Abstract: A biological waste-water treatment using a biological reactor is described where the processes are conducted in an alternating and joint, aerobic zone, anoxic zone and aerobic zone arrangement. Raw waste-water is transferred to the aerobic zone and/or to the anoxic zone. The waste-water is also transferred from the last anoxic zone to the last aerobic zone, which acts as an exit from the biological reactor. In the process of external recirculation to the aerobic zone, sludge from the bottom of the secondary precipitation tank is moved to the aerobic zone. In the process of internal recirculation the content of the last aerobic zone is divided between anoxic zone and aerobic zone. From the last aerobic zone, waste-water is transferred with the sludge to the secondary precipitation tank, where the clean waste-water is separated from the sludge on the bottom of the secondary precipitation tank.

Abstract: A racket sport training device is disclosed. The training device is usable in conjunction with any strung racket, and includes a pocket-like structure fashioned from a flexible, rip-stop nylon material. The opening of the pocket has a perimeter that approximates the perimeter of the racket frame to which it is attached, and, when the racket is used with the training device in place, air is entrapped in the pocket. The entrapped air adds additional stress to the swing so that the player using the device for warmup exercise faces higher, racket-head resistance. This results in faster warmup with the encumbered swing constituting a functional exercise--one that uses the same musculature as is used in actual play. The device is further optionally adapted for tennis service training by having one or more zippers to bleed air from the device. A scale marking is provided adjacent the zipper for reproducibly setting the level of the racket head resistance desired for service warmup.