Optimum cycle time for intermittent UASB reactors treating dairy wastewater.

Area of Science:

• Environmental biotechnology
• Wastewater treatment technologies
• Anaerobic digestion

Background:

• Dairy wastewater (DWW) presents a significant treatment challenge due to its high organic load.
• Intermittent operation of Upflow Anaerobic Sludge Blanket (UASB) reactors offers potential for enhanced efficiency in treating recalcitrant wastewaters.
• Understanding the impact of cycle duration is crucial for optimizing intermittent UASB reactor performance.

Purpose of the Study:

• To investigate the influence of varying cycle durations on the intermittent operation of mesophilic UASB reactors for dairy wastewater treatment.
• To determine the optimal cycle length for maximizing methane conversion and operational stability.
• To compare the performance of intermittent UASB operation with continuous systems for dairy effluent treatment.

Main Methods:

• Comparison of five cycle lengths (24 to 144 hours) in mesophilic UASB reactors.
• Operation with dairy wastewater at organic loading rates ranging from 2.5 to 29.0 gCOD/l/d.
• Analysis of COD (Chemical Oxygen Demand) balances to assess substrate removal and methane conversion efficiency.

Main Results:

• A feedless period is essential for efficient substrate conversion to methane.
• Longer cycle times allowed for higher maximum applicable organic loading rates.
• The 96-hour cycle (48 hours feed, 48 hours feedless) yielded the highest methane conversion and most stable operation.
• Intermittent operation achieved significantly higher stable loads (22 gCOD/l/d) compared to continuous systems (3-6 gCOD/l/d).

Conclusions:

• The 96-hour cycle (48h feed + 48h feedless) is identified as the optimum operational strategy for intermittent mesophilic UASB reactors treating dairy wastewater.
• Intermittent UASB operation demonstrates superior performance in terms of load capacity and stability for dairy effluent treatment compared to continuous systems.