Clay-Based Removal of Organic Pollutants from Urban Wastewater: The El Oued Region, Algeria

Introduction Urban wastewater management remains an environmental and public health priority, particularly in arid regions like El Oued, Algeria. Conventional treatment systems are often costly and complex. Clay minerals, abundantly available in this region, possess distinct adsorption properties favorable for pollutant removal. Previous investigations have explored various adsorption media, but local clays have not been fully utilized despite their promising chemical and structural characteristics. This article explores the suitability and performance of El Oued clays for urban wastewater purification

Existing Wastewater Treatment Systems
The city of El Oued currently uses aerated lagoons for wastewater treatment, which have shown effectiveness in removing organic matter. Studies have reported removal efficiencies of:

86.5% of BOD5 (Biochemical Oxygen Demand)
78% of COD (Chemical Oxygen Demand)
85% of TSS (Total Suspended Solids)

These systems operate with a hydraulic retention time of 12 to 20 days, meeting Algerian standards for treated effluent.
Potential of Local Clays
Research has highlighted the potential of using local clays for wastewater treatment, given their:

Abundant availability
Distinct adsorption properties
Promising chemical and structural characteristics

Using local clays could provide a cost-effective and efficient solution for urban wastewater purification in El Oued.
Benefits of Clay-Based Treatment
Clay-based treatment systems could offer several benefits, including ¹ ²:

Reduced costs: compared to conventional treatment systems
Simplified operation: minimal equipment and maintenance requirements
Effective pollutant removal: leveraging the adsorption properties of local clays

Further research is needed to fully explore the suitability and performance of El Oued clays for urban wastewater purification.

Materials and Methods

Materials

• Clay Sampling: Native clay was collected from Elmghaier in the El Oued region, consisting mainly of illite, kaolinite, and quartz in proportions of 62%, 27%, and 11% respectively.

Wastewater Source: Wastewater samples were taken from municipal treatment plants after primary treatment at the Kouinine station, north of El Oued.

• Chemical Reagents: Sulfuric acid (0.75 N) and hydrochloric acid (0.134 N) for activation; distilled water for washing and dilution.

Methods

• Clay Activation: The clay was subjected to thermal activation at 400°C and acid treatment as per optimized protocols.

Characterization: The mineralogical composition was established via X-ray diffraction (XRD), while physicochemical properties (pH, conductivity, surface area) were measured with standard procedures.

Batch Adsorption Trials: Wastewater samples were treated with various doses of activated clay; removal rates for COD, BOD, TSS, and turbidity were monitored.

Analytics: Post-treatment water quality was analyzed according to APHA (2012) standards, using spectrophotometric and gravimetric methods for pollutant quantification.

Results and Discussion

Clay Characteristics

• Activated clay exhibited enhanced surface area and adsorption capability.
• Thermo-chemical activation improved the clay’s structure, increasing pollutant uptake.

Wastewater Treatment Outcomes

• Clay performed best when acid-activated with sulphuric acid, achieving high adsorption rates for all monitored parameters.

Lower removal rates were observed with HCl-activated clay and thermal-only activation.

The adsorption process followed Freundlich isotherm kinetics, suggesting multilayer uptake mechanisms.

Comparative Discussion

• Local clays compare favorably with alternative adsorbents like biochar and bentonite, offering economic and accessibility advantages.

Integration of local clay into wastewater treatment could significantly lower operational costs and environmental impact, vital for semi-arid regions.

• The study suggests potential customization of clay activation processes to maximize efficiency based on specific wastewater profiles.

Conclusion

Locally sourced and activated clay adsorbents demonstrate high efficiency for the removal of organic pollutants from urban wastewater in the El Oued region. Acid-activated clay, particularly with sulphuric acid, delivers the best performance, suggesting practical scalability for municipal treatments. The use of clay represents a cost-effective, sustainable strategy for improving water quality in arid environments.

References

1. Babaami, N. et al. Wastewater Treatment by Improving the Local Clay. Asian Journal of Water, Environment and Pollution, 2013.