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.

Aims: Landfill leachate contains many pollutants including chemical oxygen demand (COD), biological oxygen demand, ammonia nitrogen, organic matter, minerals, and toxins. Given the importance of COD removal from landfill leachate, this study was conducted to evaluate and compare different methods used for the removal of COD from leachate. Materials and Methods: This study was conducted as a narrative review using keywords of leachate, COD, landfill in related journals issued in scientific databases such as Web of Science, PubMed, SID, and Google Scholar. We reviewed different aspects of COD removal from leachate to find better options in this respect. Results: The highest rate of COD removal was observed for batch reactor methods of anaerobic and aerobic granular activated carbon and electro Fenton by 98. 4% COD removal, and the lowest one was 22. 7% for the electro‑, Fenton method. The most commonly used methods for removing COD from solidwaste leachate have been physical and chemical methods. Conclusion: This study showed that a wide range method has been used to remove COD from leachate. It seems that combined methods are more effective to reduce the content of leachate COD. Besides, methods such as Fenton and absorption are more preferable because of simple application and low energy consumption.

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: 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.

The use of ultrasound is one of the most studied methods in treatment of water and wastewater. This study was going to remove pollutants from the supernatant of excess sludge by using of ultrasound. Initial raw supernatant with COD equal to 1600 mg/L and phosphorous equal to 80 mg/L was exposed to ultrasound. The experimental design was used to determine the experiments with variables including time (1. 5-9. 5 h), ultrasonic power (40-360 w), and the volume of sample (20-180 mL). COD and phosphorous were the responses, those were investigated in this research. Based on the Response Surface Methodology (RSM), a model for COD and phosphorous removal was obtained with a 95 % confidence interval. The optimized removal of COD (97. 39 %) and phosphorous (98. 73 %) was observed. According to the results, ultrasonic waves is a good way to remove COD and phosphorus from sludge. This method can be used in wastewater treatment plants for treatment of supernatant of excess sludge.

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.