Question

Design a 4-basin chlorine disinfection system for a plant with a winter average flow of 10.5MGD and a summer average flow of 12.8MGD, using an 8-ft deep, serpentine-channel, chlorine gas disinfection, sulfur dioxide dechlorination, and reaeration before discharge. Use 6-channels per basin. 1. Based on a 90-minute winter contact time and a channel D:W = 1:1, determine:

(a) Volume of each basin
(b) Surface area of each basin
(c) Channel width in each basin
(d) Total channel length in each basin
(e) What is the L:W each basin? Does it satisfy general geometry recommendations?
(f) Construction length of a basin
(g) Construction width of a basin

Answer 1

Part A:

Volume of each basin=621.044 m^3

Part B:

Surface Area of Each basin=254.6932 m^2

Part C:

Width of each basin is 8ft=2.4384 m

Part D:

Length of each Basin=
`(254.6932)/(8*0.3048*6) =17.408 m` (0.3048 is conversion for ft. to m)

Part E:

L:W=7.1391 (yes it satisfies the general geometry recommendation)

Part F:

Design Length will be 18 m.

Part G:

Design Width will be 8ft exactly depending on units.

Step-by-step explanation:

Given Data:

No. of Basins=n=4

Winter Average flow=10.5MGD

1MGD=3785.4118 cubic meters/day

Winter Average Flow=10.5*3785.4118=39746.82 m^3/day

Summer average flow= 12.8MGD= 12.8*3785.4118=48453.2710 m^3/day

Contact time=90 min

Solution:

Part A:

Total Volume=Winter Flow Rate*Time

1 min=1/(24*60) day (Conversion)

`Total\ Volume=39746.82*90*(1)/(24*60)`

Total Volume=2484.17625 m^3

Volume of each basin=Total Volume/ No. of Basins

Volume of each basin=
`2484.17625/4`

Volume of each basin=621.044 m^3.

Part B:

Conversion Factor:

1ft=0.3048 m

`Surface\ Area\ of\ Each\ Basin=(Volume\ of\ each\ basin)/(Depth)\\ Surface\ Area\ of\ Each\ Basin=(621.044)/(8*0.3048)\\Surface\ Area\ of\ Each\ Basin=254.6932 m^2`

Part C:

We have D:W=1:1

It means width and depth are equal so,

Width of each basin is 8ft=2.4384 m.

Part D:

Surface Area of Each Basin=Length of Basin* Width*Number of channels per Basin

Length of each Basin=
`(Surface\ Area\ of\ Each\ Basin)/(Width* No. of\ channels)`

Length of each Basin=
`(254.6932)/(8*0.3048*6) =17.408 m` (0.3048 is conversion for ft. to m).

Part E:

width=w=8 ft=8*0.4038=2.4384 m

L:W=17.408:2.4384

L:W=7.1391 (yes it satisfies the general geometry recommendation).

Part F:

Length =L= 17.408 (Calculated in Part D)

Design Length will be 18 m.

Part G:

Width W= 8ft=2.4384 m

Design Width will be 8ft exactly depending on units.