wastewater

Which of the following is not an apparatus or supplies for the Plastic Limit O flat glass plates for mixing soil and for rolling threads ) Distilled water O A length of rod 3 mm in diameter and 100 mm long ) Casagrande apparatus Based on the below data from a sieve analysis test, what is the cumulative percent retained above 1.25 mm sieve: Sieve Mass Size Retained 5.00 mm 10 2.50 mm 40 1.25 mm 30 630 pm| 120 315 um 12 8 160 μm Pan O 64% 36% O 22.5% O77.5% The hydrometer method is based on Stokes equation for the velocity of a freely 8 (Ctrl) - falling sphere. True False

A wastewater sample subjected to standard BOD5 test yields a test result of 200 mg/L. The rate constant is 0.18/day at 20°C (to the base 'e'). Another sample of the same wastewater is tested at a temperature of 30°C. The time in days after which the BOD yielded is 200 mg/L is (up to 2 decimal places).

JQuestion a) Write down the chemical equations for the reactions that take place in the DO test. b) Discuss the environmental significance of DO. c) Why should DO fixation be performed in the field rather than in the laboratory? Data Sheet Volume of solution for titration = Samples Sample A Sample B (i) (ii) (iii) (i) (ii) (iii) Average Average Titration reading Start End (+0.05mL) (+0.05mL) mL Volume of Na2S2O3 (mL) Dissolved Oxygen (DO)(mg/L)

Wasterwater civil engineering 11 and 12

What diameter would a circular clarifier have to be to remove 50 μm particles with 75% efficiency from a 4 MGD (million gallon per day) flow?  Assume the particle specific gravity is 1.5 and the temperature is 10°C.  Answer: 18 m

7. (B)

The following test results (Table Ql-2) were obtained from a raw water sample. All of the tests were performed using a sample volume of 50 mL. Table Q1-2 Weight (g) Mass of residue after drying at 105 ỏC Mass of residue after ignition at 550 ¿C Mass of residue on Whatman GF/C filter paper after drying at 0.7148 0.3818 0.3571 105 'C Mass of residue on Whatman GF/C filter paper after ignition at 550 'C 0.1418 Calculate the concentration (mg/L) of : (i) total solids. (ii) total volatile solids. (iii) total suspended solids. (iv) total dissolved solids.