Particle size distribution of chemical oxygen demand in industrial effluents: impact on effective filtration size and modelling of membrane bioreactors

Abstract

This study reviews particle size distribution (PSD) analysis for industrial effluents. Evaluation of available experimental data indicated that the approach started with arbitrary selection of size distribution. Following a pioneering study on pulp and paper effluent, sequential filtration and ultrafiltration has established itself as a prescribed methodology complementing respirometric assessment of chemical oxygen demand (COD) fractionation based on biodegradation characteristics. Results indicated that most industrial effluents exhibited a COD distribution where soluble fractions accounted for the majority of the total COD, with significant implications for the understanding of membrane bioreactor (MBR) systems. Observations on the accumulation of soluble COD in the reactor to levels much higher than the permeate COD paved the way to define an experimental PSD methodology for assessing the effective filtration size for the membrane module. This novel parameter considered in the light of reported PSD analyses showed that a portion of what was conventionally considered soluble COD would be retained by the size barrier of the membrane and recycled back to the reactor. Thus, MBR systems require a new mathematical model structure that would include a modified COD fractionation, account for the retained COD fractions as additional model components and utilize related mass balance relationships in order to yield an accurate mechanistic description of microbial reactions taking place in the system.

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

“…Table 6 outlines the PSD profile of COD in this study, along with those of selected industrial effluents 2,19,21,34,41 . Unlike domestic sewage, which is characterized by a limited soluble COD fraction of around 30%, the soluble COD was disclosed as the major COD fraction of industrial effluents; this attribute is quite significant for the application of activated sludge systems operated with membrane filtration modules 22,43 …”

“…PSD is now utilized to provide a better insight for system design and performance evaluation. Extensive reviews reporting PSD analysis of COD by means of the prescribed methodology (involving sequential filtration and ultrafiltration) provided default results for sewage 21 and these proved to be a new asset for industrial effluents, especially for strong wastes, such as landfill leachate 22 . Efforts are now focused on establishing direct relationships between PSD results, biodegradation characteristics, and COD fractionation for different wastewaters 23‐26 …”

Sustainable Alternatives for Tertiary Treatment of Pulp and Paper Wastewater

“…Nanofiltration of biologically treated P&P effluents was investigated in [42], eventually preceded by microfiltration or ultrafiltration, obtaining a permeate free of color and organic compounds; the nanofiltration concentrate was treated with ozone to improve its biodegradability and reduce lignin and turbidity levels. The importance of COD fractionation to model membrane filtration processes was highlighted in [43], showing that most industrial effluents (as the present one) are characterized by a preponderance of soluble fractions that require a dedicated modeling tool. Overall, ultrafiltration permeates were proved to be reusable in most P&P processes, except for bleaching (due to excessive Ca 2+ concentrations) [44,45].…”

Efficient energy recovery from wastewater with high rate activated sludge process: oversights and misguidances

“…A major flaw of most experimental studies carried out at the laboratory scale with a synthetic substrate is to ignore the fact that the substrate characteristics have to be associated with a designated wastewater in the field; this association should not only cover the strength in terms of the COD content, but also COD fractionation and particle size distribution with especially the soluble COD to particulate COD ratio ( S T / X T ), which is a crucially important parameter that would determine the magnitude of energy conservation 27 . As in many similar works, 15,16 the study reported in Liang et al 26 .…”