disruptors.- Filtration Systems for Small Communities.- Chemical Feeding System.- Wet Air Oxidation for Waste Treatment.- Lime Calcination.
8 Fine Pore Aeration of Water and Wastewater (S. 391-392)
Nazih K. Shammas
CONTENTS
INTRODUCTION
DESCRIPTION
TYPES OF FINE PORE MEDIA
TYPES OF FINE PORE DIFFUSERS
DIFFUSER LAYOUT
CHARACTERISTICS OF FINE PORE MEDIA
PERFORMANCE IN CLEAN WATER
PERFORMANCE IN PROCESS WATER
NOMENCLATURE
REFERENCES
1. INTRODUCTION
The supply of oxygen for aeration is the single largest energy consumer at activated sludge wastewater treatment plants, representing 50–90% of total plant energy requirements (1,2). Replacement of less-efficient aeration systems with fine pore aeration devices can save up to 50% of aeration energy costs and has resulted in typical simple payback periods of 2–6 yr (3). As a result of these very impressive cost savings, a very large number, 1000–2000 municipal and industrial wastewater treatment facilities in the United States and Canada now use fine pore aeration.
Fine pore aeration technology remains relatively new in North America, and new materials and configurations continue to be developed. This chapter provides designers, end users, and regulators information on the nature of fine pore aeration devices and their performance to promote the intelligent application of fine pore aeration technology. Standardized testing of oxygen transfer devices in both clean and processed waters is a major advancement in the field. A consensus standard for testing aeration devices in clean water has been adopted by a large segment of the industry (4). Extensive testing of aeration equipment using this standard has led to the development of a large database on the performance of aeration devices in clean water. In addition, the development of improved (more precise and accurate) field test methods has permitted the generation of data that can be used to better characterize the translation of clean water test results to process conditions (5).
Experiments on wastewater aeration in England date back to as early as 1882 (6). In these experiments, air was introduced through open tubes or perforations in air delivery pipes. In the early years, patents were granted for a variety of diffusers, including perforated metal plates, porous tubes with fibrous materials, and nozzles (7). As activated sludge process investigations progressed, greater oxygen transfer efficiency (OTE) was sought with the production of smaller bubbles created by passing compressed air through porous media of various types. Experiments conducted in the United Kingdom seeking a better porous material consists of evaluations of limestone, firebrick, sand and glass mixtures, pumice, and other materials. The first porous plates were made available as early as 1915 in the United Kingdom. In the following years, several US companies offered porous plates that became the most popular method of aeration in this country in the 1930s and 1940s (3).
Shortly after the emergence of porous diffusers it became clear that media clogging could be a problem. Work in Chicago between 1922 and 1924 prompted the use of coarse media to avoid clogging (8). Clogging was attributed to liquid-side fouling and airside clogging because of dirt and oil in the air delivery system. Emphasis at that time was on improving air filtration (9–11). Substantial experimentation was performed to develop effective air filtration devices (10,11), and the results of that early work have led to the high-efficiency air filters used today in many porous diffused air systems (9). Mechanical aeration was one answer to the clogging problem. Since the introduction of Archimedean screw-type aerators in 1916, a multitude of mechanical aeration devices has been developed and used. Today, mechanical aeration devices serve as an important function in many applications for treatment of industrial and municipal wastewaters.
