Open sarahh2000 opened 5 years ago
sarahh2000
commented
5 years ago sarahh2000
commented
5 years ago Lab session 2/9: -removed T connection, making PACl and fluoride systems independent. PACl drips directly into the fluoride stock tank. Microbore tubing was adjusted. -ran tests for 5,10,15 cm: https://docs.google.com/spreadsheets/d/1lq4xWi8Zg5Q8ckPSTdju1gC9VfiYjMYTov7gsfVikLg/edit#gid=0
Additional tasks
sarahh2000
commented
5 years ago Lab Sessions 2/23 and 2/24: -tested red dye with PACl with stirbar -did not observe flocculation, just exited as homogenous red color -in both cases floc weir is lighter than what is coming out of effluent
-decided to test with T junction to see if problem is in concept of mixing -no flocs or precipitates obsesrved -flow rate ~0.7 mL/s -effluent line is very red (suggests dye not completely binding to PACl?)
-Ran at ~0.1 mL/s to see if the problem is that the flow rate is too fast -precipitate was observed/small flocs in flocculator
-Ran at 0.13 mL/s and very large precipitates were observed
sarahh2000
commented
5 years ago Lab session 3/2: -decreased height of fluoride constant head tank, reinstalled float valve -added in T junction for PACl to drip in -ran test with red dye in fluoride tanks and PACl in PACl tanks -used arbitrary amounts of red dye and fluoride but need to look at prior research to figure out concentratoins -often began to flocculate with the addition of red dye but would stop flocculating after
For next session: -determine correlation between height and flow rate of PACl -make python program to relate system concentration of PACl with the height of PACl
sarahh2000
commented
5 years ago Lab session 3/9: -determine that optimal PACl flow rate is 0.34 mL/s to achieve system concentration of 40 mL/s using Tigran's python program -developed correlation between change of height in PACl and flow rate using measuring cylinder: https://docs.google.com/spreadsheets/d/1Q0Lt1K_bW44Oj5npH-q0set40IN-BTI8OhK4klfIkB4/edit#gid=0 -built new flocculator from 46ft of tubing (49 coils) -ran system at 0.48 mL/s and at 10cm (0.34 mL/s), observed large flocs
sarahh2000
commented
5 years ago Lab session 3/10: -noticed that red dye was floating up the sedimentation tube rather than settling out -conducted jar tests: (1) independent test: 420 microliters of PACl in 400 mL of water, 100 microliters of red dye. Stirred with stir bar and let settle (2) flocculator: PACl at system concentration of 40 mg/L mixed with red dye. Initially there was 200 mL of water in the beaker to simulate mixing in sed tank. Solution after flocculation was added until 500 mL -indicates that flocculator solution was 4-5x more diluted than independent test
In initial settling: (1) majority of red dye flocs settled to the bottom (2) majority of red dye flocs rose to the top of the container
After mixing of (2), red dye flocs seemed to settle to the bottom again
Samples were collected of independent and flocculation samples. in these samples, red dye flocs settled out.
To do: redo experiment to confirm
sarahh2000
commented
5 years ago 3/16: -measured pH of solutions: were about the same, pH ~8 -dumped out red dye, put in dye in the concentration 100uL dye/400 mL water -flocs were observed to fall into waste line
-in the event that the system is stuck: open waste line (less than main), pump water through flocculator -t junction was introduced to allow for easy pumping of water into system
-new bottom geometry was added -resuspension of flocs increased
sarahh2000
commented
5 years ago 3/23: -effluent flow rate graph noticed that flocculation did not occur (visually, the red dye was lighter in color than it was previously) -noticed that the small precipitates moved much faster at the same flow rate previously -noticed that more precipitation occurred under this supposedly lower concnetration of red dye -pH of PACl solution approximately pH 4
Hypotheses: -flow rate of PACl must be matched to system flow rate to create the right pH for flocculation -flocculation depends on all of the following: concentration of red dye, PACl concentration, and effluent flow rate -less concentrated red dye should require less concentration of PACl which needs a slower effluent flow rate
Next steps: vary concentration of red dye and map optimal flow rates of PACl and effluent -test pH of flocculator if possible
sarahh2000
commented
5 years ago 4/13: -cleaned the entire system out -did not observe any flocculation
4/14: -noticed that the red dye in both the constant head tank and the stock tank became separated -unlikely due to backflow since this is observed in both tanks
sarahh2000
commented
5 years ago 4/20: -we found that there was backflow so we lengthened tube coming from constant fluoride head tank -we added a valve after the constant fluoride head tank to isolate the t-junction -we found out that it only flocculated when it was leaking: hypothesis is incomplete mixing -we fabricated a clear t-junction from clear pvc piping and caps and connectors -clear pvc piping allows us to see what is going on in the mixing
sarahh2000
commented
5 years ago 4/21: -tested effluent flow rates with clear t-junction -problems: dripping from PACl microtubing not making it in to t-junction because of connections -flocculation very small extent, observe more flocs when we stopped system and started again --> incubation time and mixing needs to be increase, flocculator is not the issue -began fabricating recirculation device in t-junction
sarahh2000
commented
5 years ago 4/27 and 4/28: -we made t-junction vertical to enhance mixing -we made microbore tubing directly enter vertical t-junction -we noticed that when the water level was low, the system was able to flocculate, implying that there was some kind of a dosing issue. we thought that the dose was not enough -we first cut microbore tubing to increase dosing, but realized that pacl was entering too quickly -we changed the microbore tubing to a longer and thinner one
at effluent flow rate of 0.6779661017 mL/s (20 cm, top of tape) and PACl flow rate of 0.02062706271 mL/s (slightly below 10 cm, top of tape) the system was able to flocculate -the issue was not mixing after all but instead dosing
-more tests should be done to elucidate the experimental dosing of PACl with different concentrations of red dye. we should use a spectrophotometer to determine concentration of red dye. the microbore tubing may need to be made thinner to have more control over the PACl flow rate (and thus concentration) -since we changed the microbore tubing for PACl, we need to reestablish the height/flow rate curve -since the system was also altered a new effluent height/flow rate curve should be reestablished
sarahh2000
commented
5 years ago