Background information of the project

The bubble generation study in a water tank is the second stage of the Air Bleaching Test project of SIT. The project is launched for Hyflux Ltd. and funded by MOE to research and optimize the aeration diffuser design for Membrane Bioreactor(MBR) water filtration application.

Membrane Bioreactor Technology is a new waste water treatment process which includes the use of fibre membranes to clean the dirty water and Hyflux uses the bubbles generated from numerous aeration diffusers to clean the water filters in the water tanks via a process called air scouring. One of the problems of current design of the diffuser pipe is that it cannot be cleaned thoroughly. During the process, most parts of the fibres can be well-cleaned but there are always some parts which remain black. Another problem is about the cost of operation. The electricity Hyflux needs to power the air flow in the diffuser pipes is extremely high and the price of electricity is also expensive. Thus, Hyflux would like to cooperate with SIT to investigate on the correlation between the aeration diffuser design (e.g. the diameter of the aeration hole, the diameter of the fibre, the distance between the adjacent holes, etc.) and the bubble characteristics (e.g. the size, speed, frequency, etc.) to find out how it can improve the aeration diffuser design to achieve better cleaning effect as well as high cost-effectiveness.

The entire project includes three stages, namely the slug flow formation study, the bubble generation study and the study of the interaction between the fibre and the bubbles. For each stage, there will be experiment and computational simulation components to collect the data for further analysis. The purpose to have both components conducting simultaneously is to cross-check and verify the data collected in order to prevent any errors due to limitations of both components. At the point we joined the project, the researchers in SIT had done the study of the slug formation and were working on the bubble analysis. Thus, we were engaged mostly in the second stage of the project during the one month, with a rough understanding of what had been done during the first stage. We have learned basic physics knowledge behind the bubble dynamics and flow phenomena and have researched on the application of bubbles. We were also exposed to the scientific way to process pictures and data and were given the chance to practice hands-on skills of mechanical assembly.

The equipment used for the project includes a high speed camera (S$50,000), an air supply system, a water tank and specimen in the water tank. The specimen can be either an air diffuser pipe or a bubble generation plate with seven aeration holes of different diameters ranging from 1mm to 10mm. It also includes four high speed computers for simulation and four researchers are currently running simulation for this project.

1. Problem-solving skills

The most important skill I have gained through the one-month learning journey is problem-solving. Everyone at the workplace has emphasized the significance of this skill to an engineer since it is literally what any engineering-related job is all about. The job of any engineer is to invent, design or improve products to address practical issues in respective fields, ranging from our daily supplies to the cutting-edge technologies. During such processes, the knowledge one possesses is the most powerful tool to facilitate one’s work, especially under unsatisfactory conditions. In fact, engineers should always prepare for hard environments, for example, the lack of funding or equipment. Under such situations, a competent engineer should be able to either make use of his or her existing knowledge, or endeavour to obtain new knowledge by books, websites, his colleague etc., to overcome the external limitations and resolve the issue.

One of the most interesting aspects of the project is that we were given the chance to perform the experiment with our own hands. On the one hand, we were able to practice hand on skills. Touching the real equipment was without doubt more exciting than reading the theories in the paper. On the other hand, the experiment itself was very intriguing as well. The bubble formation process recording by a high speed camera was completely different from observations by naked eyes. The whole process slowed down and we could clearly see how a bubble got to its shape and how its shape changed throughout the time frame.

Moreover, we have also encountered many problems when doing the experiment. Such problems would usually not have standard answers, unlike the kind of problems we always see in our textbooks or exams. Thus, there was no way of checking whether the answer we thought of was correct, unless we actually employed the method we had come up with. The process of looking for the useful solutions and then trying them out was really engaging for me.