Automatic purification of animal wastewater by dual means of energy‐retaining anaerobic fermentation and ultrafiltration

Abstract

For the purpose of purifying animal wastewater and recovering energy during the operation, an automatic bench‐scale unit was manufactured and operated. It consisted of three pieces of an anaerobic fermentation digester, a sedimentation tank and an ultrafiltration module. The digester was equipped with fixed bacteria beds (bioreactor) and tape heaters. The sedimentation tank was equipped with a heat exchanger, through which fresh slurry passed. During automatic operations the slurry samples were taken out before, during and after the operation, and turbidity and organic matter contents were analyzed.

Comparing nylon mesh, chips of vinyl chloride pipe and crushed cement blocks, the crushed blocks were recognized best as a fixed bacteria bed. In the operating process, the supernatant fluid in the sedimentation tank was sent to the ultrafiltration module. After filtration a daily reverse cleansing was performed. All the operations worked according to the command programmed in the Controller PL40M III.

The average removal rates of organic matters in the compound slurry by the dual operations were as follows; 76.6% T‐S, 100. 0% T‐SS, 92. 655 COD, 96.5% BOD, 86. 8% NH₄‐N, 69. OX T‐N, and 98. 8% T‐P. The result of pre‐heating fresh slurry by effluent from the digester was also evaluated.

Key words:

• Animal wastewater
• Anaerobic fermentation
• Ultraf iltration
• Energy recovery
• Automatic bench‐scale unit