The Use of Advance Control to Optimize the Biological Treatment of Piggery Effluent  

Project Title: The Use of Advance Control to Optimize the Biological Treatment of Piggery Effluent

Applicant: The Hong Kong University of Science & Technology

Total Approved Grant: $129,500

Duration: 1/11/1999 - 30/9/2000

Project Status/Remarks: Completed

Scope:

To develop an efficient waste treatment system for the treatment of piggery effluent by sequencing batch reactors.

Summary of the Findings:

We have establiched a sequencing batch reactor system to treat synthetic piggery wastewater. Various compositions of synthetic wastewater were formulated to study high-strength or low-strength piggery wastewater. The operating strategies necessary to enhance piggery wastewater treatment were studied. A BOD biosensor has been used to trace the concentration of organic carbon within 10 minutes, which is much faster than any other method such as COD measurement (2 hours) or traditional BOD5 measurement (5 days). The most economic way of utilsing organic carbon consumption in piggery wastewater treatment has been investigated by tracing the concentrations of organic carbon, ammonia, nitrate, nitrite, and phosphate using the BOD biosensor and other assay kits during the SBR cycle. We found that the BOD biosensor can be used to determine the switching time from one operation condition to the other within 10 minutes after sampling. The BOD biosensor could be used to identify a pattern in the consumption of organic carbon during the anoxic/anaerobic phase. It was found the BOD sensor decreased more rapidly during denitrification than during the heterotrophic consumption that followed. The organic carbon consumption by heterotrophs in the anaerobic phase is much less important than that by the denitrifiers. Moreover, the remaining amount of organic carbon became more important when the nitrification process was considered, since the nitrification process requires large amounts of carbon dioxide, which can be produced by aerobic consumption of organic carbon in the aerobic phase of the SBR operation. This is more important in wastewater treatment when carbon content is low compared with nitrogen and phosphate. Therefore, it could be possible to save more organic carbon by reducing the anaerobic phase period in real time using the BOD biosensor as a tracer.