Experimental determination of the heterotroph anoxic yield in anoxic-aerobic activated sludge systems treating municipal wastewater

Abstract

This paper describes experimental research to directly quantify the ordinary heterotrophic organism (OHO) cell yield coefficient under anoxic and aerobic conditions with real wastewater as substrate. Until recently these two values were assumed equal in activated sludge models, despite theoretical predictions that the anoxic yield should be reduced relative to its aerobic value. In this study, parallel aerobic and anoxic batch tests were conducted on the same mixtures of wastewater and mixed liquor drawn from anoxic-aerobic activated sludge systems. By equating the readily biodegradable (RB)COD concentrations in the aerobic and anoxic batch tests, the anoxic yield was determined in terms of the respective measured oxygen and nitrate utilisations and the aerobic yield. Additionally, the aerobic and anoxic yield coefficients were directly determined by using defined quantities of the artificial RBCOD acetate. The wastewater batch tests demonstrated that the OHO anoxic yield is reduced to approximately 81% (0.54) of the aerobic value (0.67 mgCOD/mgCOD). The anoxic:aerobic yield ratio (0.81) was confirmed independently in the acetate batch tests at 0.84, and closely equals that predicted theoretically from thermodynamic and bioenergetic principles (0.83). From these investigations, it is recommended that the OHO anoxic yield be decreased to 0.54 for an aerobic yield value of 0.67 mgCOD/mgCOD.

Cod Fractions Changes During Sewage Treatment With Constructed Wetland

“…The percentage of tested soluble fractions was 45.38%, whereas 54.62% in the suspension. These values are different than the results reported by Sadecka [11,13], Ekama [16], Kalinowska [6], or IWA group [5], according to whom, the amount of soluble substances was minimum 70%, while about 20% in suspension.…”

“…Comparison of the percentage of particular COD fractions in raw sewage recorded by Myszograj and Sadecka [9,11,13], Henze [2], Keppler and Gujer [1,7], IWA group [5] with simplified methods by Ekama [16] and Kalinowska [6] are presented in Table 3. The most similar results of the percentage of individual fractions were obtained by Keppler and Gujer as well as Henze, where easily and hardly biodegradable fractions are the majority of the shares.…”

“…According to literature the data confirmed by own Table 3. Percentage of individual fractions in total COD concentration for raw sewage determined in measurements as compared to literature data [1,2,5,6,7,9,11,13,16] …”

Impact of rainwater intrusion on wastewater characterization and performance of nutrient removal activated sludge process

“…The first prerequisite for appropriate design and system appraisal is the experimental support , especially as it pertains to different aspects of influent characteristics such as design values, COD fractionation and particle size distribution 9‐12 . In a way, ‘ specific effluent limitations should be conceived as a fingerprint of the wastewater characteristics, improved by appropriate treatment’ 13 .…”

Analysis of particle size distribution of organic carbon for landfill leachate—implications for sustainable treatment

“…22 Efforts are now focused on establishing direct relationships between PSD results, biodegradation characteristics, and COD fractionation for different wastewaters. [23][24][25][26] In this context, the objective of this study was to assess the PSD of the COD as a key parameter of the leachate characteristics, emphasizing its support to better interpret its biodegradation properties. Additionally, the role and function of the PSD analysis were evaluated with insight on the distribution of soluble COD fractions (both biodegradable and inert components) for the next generation of activated sludge systems with ultrafiltration and nanofiltration modules likely to be implemented for the treatment of the landfill leachate.…”