Problem 1. A wastewater sample is examined for its solid contents. The ionic strength (μ) of wastewater is 0.01. It is known that 30% of total dissolved solids (TDS) is organic. The volumetric settleable solid concentration is determined as 20 mL/L using Imhoff Cone. It is assumed that 40% of total suspended solids (TSS) is equal to dry-settleable solids. The volumetric settleable solids composes of 2% of dried solids and 98% of water. The density of volumetric settleable solid concentration is given as 1020 g/L. Use information given in problem, calculate: a) Total Dissolved Solids (TDS) concentration as mg/L. b) Total Suspended Solids (TSS) concentration as mg/L. c) Total Solids (TS) concentration as mg/L.

A tank contains (1000) liter of brine with (15) kg of dissolved salt. Pure water enters the tank as a rate of (10) liter/min. The solution is kept thoroughly mixed and drawn from the tank at the same rate; find the amount of salts at any time.

Enter T next to the following true statements and F next to the false statements. Settling of suspended solids in secondary clarifiers is typical of Type II sedimentation. Thickening prior to digestion is common in many wastewater treatment plants because it reduces the size needed for the digester. Based on a temperature of 30°C, a design mean cell residenee time of about 20 days would be reasonable for a completely-mixed anaerobic digester without recycle. A volatile suspended solid is defined as an organic solid that can be oxidized to CO2 (g) at 250°C. The theoretical yield coefficient can be estimated from the observed yield coefficient if the specific growth rate constant is known. Air flotation would likely be more efficient for thickening waste activated sludge than primary sludge, while the opposite would be true for gravity thickening. The net mass of cells produced in the activated sludge process equals the total cell mass synthesized minus the cell mass wasted as waste…

The following data on the substrate removal rate and the substrate concentration is available for wastewater treatment (S) mol Rate, r (mol/min) 0.04 0.57 0.06 1.05 0.8 2.32 0.10 3.00 0.12 4.68 0.14 5.42 2.0 5.78 Estimate the value of substrate removal constant Km and the value of Vmax

In a BOD test, 5 ml of wastewater (with no dissolved oxygen) is diluted with 295 ml of water containing 8.5 mg/1 of dissolved oxygen. After 5 days incubation at 25°C, the dissolved oxygen content of the mixture is 5 mg/1. Temperature coefficient can be taken as 1.047 and BOD rate constant is 0.23 per day (base e) at 20°C. The ultimate biochemical oxygen demand of the wastewater is

1. The following information is provided for an activated sludge system design: Parameter Symbol Value Units Flow rate Q 10000 m³/d Influent BOD So 150 mg/L Effluent BOD S 2 mg/L Hydraulic residence time Ꮎ 4 hr Mean cell residence time Oc 6 d Maximum specific growth rate μm 3 1/d Half saturation constant Ks 40 mg/L Yield coefficient Y 0.5 Endogenous decay coefficient b 0.08 1/d Death rate coefficient γ 0.04 1/d Determine: a) The aeration tank biomass concentration (X) in mg/L b) The aeration tank oxygen requirement in kg/d c) The rate of biomass wasting in kg/d

Q- If the BOD3 of a wastewater sample is 75 mg/L and reaction rate constant k (base e) is 0.345 per day, find the amount of BOD remaining in the given sample after 10 days.

In a BOD test, the amount of organic matter remaining in the wastewater was measured at certain time intervals, instead of measuring the dissolved oxygen content. The amount of organic matterremaining after 4 and 9 d was measured as 52.86 mg/L and 8.11mg/L, respectively. Calculate the ultimate BOD and BOD rate constant k for the wastewater.

Question 8A 200 g/l solution of common salt was discharged into a stream at a constant rate of 25l/s. The background concentration of the salt in the stream water was found to be 10 ppm. At a downstream section where the solution was believed to have been completely mixed, the salt concentration was found to reach an equilibrium value of 45 ppm. Estimate the discharge in the stream.