Olive mill wastewater treatment using coagulation/flocculation and filtration processes

Area of Science:

• Environmental Science
• Water Treatment Technologies
• Agricultural Engineering

Background:

• Olive mill wastewater (OMWW) is a highly polluting effluent from olive oil production, characterized by high chemical oxygen demand (COD), acidity, and phenolic compounds.
• The ecological challenge posed by OMWW necessitates effective treatment methods for potential water reuse, especially in water-scarce regions.
• Existing OMWW treatment methods often face challenges with efficiency and cost-effectiveness, particularly for artisanal olive mill operations.

Purpose of the Study:

• To investigate the efficacy of combined coagulation/flocculation and filtration processes for treating OMWW.
• To determine optimal conditions for coagulant dosage and filtration media for maximum pollution load reduction.
• To assess the potential for reusing treated OMWW in olive orchard irrigation and valorizing the generated sludge.

Main Methods:

• Two successive coagulation/flocculation steps using lime and aluminum sulfate (alum) at varying concentrations.
• Filtration experiments utilizing activated carbon and natural materials (olive stones, leaves, sand, gravel).
• Monitoring of key parameters: pH, electrical conductivity (EC), total solids (TS), chemical oxygen demand (COD), and phenolic compounds.

Main Results:

• Optimal coagulation/flocculation (8g/L lime + 7g/L alum, then 5g/L lime + 4g/L alum) achieved significant reductions in EC (10%, 37%), TS (41%, 37%), and COD (48%, 67%).
• Filtration with activated carbon and gravel proved most effective, reducing EC by 51%, TS by 37%, and COD by 26%.
• The combined treatment substantially eliminated phenolic compounds (up to 97% reduction) and produced sludge with a calorific value of 3295.79 cal/g, suitable for alternative fuel.

Conclusions:

• The integrated coagulation/flocculation and filtration process offers a viable solution for OMWW treatment, significantly reducing pollution loads.
• Treated OMWW meets quality standards for reuse in olive orchard irrigation (170 m³/ha), addressing water scarcity issues.
• Valorization of sludge as an alternative fuel presents an additional economic benefit for olive mills.