Paul Palazolo

Performance of pilot-scale constructed wetlands for secondary treatment of chromium-bearing tannery wastewaters

Tannery operations consist of converting raw animal skins into leather through a series of complex water- and chemically-intensive batch processes. Even when conventional primary treatment is supplemented with chemicals, the wastewater requires some form of biological treatment to enable the safe disposal to the natural environment. Thus, there is a need for the adoption of low cost, reliable, and easy-to-operate alternative secondary treatment processes. This paper reports the findings of two pilot-scale wetlands for the secondary treatment of primary effluents from a full tannery operation in terms of resilience (i.e., ability to produce consistent effluent quality in spite of variable influent loads) and reliability (i.e., ability to cope with sporadic shock loads) when treating this hazardous effluent. Areal mass removal rates of 77.1 g COD/m2/d, 11 g TSS/m2/d, and 53 mg Cr/m2/d were achieved with a simple gravity-flow horizontal subsurface flow unit operating at hydraulic loading rates of as much as 10 cm/d. Based on the findings, a full-scale wetland was sized to treat all the effluent from the tannery requiring 68% more land than would have been assumed based on literature values. Constructed wetlands can offer treatment plant resilience for minimum operational input and reliable effluent quality when biologically treating primary effluents from tannery operations.

Chromium Fate in Constructed Wetlands Treating Tannery Wastewaters

Nine experimental wetlands were built to determine chromium partitioning inside systems treating tannery wastewaters. Results showed 5-day biochemical oxygen demand and chromium removals of 95 to 99% and 90 to 99%, respectively. The majority of chromium was found in association with media (96 to 98%), followed by effluents (2.9 to 3.9%), and the least was found in plant parts (0.1%). Chemical speciation modeling of solutions and scanning electron microscope analysis suggest two potential chromium removal mechanisms--sorption/coprecipitation with iron hydroxides or oxyhydroxides and biomass sorption. The release of the majority of chromium in the iron- and organic-bound phases during sequential extractions supports the proposed dominant removal mechanisms. The use of a mixture of peat and gravel resulted in lower removal efficiencies and stronger partitioning in organic phases during sequential extractions. Chromium was efficiently removed by wetlands, retained through chemical and biological processes. Future research will focus on further exploring removal mechanisms and proposing management strategies for the chromium-containing wetland media.

Attracting Students to Transportation Engineering: Gender Differences and Implications of Student Perceptions of Transportation Engineering Careers

With a significant fraction of the nations transportation workforce nearing retirement age, it is essential to attract new talent to transportation fields and to retain that talent. In addition, it is also important to attract a diverse workforce, because women and minorities are still significantly under-represented in transportation engineering and related fields. To address the nations transportation workforce needs, FHWA, the U.S. Department of Transportation, the Institute of Transportation Engineers, and other leading transportation organizations emphasize the importance of outreach activities in kindergarten through 12th grade. In particular, programs directed at middle and high school students are essential for increasing the pipeline of transportation students and professionals. One such program at the University of Memphis in Tennessee, Transportation Engineering Careers (TREC), is designed to increase high school students’ interest in transportation careers through a week-long, fast-paced, active learning environment. This paper first provides a review of relevant literature and then presents assessment findings from the first 2 years of the TREC program regarding gender differences and student perceptions of transportation engineering. Finally, lessons learned and implications for similar efforts are also presented.

Transportation Engineering Careers: Strategies for Attracting Students to Transportation Professions

Critical to building an American workforce with 21st century skills is the recruitment and graduation of students in science, technology, engineering, and mathematics fields. However, a nationwide lack of student interest and preparation in these fields results in a shortage of workforce talent. The transportation field is not immune to this shortage and faces significant issues related to attracting and retaining transportation professionals. Thus, it is crucial to raise awareness of opportunities available through the transportation profession with precollege students. The Transportation Engineering Careers (TREC) program at the University of Memphis is designed to engage students in active challenge-based learning, to showcase the variety of transportation engineering career opportunities through visits from industry professionals, and to provide interaction with peer role models through a structured mentoring component. This paper presents a brief review of relevant literature, a description of the University of Memphis TREC program and its evolution since 2010, the evaluation results from four years of participants, and preliminary results from a longitudinal survey. Lessons learned from the program assessment in attracting students to transportation professions are also discussed.