Continuous fill intermittent decant type sequencing batch reactor application to upgrade the UASB treated sewage

Area of Science:

• Environmental Engineering
• Wastewater Treatment Technologies
• Water Quality Management

Background:

• Upflow anaerobic sludge blanket (UASB) reactors are widely used for domestic wastewater treatment.
• Post-treatment of UASB effluent is often necessary to meet stringent discharge standards.
• Continuous flow intermittent decant (CFID) reactors offer potential for enhanced effluent polishing.

Purpose of the Study:

• To investigate the performance of a CFID reactor as a post-treatment for UASB reactor effluent.
• To determine the optimal operating conditions (hydraulic retention time and dissolved oxygen levels) for the CFID reactor.
• To evaluate the removal efficiencies of key pollutants including BOD, TSS, ammonia nitrogen, and fecal coliforms.

Main Methods:

• The CFID reactor was fed with effluent from a domestic wastewater UASB reactor.
• Experiments were conducted at three different hydraulic retention times (HRTs): 22, 8, and 6 hours.
• Three dissolved oxygen (DO) patterns were tested: <0.5 mg/L, 2.5-3.5 mg/L, and 3.5-4.5 mg/L.

Main Results:

• The highest effluent quality was achieved at an 8-hour HRT and a DO concentration of 2.5-3.5 mg/L.
• Under optimal conditions, average removal efficiencies were 83% for BOD, 90% for TSS, 74% for ammonia nitrogen, and 99% for fecal coliforms.
• The CFID reactor demonstrated significant pollutant removal, improving overall wastewater treatment.

Conclusions:

• The CFID reactor is a viable and promising post-treatment technology for existing UASB systems.
• Optimal operation at 8-hour HRT and 2.5-3.5 mg/L DO ensures effluent quality suitable for receiving waters and reuse.
• CFID technology can help wastewater treatment plants meet regulatory requirements and promote water reuse.