Process and optimization
For this phase, hydraulic retention time, acid circulation rate and concentration as well as membrane thickness were optimized for the reactor. HRT wise the harvesting efficiency increases linearly between 2 and 12 hours. Based on retention time tests a correlation curve with membrane surface area was drawn. By adding membrane surface area, it is possible to decrease retention time without harvesting efficiency going down. Membrane thickness did not have any significant effect on harvesting efficiency. Results regarding the composting waters were similar to digester water results. Sulphuric acid and phosphoric acid work equally well.
|
Dates |
Number of runs |
HRT (h) |
Acid flow (l/h) |
Acid type |
Notes |
|---|---|---|---|---|---|
|
8.5.-17.5.17 |
4 |
8 |
1-9 |
H2SO4 |
Acid flow optimization |
|
19.5.-31.5.17 |
6 |
2-120 |
9 |
H2SO4 |
HRT optimization |
|
20.6.-23.6.17 |
2 |
8 |
9 |
H2SO4 |
Reject water pH optimization |
|
27.6.17 |
1 |
8 |
9 |
H3PO4 |
Different acid type |
|
3.7.17 |
2 |
28 |
9 |
H2SO4 |
Membrane thickness |
|
July 2017 |
Composting plant reject tests |
The process has been tested in lab scale with urea and reject water. Produced substances are commercial-like white powder. From left to right: commercial ammonium sulfate, ammonium sulfate produced from urea, ammonium phosphate produced from reject water and solid phosphate compound.
Results are as follows:
- The recovery efficiency improved linearly between 2 to 8-hour hydraulic retention time (HRT)
- 60 % recovery efficiency was reached in 8 hours
- Optimal acid circulation rate was determined to be 300 l/h/m2 related to reactor membrane surface area.
- The efficiency was also affected by the pH of the reject water.
- Higher pH -> better efficiency
- Membrane thickness and acid type did not have any significant impact on harvesting efficiency.
- Published:
- Updated: