Oxygen Transfer Testing Research Articles

Three decades of oxygen transfer tests in clean water in a pilot scale test tank with fine-bubble diffusers and the resulting conclusions for WWTP operation

Abstract We summarized the experience from three decades of oxygen transfer testing and aeration research at the Technical University of Darmstadt to validate the oxygen transfer efficiency of modern fine-bubble diffusers. A total of 306 oxygen transfer tests in clean water of 65 different fine-bubble diffusers, carried out in the same test tank under identical test conditions, were analysed and compared with previous results. As a result, we could show that the performance of fine-bubble aeration systems has increased by 17% over the last three decades. Therefore, modern well-designed and operated aeration systems can achieve specific standard oxygen transfer efficiency (SSOTE) values between 8.5 and 9.8% · m−1. Additionally, a comparison of various diffuser types and diffuser densities was done. Based on the new results, an exemplary cost/benefit analysis for a 100,000 PE WWTP shows the calculation of an optimized diffuser density with respect to investment and operating costs.

Oxygen Transfer Parameter Estimation: Impact of Methodology

Oxygen transfer is an important part of wastewater treatment and accounts for as much as 60% of energy consumption in the activated sludge process. Prior to 1984, no standard method for quantifying oxygen transfer existed, which created problems in the design and warranties for treatment plants. The ASCE standards for the measurement of oxygen transfer in clean water and the Standard Guidelines for In-Process Oxygen Transfer Testing have found widespread application and have reduced design variability. The standard has allowed operators and engineers to better evaluate process operation of existing treatment plants. This paper illustrates the key concepts of the standard and shows why they are important and how they reduce the variability of oxygen transfer testing. The reasons for the standard’s success are described, as are the pitfalls of earlier approaches. The paper also highlights key new areas of the revised clean water standard, including an optional correction for test water total dissolved solid...

Energy saving in activated sludge plants by the use of more efficient fine bubble diffusers

Many activated sludge plants (ASP) use fine bubble diffused air as their source of oxygen. Blowers are attached to air pipework, which distributes air to a network of diffusers installed on the floor of the ASP tank. Modern diffusers are made from a rubber membrane which flexes to allow fine bubbles of air to pass through holes in the diffusers which then pass into the mixed liquors in the tank. The diffusers come as circular discs, tubes and more recently mats or panels. Yorkshire Water is in the process of building new ASP at some of their biggest sewage treatment works to meet new final effluent consent standards associated with the freshwater fisheries directive (FFD). These new works will treat sewage from a combined population of over two million people in the Yorkshire area. Black & Veatch is involved in some of the first works to have a new type of fine bubble diffuser installed in the ASP basins. These diffusers resemble a mat or panel and are fixed to the floor of the tank as opposed to circular and tubular diffusers which as fixed above the floor. Oxygen transfer testing has been carried out to show the efficiency of these aeration systems, which may offer significant savings in operating costs to water operators. This paper examines the results from the tests and compares them with other tests carried out in the United States and tests that have been carried out on other types of diffusers. The paper will discuss the results of the oxygen transfer tests and present capital and net present costs (NPC) for various diffuser installations.

Non-Steady State Oxygen Transfer Testing of New High Purity Oxygen Dissolution and Mixing Device for Activated Sludge Aeration

Non-Steady State Oxygen Transfer Testing of New High Purity Oxygen Dissolution and Mixing Device for Activated Sludge AerationAir Products and Chemicals, Inc. (APCI) and Aqua-Aerobic Systems, Inc. (AAS) have jointly developed an oxygen injection and mixing system, OxyMixTM, for the activated sludge wastewater treatment process. The OxyMixTM concept utilizes a high-speed, direct-drive floating mixer fed with high purity oxygen to provide all the necessary aeration and mixing for an activated sludge basin. Clean water...Author(s)Annemarie O. WeistMichelle A. FitzgeraldBulent OzbasChristopher A. HarveyBob ColehourTerry ReidLloyd JohnsonDavid T. RedmonSourceProceedings of the Water Environment FederationSubjectSession 105 - Innovative Technology Forum IIDocument typeConference PaperPublisherWater Environment FederationPrint publication date Jan, 2009ISSN1938-6478SICI1938-6478(20090101)2009:8L.6954;1-DOI10.2175/193864709793957832Volume / Issue2009 / 8Content sourceWEFTECFirst / last page(s)6954 - 6964Copyright2009Word count167Subject keywordsOxygen transferhigh purity oxygenactivated sludgeaerationkLadissolved oxygencomputational fluid dynamics

Comparison of different oxygen transfer testing procedures in full-scale membrane bioreactors

Membrane bioreactors (MBRs) for wastewater treatment offer the advantage of a complete removal of solids from the effluent. The secondary clarifier is replaced by a membrane filtration and therefore high biomass concentrations (MLSS) in the reactor are possible. The design of the aeration system is vital for an energy efficient operation of any wastewater treatment plant. Hence the exact measurement of oxygen transfer rates (OTR) and alpha-values is important. For MBRs these values reported in literature differ considerably. The OTR can be measured using non-steady state methods or using the off-gas method. The non-steady state methods additionally require the determination of the respiration rate (oxygen uptake rate OUR), which usually is measured in lab scale units. As there are differences of OUR between lab scale and full scale measurements, off-gas tests (which do not require an additional respiration test) were performed in order to compare both methods at high MLSS concentrations. Both methods result in the same average value of OTR. Due to variations in loading and wastewater composition variations of OTR in time can be pointed out using the off-gas method. For the first time a comparison of different oxygen transfer tests in full scale membrane bioreactors is presented.

Oxygen Transfer Testing in an Oxidation Ditch Process

Oxygen Transfer Testing in an Oxidation Ditch Process

Experiences in Field Testing a Variety of Aeration Equipment in Sweden and in the U.S.A. by Offgas Analysis

The background and theory of the offgas analysis procedure used in oxygen transfer testing of diffused aeration tanks is reviewed. Correlation of this method with other applicable procedures in parallel tests is reported. State-of-the-art equipment and accessories are described. Advantages of the procedure are identified, as are precautionary considerations regarding its use. Applications considered appropriate for its employment are delineated. Experience and test results in both Sweden and the U.S.A. on a variety of aeration devices are disclosed.

Experiences with Oxygen Transfer Testing of Diffused Air Systems under Process Conditions

This paper outlines three procedures used to evaluate oxygen transfer under process conditions. Steady state procedures, a radioactive tracer technique and off gas methods are described and methods of calculation are outlined. Two case histories, an industrial waste site and a municipal site, are presented.