Wastewater quality improvement through storage: a case study in Sicily

Area of Science:

• Environmental Engineering
• Water Quality Management
• Wastewater Treatment

Background:

• Wastewater storage is crucial for managing effluent quality and meeting irrigation demands.
• Earth reservoirs are common for storing treated wastewater, but their impact on water quality requires detailed evaluation.
• Understanding storage effects is vital for optimizing wastewater reuse in agriculture.

Purpose of the Study:

• To evaluate the impact of storage in an earth reservoir on the characteristics of secondary treated wastewater.
• To determine the removal efficiencies of key pollutants and microbial indicators during wastewater storage.
• To identify reservoir design and operational parameters influencing water quality changes.

Main Methods:

• Wastewater from the Caltagirone plant was stored in a 25,000 m3 earth reservoir.
• Continuous inflow and discontinuous discharge operations were maintained.
• Water quality parameters, including BOD5, COD, and microbial counts (faecal coliforms, faecal streptococci, E. coli), were monitored.
• Statistical analyses, including single and multiple regressions, were employed.

Main Results:

• Storage in the earth reservoir demonstrated significant removal efficiencies for pollutants.
• Biochemical Oxygen Demand (BOD5) and Chemical Oxygen Demand (COD) removal efficiencies exceeded 50%.
• Logarithmic reductions of 2 to 5 units were observed for faecal coliforms, faecal streptococci, and Escherichia coli.

Conclusions:

• Earth reservoir storage is an effective method for further treating secondary wastewater.
• Reservoir operation regime and influent characteristics significantly influence pollutant removal efficiency.
• Reservoir design and operational parameters can be optimized to enhance water quality for reuse.