a. The following test results were obtained for a wastewater sample taken at headwork’s to an industrial wastewater treatment plant. The samples used in the solid analysis were all either evaporated, dried or ignited to constant weight. The size of the sample used for the analysis was 150 mL. The laboratory data obtained are provided in TABLE Q1.
Table Q1: Laboratory data on water analysis
Item
Weight, g
Tare mass of evaporating dish
54.6423
Mass of evaporating dish plus residue after evaporation at 105°C
54.7173
Mass of evaporating dish plus residue after ignition at 550°C
54.6893
Tare mass of Whatman GF/C filter
1.5347
Mass of Whatman GF/C filter plus residue after drying at 105°C
1.5586
Mass of Whatman GF/C filter plus residue after ignition at 550°C
1.5454
Using the provided data, estimate the solid contents in terms of total solid (TS), total volatile solids (TVS), total suspended solids (TSS), volatile suspended solids (VSS) and total dissolved solids (TDS), volatile dissolved solids (VDS).
[10 marks]
b. For an unseeded wastewater Biological Oxygen Demand (BOD) test of 20.0 mL in a 200 mL bottle, the estimated initial Dissolved Oxygen (DO) and a 5-day DO are 9.8 mg/L and 6.3 mg/L respectively. Estimate the BOD and ultimate BOD (UBOD), if k = 0.10 per day.
[6 marks]
c. Interpret the significance of BOD as a measure for determining level of pollution in a water body. Outline the differences compared to Chemical Oxygen Demand (COD)?
[4 marks]