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Most cold-climate biological nutrient removal facilities experience poor settling mixed liquor during winter, resulting in treatment capacity throughput limitations. The Metro Wastewater Reclamation District in Denver, Colorado, operated two full-scale secondary treatment trains to compare the existing biological nutrient removal configuration (Control) to one that was modified to operate with an anaerobic selector and with hydrocyclone selective wasting (Test) to induce granulation. Results from this evaluation showed that the Test achieved significantly better settling behaviour than the Control. The difference in the mean diluted SVI30 between the Test and Control were statistically significant (P < 0.05), with values of 77 ± 17 and 135 ± 25 mL/g observed for the Test and Control respectively. These settling results were accompanied by differences in the particle size distribution, with notably higher settling velocities commensurate with increasing particle size. The degree of granulation observed in the Test train was between 32 and 56% of the mass greater than ≥250 μm in particle size whereas 16% of the mixed liquor in the Control was ≥250 μm over the entire study period. The improved settling behaviour of the Test configuration may translate into an increase of secondary treatment capacity during winter by 32%.

Sikorsky Aircraft and Boeing are one of two defense-contractor teams building models of vertical-lift aircraft designed to replace the U.S. Army's aging fleet of Apache and Blackhawk helicopters.

Boys and girls are intrigued by the fact that I got to meet and interview stars of the pitch - including David Beckham, Cristiano Ronaldo, Sir Alex Ferguson and Lionel Messi - in my former role as editor of the Football Association's website.

[...]when I was the age of the children I'm usually addressing I steadfastly refused to read anything at all. [...]stop for a minute and think about what his brain is capable of doing: as a volley is dropping to him, 30 yards from goal, not only can he calculate the timing, power, trajectory, angle and speed required to crash the ball into the net within the space of a millisecond, but his body can make it happen.