1. A beef stick manufacturing plant proposes to discharge a wastewater flow with
ID: 1822693 • Letter: 1
Question
1. A beef stick manufacturing plant proposes to discharge a wastewater flow with a high salt content to a river. Upon reviewing the proposal, the governing regulatory agency set a 250 mg/L salt maximum level in the river downstream of the plant.The flowrate and salt content of the wastewater stream are as follows:
-->Wastewater flowrate, QW = 2,000 m3/day
-->Wastewater salt concentration, CW = 120,000 mg/L (Initial, no treatment)
The stream flowrate and salt content upstream of the discharge point are as follows:
-->River Upstream flowrate, QU = 34,000 m3/day
-->River Upstream Salt concentration, CU = 50 mg/L
Questions:
a) What is the maximum concentration of salt that permissible in the waste flow after treatment (CE)?
b) What is the concentration of salt in the brine stream leaving the salt removal process (CB)?
c) What fraction of the salt must be removed from the wastewater stream at the plant before discharging to river to comply with the requirement?
Approach: Use the Material Balance Technique. Solve Part a) first, then Part b), then Part c).
Explanation / Answer
a) the maximum concentration of salt in the waste flow is 200mg/l as paemissible is 250mg/l and river water alredy contain 50mg/l of salt.
b)the concentraton of salt wiil be120000+50=12050mg/l.
c) 120000-50/120000= 0.99995 or 99.95%.
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