Provide answers to the following questions related to characterization of water contaminants and their measurement, biochemical oxygen demand and sedimentation. (i) A drinking water treatment plant uses surface water from a river where the water intake is downstream of a heavily farmed community. Give one (1) inorganic and one (1) microbiological contaminant that typically need to be treated for surface water supplies. Provide two (2) treated water measurement methods (one for each contaminant type) that may be used to ensure the water is free from the inorganic and microbiological contaminants identified. Briefly discuss how you would ensure that the measurement methods used will provide a guarantee that contaminants are sufficiently reduced. (ii) A BOD test is conducted at standard temperature conditions using 300mL of tertiary effluent mixed with 150mL of water. The initial DO in the mix is 8mg/L. After 5 days, the DO is 2mg/L and after 20 days the DO has stabilized at 0.2mg/L. Assume that nitrification has been inhibited so that only CBOD5 (5-day carbonaceous biochemical oxygen demand) is being measured. (3) (a) Calculate the 5-day CBOD of the final effluent in mg/L; and (3) (b) Estimate the ultimate CBOD in mg/L. (6) (iii) Give three (3) important design parameters for a secondary sedimentation system (i.e., a secondary clarifier), briefly explain how the three (3) parameters influence the performance of the system and give typical design values (with units for each parameter) used in any wastewater treatment application. A typical secondary clarifier unit is shown below