Document Type : Original Article
Authors
1
Ph. D student of Civil Engineering, Department of Civil Engineering, Arak Branch, Islamic Azad University, Arak, Iran, Iran.
2
Associate Professor, Department of Water Engineering, Kermanshah Branch, Islamic Azad University, Kermanshah, Iran.
3
Associate Professor, Department of Civil Engineering, Arak Branch, Islamic Azad University, Arak, Iran.
4
Assistant Professor, Department of Textile Engineering, Arak Branch, Islamic Azad University, Arak, Iran.
5
Associate Professor, Department of Chemical Engineering, Arak Branch, Islamic Azad University, Arak, Iran.
Abstract
Introduction
The Dez River, as the third largest river in the country, plays an essential role in the economic, social and environmental life of North Khuzestan. Also, it is very important because it supplies water to more than 125 thousand hectares from the Dez plain and the lands downstream of this plain to the place of Bituminous Dam and provides a significant part of the environmental needs of the Karun River. The purpose of this research is to investigate the trend of quality and pollution along the Dez River and evaluate the effects of urban, agricultural and industrial wastewater discharges on the trend of pollution and quality of the Dez River in 131 intervals based on the QUAL2KW model.
Methodology
The QUAL2Kw model simulates the river in one dimension (one dimension along the length of the river) along with non-uniform permanent flow and can consider the effect of loading both point and non-point. In this model, in order to determine the concentration of qualitative parameters, the finite difference method is used to numerically solve the displacement-diffusion equation (Chapra et al., 2006). In this research, the QUAL2KW model was used to simulate the process of pollution and quality in Dez River. This model is able to solve the equations related to the river in both permanent and quasi-dynamic conditions. Also, simulate parameters such as dissolved oxygen, biochemical oxygen demand, temperature, ammonia nitrogen, etc. in the river network. In this model, the qualitative simulation is done based on the river course spacing. Spacing is done according to the hydraulic conditions of the river and the place of discharge of pollutants. Therefore, the distance between the regulatory dam and Bandaghir was divided into 131 intervals with variable lengths. In the calibration and validation stages of the model, it was determined that wide parameters such as flow geometry, river hydraulic conditions, water flow rate, aeration coefficients, pollutant entry points, nitrification rate, oxygen demand, etc. in the river are involved in qualitative modeling results.
Results and discussion
The results showed that QUAL2KW water quality model is highly accurate in simulating quality parameters and pollution in Dez River. The trend of changes in quality parameters and pollution in the Dez River showed that this river is better in terms of BOD pollution due to the discharge of urban and industrial sewage, in terms of EC pollution due to the discharge of agricultural land drains (mainly sugarcane plan) and in terms of N-NH4 pollution It is in a critical condition due to urban and industrial sewage and drainage of agricultural land. Therefore, it is suggested that all sewage of Dezful city, sewage of fish farming, Haft Tepe complex and Pars paper factory be treated and then discharged, but regarding agricultural drains, corrective measures such as improvement in the type of irrigation systems, fertilizers , the cultivation pattern of the area, etc., should be done at the source.
Conclusions
The construction of a treatment plant as a solution for all polluting sources seems to be expensive and impossible. Therefore, it is suggested that all sewage of Dezful city, sewage of fish farming, Haft Tepe complex and Pars paper factory be treated and then discharged, but regarding agricultural drains, corrective measures such as improvement in the type of irrigation systems, fertilizers , the cultivation pattern of the area, etc., should be done at the source.
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