Prediction of chemical oxygen demand (COD) with total organic carbon (TOC) to eliminate the interferences of high concentration of chloride ion in oilfield wastewaters

Long, Huai-Yuan; Gu, Hui‐Wen; Jalalvand, Alí R.; Zhang, Shan-Hui; Yang, Linjun; Chen, Wu

doi:10.1080/03067319.2019.1678604

Cited by 4 publications

(3 citation statements)

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“…Due to the critical nature of the COD parameter in environmental compliance monitoring, it is one of the commonly used indexes to assess environmental water quality (11) and COD is a widely used surrogate measure for carbon bioavailability in environmental matrices (28) . COD determination in complex industrial wastewater has been a challenge due to the interference from components inherent in the sample matrix and there is an urgent need for a simple, reliable, and fast method (9) to overcome the issues with several industrial wastewaters.…”

Section: Resultsmentioning

confidence: 99%

“…In a study, strategies like masking and correction were investigated for the effectiveness in suppressing bromide interference during COD analysis and suggested the correction strategy to eliminate bromide interference in standard COD determination (15) . In chloride-rich oilfield wastewater, TOC was proposed as an alternate index for COD and studies reported an acceptable correlation between TOC and COD in oilfield wastewater (11) . A study by Zhang et al, reported the feasibility of dichromate method using low concentration oxidant for high chloride oilfield wastewater (29) .…”

Section: Resultsmentioning

confidence: 99%

“…Because of the easy applicability to a wide range of wastewaters and better oxidation potential, dichromate is the most preferred oxidant for COD determination (7) . Nevertheless, conventional analytical methods have bottlenecks associated with the lengthy procedure, long turnaround time, use of toxic reagents (1,5,9) , low detection sensitivity (5) , inconsistent oxidation efficiency (10) , chloride interference (4) , and inherent potential for secondary pollution (4,5,9,11) . However, the most crucial disadvantages of conventional COD analysis are the susceptibility to the presence of interfering substances, inadequate oxidation of certain organic compounds, and substantial error due to oxidant-consuming inorganic matter, especially chloride ion (7) .…”

Section: Introductionmentioning

confidence: 99%

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Validation of a Modified Procedure for the determination of Chemical Oxygen Demand using standard dichromate method in industrial wastewater samples with high calcium chloride content

Gnanavelu¹,

Ltd²,

Shanmuganathan³

et al. 2021

IJST

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Background/ Objectives: Chemical Oxygen Demand (COD) is a widely used aggregate organic pollutant index in national discharge standards and is one of the critical parameters for water quality assessment. The conventional COD determination by wet oxidative method encounters the problem of chloride interference in water samples with high chloride content. The dichromate reflux method oxidizes 85-95% of organic matter and also 100% of chloride ions in the samples, without an appropriate chloride masking strategy. The standard method cannot measure COD accurately in samples containing more than 2000 mg L -1 chloride. The present study demonstrates and validates a modified procedure for the determination of COD in industrial sample with high calcium chloride content and low organic load. Method: Petrochemical industries manufacturing Propylene Oxide and Propylene Glycol via chlorohydrin route generate wastewater with high calcium chloride content. Due to high chloride content, the standard analysis method could not produce reliable data for COD values with known precision and accuracy. The standard method based on dichromate was modified, with an additional mixing step for a specified time to enhance the chloride masking by mercuric sulphate. Undiluted sample (20 mL) was mixed with the required amount of mercuric sulpahte to maintain 10:1 ratio to chloride content and 10 mL of sulphuric acid at 150-175 RPM for 20 minutes at room temperature to increase the contact time/ chloride masking. Method validation attributes of the modified procedure were assessed and found to be complying with the acceptance criteria. Findings: We developed a modified procedure for the standard dichromate based chemical oxygen demand (COD) determination in industrial wastewater samples rich in calcium chloride. An additional mixing step is introduced in the standard procedure to enhance the chloride masking with mercuric sulphate in samples containing high chloride. The amended procedure resulted in accurate COD values in samples with low organic load, rich in calcium chloride and the modified

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Section: Resultsmentioning

confidence: 99%