Process and optimization

Optimization tests were run with a lab scale pilot plant. The reject water tested came from HSY (Helsingin seudun ympäristöpalvelut, Environmental services for Helsinki area) Viikinmäki waste water treatment plant and HSY Ämmässuo biogas plant.

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.

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:
Share
URL copied!