Introduction: Chemical pollution of surface water is one of the serious issues that threaten the quality of water. This would be more important when the surface waters used for human drinking supply. One of the key parameters used to measure water pollution is BOD. Because many variables affect the water quality parameters and a complex nonlinear relationship between them is established conventional methods can not solve the problem of quality management of water resources. …

In this study ,the environmental condition of the Zayandehrood river was theoretically and experimentally investigated. Therefore, a dynamic mathematical model with multiple pollution sources was formulated to predict the parameters such as BOD, DO, and temperature of water in the different locations of the river. Also, the water samples were collected from 120 kilometers of the river starting from the south Isfahan municipal wastewater treatment plant and the BOD, DO, and temperature of the samples were measured in the four seasons of the year 1377.The comparison of the obtained experimental data with the results of computer simulation revealed the extent of accuracy of the model. Using the mathematical simulation, it is possible to predict the Zayandehrood river environmental conditions in future with respect to industrial development and yearly rainfall. Thus by utilizing the model's theoretical results, one is able to make the proper decisions in order to achieve a sustainable development in the Isfahan province.  

Sampling in 5 stations was carried out from July 1999 to June 2000. Water temprature, pH and EC were measured on site. Maximum water temprature was observed in July and August, and maximum level of dissolved oxygen occured in November and February. Range of pH was between 7.2 to 9.4, in acceptable range for aquatics. The results showed that Shadegan marsh is a hard and brackish water body. Dissolved oxygen level was more than 5 ppm in most of the cases, and is optimum for fish growth and reproduction. Amount of BOD5 was 3-10 ppm. COD levels showed an increase in Autumn. With respect to N.NO3 and N.NO2, the water could be considered as unpolluted water. According to the statistical analysis of data, Mansoreh and Ataysh stations showed the same water quality. Study in various years showed that water quality in Shadegan Marsh has been diminished, probably due to decreasing run off and increasing pollution in Shadegan Marsh.

Among surface water resources, wetlands have special importance in providing habitat for various plant and animal species due to their ecological roles. Wetlands are swampy areas, reservoirs, and natural and man-made ponds that have static or flowing water, fresh or saline, permanent or temporary. One of the most important but little known traits of wetlands is to improve surface water quality. These systems can provide effective treatment for a variety of contaminants in the water, hence they are known as "natural water purifiers". Removal of pollutants occurs by the effect of simultaneous operation of physical, chemical, and biological processes including deposition, filtration, chemical reduction, adsorption, biodegradation, photo-oxidation, consumption by animals and plants, etc. The mechanisms and interdependencies between the ecological components of the wetland are complex and many of them are not yet fully understood. With the development of technology and the use of computers in engineering processes, the use of computer models to simulate ecological processes in natural ecosystems has become very common during the last years. Therefore, making an appropriate hydrodynamic model of the water body with the ability to simulate the affecting processes for the fate and transmission of the pollutant, has become a technical necessity. So far, several field studies and computer simulations have been reported to evaluate the efficiency of the wetlands to improve water quality under the predicted load of pollution entering the wetlands. The experience of using mathematical models for the simulation of the wetlands has shown the high ability of these models for the simulation of the complex ecological processes. So the computer models have seriously been considered as a modern tool for the management of wetlands and improving its purification efficiency. In the current study, the experiences of Babol city in the province of Mazandaran for the planning of a city wetland i. e. GoleNilofar wetland, to the common space is reported. The hydraulic retention times in wetland different basins are about 20 to 60 days. The inflow to the wetland is not changing along the seasons and was measured about 0. 153 m3/s in spring, 0. 157 m3/s in summer, 0. 273 in fall and 0. 217 m3/s in winter In this study, the computer model of the GoleNilofar wetland is developed using Hydrodynamic and ECOLab modules of the MIKE3 software. The FM hydrodynamic model is a basic numerical model for the flow simulation in MIKE3 that can be used in all water bodies i. e. the wetlands, rivers, bays, coastal waters, and open oceans. This model can simulate the flow unsteady three-dimensional features in the conditions of density changes in the environment. The model can simulate the impacts of external forces including meteorological and tidal parameters. The EcoLab module of MIKE software was developed as a modeling tool to investigate the effects of natural aeration, sunlight photooxidation, and sedimentation together with the plants and bacterial uptakes on the fate of organic matter and purification capability of the different water bodies. In the simulations, only BOD (Biochemical Oxygen Demand) time variations and spatial changes in the wetland were investigated. The amount of oxygen needed by microorganisms for the oxidation of degradable materials within 5 days is called BOD5 i. e. 5-day biological oxygen demand. Biological oxygen demand is one of the most important indicators of water pollution. Water contamination is caused by external material in a suspended or dissolved form that changes the physical, chemical, and biological properties of water. The BOD of the inflow was measured by sampling the incoming current in different seasons along 1398 (2019-2020). The BOD together with the discharge flow rate, temperature, and density of the water are modeling inputs that are required for the simulation. Here in this paper, the results of the wetland ecological simulations have been reported for the season of the spring. This season is selected as it is the beginning of a growing season in the wetland. To better investigate the distribution of pollutants and the changes in the flow properties, the water body of the wetland is assumed to be stationary and the concentration of BOD is considered equal to zero at the beginning of the simulation. So the inflow to the wetland (to the pond 1) was measured 0. 153 m3/s and the BOD of incoming water was measured 5. 5 mg/l, both of which did not change significantly during the spring. The time interval of 3 hours and the number of steps of 735, equivalent to one whole season is introduced to the model. Finally, the simulation results at the end of spring were compared with the observed values from the field sampling at the beginning of summer. As a result of hydrodynamic modeling when the wind speed is at its maximum during the season, i. e. 9 m/s, the flow velocity in the wetland is also at its maximum. For wind speeds of 9 m/s, the velocity of the surface flow was above 0. 37 m/s, which due to the closed boundaries of the environment, lead to deep current and material conduction to water depth. Ecological modeling exhibited that due to the chemical and biological processes, as well as the long retention time of the pollution in the wetland, distancing from the entrance, the BOD decreases clearly. According to the discharge flow rate and volume of each pond, the retention time in the first pond is about 18 days, in the second pond 24 days, and the third pond 73 days. The results also showed that the amount of BOD entering the wetland (5. 5 mg/l) at the end of spring and early summer reaches 4. 7 mg/l at output 1 and about 3 mg/l at output 2. The field measurements of BOD at the beginning of summer in both outlets showed the values of 4 and 3. 4 mg/l, respectively. Comparison of the modeling results with our field observation at the end of this season exhibited that the model can predict the BOD concentration with 80% accuracy without adjusting the coefficients and only using the values reported for similar conditions in previous studies. In this work, an ecological model has developed using the ECOLab module of MIKE3 for the Gole-Niloufar wetland which is an urban wetland in the city of Babol, north of Iran. The cpability of the wetland to improve the quality of incoming water has been discussed. This waterbody is a valuable natural resource in the region in terms of entertainment and recreation and has been used to supply water to rice farms downstream. In the developed model, the wetland is simulated during the spring for 93 days with 735 of 3-hour time steps in which the actual data of the inflow and BOD have been utilized. The BOD parameter was selected as an indicator of contamination to the organic matters and the process of transfer, diffusion, and decomposition were investigated by hydrodynamics modeling of the flow and the simulation of the BOD degradation in the wetland. The calculated values were compared with the field measurements at the end of the season and the accuracy of the model was investigated. A comparative study of the results with the field data exhibited that the model can predict the degradation of BOD concentration in the ponds. The results of this study showed that due to the high retention time, low flow rate, and the natural rehabilitation and purification, this wetland can reduce pollution to a desirable level. It has also been observed that the water quality of the wetland depends on the physical, chemical, and biological processes of wetland beside the properties of the incoming water. So improving the wetland performances from this perspective can ensure the safe use of water downstream.

Background: Tofu derived from processed soybeans is popular among the public, but its production has an unfavourable effect. After all, it produces liquid waste that causes quite high pollution because it contains quite high organic components. The present study aimed to reduce the content of biochemical oxygen demand (BOD), chemical oxygen demand (COD), and ammonia (NH3) in the liquid waste of a tofu factory. The scope of this research is limited to reducing the content of BOD, COD, and NH3 using an anaerobic-aerobic biofilm aeration system. Methods: This is an experimental study with a pre-post test only design and one group post-test design. The study population in this study is the tofu industry, and the sample in this study is partly water from the tofu waste. Sample examination was carried out at the Regional Health Laboratory of Jambi province, Indonesia. Results: The results showed a decrease in BOD, COD, and NH3 after passing through a tofu waste treatment machine using anaerobic and aerobic biofilms with BOD, COD, and ammonia values of 64. 6%, 49. 6%, and 79. 8%, respectively. Tofu waste treatment using anaerobic and aerobic biofilms can lower the temperature and increase the pH of the waste. Conclusion: On the surface of the bioball used, the growth of the biofilm was found, and to increase the ability of the equipment, an initial treatment, such as filtration and sedimentation of waste, and reducing acidity with the help of quicklime was needed.

Shortage of water resources and renewable per capita in last 30 years is put Iran on crisis threshold. Wastewater reuse is one of the battle solutions for water shortage and prevents wastewater depletion and environmental pollution. Thus, a pilot scale experiment was carried out to evaluate an integrated anaerobic/aerobic treatment for removal of BOD5 and COD, also to reduction of hydraulic retention time by considering optimum removal efficiency. The pilot was an anaerobic/aerobic bioreactor type under continuous-feeding regime based on a central composite design. The pilot was studied in different retention time and aeration was carried out between 5-15 hours. According to different retention times for COD removal efficiency, 24 hours was selected as optimum hydraulic retention time, that it is comparable to those obtained for 48 hours and over in plant roughly and could remove COD and BOD in acceptable ranges, results showed that average removal efficiency for BOD5 were 63. 86 and 83. 99 percent in aerobic and anaerobic phases, respectively. The average removal efficiency for COD was 76. 5 and 74. 35 percent for anaerobic and aerobic sections, respectively. The average removal efficiency for BOD5 and COD in this integrated aerobic-anaerobic pilot 95. 24 and 94. 8 percent, respectively.

This research evaluated the efficiency of combined anaerobic-aerobic processes for the treatment of slaughterhouse wastewater. The anaerobic reactor consists of a 3. 95 L Plexiglas column with 60 mm diameter and 140 cm height. The cylindrical particles of polyvinyl chloride with 2 mm diameter and 1250 kg m-3 density packed to 60 cm of column were used as biomass saving material. The designed aerobic reactor also has a Plexiglas column with 10 cm internal diameter, 90 cm height and 60 cm useful height. Anaerobic fluid bed and aerobic mobile bed reactors were exploited for retention times of 18, 24, 32, 40 and 48 h. The efficiency of total suspended solids, biological oxygen demand and chemical oxygen demand removing were evaluated in different stages. Under the applied condition, chemical oxygen demand, biological oxygen demand and suspended solids were removed by 85. 94, 92 and 66%, respectively. Maximum methane production of 3765 mL per day was obtained after 31 h at the residence time of 18 h. The anaerobic reactor plays very important role in reduction of the chemical oxygen demand, and the aerobic reactor is necessary to clear the anaerobic treated wastewater and ensure the quality of the final waste.

This study was conducted to monitor the current water quality of Beshar River by the Iranian Surface Water Quality Index (IRWQIsc). Monitoring of the river water quality was done based on sampling 12 stations along the river in October of 2021 as the period of water shortage and January of 2022 as the period of high water flow simultaneously with sampling two other stations (fish farm effluent and Yasuj wastewater treatment plant effluent) as the point source pollution entries. The results of zoning Beshar River based on IRWQIsc in the period of water scarcity showed a decrease in river water quality from the upstream to the downstream part. 41. 66% of the upstream part of the river (Tang-e Tizab to Dehno) was in a relatively good condition, 8. 34% of the river (entrance of Yasuj City) was in a good condition, 8. 33% (middle part of the river in Shah Mokhtar Area) was in a relatively bad condition and 41. 66% (downstream of the river) was in a moderate condition. Despite the increase in discharge and rainfall, no significant increase in water quality was observed in the high water flow period. In this period, 25% of the river (Tang-e Tizab, Tang-e Sorkh, and downstream of Qalat) was in a moderate condition and 75% of the river was in a relatively good condition based on IRWQIsc. Comparison of the flow rates and IRWQIsc indices showed that only during the high water flow period in the lower reaches of the river, the increased river discharge enhanced the river water quality, but no relationship between the river flow and the IRWQIsc was found at the upstream part of the river and in the period of water scarcity.

Housing large and heavy industries, Isfahan Province is facing water shortage, encouraging investigations aimed at reusing industrial effluents in agriculture. Using average values obtained from tests of samples taken every 15 days over a period of two months from industrial effluents in northeast Isfahan, the present descriptive cross-sectional study was implemented to determine whether the effluents would pass quality standards for agricultural reuse. The average values of BOD, COD, TSS, pH, and turbidity as well as Fe, Zn, Pb, Cd, Co, Cr, Cu, Vanadium, Ag, Mn, and Nickel concentrations in addition to total and fecal coliform counts were compared with the quality standards recommended by EPA. It was found that average BOD, COD, TSS, pH, and turbidity values did not exceed standard values while total coliform counts as well as oil, fat, detergent, and heavy metal (e. g., cadmium, copper, vanadium, and cobalt) contents in some samples did exceed the relevant allowable limits. Based on the results obtained, the treated effluents exhibited certain limitations (e. g., high cadmium, copper, vanadium, and cobalt contents) that need to be addressed before reuse in agricultural irrigation. To avoid the adverse environmental effects of the effluents on soil, they may be recommended for irrigating non-edible trees and industrial plants such as cotton.