Water Quality 2

Water Quality 2 - Water Quality and Pollution: River...

Info iconThis preview shows pages 1–7. Sign up to view the full content.

View Full Document Right Arrow Icon
Water Quality and Pollution: River Systems Text Reading: Chapter 9, pp. 357-374 Plug-flow reactor model DO resources in rivers and streams DO sag curve – sources and sinks Streeter-Phelps equation development Other considerations
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Plug-Flow – our third reactor “type” 1. Batch 2. Completely Mixed 3. Plug Flow Q Q x x + x Here, we do a mass balance around the volume V = Α∆ x Note: velocity = u = Q/A We will also assume first-order decay. cross-sectional area = A dt d(CV) = QC in – QC ± reactions
Background image of page 2
Plug-Flow – Mass Balance x x x x x x x x)C k(A - uAC - uAC dt dC ) x A ( + + + = Making appropriate substitutions into the mass-balance equation: x x x x x x x kC - x uC - x uC dt dC + + + = x x x x x x x kC - ) C C ( x u dt dC + + + - = : 0 x as C C and x C - x C C x x x x x = = - + + kC - x C u - t C =
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Plug-Flow – Mass Balance Please note that x = distance in the reactor (or distance downstream in a river) and u is the velocity of flow. So, time of flow = x/u. Now we have: If we now assume steady-state, that is, concentration will only vary with distance, not with time: kC - dx dC u and 0 t C = = kC - dt dC = Look familiar? Plug Flow: C = C o e -kt Note: t = θ in a PF reactor, and = time-of-travel in a river
Background image of page 4
Oxygen Resources in Streams – “DO Sag” Adding organic material (O 2 consumption)
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Oxygen Resources in Streams River health is directly related to DO levels. The critical level of DO for “good” health is 4 to 5 mg/L O 2 . When DO concentrations are below this, many problems occur as we have
Background image of page 6
Image of page 7
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 18

Water Quality 2 - Water Quality and Pollution: River...

This preview shows document pages 1 - 7. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online