3. the design criteria for oxidation ponds (also called facultative ponds, aerated facultative ponds) specified that (1) bod loading into the primary cell (or pond) shall not exceed 25 lbs bod/acre/day, (2) the minimum total water retention time, based on influent flow and all cells at water depth of 5 ft should not be less than 120 days., (3) the volume of winter storage between the water depths of 1.5 and 5 ft shall be sufficient so that no discharge is necessary for a four-month period, and (4) pond system should have at least two primary cells and one or more secondary cells. size the ponds for a community that generates 160,000 gpd wastewater with a bod of 220 mg/l. based on the climate of the area, the net water loss (evaporation plus seepage minus precipitation) during the storage months is 1.0 inch/month.

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.

Acertain flow of air (at stp) has a velocity distribution given by v i (in ft/s). if this flow is going through a 4 ft square area in the yz-plane (centered at the origin), what is the mass flow rate (in lbm/s)?

Tom is having a problem with his washing machine. he notices that the machine vibrates violently at a frequency of 1500 rpm due to an unknown rotating unbalance. the machine is mounted on 4 springs each having a stiffness of 10 kn/m. tom wishes to add an undamped vibration absorber attached by a spring under the machine the machine working frequency ranges between 800 rpm to 2000 rpm and its total mass while loaded is assumed to be 80 kg a) what should be the mass of the absorber added to the machine so that the natural frequency falls outside the working range? b) after a first trial of an absorber using a mass of 35 kg, the amplitude of the oscillation was found to be 10 cm. what is the value of the rotating unbalance? c) using me-3.5 kg.m, find the optimal absorber (by minimizing its mass). what would be the amplitude of the oscillation of the absorber?