2.3 You have been asked to design a circular de-chlorination basin for 2 MGD treated wastewater. If use Na2S2O3 and the depth of the tank is to be 4.5 ft, what would you suggest the diameter of this tank? a) 50 ft c) not enough information 2.4 Alum required for a 1.5 mg/L dose and for a plant treat 10 MGD of drinking water is: a) 68.3 Ib/day b) 42 ft b) 125.11b/day d) no need for tank c) 62.6 Ib/day = d) 72.8 Ib/day

Your organization has been hired to provide a water treatment process or device toremove toxic Chromium 6 [Cr(VI)] from water emanating from an underground source.Your organization has developed a treatment process that removes most of the Cr(VI)from the water to a residual concentration of 0.05 mg/L which is an acceptable level inline with the World Health Organisation. The underground water flows at 40 m3/h andhas Cr(VI) concentration of 100mg/L. The effluent flow rate is 97% of the influent flowrate, and the remainder of the water is discharged as wastewater. Calculate theconcentration of Cr(VI) in wastewater.

A water source has a flow of 10 MGD, alkalinity of 275 mg/L in CaCO3, and a pH of 8.85. What will the alkalinity be after addition of 150 mg/L NaOH? Present your answer in mg/L as CaCO3. Assume a close system.

QUESTION: An industrial wastewater from glucose production facility will be treated in an activated sludge treatment process. It is determined that 90% of glucose is biodegradable. It is also tested that the activated sludge treatment provides 100% BOD removal. This wastewater initially contains 2000 mg/L of glucose (C6H12O6), but no other organic and inorganic species. a) Calculate input TOC, COD and BOD of wastewater before treatment.b) Calculate output TOC, COD and BOD of wastewater after treatment.

Trickling filter is a fixed-bed biological reactor that operates under aerobic conditions. It is used to remove organic matter from wastewater. It is required to design a trickling filter for the following conditions as given in Table Q4. Table Q4 Flow rate to the Trickling filter (MLd) 6.5 Influent BOD (mg/L) 230.0 Effluent BOD (mg/L) 40.0 Daily Organic loading rate (g/m³) 250.0 BOD removal in primary sedimentation (%) 30.0 Filter depth (m) 2.0 Calculate (i.) Volume of Trickling filter (m3) (ii.) Trickling filter area (m2) and diameter (m) (iii.) Hydraulic loading rate (m/d) NRC Equation 100 E = W 1+ 0.44 (7 W=BOD Load applied to the filter V=Volume of the filter F =Recirculation factor

2. A wastewater treatment plant disposes of its effluents into a stream at a point A. Characteristics of the stream at a location fairly upstream of A and of the effluent are as below: Item Units Effluent Stream m3 /s mg l1 Flow 0.20 0.50 Dissolved 0xygen 2.00 8.00 Temperature °C 26 22 BOD, at 20°C mgll 40 3. Assume that the deoxygenation constant K, at 20°C (base e) = 0.20 d-l and the re-aeration constant K, at 20°C (base e) Equilibrium concentration of dissolved oxygen C, for the fresh water is as follows: 0.40 d-1 for the mixture. %3D Temperature °C 18 20 22 23 24 25 26 C, (mg/1) 9.54 8.99 8.83 8.53 8.38 8.22 9.17 The velocity of the stream downstream of the point A is 0.2 m/s. Determine the critical oxygen deficit and its location. [Use temperature coefficients of 1.04 for K, and 1.02 for K,)

The wastewater from a synthetic textile manufacturing plant is discharged to a municipal treatment plant for processing with domestic wastewater. The characteristics of the synthetic textile wastewater are 1500 mg/L BOD, 2000 mg/L SS, 30 mg/L nitrogen, and no phosphorus. The characteristics of the domestic wastewater are 200 mg/L BOD, 240 mg/L SS, 35 mg/L nitrogen, and 7 mg/L phosphorus. Find the BOD, SS of the mixture. The ratio of flow rate is domestic/textile = 4/1

Q- The wastewater having an organic concentration of 54 mg// is flowing at a steady rate of 0.8m³ /day through a detention tank of dimensions 2mx4mx2m. If the contents of the tank are well mixed and the decay constant is 0.1 per day, the outlet concentration (in mg/l, up to one decimal place) is

2. Cadmium is a pollutant of concern in mining. The initial concentration of cadmium in a mining wastewater (also called acid mine drainage) is 0.1 mg/L, and the EPA Maximum Contaminant Level (MCL) is 0.005 mg/L. What must the pH be so that the wastewater does not exceed the EPA MCL? Given: Cd(OH)2 → Cď²* + OH (unbalanced) K, = 5.33 x 1015 Cd(OH)2: Cd2+ = 112.4 g/mol 17.0 g/mol = 146.4 g/mol OH- =

Working for the local wastewater treatment plant, you are asked by the labtechnician to help her set up BOD5 tests. The issue here is what dilution to use to get the BOD5 test to give an acceptable result. Of course, you do not know the actual BOD5 value, but you are able to determine from past tests that the total ultimate BOD (NBOD + L0) of the wastewater is546 mg/L and the organic Nitrogen (TKN) concentration of the wastewater is 32 mg N/L. You also know that the first order rate constant for the BOD test is 0.25 day-1. When you ask, the technician tells you that the normal DO concentration at the start of the test is 8.3 mg/L.Based on all this information, tell the lab technician which of the following wastewater sample volumes added to a standard BOD test bottle (300 mL) is going to produce an acceptable final result: 1 mL/3 mL/9 mL/30 mL/90 mL NOTE: Acceptable BOD test should comply with the two essential criteria: DOfinal ≥ 2 mg/L and DOinitial – DOfinal ≥ 2 mg/L.