Environmental Engineering Reference
In-Depth Information
Example 9.6
Problem:
The chlorine dose is 8.8 mg/L, and the flow rate is 3.28 MGD.
The hypochlorite solution is 71% available chlorine and has a specific
gravity of 1.25. How many pounds of hypochlorite must be used?
Solution:
8.8mg/L3.28MGD
×
×
8.34 lb/MG/m
g/L
Hypochlorite
=
=
32.5 gpd
0.71
×
8.34 lb/gal
×
1.25
9.2.8.7 Ordering Chlorine
Because disinfection must be continuous, the supply of chlorine
must never be allowed to run out. The process consists of three steps,
and the following calculation provides a simple method for determining
when additional supplies must be ordered:
1. Adjust the flow and use variations if projected changes are
provided.
2. If an increase in flow or required dosage is projected, the current
flow rate or dose must be adjusted to reflect the projected change.
3. Calculate the projected flow and dose:
Projected Flow = Current Flow (MGD) × (1.0 + % Change)
(9.7a)
Projected Dose = Current Dose (mg/L) × (1.0 + % Change)
(9.7b)
Example 9.7
Problem:
Based on the available information for the past 12 months, the
operator projects that the effluent flow rate will increase by 7.5% during
the next year. If the average daily flow has been 4.5 MGD, what will be the
projected flow for the next 12 months?
Solution:
Projected Flow = 4.5 MGD × (1.0 + 0.075) = 4.84 MGD
To determine the amount of chlorine required for a given period:
Chlorine Required = Feed Rate (lb/day) × No. of Days Required
Example 9.8
Problem:
The plant currently uses 90 lb of chlorine per day. The
town wishes to order enough chlorine to supply the plant for 4 months
(assume 31 days per month). How many pounds of chlorine should be
ordered to provide the needed supply?
