A BOD test is run using 30 mL of wastewater and 270 mL of dilution water. The initial DO of the mixture is 9.0 mg/L. After 5 days, the DO is 4 mg/L. After 30 days, the DO in the bottle is 2 mg/L and it now longer seems to be dropping. At the beginning of the test, we added a nitrification inhibitor so we can assume that the nitrification is not occurring. Thus, the only BOD being measured is carbonaceous BOD a) What is the BODs of the wastewater?
b) What is the ultimate carbonaceous BOD?
c) How much BOD remains after 5 days?
d) Based on the data above, estimate the reaction rate constant k (1/day)

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.

Which of the following ziegler nichols tuning methods the response of the controller to a step input should exhibit an s-shaped curve? a)-open loop mode b)-closed loop mode c)-both modes (open & closed) d)-none of the modes (open & closed)

Aseries piping system conveys methyl alcohol. the system consists of 70 m of 1- nominal pipe follow by 50 m of 2-nominal pipe, both schedule 40 commercial steel. the 1-nominal pipe contains 3 90° elbows (regular) anda fully open gate valve, all threaded. the pressure drop through the system is 150 kpa. determine the volume flow rate through the system that is horizontally laid.