Final Aerobic Sampling (Day 7) on 20 December 2010 (Monday)

  
On this final test, we split the group to fulfill 3 different tasks simultaneously:

• Marcus: Sample Testing and Data Tabulation
• Brenda: Sample Collection and Planting with fertilisers from aerobic stage
• KH: Digestors Decommissioning and Washing, Packing up of equipment
• All 3: Switching of Compressed Air Tank (the initial one had run out)

This is the new Thermoractor. The compartment of the left is used for COD and TOC tests; the rectangular plate on the left serves as a heating plate:

Switching the compressed air cylinder:

 

 Marcus's performing sampling:

TOC Test for all 6 sample cells:
Left: before settling. Right: observe 3 distinct layers for the same test.

KH draining and washing the Grey & Orange Digestors:

 

 

The concept of the back-wash valve worked!! We managed to free the sight glass from clogging and algae. Good that we foresaw the issue of plugging (for slurry application) during the "DESIGN" stage:

Before washing:

After back-flushing:

Packing up and disposing the waste chemicals:

 

Yet another night shift (we left farmmart at 9 pm):

Key Testing Results & Findings:

1. Sulphate, COD and TOC concentration dropped progressively
2. Phosphate and Nitrate concentration rose (increase in fertiliser quality)
3. High quality of biogas (70-100% LEL)
4. pH remained consistently in the alkaline range (optimum 7.2 - 7.4)
5. Volatile Acid rose and then dropped
6. Sludge density showed a decreasing trend
7. Operation for both stages were non-auto-thermal, despite the initial claims of an ATAD (auto-thermal thermophilic aerobic digestion) process. Temperature remained in the region of 30 Degrees Celsius.
8. Pollution level was extremely low (COD levels reached "0")
9. High fertiliser quality (when compared to blank and commercial fertiliser); plant height >10 cm after 1 week.

Kian How, signing off on 21/12/10, 12pm.