QUESTION 1:
(a) With the help of a labeled drawing, discriminate between the first-stage Biochemical Oxygen Demand (BOD) and second-stage BOD. Explain in detail the procedure for determining the BOD of an industrial wastewater sample which is expected to be in the range of 250 - 300 mg/L.
(b) Thrash out the factors that cause variation in the BOD reaction rate constant k and explain the use of this information in wastewater treatment. Draw outline to show how the BOD profiles would differ between 2 different wastewaters having
(i) Diverse k values but same BOD5
(ii) Diverse k values but same ultimate BOD
(c) If the 5-day BOD of a river is 200 mg/L at 20 °C, what will be the value of the ultimate first-stage BOD and 1-day BOD at that same temperature? Suppose k = 0.23 d-1 (base e) at 20 °C. Work from first principles, deriving the appearance for the first-stage BOD.
(d) Classify the term Chemical Oxygen Demand (COD) and explain how the COD of an example can be measured in the laboratory. The role of all reagents used in the test must be explained.
QUESTION 2:
(a) Name the standard unit of colour and differentiate between "apparent" and "true" colour of surface waters.
(b) Describe the rationale behind the utility of coliform organisms to evaluate the microbiological quality of drinking waters.
(c) The subsequent test results were obtained for a wastewater sample taken at an industrial facility. All of the tests were performed using a sample size of 100mL. Determine the concentration of total solids, total volatile solids, suspended solids, dissolved solids and volatile suspended solids. State your results in mg/L.
Tare mass of evaporating dish = 52.1533 g
Mass of evaporating dish plus residue after evaporation at 105 ºC = 52.1890 g
Mass of evaporating dish plus residue after ignition at 550 ºC = 52.1863 g
Tare mass of Whatman GF/C filter = 1.5413 g
Residue on Whatman GF/C filter after drying at 105 ºC = 1.5541 g
Residue on Whatman GF/C filter after ignition at 550 ºC = 1.5519 g
(d) With the help of a labelled drawing, describe the different phases of a typical Oxygen Sag Curve for the organic pollution of a stream. Give details the shape of the curve and list the factors influencing the Oxygen Sag curves for a stream.
QUESTION 3:
(a) With the help of a sketch, give details of the different phases in the generation of landfill gas.
(b) State and briefly illustrate TEN factors that must be considered in the siting of a sanitary landfill.
(c) In your first position as a junior city engineer, you are assigned by your supervisor to report on the generation rates, andcomposition, of solid wastes for various sources in your community. Describe how you would go about it if these data were needed within 30 days and thus giving you no time to measure seasonal effects.
QUESTION 4:
(a) Declare and briefly depict six factors affecting the process of composting important for consideration in a typical yard composting facility.
(b) Declare and briefly portray the main characteristics of hazardous wastes and highlight the short-term and long-term hazards associated with hazardous wastes.
(c) Confer in detail the important priorities that are involved in an integrated hazardous waste management plan.