Team:Calgary/Results
Results
Process Development Results
Methods for VFA quantification and characterization
As mentioned in our journal, determination of the total VFA concentration in the solution was an important step in the process – knowing how to quantify total VFAs in the solution helped to prove that the fermentation of human feces with naturally occurring bacteria increases the VFA concentration, as well as it helped to prove VFA presence in both - fermented and unfermented synthetic feces.
Titration is commonly employed by the wastewater treatment plants to give a rapid estimate of the VFA concentration in the solutions. We were able to successfully perform “Simple titration” experiments. The results (summarized below) indicate that the method tends to give a slight overestimate of the total concentration – yet it can be used for quick estimations, as well as for determination of VFA concentration increase/decrease.
| Trial 1 | Trial 2 | Trial 3 | |
| Actual VFA Conentration (mg/L) | 60 | 60 | 60 |
| Sample volume (mL) | 40 | 40 | 40 |
| Acid normality | 0.1 | 0.1 | 0.1 |
| Original pH | 6.61 | 6.6 | 6.61 |
| Volume of acid added to titrate to pH 5 (mL) | 0.53 | 0.53 | 0.536 |
| Volume of acid added to titrate to pH 4.3 (mL) | 0.745 | 0.75 | 0.785 |
| Volume of acid added to titrate to pH 4 (mL) | 0.825 | 0.830 | 0.858 |
| Calculated VFA concentration (mg/L) | 66.1 | 67.7 | 74.9 |
HPLC is another method commonly employed in laboratory setting for the VFA concentration determination. The advantage of the method is the fact that it provides the breakdown: the concentration of different volatile fatty acids in the solution.
Process results
VFA fermentation results Liquid-solid separation resultsThe very fist experiments for the solid-liquid separation were "Gravity driven sedimentation" and "gravity driven filtration" experiments The results are summarized in the two tables below:
|
Gravity driven filtration |
Weigt of water present in sample (g) |
Weight of liquid recovered after 24 hours (g) |
Percent of liquid recovered (%) |
|
Sample 1 |
15 |
0 |
0.00 |
|
Sample 2 |
40 |
20.4 |
51.00 |
|
Sample 3 |
65 |
52.5 |
80.77 |
|
Gravity Driven sedimentation |
Weigt of water present in sample (g) |
Weight of liquid pipetted out after 24 hours (g) |
Percent of liquid recovered (%) |
|
Sample 1 |
15 |
0 |
0.00 |
|
Sample 2 |
40 |
21.4 |
53.50 |
|
Sample 3 |
65 |
47.5 |
73.08 |
It as clear the gravity alone would not do the required job, hence the"Staged Filtration" experiment was conducted using 25g of synthetic feces (recipe 2). The original sample contained 15g of water, yet only 10% of it was recovered, meaning that a more advanced and power intensive technology has to be considered for this stage of the process.
|
Filtration type |
Weight of liquid recovered (g) |
Liquid lost due to transfer (g) |
comments |
|
Strainer |
18.6 |
1.1 |
Yellow thick liquid went through. Yeast bodies we visible in the filtrate. |
|
"Paper towel" filter |
13.9 |
1.8 |
A thick creamy-yellow sludgy layer remained on the filter and could be scraped down. Yeast bodies could still be visible |
|
Coffee filter |
8.6 |
1.5 |
Another similar looking creamy-yellow layer was scraped down. The yeast bodies were not visible in the liquid any more |
|
11 micron filter |
5.8 |
1.2 |
|
|
0.2micron filter |
1.5 |
|
The majority of the liquid was not recovered because the filter got clogged. The recovered liquid had a brown tint, but appeared clear and transparent. |
Finally, we decided to investigate the efficiency of centrifugal based extraction methods using the "Centrifugation for solid-liquid separation" experiment. When a 50g undiluted sample of synthetic feces (recipe 2) was tested, the mass of water recovered was 19.6g, while the mass of initial water present in the sample was 30g, meaning 65% water recovery. Such result indicated that centrifugal based solid-liquid separation technology would be the best fit for our application.
PHB Extraction resultsPHB characterization
HPLC Nile red staining
