NSERL Back Dock Chemical Neutralization
pH Monitor
RR
Secondary (Neutralized) Tank
14
13
New H2SO4 Pump added to
pH at Discharge Tank
12
11
Too Caustic Region
City UL
10.5
10
9
UTD Trigger
8
UTD Trigger
7
6
5
City LL
5.5
Too Acidic Region
4
3
2
1
New Servo Feedback parameters
0
Date
NOTE: This graph charts the pH level of the water leaving the active chemical drain neutralization
system from the
Natural Science and Engineering Cleanroom laboratory on the UTD campus.
- The servo deadband is shown by Purple UL and LL boundary lines.
- We found that the shifting experimental chemistries caused the discharge pH to singificantly drift up
and down over time.
- This required both base and acid neutralization, so early in 2012, we added a base-neutralizing acid
system
to the servo system controlling the discharge pH. This has stabilized the drift inside the servo deadband (+/- 0.8 unit of pH)
- In 2016 we reset the pH Neutralizing servo parameters to avoid self oscillation and minimize
overshooting the city limits
via short term spikes from unexpected large user dumps of very low pH chemicals.
The pH measures the acidity of the water leaving this system and entering the Richardson City sanitary
sewer.
City pH Limits UL = 10.5, LL = 5.5
REF: pH=7 is Neutral, pH<7 is acidic, pH>7 is basic (caustic) pH is monitored daily.
NOTE: The fluid discharge rate from the lab is on the order of 2 gallons per minute of city water used to
flush chemicals.
The Chemical discharge volume is highly variable but is estimated to be less than 2 or 3 gallons per
day.