1
|
Hou S, Zhang Y, Yuan D, Feng X, Zhang Y. Determination of seawater COD spectra using double-loop contraction and sorted frog optimization. WATER SCIENCE AND TECHNOLOGY : A JOURNAL OF THE INTERNATIONAL ASSOCIATION ON WATER POLLUTION RESEARCH 2024; 89:1613-1629. [PMID: 38619893 DOI: 10.2166/wst.2024.101] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/26/2023] [Accepted: 02/02/2024] [Indexed: 04/17/2024]
Abstract
This study develops a novel double-loop contraction and C value sorting selection-based shrinkage frog-leaping algorithm (double-contractive cognitive random field [DC-CRF]) to mitigate the interference of complex salts and ions in seawater on the ultraviolet-visible (UV-Vis) absorbance spectra for chemical oxygen demand (COD) quantification. The key innovations of DC-CRF are introducing variable importance evaluation via C value to guide wavelength selection and accelerate convergence; a double-loop structure integrating random frog (RF) leaping and contraction attenuation to dynamically balance convergence speed and efficiency. Utilizing seawater samples from Jiaozhou Bay, DC-CRF-partial least squares regression (PLSR) reduced the input variables by 97.5% after 1,600 iterations relative to full-spectrum PLSR, RF-PLSR, and CRF-PLSR. It achieved a test R2 of 0.943 and root mean square error of 1.603, markedly improving prediction accuracy and efficiency. This work demonstrates the efficacy of DC-CRF-PLSR in enhancing UV-Vis spectroscopy for rapid COD analysis in intricate seawater matrices, providing an efficient solution for optimizing seawater spectra.
Collapse
Affiliation(s)
- Shiwei Hou
- Qilu University of Technology (Shandong Academy of Sciences), Institute of Oceanographic Instrumentation, Shandong Provincial Key Laboratory of Ocean Environmental Monitoring Technology, National Engineering and Technological Research Center of Marine Monitoring Equipment, No 37 Miaoling Road, 266061 Qingdao, China
| | - Yingying Zhang
- Qilu University of Technology (Shandong Academy of Sciences), Institute of Oceanographic Instrumentation, Shandong Provincial Key Laboratory of Ocean Environmental Monitoring Technology, National Engineering and Technological Research Center of Marine Monitoring Equipment, No 37 Miaoling Road, 266061 Qingdao, China E-mail:
| | - Da Yuan
- Qilu University of Technology (Shandong Academy of Sciences), Institute of Oceanographic Instrumentation, Shandong Provincial Key Laboratory of Ocean Environmental Monitoring Technology, National Engineering and Technological Research Center of Marine Monitoring Equipment, No 37 Miaoling Road, 266061 Qingdao, China
| | - Xiandong Feng
- Qilu University of Technology (Shandong Academy of Sciences), Institute of Oceanographic Instrumentation, Shandong Provincial Key Laboratory of Ocean Environmental Monitoring Technology, National Engineering and Technological Research Center of Marine Monitoring Equipment, No 37 Miaoling Road, 266061 Qingdao, China
| | - Ying Zhang
- Qilu University of Technology (Shandong Academy of Sciences), Institute of Oceanographic Instrumentation, Shandong Provincial Key Laboratory of Ocean Environmental Monitoring Technology, National Engineering and Technological Research Center of Marine Monitoring Equipment, No 37 Miaoling Road, 266061 Qingdao, China
| |
Collapse
|
2
|
Sustainable and green persulfate-based chemiluminescent method for on-site estimation of chemical oxygen demand in waters. Anal Chim Acta 2022; 1223:340196. [DOI: 10.1016/j.aca.2022.340196] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2022] [Revised: 07/18/2022] [Accepted: 07/21/2022] [Indexed: 11/17/2022]
|
3
|
Bertoldi B, Bardsley CA, Baker CA, Pabst CR, Gutierrez A, De J, Luo Y, Schneider KR. Determining Bacterial Load and Water Quality Parameters of Chlorinated Tomato Flume Tanks in Florida Packinghouses. J Food Prot 2021; 84:1784-1792. [PMID: 34086886 DOI: 10.4315/jfp-21-100] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2021] [Accepted: 06/01/2021] [Indexed: 11/11/2022]
Abstract
ABSTRACT Monitoring and maintenance of water quality in dump tanks or flume systems is crucial to maintaining proper sanitizer levels to prevent pathogen cross-contamination during postharvest washing of tomatoes, but there is limited information on how organic matter influences sanitizer efficacy in the water. The main objective of this study was to monitor water quality in flume tanks and evaluate the efficacy of postharvest washing of tomatoes in commercial packinghouses. Flume tank water samples (n = 3) were collected on an hourly basis from three packinghouses in Florida and analyzed for pH, total dissolved solids (TDS), free chlorine, chemical oxygen demand (COD), oxidation-reduction potential, and turbidity. Additionally, three flume-water samples were collected and tested for total aerobic plate count (APC), total coliforms (TC), and Escherichia coli. Fresh tomatoes (n = 3), both before and after washing, were collected and analyzed for the same bacterial counts. Turbidity, COD, and TDS levels in flume water increased over time in all packinghouses. Correlations observed include COD and turbidity (r = 0.631), turbidity and TDS (r = 0.810), and oxidation-reduction potential and chlorine (r = 0.660). APC for water samples had an average range of 0.0 to 4.7 log CFU/mL and TC average range of 0.0 to 4.7 log CFU/mL. All water samples were negative for E. coli. The average APC for pre- and postflume tomatoes from the three packinghouses was 6.0 log CFU per tomato and ranged from 2.2 to 7.4 log CFU per tomato. The average TC count was <1.5 and 7.0 log CFU per tomato for pre- and postwash tomatoes, respectively. There was no significant effect (P > 0.05) of postharvest washing on the microbiological qualities of tomatoes. Water quality in flume tanks deteriorated over time in all packinghouses during a typical operational day of 4 to 8 h. HIGHLIGHTS
Collapse
Affiliation(s)
- Bruna Bertoldi
- Department of Food Science and Human Nutrition, University of Florida, Gainesville, Florida 32611
| | - Cameron A Bardsley
- Department of Food Science and Human Nutrition, University of Florida, Gainesville, Florida 32611
| | - Christopher A Baker
- Department of Food Science and Human Nutrition, University of Florida, Gainesville, Florida 32611
| | - Christopher R Pabst
- Department of Food Science and Human Nutrition, University of Florida, Gainesville, Florida 32611
| | - Alan Gutierrez
- Department of Food Science and Human Nutrition, University of Florida, Gainesville, Florida 32611
| | - Jaysankar De
- Department of Food Science and Human Nutrition, University of Florida, Gainesville, Florida 32611
| | - Yaguang Luo
- Environmental Microbial and Food Safety Laboratories, Agricultural Research Service, U.S. Department of Agriculture, Beltsville, Maryland 20705, USA
| | - Keith R Schneider
- Department of Food Science and Human Nutrition, University of Florida, Gainesville, Florida 32611
| |
Collapse
|
4
|
Basereh Taromsary N, Bonakdarpour B, Amoozegar MA, Fallah N, Fadaei Tehran A. Quantifying the organic content of saline wastewaters: Is chemical oxygen demand always an achievable parameter? Talanta 2019; 197:509-516. [PMID: 30771969 DOI: 10.1016/j.talanta.2019.01.028] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2018] [Revised: 01/06/2019] [Accepted: 01/07/2019] [Indexed: 10/27/2022]
Abstract
The study presented in this paper takes a comprehensive approach to the measurement of the COD of saline industrial wastewaters taking into account both their widely varying salinity levels and the substantial interference of chloride with the conventional method of COD measurement. To this end, three approaches for combating the chloride interference associated with the measurement of COD using the conventional method were considered. The dilution of saline samples prior to analysis yielded reasonably accurate COD results as long as the COD after dilution was 40 mg L-1 or above. In the second approach, the previously reported modifications of the standard method were stretched to their practical limits (increasing HgSO4 to 130 g L-1 and decreasing K2Cr2O7 to 1.022 g L-1) accompanied by prior addition of HgSO4:Cl- at a ratio of 20:1 combined with chloride interference error estimation. This brought about an increase in chloride interference threshold of the standard method to 42.5 g L-1, which is considerably higher than previous reports. Since some raw or treated saline industrial wastewaters have a combination of chloride and COD concentration which makes the first two approaches inapplicable, the approach of chloride removal from the sample via a modification of DIN 38409-H41-2 and subsequent measurement of COD using a slight variation of the closed reflux standard method was also considered. Fairly accurate COD determinations for samples with chloride concentrations up to 148.6 and 182 g L-1 for COD contents of 50 and 900 mg L-1, respectively were achieved. However, excessive precipitation of the desalination reaction products made the method inapplicable to samples with chloride concentrations above 182 g L-1.
Collapse
Affiliation(s)
| | - Babak Bonakdarpour
- Department of Chemical Engineering, Amirkabir University of Technology, Tehran, Iran.
| | - Mohammad Ali Amoozegar
- Department of Microbiology, School of Biology, College of Science, University of Tehran, Tehran, Iran
| | - Narges Fallah
- Department of Chemical Engineering, Amirkabir University of Technology, Tehran, Iran
| | - Arezou Fadaei Tehran
- Department of Chemical Engineering, Amirkabir University of Technology, Tehran, Iran
| |
Collapse
|
5
|
Salihu SO, Bakar NKA. Modified APHA closed-tube reflux colorimetric method for TOC determination in water and wastewater. ENVIRONMENTAL MONITORING AND ASSESSMENT 2018; 190:369. [PMID: 29850927 DOI: 10.1007/s10661-018-6727-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2018] [Accepted: 05/11/2018] [Indexed: 06/08/2023]
Abstract
The analysis of total organic carbon (TOC) by the American Public Health Association (APHA) closed-tube reflux colorimetric method requires potassium dichromate (K2Cr2O7), silver sulfate (AgSO4), and mercury (HgSO4) sulfate in addition to large volumes of both reagents and samples. The method relies on the release of oxygen from dichromate on heating which is consumed by carbon associated with organic compounds. The method risks environmental pollution by discharging large amounts of chromium (VI) and silver and mercury sulfates. The present method used potassium monochromate (K2CrO4) to generate the K2Cr2O7 on demand in the first phase. In addition, miniaturizing the procedure to semi microanalysis decreased the consumption of reagents and samples. In the second phase, mercury sulfate was eliminated as part of the digestion mixture through the introduction of sodium bismuthate (NaBiO3) for the removal of chlorides from the sample. The modified method, the potassium monochromate closed-tube colorimetry with sodium bismuthate chloride removal (KMCC-Bi), generates the potassium dichromate on demand and eliminates mercury sulfate. The semi microanalysis procedure leads to a 60% reduction in sample volume and ≈ 33.33 and 60% reduction in monochromate and silver sulfate consumption respectively. The LOD and LOQ were 10.17 and 33.90 mg L-1 for APHA, and 4.95 and 16.95 mg L-1 for KMCC-Bi. Recovery was between 83 to 98% APHA and 92 to 104% KMCC-Bi, while the RSD (%) ranged between 0.8 to 5.0% APHA and 0.00 to 0.62% KMCC-Bi. The method was applied for the UV-Vis spectrometry determination of COD in water and wastewater. Statistics was done by MINITAB 17 or MS Excel 2016. ᅟ Graphical abstract.
Collapse
|
6
|
Li J, Luo G, He L, Xu J, Lyu J. Analytical Approaches for Determining Chemical Oxygen Demand in Water Bodies: A Review. Crit Rev Anal Chem 2017; 48:47-65. [DOI: 10.1080/10408347.2017.1370670] [Citation(s) in RCA: 47] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Affiliation(s)
- Ji Li
- School of Environment and Civil Engineering, Jiangnan University, Wuxi, China
| | - Guobing Luo
- Wuxi City Water Supply and Drainage Monitoring Station, Wuxi, China
| | - LingJun He
- Department of Housing and Urban Rural Development of Jiangsu Province, Nanjing, China
| | - Jing Xu
- Wuxi City Water Supply and Drainage Monitoring Station, Wuxi, China
| | - Jinze Lyu
- School of Environment and Civil Engineering, Jiangnan University, Wuxi, China
| |
Collapse
|
7
|
Geerdink RB, Sebastiaan van den Hurk R, Epema OJ. Chemical oxygen demand: Historical perspectives and future challenges. Anal Chim Acta 2017; 961:1-11. [DOI: 10.1016/j.aca.2017.01.009] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2016] [Revised: 01/06/2017] [Accepted: 01/07/2017] [Indexed: 10/20/2022]
|
8
|
Determination of chemical oxygen demand employed manganese as an environmentally friendly oxidizing reagent by a flow injection method based on microwave digestion and speciation coupled to ICP-OES. Microchem J 2013. [DOI: 10.1016/j.microc.2012.09.007] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
|
9
|
Bertin L, Bettini C, Zanaroli G, Frascari D, Fava F. A continuous-flow approach for the development of an anaerobic consortium capable of an effective biomethanization of a mechanically sorted organic fraction of municipal solid waste as the sole substrate. WATER RESEARCH 2012; 46:413-424. [PMID: 22118905 DOI: 10.1016/j.watres.2011.11.001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/27/2011] [Revised: 10/30/2011] [Accepted: 11/01/2011] [Indexed: 05/31/2023]
Abstract
An effective mesophilic continuous anaerobic digestion process fed only with a mechanically sorted organic fraction of municipal solid waste (MS-OFMSW) was developed. During a preliminary 3-month experimental phase, the microbial consortium was acclimated toward MS-OFMSW by initially filling the reactor with cattle manure and then continuously feeding it with MS-OFMSW. The Hydraulic Retention Time (HRT) and Organic Loading Rate (OLR) were 23 days and 2.5 g/L/day, respectively. After 4 weeks, the reactor reached stationary performances (84% COD removal yield, 0.15 L(CH₄)/g(COD removed) methane production yield). The acclimated consortium was then employed in a second run in which the reactor was operated under steady state conditions at the previous HRT and OLR for 73 days. The COD removal and the methane production yield increased up to 87% and 0.25 L(CH₄) /g(CODremoved), respectively. The capability of the acclimated consortium to biomethanize MS-OFMSW was further studied via batch digestion experiments, carried out by inoculating the target waste with reactor effluents collected at the beginning of first run and at the end of the first and second run. The best normalized methane production (0.39 L(CH₄) /g(initial COD)) was obtained with the inoculum collected at the end of the second run. Molecular analysis of the microbial community occurring in the reactor during the two sequential runs indicated that the progressive improvement of the process performances was closely related to the selection and enrichment of specific hydrolytic and acidogenic bacteria in the reactor.
Collapse
Affiliation(s)
- Lorenzo Bertin
- Department of Civil, Environmental and Materials Engineering (DICAM), Faculty of Engineering, University of Bologna, via Terracini 28, 40131 Bologna, Italy.
| | | | | | | | | |
Collapse
|
10
|
Dubber D, Gray NF. Replacement of chemical oxygen demand (COD) with total organic carbon (TOC) for monitoring wastewater treatment performance to minimize disposal of toxic analytical waste. JOURNAL OF ENVIRONMENTAL SCIENCE AND HEALTH. PART A, TOXIC/HAZARDOUS SUBSTANCES & ENVIRONMENTAL ENGINEERING 2010; 45:1595-600. [PMID: 20721800 DOI: 10.1080/10934529.2010.506116] [Citation(s) in RCA: 94] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Chemical oxygen demand (COD) is widely used for wastewater monitoring, design, modeling and plant operational analysis. However this method results in the production of hazardous wastes including mercury and hexavalent chromium. The study examined the replacement of COD with total organic carbon (TOC) for general performance monitoring by comparing their relationship with influent and effluent samples from 11 wastewater treatment plants. Biochemical oxygen demand (BOD5) was also included in the comparison as a control. The results show significant linear relationships between TOC, COD and BOD5 in settled (influent) domestic and municipal wastewaters, but only between COD and TOC in treated effluents. The study concludes that TOC can be reliably used for the generic replacement of both COD (COD=49.2+3.00*TOC) and BOD5 (BOD5=23.7+1.68*TOC) in influent wastewaters but only for COD (COD=7.25+2.99*TOC) in final effluents.
Collapse
Affiliation(s)
- Donata Dubber
- Water Technology Research Group, Centre for the Environment, School of Natural Sciences, Trinity College Dublin, Dublin, Ireland.
| | | |
Collapse
|
11
|
Bertin L, Lampis S, Todaro D, Scoma A, Vallini G, Marchetti L, Majone M, Fava F. Anaerobic acidogenic digestion of olive mill wastewaters in biofilm reactors packed with ceramic filters or granular activated carbon. WATER RESEARCH 2010; 44:4537-49. [PMID: 20619436 DOI: 10.1016/j.watres.2010.06.025] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/15/2010] [Revised: 06/04/2010] [Accepted: 06/11/2010] [Indexed: 05/16/2023]
Abstract
Four identically configured anaerobic packed bed biofilm reactors were developed and employed in the continuous acidogenic digestion of olive mill wastewaters to produce volatile fatty acids (VFAs), which can be exploited in the biotechnological production of polyhydroxyalkanoates. Ceramic porous cubes or granular activated carbon were used as biofilm supports. Aside packing material, the role of temperature and organic loading rate (OLR) on VFA production yield and mixture composition were also studied. The process was monitored through a chemical, microbiological and molecular biology integrated procedure. The highest wastewater acidification yield was achieved with the ceramic-based technology at 25 degrees C, with an inlet COD and an OLR of about 17 g/L and 13 g/L/day, respectively. Under these conditions, about the 66% of the influent COD (not including its VFA content) was converted into VFAs, whose final amount represented more than 82% of the influent COD. In particular, acetic, propionic and butyric acids were the main VFAs by composing the 55.7, 21.5 and 14.4%, respectively, of the whole VFA mixture. Importantly, the relative concentrations of acetate and propionate were affected by the OLR parameter. The nature of the packing material remarkable influenced the process performances, by greatly affecting the biofilm bacterial community structure. In particular, ceramic cubes favoured the immobilization of Firmicutes of the genera Bacillus, Paenibacillus and Clostridium, which were probably involved in the VFA producing process.
Collapse
Affiliation(s)
- Lorenzo Bertin
- Department of Applied Chemistry and Material Science (DICASM), Faculty of Engineering, University of Bologna, via Terracini 28, 40131 Bologna, Italy.
| | | | | | | | | | | | | | | |
Collapse
|
12
|
Geerdink RB, Brouwer J, Epema OJ. A reliable free chemical demand () method. ANALYTICAL METHODS : ADVANCING METHODS AND APPLICATIONS 2009; 1:108-114. [PMID: 32938149 DOI: 10.1039/b9ay00146h] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
A simple, but reliable mercury free method to analyse chemical oxygen demand is introduced. The method is based on international standard procedures but avoids the highly toxic mercury. In the procedure the oxidation temperature is brought down from 148 °C to 120 °C. At this temperature the chloride interference is reduced to a large extent, whereas the oxidation of most compounds is still complete. Chloride interference is further reduced by addition of silver ions and practically absent at a molar ratio Ag+/Cl- over 1.7. Compounds that are difficult to oxidise even at 148 °C or only in the presence of silver ions are investigated at 120 °C. A slight reduction in recovery of 20-35% is observed for compounds like acetic acid, ethanol or lauryl sulfate in the absence of chloride. In the presence of 3000 mg L-1 chloride only the reduction for acetic acid is more pronounced due to the low availability of silver ions. The other compounds studied showed no further decrease in recovery. The interference of bromide is about 50% less at 120 °C than at 148 °C. The interference of ammonium in the presence of chloride is not confirmed in this method. The recovery of the method at high chloride and low COD concentration, i.e., at 3000 mg Cl- L-1 and 25 mg COD L-1, is acceptable (122%) whereas at 2000 mg Cl- L-1 and 25 mg COD L-1 it is better (110%). Precision is good; Relative standard deviations are 5.6% respectively 2.6%. The results of 99 wastewater samples over a wide range of chloride concentrations are similar compared to analyses based on ISO 15705 (cuvette) or ISO 6060. With the addition of 20 mL silver sulfate-sulfuric acid solution, the chloride in samples up to 3000 mg L-1 chloride is largely precipitated. More volume silver sulfate-sulfuric acid solution or a higher concentration of silver sulfate increases the range of samples that can effectively be analysed. The believed favourable effect of addition of Cr3+ to samples has not been confirmed. In the Netherlands 95% of about 100 000 wastewater samples that are analysed for COD each year have chloride concentrations below 3000 mg L-1 and could be analysed without the use of mercury. This may save as much as 10 kg mercury per annum. It will however require the additional use of about 0.5 kg of silver.
Collapse
Affiliation(s)
- Renà Bernard Geerdink
- Rijkswaterstaat, Centre for Water Management, PO Box 17, 8200 AA, Lelystad, The Netherlands.
| | - Joyce Brouwer
- Rijkswaterstaat, Centre for Water Management, PO Box 17, 8200 AA, Lelystad, The Netherlands.
| | - Onno Jacob Epema
- Rijkswaterstaat, Centre for Water Management, PO Box 17, 8200 AA, Lelystad, The Netherlands.
| |
Collapse
|
13
|
Domini CE, Vidal L, Canals A. Trivalent manganese as an environmentally friendly oxidizing reagent for microwave- and ultrasound-assisted chemical oxygen demand determination. ULTRASONICS SONOCHEMISTRY 2009; 16:686-91. [PMID: 19250852 DOI: 10.1016/j.ultsonch.2009.01.008] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/25/2008] [Revised: 01/20/2009] [Accepted: 01/22/2009] [Indexed: 05/14/2023]
Abstract
In the present work manganese(III) has been used as oxidant and microwave radiation and ultrasound energy have been assessed to speed up and to improve the efficiency of digestion step for the determination of chemical oxygen demand (COD). Microwave (MW) and ultrasound-assisted COD determination methods have been optimized by means of experimental design and the optimum conditions are: 40psi pressure, 855W power and 1min irradiation time; and 90% of maximum nominal power (180W), 0.9s (s(-1)) cycles and 1min irradiation time for microwaves and ultrasound, respectively. Chloride ion interference is removed as hydrochloric acid gas from acidified sample solutions at 150 degrees C in a closed reaction tube and captured by bismuth-based adsorbent suspended above the heated solution. Under optimum conditions, the evaluated assisted digestion methods have been successfully applied, with the exception of pyridine, to several pure organic compounds and two reference materials. COD recoveries obtained with MW and ultrasound-assisted digestion for five real wastewater samples were ranged between 86-97% and 68-91%, respectively, of the values obtained with the classical method (open reflux) used as reference, with relative standard deviation lower than 4% in most cases. Thus, the Mn(III) microwave-assisted digestion method seems to be an interesting and promising alternative to conventional COD digestion methods since it is faster and more environmentally friendly than the ones used for the same purpose.
Collapse
Affiliation(s)
- Claudia E Domini
- Departamento de Química, Universidad Nacional del Sur, Av. Além 1253, 8000 Bahía Blanca, Argentina
| | | | | |
Collapse
|
14
|
Anderson JE, Mueller SA, Kim BR. Incomplete oxidation of ethylenediaminetetraacetic acid in chemical oxygen demand analysis. WATER ENVIRONMENT RESEARCH : A RESEARCH PUBLICATION OF THE WATER ENVIRONMENT FEDERATION 2007; 79:1043-9. [PMID: 17910374 DOI: 10.2175/106143007x184104] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
Ethylenediaminetetraacetic acid (EDTA) was found to incompletely oxidize in chemical oxygen demand (COD) analysis, leading to incorrect COD values for water samples containing relatively large amounts of EDTA. The degree of oxidation depended on the oxidant used, its concentration, and the length of digestion. The COD concentrations measured using COD vials with a potassium dichromate concentration of 0.10 N (after dilution by sample and sulfuric acid) were near theoretical oxygen demand values. However, COD measured with dichromate concentrations of 0.010 N and 0.0022 N were 30 to 40% lower than theoretical oxygen demand values. Similarly, lower COD values were observed with manganic sulfate as oxidant at 0.011 N. Extended digestion yielded somewhat higher COD values, suggesting incomplete and slower oxidation of EDTA, as a result of lower oxidant concentrations. For wastewater in which EDTA is a large fraction of COD, accurate COD measurement may not be achieved with methods using dichromate concentrations less than 0.1 N.
Collapse
Affiliation(s)
- James E Anderson
- Systems Analyses and Environmental Sciences Department of Research and Advanced Engineering, Ford Motor Company, Dearborn, Michigan, USA.
| | | | | |
Collapse
|
15
|
|