Impact assessment of the Ahvaz sewage master plan on water quality of the Karun River using QUAL2Kw model

Document Type : Research Paper

Authors

1 PhD Student, Department of Water Engineering and Sciences, Imam Khomeini International University of Qazvin.

2 associate professor, water eng. group, Imam Khomeini International University، Qazvin

10.22059/ijswr.2024.379576.669757

Abstract

Despite its significant importance, the Karun River is under serious threat from pollution caused by urban and industrial wastewater. Given the river's critical role in supplying drinking water, supporting agriculture, and facilitating industrial activities, maintaining its water quality is of vital importance. This study investigates the impact of the Ahvaz comprehensive sewage plan on the water quality of the Karun River using qualitative modeling. In this research, the QUAL2Kw model was employed to simulate water quality changes along a 28-kilometer stretch of the river. After validating the model, various wastewater management scenarios were examined, including the current situation, the operation of the eastern treatment plant, the expansion of the western treatment plant, full implementation of the Ahvaz comprehensive sewage plan, and drainage control measures. The results showed that the full implementation of the Ahvaz comprehensive sewage plan significantly improves water quality by reducing pollutants such as BOD, ammonium, organic and inorganic phosphorus. For instance, BOD concentration decreased from 6.1 to 2.6 mg/L, organic nitrogen concentration from 425 to 234 µg/L, organic phosphorus concentration from 135 to 35 µg/L, inorganic phosphorus concentration from 251 to 0.23 µg/L, and dissolved oxygen concentration increased from 5.55 to 6.79 mg/L. Additionally, controlling agricultural drainage also had a positive effect by reducing nitrate concentrations, EC, and enhancing overall water quality. This study demonstrates that proper and comprehensive wastewater management, especially in densely populated urban areas, can significantly improve river water quality.

Keywords

Main Subjects

EXTENDED ABSTRACT

 

Objective

The Karun River, located in southwestern Iran, is susceptible to pollution from urban and industrial wastewater. Given the vital role of the Karun River in providing drinking water, agricultural use, and industrial activities, its water quality is of critical importance. The aim of this research is to investigate the water quality of the Karun River and the impact of the comprehensive urban wastewater project in Ahvaz on its water quality parameters. This study focuses on assessing spatial variations in water quality trends under different scenarios of wastewater management, including current conditions, operation of the East wastewater treatment plant, completion of the West wastewater treatment plant capacity, full implementation of the comprehensive urban wastewater project in Ahvaz, and controlling drainage inputs.

Methodology

In this study, the QUAL2Kw model, a one-dimensional computer model for simulating water quality in rivers, was employed to investigate the water quality of the Karoun River. Data on flow, depth, velocity, temperature, electrical conductivity (EC), dissolved oxygen (DO), BOD, organic nitrogen, ammonia nitrogen, nitrate, organic phosphorus, inorganic phosphorus, alkalinity, and pH were collected at four stations along the Karoun River. August 2018 data were used for model calibration and September 2018 data were used for model validation. The accuracy of the model was evaluated using the RMSE, MAPE, and PBIAS error indices. After confirming the validity and accuracy of the model in the calibration and validation stages, the developed model was used to investigate different scenarios in the Karoun River. Considering the construction of wastewater treatment plants and the possibility of eliminating wastewater inputs into the river, the water quality in the downstream reach of the river was examined under different wastewater input scenarios.

Findings

The results indicated that the QUAL2Kw model satisfactorily simulated both hydraulic parameters (depth, velocity, flow rate) and quality parameters (EC, DO, BOD, organic nitrogen, ammonia nitrogen, nitrate, alkalinity, pH). The water quality of the Karun River deteriorates for all parameters as it moves from upstream to downstream. The main factors affecting water quality are the discharge of urban and industrial wastewater, agricultural drainage, and agricultural activities. Additionally, the impact of the comprehensive wastewater plan for Ahvaz was examined under various scenarios, with results showing a significant improvement in river water quality upon full implementation of the plan.

Conclusion

Based on the findings of this study, the QUAL2Kw model is an efficient tool for simulating the water quality of the Karun River. The results indicate that the water quality of the Karun River is in a poor state, necessitating effective measures to control and reduce pollutants entering the river. Implementing the comprehensive wastewater plan for Ahvaz and controlling drainage systems could significantly reduce the concentrations of pollutants such as BOD, nitrate, nitrite, ammonium, phosphorus, and heavy metals in the Karun River. Consequently, the implementation of this plan would improve water quality and mitigate environmental threats. Therefore, it is recommended that the implementation of this plan be pursued seriously and that necessary actions be taken to enhance the water quality of the Karun River.

Author Contributions

All authors contributed equally to the conceptualization of the article and writing of the original and subsequent drafts.

Data Availability Statement

Data available on request from the authors.

Acknowledgements

The authors gratefully acknowledge the financial support of the Iran National Science Foundation (INSF), Grant No. 4024661, and Imam Khomeini International University (IKU) for conducting this research.

Ethical considerations

The authors avoided data fabrication, falsification, plagiarism, and misconduct.

Conflict of interest

The author declares no conflict of interest. 

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Iranian Journal of Soil and Water Research
Volume 55, Issue 10
December 2024
Pages 1761-1785

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