Asedimentation basin is used to remove suspended solids from a wastewater. the rate of flow of wastewater into the tank is 10 l/s, and the influent concentration of suspended solids is 200 mg/l. the removal efficiency of the settling tank for suspended solids is 60%. calculate the amount of suspended solids (sludge) accumulating in the sludge zone each day. you may assume that the amount of water withdrawn when pumping out the sludge from the sludge zone is very small compared to the inflow of wastewater to the tank and can therefore be ignored.

An external consultant recommends that a plant installs a bank of capacitors for power factor correction. this will reduce the peak electrical demand charges by an average of 93 kw every month. the plant current pays $13 per kw in peak demand charges. the capacitor bank will include 223 kw of fixed capacitors, and 183 of variable capacitors. the fixed capacitors cost $59 per kw, and the variable capacitors will cost $65 per kw. the consultant charges 21% of the equipment costs to install the capacitors. because this project will reduce the demand for the electric utility, they are prepared to provide a one-time rebate of $42 per kw of reduced demand. what is the simple payback period for this project (in years)?