Biofilm formation and permeate quality improvement in Gravity Driven Membrane ultrafiltration

Abstract

The effects of biofilm development on ultrafiltration membranes with regard to permeate stability and permeation rates were investigated using Gravity Driven Membrane (GDM) filtration. The first part of the study aimed at evaluating the influence of the biofilm on permeate flux quality and quantity with regard to Assimilable Organic Carbon (AOC) degradation. In addition, two types of biological pre-treatments were evaluated: slow sand filtration and packed bed bio-reactor, compared to a control (no treatment). Biofilm formation helped to decrease the AOC content of permeate water, compared to the influent. Both pre-treatments additionally reduced the AOC level in the permeate and thus increased its biological stability, however none of the systems were able to guarantee microbiologically stable water. Removal of AOC before the GDM filtration reduced the biofilm growth potential, which in turn influenced its physical structure and enhanced the permeation rates. Influence of inorganic particle removal by pre-sedimentation and its effect on biofilm structure were also studied. Pre-sedimentation of particle populations selected fine and homogeneous particle fractions, which led to the formation of a homogeneous biofilm structure characterised by an increased hydraulic resistance. This was clearly visible between horizontally and vertically installed membranes where the latter ones had a significantly reduced flux despite lower deposited particle mass. The presence of larger, heterogeneous particle fractions counterbalanced the negative effects of the fine particles, which overall resulted in enhanced permeation rates.

Improved performance of gravity-driven membrane filtration for seawater pretreatment: Implications of membrane module configuration

“…It is noted that the DOC contents in the feed (1.08±0.16 mg/L, Table 3) and effluent (1.10±0.10 mg/L, Table S3) of pilot GDM reactor were less than that in the permeate of the pilot (1.29±0.33 mg/L, Table 3). This phenomenon was also observed in the previous studies (Akhondi et al, 2015;Chomiak et al, 2014;Wu et al, 2016), which was proposed to be possibly related to the hydrolysis of suspended organic material within the biofilm and carbon fixation activity within the microbial biofilm.…”

Relationships among Permeability, Membrane Roughness, and Eukaryote Inhabitation during Submerged Gravity-Driven Membrane (GDM) Filtration

“…In Figure 8b, permeability increased with increasing biomass concentration in the fouling layer (R 2 = 0.74). This result was contrary to reports that the fouling layer deposited on membrane surfaces decreased permeability due to pore blocking and/or pore constriction [42][43][44]. However, the presence of eukaryotes (i.e., nematodes in this study) inhabiting the fouling layer increased the permeate flux by 50-170% during GDM filtration in a previous study [9].…”

Effect of thickness of textile filter on organic compounds and nutrients removal efficiency at changeable wastewater surface level

“…On the one hand it can be assumed that higher biomass (assuming stable concentration thicker layer -higher biomass content) causes better efficiency (Chomiak et al, 2014a;Wang et al, 2008). On the other hand there are several other factors, which can correspond in an opposite manner to filtering layer thickness, oxygen accessibility being one example.…”