In a certain situation, waste water having dissolved oxygen of 2.36 mg/lt is discharged at 1.25 m3/sec rate in the river flowing with 9.5 m3/sec. After mixing the dissolved oxygen at the point of discharge is 7.36 mg/lt. The initial dissolved oxygen in the river water before discharge of waste water is,

A centrifuge dewaters digested sludge from ananaerobic digester. Pertinent performance data are; raw sludge feed rate to the anaerobicdigester = 60,000 lb/day on a dry solids basis, digester suspended solids removalefficiency = 55 percent, suspended solids concentration in digested sludge fed to thecentrifuge = 5.0 percent by weight, centrifuge cake solids concentration = 30 percent byweight, centrifuge solids capture = 90 percent. Sketch a process flow schematic of the system showing both the digester andcentrifuge and all flowing fluid streams, clearly identify the appropriate control surface(s)for mass balance analyses, and then determine;(i) dewatered sludge mass flow rate (lb/day)(ii) centrate flow rate (gal/day)(iii) centrate suspended solids concentration (mg/l).

The discharge from the Renenutet sugar beet plant causes the DO at the critical point to fall to 4.0 mg/L. The Meskhenet Stream has a negligible BOD and the initial deficit after the river and wastewater have mixed is zero. What DO will result if the concentration of the waste(L_w) is reduced by 50%? Assume that the flows remain the same and that the saturation value of DO is 10.83 mg/L in both cases.

An anaerobic digester (AD) is designed with the following data. Organic loading rate 1.0 kg VSS/m³.day VSS load 120 kg/day (i). (ii). Estimate the volume of the AD. If the VSS is 12 kg/m³, estimate the retention time.