Development of CHEMICAL OXYGEN DEMAND (COD) flow system has been conducted by using TiO2/Ti electrode. This study aims to develop the flow system portable reactor can be used for determination of COD value as a model design in a river, gutter, and disposal of industrial wastewater. A highly ordered the TiO2 nanostructure was grown onto Ti plate by anodizing method then calcinated in temperature 500 ° C for 1. 5 h. The electroCHEMICAL test on TiO2/Ti electrode was performed by using Linear Sweep Voltammetry technique to investigate the high photo-oxidation when ultraviolet (UV) light irradiation. Specifically, the determination of COD value of Sodium Lauryl Sulfate, Hexadecyltrimethylammonium bromide, and 4-oktilfenol poly-ethoxylate surfactants in flow system was applied by using Multi-Pulse Amperometry technique based on Faraday’ s Law (Q=∫ Inet dt). The excellent sensing of COD value using TiO2/Ti electrode by flow system showed that SLS, HDTMA-Br, and Triton X-100 surfactants in the concentrations of 1. 0 mg/L, 3. 0 mg/L, 5. 0 mg/L, 7. 0 mg/L, and 9. 0 mg/L were (1. 33 mg/L, 2. 92 mg/L, 4. 63 mg/L, 6. 68 mg/L and 9. 43 mg/L); (0. 78 mg/L, 3. 25 mg/L, 5. 21 mg/L, 7. 42 mg/L and 9. 06 mg/L), and (0. 71 mg/L, 3. 21 mg/L, 5. 05 mg/L, 7. 42 mg/L and 8. 61 mg/L), respectively.

When a new wastewater treatment plant is being designed by computer simulation, detailed data about organic fractions of influent wastewater (measured as CHEMICAL OXYGEN DEMAND) are usually not available, but knowledge of the typical ranges of these fractions is indispensable. The influent CHEMICAL OXYGEN DEMAND fractions can substantially influence the results of simulation-based design such as reactor volumes, solids residence time, effluent quality, OXYGEN DEMAND, sludge production, etc. This article attempts to give an overview of wastewater organic fractions as modeling parameters and presents new CHEMICAL OXYGEN DEMAND fractionation results from Hungary. According to the data from literature, the ratio of CHEMICAL OXYGEN DEMAND components in raw wastewater is very different and the average composition is as follows: Inert particulate = 17.1 %, slowly biodegradable = 57.9 %, inert soluble = 7.8 % and readily biodegradable = 17.5 %. The Hungarian wastewater samples were analyzed according to STOWA (Dutch foundation for applied water research) protocol and the obtained results were not much different from those of literature (inert particulate = 23.7 %, slowly biodegradable = 49.8 %, inert soluble = 4.6 % and readily biodegradable = 21.9 %), but some typical characteristics were observed.

Background and Objectives: Advanced Sequencing batch reactors (SBR) are one of the most suitable modified activated sludge systems. Due to low cost, optimal efficiency, and easy operation, they are recognized as an effective biological treatment system. The purpose of this study was to determine the performance of the SBR biological process in the removal of organic matter and nutrients from Yazd city wastewater. Materials and Methods: This descriptive study examines the trend of organic matter and nutrients changes in the biological process of advanced SBR. In this study, the samples were taken from the input and output of the SBR process four times a month for 9 months in 2019. A total of 72 samples were taken. Then COD (CHEMICAL OXYGEN DEMAND) and BOD5 (bioCHEMICAL OXYGEN DEMAND) and nutrients (phosphate ( )), total phosphorus, ammonium ( ), nitrate ( ), and nitrite ( ) were measured. Finally, the results were analyzed by one-sample t-test at a significance level of 0. 05. Results: The concentration of COD and BOD5 in the effluent was 42 and 14 mg/L, respectively. The concentration of total phosphorus, phosphate, ammonium, nitrate, and nitrite in the effluent was also shown to be 2. 9, 2. 4, 6. 3, 9. 01, and 0. 92 mg/L, respectively. Conclusion: The results showed that the active sludge system in the Yazd wastewater treatment plant has a good and acceptable situation. This has caused a significant reduction in organic matter and nutrients. These results are in accordance with the standards of the Iranian Environment Organization in the reuse of wastewater.

Background: In the presence of chloride, bromide and iodide the reported values for CHEMICAL OXYGEN DEMAND (COD) are not real and contain error. The purpose of this study was determining the error in calculating the COD based on Water and Wastewater Standard Testing Methods, in presence of the chloride ion, in various concentrations of COD.Methods: The experiment was done via two methods: without any removal of the chloride ion in the first method and using the proposed method of removing the chloride ion by Water and Wastewater Standard Testing Methods in the second method. In order to remove the impact of the chloride ion a HgSO4: Cl ratio equal to 10: 1 was used in this method. There were 22 samples that were evaluated twice. NaCl and COD ratios in samples were varied between 1.5-5 g/L and 400-1500 mg/L respectively. Samples divided into two groups, one group without NaCl, the spike sample, and other group unspike sample that had various concentrations of NaCl.Findings: The error value in the first method was 16% and in second method was 10.2%. In the second methods 63.6% of the values were lower than the real values; however in the first method 36.4% of values were lower than the real values that can be due to oxidation of chloride ion with potassium dichromate (K2Cr2O7).Conclusion: Presence of chloride ion in saline wastewater can lead to an error in determining the COD value. Sometime this error is positive and sometime negative. These errors are greater in high concentration of COD which could be due to chloride ion oxidation by dichromate and remained some non oxidation organic materials.

Anzali Wetland is a distinguished coastal wetland in the southern coast of the Caspian Sea in north of Iran. This wetland is connected to the Caspian Sea through the Shipping Channel and is supported with freshwater by 10 major rivers. Anzali Wetland plays a key role as a habitat for many indigenous plant and animal species. It is believed that the ecosystem of the wetland is threatened by inflow of excessive amounts of CHEMICAL OXYGEN DEMAND (COD), Total Nitrogen and Total Phosphorus. CHEMICAL OXYGEN DEMAND (COD) is a representation of organic pollution. Changing in discharge of rivers and precipitation and Caspian Sea level changes due to seasonal climate changes has some effects on COD concentration of the Wetland. In this paper, a two-dimensional depth-averaged model for hydrodynamic and advection-dispersion is used to determine COD distribution in Anzali Wetland. Forcing actions of Caspian Sea fluctuations, evaporation and precipitation, rivers input and wind is taken into account. According to available field data, the model is executed for three periods which are dry (23rd August-1st September), early rainy (13th October-25th October) and mid-rainy (2nd December-14th December) season. The simulated values are compared with observed ones at 16 stations. The results indicate that COD concentrations at all the stations were high denoting noticeable organic pollution in the wetland especially in the dry season.

In this study, CHEMICAL OXYGEN DEMAND (COD) from a pharmaceutical wastewater (PhW) was reduced by several techniques such as electro-Fenton (EF), photo electro-Fenton (PEF) and activated sludge (AS) processes and the obtained data were compared with each other. The effects of several parameters such as pH, current density, H2O2/Fe2+ molar ratio, volume ratio of H2O2/PhW, reaction time and UVA light were studied on the COD reduction through the EF and PEF processes. The Box-Behnken Design (BBD) under Response Surface Methodology (RSM) was applied to design and then optimize these processes. The optimal conditions for 87% of COD removal through the EF process were at pH of 3. 27, current density of 57 mA/cm2, H2O2/Fe2+ molar ratio of 3. 5, volume ratio of H2O2/PhW of 1. 34 ml/l and reaction time of 56. 32 min while the optimal conditions for 91. 6% of COD removal through PEF process were at pH of 3. 5, current density of 57. 5 mA/cm2, H2O2/Fe2+ molar ratio of 3. 81, volume ratio of H2O2/PhW of 1. 5 ml/l, reaction time of 10. 12 min and 6 W UVA light while 77. 70% of COD removal was obtained by the AS process with residence time of 1020 min. According to the kinetic study, the second order reaction (with high R2 data) could properly model the EF and PEF processes.

BACKGROUND AND OBJECTIVE: Leachate, which contains large amounts of ammonium and hazardous organic compounds, can lead to the pollution of surface water and groundwater; consequently, leachate collection and treatment are essential before discharge into the environment. Anaerobic digestion is one of the most cost-effective methods of contaminated wastewater treatment. In this study, we aimed to evaluate the efficiency of an anaerobic digester in simultaneous removal of CHEMICAL OXYGEN DEMAND (COD) and ammonium from landfill leachate.METHODS: In this experimental study, a cylindrical anaerobic digester, made of Plexiglas sheets (with an inner diameter of 240 mm and useful volume of 10 L), was loaded with landfill leachate in Ghaemshahr, Iran. The effects of temperature (ambient temperature, 35oC, and 55oC) and various hydraulic retention times (1-5 days) on anaerobic digestion efficiency in COD and ammonium removal were assessed.FINDINGS: At a hydraulic retention time of five days, maximum COD and ammonium removal (94% and 36%, respectively) was reported at thermophilic and ambient temperatures, respectively. The increase in hydraulic retention time had a positive impact on the efficiency of the digester in removing organic compounds and ammonium. Moreover, the rise in anaerobic digester temperature improved COD and ammonium removal.CONCLUSION: According to our findings, the developed anaerobic digester could be used as a convenient and efficient tool for removing organic matters from landfill leachate. However, given the low efficiency of this digester in ammonium removal, an additional aerobic stage is required for wastewater treatment.

Background: It is necessary to monitor the performance of the industrial wastewater treatment plants in order to achieve the desired environmental standards. This study was carried out to determine the efficiency of the nitrogen removal, phosphorus compounds and CHEMICAL OXYGEN DEMAND (COD) and comparing the effluent standard with the effluent industrial wastewater treatment plant of Agh Ghala, Iran.Methods: The present cross sectional study was conducted in 2011 during six months. Sampling was performed two times per week from the incoming wastewater, pond aeration and effluent. Composite sampling was conducted for the treatment plant input, and for the other units it was done momentarily. Overall, 48 times wastewater sampling and testing was performed.Findings: The mean concentrations of total nitrogen, phosphorus and COD in influent were 7.36±4.23 mg N/l, 68.1±26.4 mg P/l and 5.7±3.6 and 294.2±183.5 mg/l. Total nitrogen, phosphorus and COD showed a removal of about 86%, 67% and 95%, respectively. According to the standard, discharge of effluent wastewater treatment to surface water was acceptable (except phosphorus).Conclusion: The effluent quality of this treatment plant was according to the effluent disposal standards except for phosphorus. However, this problem is solvable by accurate management and supervision on wastewater treatment plant.

Background and Objective: The increasing development of agricultural and aquaculture activities along the rivers has reduced the quality of running water. The aim of this study was to evaluate Chehel-chai River water quality with national sanitation foundation water quality index (NSFWQI), Iran water quality index for surface water (IRWQISC), Canadian water quality index (CWQI). Methods: This descriptive-analytical study, was performed on all of 7 sampling stations based on standard factors such as availability, land use type, geology and dispersion along the river, 12 water quality parameters including dissolved OXYGEN, fecal coliform, pH, bioCHEMICAL OXYGEN DEMAND (BOD), CHEMICAL OXYGEN DEMAND (COD), temperature, organic phosphate, nitrate, ammonium, turbidity, total soluble solids and electrical conductivity and 5 cations (sodium, calcium and magnesium) and anion (chloride and sulfate) along the river for summer and autumn seasons 2018 (42 sample) with the standard method was measured. Results: The amount of phosphate and turbidity increased from station 2 to downstream due to the existence of fish ponds and agricultural drainage. BOD, COD and fecal coliform values at station 6 have increased significantly with due to urban effluent output. River pollution in the summer has increased due to reduction of river flow and after station 3 (promenade) to the downstream, which is due to the entry of agricultural fertilizers and urban wastewater discharge. According to the average of IRWQISC and NSFWQI, the water quality of Chehel-chai River in the sampling station in the area of Minoodasht city (station 6) is in bad class. The CWQI index showed that the water of the Chehel-chai River is suitable for drinking and aquaculture at the border of the class, for agriculture in the bad class, and in terms of recreation and livestock use in the higher class. Conclusion: The mean values of the above indices indicate high pollution quality class, and since this river is used for water supply for agricultural and aquaculture, management strategies are necessary.