• Journal of Electrochemical Science and Technology
• /
• v.14 no.3
• /
• pp.215-221
• /
• 2023

A rapid and environment-friendly electrochemical sensor to determine the chemical oxygen demand (COD) has been developed. The boron-doped diamond (BDD) thin-film electrode is employed as the anode, which fully oxidizes organic pollutants and provides a current response in proportion to the COD values of the sample solution. The BDD-based amperometric COD sensor is optimized in terms of the applied potential and the solution pH. At the optimized conditions, the COD sensor exhibits a linear range of 0 to 80 mg/L and the detection limit of 1.1 mg/L. Using a set of model organic compounds, the electrochemical COD sensor is compared with the conventional dichromate COD method. The result shows an excellent correlation between the two methods.

• Korean Journal of Ecology and Environment
• /
• v.33 no.1 s.89
• /
• pp.23-30
• /
• 2000

n situ sediment oxygen demand (SOD), which takes place with the uptake of dissolved oxygen for biological metabolism and chemical oxidation in sediments, ranged from 1.57 to $12.55\;mg\;O_2\;m^{-2}\;h^{-1}$ in onshore of Lake Paldang from April to November 1999. SOD was influenced by the amount of organics and oxygen diffusion. Comparing the oxygen demands partitioning between overlying water and sediment during initial phase, SOD accounted for $63.8{\sim}94%$ of total oxygen demand in Lake Paldang. The chemical SOD and nitrogenous oxygen demand ranged $1.2{\sim}18.3%$ and $8.3{\sim}51.7%$ of total SOD, respectively. This result indicated that SOD in Lake Paldang occurred mainly by aerobic respiration and nitrification. Although the flow velocity could increase SOD within a certain limit, the effect of sediment depth on SOD was dependent on physicochemical properties of the sediment. This study showed that SOD can represent a significant portion of the total oxygen up-take in Lake Paldang. Therefore, the assessment of SOD might be necessary for the control of water quality.

• Bulletin of the Korean Chemical Society
• /
• v.10 no.4
• /
• pp.406-407
• /
• 1989

• Membrane and Water Treatment
• /
• v.9 no.6
• /
• pp.455-462
• /
• 2018

The measurement and monitoring of the biochemical oxygen demand (BOD) play an important role in the planning and operation of wastewater treatment plants. The most basic method for determining biochemical oxygen demand is direct measurement. However, this method is both expensive and takes a long time. A five-day period is required to determine the biochemical oxygen demand. This study has been carried out in a wastewater treatment plant in Turkey (Hurma WWTP) in order to estimate the biochemical oxygen demand a shorter time and with a lower cost. Estimation was performed using artificial neural network (ANN) method. There are three different methods in the training of artificial neural networks, respectively, multi-layered (ML-ANN), teaching learning based algorithm (TLBO-ANN) and artificial bee colony algorithm (ABC-ANN). The input flow (Q), wastewater temperature (t), pH, chemical oxygen demand (COD), suspended sediment (SS), total phosphorus (tP), total nitrogen (tN), and electrical conductivity of wastewater (EC) are used as the input parameters to estimate the BOD. The root mean squared error (RMSE) and the mean absolute error (MAE) values were used in evaluating performance criteria for each model. As a result of the general evaluation, the ML-ANN method provided the best estimation results both training and test series with 0.8924 and 0.8442 determination coefficient, respectively.

• Korean Journal of Microbiology
• /
• v.10 no.3
• /
• pp.97-104
• /
• 1972

The extent of water pollution was investigated at 4 stations in Kyonggi Bay during the summer seasons in 1970 and 1971. The concentrations of dissolved oxygen, total hardness, ammonia, nitrate, nitrite, phosphate, chemical oxygen demand, salinity, biochemical oxygen demand, coliform bacteria and facel coli were examined together with the measurement of pH and transparency. The relationship between the extent of pollution and the distance from the Inchon Bay also was examined. The concentrations of biochemical oxygen demand, chemical oxygen demand, ammonia, nitrate, nitrite, phosphate, coliform bacteria nad fecal coli were all highest at station 1, and lowest at station 4. Values were somewhat higher at low tide level in general. On the contrary, dissolved oxygen concentration was highest at station 4 and lowest at station 1. The highest and lowest values of biochemical oxygen demand were 10.88 ppm at station 1 and 0.27 ppm at station 4. The chemical oxygen demand concentrations at station 1 and 4 were 1.90 ppm and 0.63 ppm. Ammonia concnetration at station 1 was 0.43 pp, and was nearly 5 times as much as that at station 4. The values were $2.45{\times}10^{-4}$ ppm at station 1, and $6{\times}10^{-4}$ ppm at station 4. Nitrite concnetration at station 1 was $3{\times}10^{-4}$ppm and was the highest, while the lowest was $9.45{\times}10^{-5}$ ppm at station 4. Phosphate value at station 1 too was the highest and was about 4 times as much as that at station 4. Coliform bacteria were most abundant at station 1, and were counted to be 1.$1.7{\times}10^{-5}$cells/ml. At station 4, the number greatly reduced to 8 * 10$^{2}$ cells/ml. The number of fecal coli at station 1 was $2{\times}10^{-4}$ cells/ml. But at station 4, no fecal coli was detected at high tide level. At low tide level, 3 cells/ml were counted at station 4. In all of these, the highest data were obtained at low tide level, while most of the lowest value, at high tide level. Generally, values at statio 1 were 3-5 times as much as those at station 4. Concentration of dissolved oxygen at station 1 was 0.366 mg-atoms/1 and was the lowest. The highest value was 0.420 mg-atoms/1 and was recorded at station 4. The highest at station 4, which certainly were believed to be the result of the dilution by the fresh water of the Han river flowing into the Inchon Bay. As we can see from the data above, the extent of pollution was highest at station 1, the nearest from Inchon harbor, and lowest at station 4, where is the farthest, Station 1 and 2 were proved to be much polluted, but station 3 and 4, not.

• Environmental Engineering Research
• /
• v.25 no.3
• /
• pp.400-408
• /
• 2020

Hydrodynamic study of Activated Sludge Process (ASP) is important to optimize the reactor performance and detect anomalies in the system. Residence time distribution (RTD) study has been performed using LiCl as tracer on a pilot scale aeration tank (AT) and ASP, treating the pulp and paper mill effluent. The hydraulic performance and treatment efficiency of the AT and ASP at different operating parameters like residence time, recycle rate was investigated. Flow anomalies were identified and based on the experimental data empirical models was suggested to interpret the hydrodynamics of the reactors using compartment modelling technique. The analysis of the RTD curves and the compartment models indicated increase in back-mixing ratio as the mean hydraulic retention time (MHRT) of the tank was increased. Bypassing stream was observed at lower MHRT. The fraction of dead zone in the tank increased by approximate 20-25% with increase in recycle rate. The fraction of the stagnant zone was found well below 5% for all performed experiments, which was under experimental error. The substrate removal of 91% for Chemical oxygen demand and 96% for Biochemical oxygen demand were observed for the ASP working at a hydraulic mean residence time 39 h MRT with a 20% recycling of activated sludge.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.8 no.3
• /
• pp.317-326
• /
• 2003

In order to improve our knowledge of the characteristics of organic compounds in coastal waters, water samples were collected from the Incheon coastal region, the Hyungsan River in Youngil Bay and the Busan coastal region. Also, mooring was carried out near the Kanghwa Island and Seo Island. In this study, the relationship between the total organic carbon (TOC) and salinity, chemical oxygen demand (COD) and salinity were evaluated and determined. Riverine end-member of TOC into the Korean coastal area and its COD estimated from these relationships were 5.32 mg C/l and 8.87 mg O$_2$/l, respectively. The oxidation efficiency of COD to TOC estimated using the high-temperature catalytic oxidation method was about 47％. The linear relationship between TOC and COD was derived as COD (mg O$_2$/l)=0.61${\times}$TOC (mg C/l) -0.03, (R$^2$=0.66). Therefore, it is possible to estimate total organic carbon using this equation from previously reported chemical oxygen demand.

• 제어로봇시스템학회:학술대회논문집
• /
• 2001.10a
• /
• pp.97.1-97
• /
• 2001

One of the main problems to constitute control method on biologically oriented wastewater purification processes, e.g. activated sludge process, sequential batch reactor, rotating bio-disk contactor, etc. is that it is hard to control the target component directly. For instance, while biochemical oxygen demand, suspended solids, and chemical oxygen demand are the key components to check the process performance, one may not control them directly since they are the results of microbial activities related to numerous physiochemical factors. Therefore controllers for bioprocess should be designed to make favorable condition for microorganisms´ living, e.g. dissolved oxygen level favorable, mixed liquor suspended solids concentration suitable ...

• Journal of Sensor Science and Technology
• /
• v.23 no.4
• /
• pp.272-277
• /
• 2014

At present, the index of chemical oxygen demand (COD) is widely used as an indicator of organic water pollution with biochemical oxygen demand (BOD). But, traditional COD measurement method are not only with various chemical reagents exhausted, but also long time consumed, the operation procedure and the modification are much professional. This paper reported a novel COD measurement system using double-beam and multiple wavelength analysis UV-VIS spectrometries. It consists of pulsed xenon lamp, two-way optical fiber, optical switch, spectrometer and main processor. Proposed COD measurement system obtains any spectral information of water sample (KHP standard sample and two river water and wastewater) and reference sample (distilled water) in the range of 200~520 nm, corresponding to the COD concentration from 0 to 300 mg/L through calculating the UV absorbance. The system show improved precision and can work continuously fast at time interval about 25 seconds.

• Journal of Environmental Science International
• /
• v.7 no.2
• /
• pp.203-208
• /
• 1998

A simple on-line measurement system consisting of a conventional peristaltic pump, a HPLC-type heater, and a flow-through spectrophotometer is introduced for the determination of chemical oxygen demand(CODI. The system was configured such that the reaction mixture in the highly concentrated surffuric acrid medium flowing through the PTFE reaction tubing was heated at 150℃ and the absorbance of dichromate was continuously moutored at 445 m. The same addation principle as in the standard procedure was employed akcept the use of CoSO4 as a new effective catalyst. To test the system, potassium hydrogen phthalate was selected as a COD standard material. With suitably optimized reaction condition, the applicable concentration range depends on the concentration of potassium dichromate in the oxidizing reagent. With 2.0×10-3 M and 5.0×10-4M dichromate, the linear dynamic range was observed up to 400 ppm and 100 ppm, respectively. The standards in the Unear ranges were shown to be completely oxidized, which was confirmed with sodium oxalate or Mohr's salt. In all cases, the typical reproduclbility for betweenruns was 2% or less. The proposed measurement system provides the valuable in- formation for the further development of automated analysis system based on the present standard procedure.