UASB-polishing ponds design parameters: contributions from a pilot scale study in southeast Brazil

Area of Science:

• Environmental Engineering
• Water Treatment Technologies
• Microbiology

Background:

• Wastewater treatment plants are crucial for public health and environmental protection.
• Optimizing treatment processes, such as those involving biofilters and polishing ponds, is essential for achieving high effluent quality.
• Understanding the removal dynamics of pollutants like ammonia and E. coli is key to effective wastewater management.

Purpose of the Study:

• To evaluate the performance of a wastewater treatment system including a UASB reactor, submerged aerated biofilter, and polishing ponds over five years.
• To assess the efficiency of shallow polishing ponds in removing ammonia and E. coli.
• To validate existing models for predicting pollutant removal in pond systems for polishing pond applications.

Main Methods:

• Field-scale monitoring of a wastewater treatment plant in southeast Brazil.
• Pilot-scale operation of shallow polishing ponds in series.
• Analysis of effluent quality for ammonia and E. coli concentrations.
• Application and validation of established mathematical models for pollutant removal.

Main Results:

• The treatment system, particularly the three-pond series, achieved high effluent standards for ammonia and E. coli.
• A fourth polishing pond did not significantly improve effluent quality.
• Established models for ammonia and E. coli removal in facultative/maturation ponds showed applicability to polishing ponds.
• Variations in pH and E. coli die-off rate constants were observed along the pond series.

Conclusions:

• Shallow polishing ponds in series can be effective for achieving high-quality wastewater effluent, specifically for ammonia and E. coli removal.
• The number of ponds in series should be optimized, as additional ponds may not yield further treatment benefits.
• Existing models for pond treatment are adaptable for predicting performance in polishing pond systems, aiding in design and operation.
• Understanding parameter variations within pond systems is important for accurate performance prediction and management.