Determination of Chemical Oxygen Demand in Heterogeneous Solid or Semisolid Samples Using a Novel Method Combining Solid Dilutions as a Preparation Step Followed by Optimized Closed Reflux and Colorimetric Measurement

Abstract

This paper reports the development of an innovative sample preparation method for the determination of the chemical oxygen demand (COD) in heterogeneous solid or semisolid samples, with high suspended solids and COD concentrations, using an optimized closed reflux colorimetric method. The novel method, named solid dilution (SD), is based on a different technique of sample preparation, diluting the sample with magnesium sulfate (MgSO(4)) previous to COD determination. With this, it is possible to obtain a solid homogeneous mixture much more easily analyzable. Besides, a modification of concentration and ratio of reagents was optimized to make the closed reflux colorimetric method suitable for complex substrates with COD levels ranging from 5 to 2500 g O(2) kg(-1) TS. The optimized method has been tested with potassium hydrogen phthalate (KHP) as primary solid standard and using different solid or semiliquid substrates like pig slaughterhouse waste and sewage sludge, among others. Finally, the optimized method (SD/SM-CRC) was intensively tested in comparison to the standard titrimetric method (SM-ORT) using different certified reference materials (CRM). The developed method was found to give higher accuracy, 1.4% relative standard deviation (RSD) vs 10.4%, and bias of 2.8% vs 8.0%, in comparison to the standard open reflux titrimetric method.

Characterization of microbial community dynamics during the anaerobic co-digestion of thermally pre-treated slaughterhouse wastes with glycerin addition

“…Total and volatile solids (TS, VS) of all the samples were measured following standard methods [18]. Total chemical oxygen demand (CODt) was determined following the adapted method for solid samples [19]. Further information about the chemical composition of the samples (NH4 + , volatile fatty acids (VFA), COD, etc.)…”

“…to Petrimonas sulfuriphila (band6,12,13,17,19 and 20: sequence homology 92%), Clostridium disporicum (band 10, 11, 14 and 15: sequence homology 98%), Pseudomonas pertucinogena (band 8: sequence homology 95%) and Ruminofilibacter xylanolyticum (band 9 and 18: sequence homology 100%). P. sulfuriphila is a mesophilic, strictly anaerobic, fermentative bacterium that was isolated previously from a biodegraded oil reservoir[31].…”

Power and Limitations of Biochemical Methane Potential (BMP) Tests

“…For liquid and sludge samples, the theoretical value can be calculated based on the COD and the theoretical methane yield of COD, i.e., 0.35 L CH4 /g COD (Buffiere et al, 2006). Determine the COD of particulate organic matter is also possible, but difficult (Noguerol-Arias et al, 2012). These approaches are based on the same principles of redox chemistry and expected values are identical.…”

Optimization of the anaerobic co-digestion of pasteurized slaughterhouse waste, pig slurry and glycerine

“…Total carbon (TC) and total nitrogen (TN) were determined by elemental analysis (Leco, USA). Total chemical oxygen demand (COD) was determined by a modified Standard Methods procedure (Noguerol-Arias et al, 2012). Free ammonia (FAN) content was calculated using the formula given by Hansen et al (1998).…”