Improved Ballast Recovery in Water Treatment

SUEZ Environnement’s Densadeg XRC™ is a high throughput water clarification unit capable of removing total suspended solids (TSS) with the aid of a high density ballast material. The ballast material is separated from the waste solids through a hydrocyclone and recycled into the system. Separation is inefficient and the unit experiences loss of ballast at 7 to 14 lbs per million gallons of treated water through the overflow of the hydrocyclone. Currently, ballast must be added at the loss rate to maintain the proper concentration to remove TSS. This requires that water treatment plants must provide storage space for ballast material, manpower to add the ballast, and a method to measure ballast concentration. To recover ballast material, a scale model of the overflow of the hydrocyclone was constructed and an angled pipe was added to settle the ballast into a collection sump. The effects of angle and linear flow velocity in the settling pipe were tested in a Design of Experiment (DOE) analysis to determine the critical process parameters. The maximum linear velocity in the settling pipe to settle ballast was also determined and used as the design criteria for the pilot scale. The results of this study will provide a basis for engineers from SUEZ to begin a long-term study of the economic impacts of using this ballast recovery method. Success in this project will allow SUEZ to provide this solution as an addition to the existing and future Densadeg XRC™ units.https://scholarscompass.vcu.edu/capstone/1088/thumbnail.jp

\u3ci\u3eDrosophila\u3c/i\u3e Muller F Elements Maintain a Distinct Set of Genomic Properties Over 40 Million Years of Evolution

The Muller F element (4.2 Mb, ~80 protein-coding genes) is an unusual autosome of Drosophila melanogaster; it is mostly heterochromatic with a low recombination rate. To investigate how these properties impact the evolution of repeats and genes, we manually improved the sequence and annotated the genes on the D. erecta, D. mojavensis, and D. grimshawi F elements and euchromatic domains from the Muller D element. We find that F elements have greater transposon density (25–50%) than euchromatic reference regions (3–11%). Among the F elements, D. grimshawi has the lowest transposon density (particularly DINE-1: 2% vs. 11–27%). F element genes have larger coding spans, more coding exons, larger introns, and lower codon bias. Comparison of the Effective Number of Codons with the Codon Adaptation Index shows that, in contrast to the other species, codon bias in D. grimshawi F element genes can be attributed primarily to selection instead of mutational biases, suggesting that density and types of transposons affect the degree of local heterochromatin formation. F element genes have lower estimated DNA melting temperatures than D element genes, potentially facilitating transcription through heterochromatin. Most F element genes (~90%) have remained on that element, but the F element has smaller syntenic blocks than genome averages (3.4–3.6 vs. 8.4–8.8 genes per block), indicating greater rates of inversion despite lower rates of recombination. Overall, the F element has maintained characteristics that are distinct from other autosomes in the Drosophila lineage, illuminating the constraints imposed by a heterochromatic milieu