جستجوی مقالات مرتبط با کلیدواژه « self-purification » در نشریات گروه « آب و خاک »

Today, one of the most effective ways to manage and protect surface water resources is to use the capacity of rivers to accept limits of pollution. In this study, the self-purification capacity of the Abbasabad river in Hamedan using the QUAL2KW model, based on the simulation of DO, BOD and COD parameters, taking into account the water quality standards in two areas for drinking (1.86 km) and agriculture (4.33 km) was evaluated. The accuracy of the simulated values was calculated through the calculation of statistical indices such as R2, SE, RMSE and NRMSE. The RMSE values in the validation stage for DO, BOD and COD values were calculated as 0.26, 1.82 and 2.62, respectively. The simulation results showed that the amount of dissolved oxygen decreased by -3.21% in the first period and by -1.66% in the second period. Also, the concentration of BOD and COD increased by 30.13 and 27.94% in the first period and by 70.84 and 60.81% respectively in the second period. Also, TMDL results showed that in the first period, the amount of input load should be reduced, but in the second period, it is possible to increase the input load. For BOD and COD parameters, the maximum load was calculated based on the agricultural standard at the two watersheds, as 49.80 mg/liter and 99.15 mg/liter.

Ensuring the health and sustainability of the environment is one of the secondary goals of hydraulic structures. Water pollution and the reduction of its quality are serious threats to the health of the earth and will turn rivers into channels for polluted industrial wastewater. Increasing the residence time of flow in rivers by constructing hydraulic structures such as gabion spur dikes can increase the self-purification capacity. In this research, a laboratory investigation of pollution transport using NaCl tracer material in a laboratory channel with a sediment bed with a medium diameter (D50) of 11.85 mm, thickness of 12 cm, and length of 12 meters in a different number of fine-grained or coarse-grained gabion spur dikes from 1 to 4 were performed. Analytical solutions of Advection-Dispersion equation (ADE), OTIS model, and solution of Transient Storage Model (TSM) were used for numerical simulation. Laboratory results showed that gabion spur dikes with fine-grained materials reduce the peak concentration of pollution (Cmax) compared to coarse-grained materials. The results showed that the gabion spur dikes in the flow path increase the residence time of the pollutant by increasing hyporheic exchanges. The advection-dispersion equation (ADE) has low accuracy in the simulations due to the lack of attention to the role of the storage zone exchanges, with a determination coefficient (R2) of 0.71 to 0.83. On the other hand, the OTIS model, which is based on the transient storage model (TSM), considering the role of the porous zones of spur dikes in the transient storage of solute, has high accuracy with a determination coefficient (R2) of 0.91 to 0.98. The estimated coefficients of longitudinal dispersion (Dx) and storage zone exchange (α) by the temporal moment analysis were evaluated lower than the estimates of OTIS model in most of the simulations.

Accurate estimation of pollution decay coefficient is due to its effect on the oxygen consumption of the river’s solution of important issue, in managing the quality of water resources. The main purpose of this paper is to determine the decay factor of two rivers of Iran, named Talar and Babolrood Rivers. It has been done by measuring the field and elucidating the common empirical equations in two seasons of spring and summer. The qualitative parameters including DO, BOD, pH, EC, nitrate, phosphate and temperature in Talar River were measured in 5 sections of a total length of 4 km long, and in Babolrood River in 3 sections at a total length of 2.8 km, in May and August 2018. Then the decomposition coefficient was estimated using Streeter-Phelps Analytic Model. DO and BOD values were also analyzed in both spring and summer seasons. Based on the results in both case studies, the decay rate in summer was more than spring. The decay rate in Talar River was calculated equal to 1.57 in spring and 6.11 in summer, and in Babolrood, spring was 1.2 and in the summer was 8.34 (1/ day). Also, based on the slope changes, the dissolved oxygen content in both rivers increased in spring and decreased in the summer. In Talar River the BOD was equal to 4.34, in spring and 7.44 mg per liter in summer, and in Babolrood River in spring was equal to 2.5 and in the summer equal to 3.2 mg per liter.