Chptr6PrblmSolns

Chptr6PrblmSolns - 6.1 a. A primary standard is an...

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6.1 a. A primary standard is an enforceable limit on the concentration of a contaminant in water or an enforceable requirement that a particular treatment technique be implemented. Primary standards apply only to contaminants that impact human health. A secondary standard is a recommended limit on the concentration of a water constituent or on the measured value of a water quality parameter (e.g., turbidity). Secondary standards apply to factors that affect a drinking water’s aesthetic but not human health attributes. b. An MCL is a primary standard, whereas an MCLG is a maximum concentration goal for a drinking water contaminant, which would be desirable based on human health concerns and assuming all feasibility issues such as cost and technological capability are not considered. An MCLG is not an enforceable limit, but does provide the health-based concentration, which the MCL should seek to approach as closely as possible within the constraints of practical feasibility. There are many contaminants with MCLGs, but no numeric MCL. These include acrylamide, copper and lead. 6.2 The CWA sets up a system by which the maximum concentration of contaminants in discharges to surface waters and in the surface waters themselves are set and enforced, while the SDWA provides the legislative mechanism necessary to set and enforce the maximum contaminant concentrations in drinking water. The CWA is designed to ensure that the quality of surface waters in the U.S. is, at a minimum, appropriate for the beneficial uses for which the water is designated. The SDWA is designed to ensure that water supplied by public water systems for human consumption meets acceptable health standards at the point of use.
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6.3 a. The hydraulic detention time is: () ( ) hr 4.17 d 0.174 gal 7.4805 ft gal/d 10 2.5 ft 0 . 10 ft 43.0 3 6 2 = = × = = π θ Q V b. The critical velocity is: ( ) hr ft ft 2.40 ft 43.0 hr 24 d gal 7.4804 ft d gal 10 2.5 2 3 2 3 6 b o = × = = A Q v c. The weir loading rate is: ( ) hr ft ft 51.5 ft 43.0 2 hr 24 d gal 7.4804 ft d gal 10 2.5 rate loading weir 3 3 6 w = × = = L Q
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6.4 From Appendix C: At 20°C, ρ = 998.2 kg·m -3 and μ = 0.00100 kg·m -1 ·s -1 a. The particle settling velocity is: () ( )( )( ) s m 10 2.18 s m kg 00100 . 0 18 m 10 0 . 1 kg/m 2 . 998 4 . 0 m/s 9.807 18 - 5 - 2 -5 3 2 2 p p s × = × = = ρρ d g v b. s m 10 2.89 m 30 m 10 s 60 60 24 d d / m 7,500 4 - 3 b o × = = = A Q v Since v o > v s , less than 100% of the particles will be removed. c. The settling velocity of the smallest particle which is 100% removed is equal to v o . So, s μ m 36.5 s m 10 3.65 m kg 2 . 998 4 . 0 s m 9.807 s m 10 89 . 2 s m kg 0.00100 18 - 18 5 - 2 1 3 2 4 - 2 1 p s p = × = × = = g v d
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6.5 From Appendix C: At 20°C, ρ = 998.2 kg·m -3 and μ = 0.00100 kg·m -1 ·s -1 The length to width ratio is 5, so A b = 5 w 2 Set v o = v s and solve for w : () m 42.7 m 10 m kg 998.2 - 200 , 1 s m 9.807 5 s m kg 00100 . 0
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Chptr6PrblmSolns - 6.1 a. A primary standard is an...

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