A modified method to determine biomass concentration as COD in pure cultures and in activated sludge systems

Abstract

A simple technique to determine biomass concentration as chemical oxygen demand (COD) was developed as an alternative to the standard volatile suspended solid (VSS) method. The proposed technique for biomass measurement as COD is based on the determination of the biomass COD (COD B) as the difference between total COD (COD T) and the soluble COD (COD S) of the sample. The obtained results show that this technique was quicker and simpler than the traditional VSS method. The validity of the proposed methods was tested with pure cultures of a filamentous microorganisms (Sphaerotilus natans), a floc-forming bacteria and activated sludges. The method was also used for estimating the conversion factor (f CV) from VSS to COD units. A modification of the standard VSS technique was also proposed using two membranes in the filtration device; this technique allowed the biomass determination in 1 µm size bacteria cultures that cannot be detected by the standard VSS method because cells are not retained by the 1.5 µm diameter pore glass-fibre filter. Notation BOD = biochemical oxygen demand (mg•l-¹) COD = chemical oxygen demand (mg•l-¹) VSS = volatile suspended solid (mg•l-¹) f CV = conversion factor = ratio between COD B and VSS COD B = biomass as COD (mg•l-¹) COD T = total COD of the sample containing the biomass (mg•l-¹) COD S = soluble COD (mg•l-¹) CV = coefficient of variation

Modelling Cr(VI) removal by a combined carbon-activated sludge system

“…The absorbance was measured at 540 nm with a Hach spectrophotometer. Biomass concentration was measured as chemical oxygen demand [12] using a commercial kit (Hach). All assays were performed at room temperature (20 ± 2 • C).…”

Effectiveness of chlorination and ozonation methods on pure cultures of floc-forming micro-organisms and activated sludge: A comparative study

“…Biomass concentration of the pure culture (A. anitratus) and activated sludge was measured by chemical oxygen demand (COD) and transformed into volatile suspended solids (VSS) using a calibration curve previously determined (Contreras et al, 2002). COD measurements were performed with a commercial kit (Hach Corp., Loveland, USA).…”

“…COD measurements were performed with a commercial kit (Hach Corp., Loveland, USA). The use of COD to determine biomass concentration was reported by many authors (Bullock et al, 1996;Contreras et al, 2002). When the chemostat apparatus and the continuous flow activated sludge reactor was considered to run under steady state conditions, samples were drawn to measure the total chemical oxygen demand (COD T ).…”

“…Another portion was filtered through a 0.45 µm membrane (Millipore HA) and soluble chemical oxygen demand (COD S ) was measured. Biomass concentration (COD B ) was calculated as the difference between COD T and COD S (Contreras et al, 2002).…”

A simple cost-effective manometric respirometer: design and application in wastewater biomonitoring

“…A rough estimation of Y by Eq. (27), however, seems satisfactory for respirometric analysis of biodegradation assuming an average value of O x in the range of 1.42-1.48 (Contreras et al 2002;Chiil et al 2008).…”