An activated sludge tank treats 1 mgd from the primary clarifier and has an x or 2,200 ppm ss. the water effluent is 0.9 mgd. 1.0 mgd of the sludge is recycled back into the tank and has a [ss] of 3,980 ppm. the concentration of bod exiting the primary clarifier is 200 ppm.
(a) find qw and xw.
(b) find qc and xc.
(c) find q1 and x1.
(d) find xe.
(e) calculate the volume of the tank that will satisfy the following requirements: a. bod loading < 35 lb bod/1000 ft3 day b. sludge age > 5 days c. aeration period > 4hr

Aloaded platform of total mass 500 kg is supported by a dashpot and by a set of springs of effective stiffness 72 kn/m. it is observed that when the platform is depressed through a distance x = 12.5 cm below its equilibrium position and then released without any initial velocity; it reaches its equilibrium position in the shortest possible time without overshoot. find the position and velocity of the loaded platform 0.10 sec. after its release. if a further load of 400 kg is added to the platform, find, i) the frequency of damped vibrations, and i) the amplitude of vibration after 2 complete oscillations, given that the initial amplitude is 15 cm.

If a particle moves along a path such that r : (3 sin t) m and ? : 2t rad, where t is in seconds. what is the particle's acceleration in m/s in 4 seconds? a)- 16.43 b)- 16.29 c)- 15.21 d)- 13.79

Fluids at rest possess no flow energy. a)- true b)- false