A treatment plant treats water at an average daily flowrate of 2.7 m3/s. The water is chlorinated before it flows into a 15000 m3 reservoir. The water flowing into the reservoir has a chlorine concentration of 3 mg/L. Chlorine decays at a rate of 0.24 h-1. Assume the reservoir is well-mixed and the system is at steady-state condition. (a) Determine the chlorine concentration at the discharge point of the reservoir. (b) The treated water flows from the reservoir into a transmission main. The pipe carrying the water has a diameter of 2 m and flows full. In the transmission main, chlorine decays at a rate of 0.19 h-1. Determine the concentration of chlorine 2 km from the treatment plant.

Note:hand written solution should be avoided.

using thCNK Tormulas. 4 Consider the feasibility of treating the wastewater from the town of Nancy (Problem 12.31) in a single-stage trickling-filter plant, as diagrammed in Figure 12.21, using high- density cross-flow media with a specific surface area of 42 ft²/ft³. Use the same filter sur- face area as calculated for stone-media filtration in Problem 12.31 (A = 4600 ft²) and a recirculation ratio of 0.5. The design wastewater temperature is 15°C. As determined from laboratory testing, the soluble (filtered) BOD of the primary effluent is 100 mg/l or less, compared to the unsettled unfiltered BOD of 160 mg/l. The soluble effluent BOD concen- tration of trickling-filter plants treating similar wastewaters is approximately 50% of the unfiltered BOD concentration. From pilot-plant studies and full-scale experience, the manufacturer of the cross-flow media recommends a reaction-rate coefficient at 20°C of 0.0030 (gpm/ft2)0.5 for a media depth of 6.6 ft (2.0 m). From these data, calculate…

A water treatment plant is required to process 28800 m³/d or raw water (density = 1000 kg/m³, kinematic viscosity = 106 m²/s). The rapid mixing tank imparts a velocity gradient of 900 s¹ to blend 35 mg/l of alum with the flow for a detention time of 2 minutes. The power input (W) required for rapid mixing is..