Teaching sustainability: does style matter?

Purpose: This paper aims to analyze how a tangram activity improved students' abilities to explain sustainability, articulate a positive perception of sustainable design and relate sustainability with innovation in engineering design. Design/methodology/approach: The concept of paradigm shift was introduced in the classroom by using a tangram activity to help students understand that sustainable design requires out-of-the-box thinking. Instructors from three institutions teaching various levels of sustainability courses to engineering majors used the activity to introduce sustainable design, then measured the understanding and appreciation of the concepts introduced through the tangram activity with pre- and post-activity surveys. Findings: Findings from the study indicate that students' perceptions of sustainability significantly improved due to the activity, without regard to the institution. The activity also significantly improved students understanding of the connection between sustainability and innovation, across all three institutions, across all majors and across all years of study except second-year students. Improving engineering students' views on sustainability may lead, over time, to changes in the industry, in which environmental performance is incorporated into the engineering design process. Originality/value: Active learning approaches are needed for affective-domain learning objectives in the sustainability field for students to learn the necessary attitudes, values and motivations to implement sustainability in engineering design. Simple, easily implemented active learning techniques, such as the tangram activity presented here, can be implemented across the curriculum or to the public to introduce the paradigm shift necessary with sustainable design.

Biofilm growth-percolation models and channeling in biofilter clogging.

Biomass accumulation is a load-limiting factor in the operation of biofilters used for air pollution control. As the biofilm thickens, portions at the base are no longer exposed to contaminants and oxygen and, thus, provide no treatment. Smaller pores are filled with biomass so that air no longer flows into them. As airflow paths are restricted, air may be prevented from reaching some pores even before they are filled. Eventually blockage becomes sufficiently widespread so that increasing head loss and decreasing removal efficiency require that the system be shut down. Optimization of biofilter design requires a better understanding of the mechanisms by which biofilters clog. In this work, a numerical percolation model of the blockage process was developed for application to biofilters. It allows comparison of pore blockage histories for various pore size distributions and predicts biomass accumulation, head loss, and treatment efficiency as a function of time, as well as total time, until blockage prevents further operation. Although the model was reasonably accurate in predicting the time before complete clogging, it underestimated intermediate values of head loss. Observations of a clogged biofilter suggest that this occurs because clogging later in the process is nonuniform at scales that are large in comparison with individual pores.

Removal of ultrafine and fine particulate matter from air by a granular bed filter.

The removal efficiency of granular filters packed with lava rock and sand was studied for collection of airborne particles 0.05-2.5 microm in diameter. The effects of filter depth, packing wetness, grain size, and flow rate on collection efficiency were investigated. Two packing grain sizes (0.3 and 0.15 cm) were tested for flow rates of 1.2, 2.4, and 3.6 L/min, corresponding to empty bed residence times (equal to the bulk volume of the packing divided by the airflow rate) in the granular media of 60, 30, and 20 sec, respectively. The results showed that at 1.2 L/min, dry packing with grains 0.15 cm in diameter removed more than 80% (by number) of the particles. Particle collection efficiency decreased with increasing flow rate. Diffusion was identified as the predominant collection mechanism for ultrafine particles, while the larger particles in the accumulation mode of 0.7-2.5 microm were removed primarily by gravitational settling. For all packing depths and airflow rates, particle removal efficiency was generally higher on dry packing than on wet packing for particles smaller than 0.25 microm. The results suggest that development of biological filters for fine particles is possible.