Membrane filtration device for studying compression of fouling layers in membrane bioreactors

Jørgensen, Mads Koustrup; Bugge, Thomas Vistisen; Larsen, Poul; Nielsen, Per Halkjær; Christensen, Morten Lykkegaard

doi:10.1371/journal.pone.0181652

Cited by 6 publications

(4 citation statements)

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“…The measured flux profiles are shown in Figure 3. After fitting the flux model described previously by Jørgensen, Bugge, et al (2017), filtration parameters were determined, see Table 3. It was clear from the results that the model works for “sludge‐like” suspensions that form compressible cakes on the membrane and that the bacterial suspension did not show the same behavior (Figure 3).…”

Section: Resultsmentioning

confidence: 99%

“…The filtration system was a flat sheet system with aerated membranes, the so‐called Aalborg Filtration Property Analyzer (AaFPA) which was previously described by Jørgensen, Bugge, Bugge, Larsen, Nielsen, and Christensen (2017). The total volume of the reactor was 5 L, and the active membrane area was 84 cm 2 of an Alfa Laval MFP2 flat sheet membrane.…”

Section: Methodsmentioning

confidence: 99%

“…Between each step, a 1‐hr relaxation step was applied to remove reversible fouling. Another mathematical flux model was fitted to the experimental flux data to obtain limiting flux, J LIM , specific resistance at no pressure, α 0 , and a compressibility parameter, P a , as described in (Jørgensen, Bugge, et al, 2017). The flux was modeled as function of TMP with the following equation, assuming that the main fouling mechanism is cake formation:

J = \frac{TMP}{μ (R_{m} + R_{c})}

in which R m and R c are the hydraulic resistances of the membrane and cake (m −1 ), of which the cake resistance and is the product of the specific cake mass, ω (kg/m 2 ), and the average specific cake resistance, α (m/kg).…”

Section: Methodsmentioning

confidence: 99%

“…The slope of a α ‐TMP plot, that is, the ratio α 0 / P a , denotes the cake compressibility, k . The amount of cake is simulated by solving the following equation numerically by a simple Euler approach, as described in (Jørgensen, Bugge, et al, 2017).

\frac{d ω}{italicdt} = (J ‐ J_{italicLIM} (1 ‐ e^{‐ ω / ω_{italiccrit}})) C_{b}

In Equation (), C b is the bulk sludge concentration, J LIM is the limiting flux (m/s), whereas ω crit is the critical specific mass of cake (m/kg).…”

Section: Methodsmentioning

confidence: 99%

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Fouling of membranes in membrane bioreactors for wastewater treatment: Planktonic bacteria can have a significant contribution

Hansen

Nierychlo

Christensen

et al. 2020

Water Environment Research

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Membrane bioreactors (MBRs) for wastewater treatment show great potentials in the sustainable development of urban environments. However, fouling of membranes remains the largest challenge of MBR technology. Dissolved extracellular polymeric substances (EPS) are often assumed be the main foulant in MBRs. However, single bacterial cells are often erroneously measured as EPS in traditional spectrophotometric analysis of EPS in activated sludge, so we hypothesized that single cells in many cases could be the true foulants in MBRs for wastewater treatment. To study this, raw MBR sludge and sludge supernatant with varying concentrations of planktonic cells were filtered on microfiltration (MF) membranes, and we found a direct correlation between the cell count and rate of flux decline. Addition of planktonic cells to fresh MBR sludge dramatically increased the flux decline. The identity of the most abundant planktonic cells in a full‐scale MBR water resource recovery facility was determined by DNA fingerprinting. Many of these genera are known to be abundant in influent wastewater suggesting that the influent bacterial cells may have a direct effect on the fouling propensity in MBR systems. This new knowledge may lead to new anti‐fouling strategies targeting incoming planktonic bacteria from the wastewater feed. Practitioner points Planktonic cells constituted up to 60% of the total protein content of “soluble extracellular polymeric substances” in membrane bioreactor sludge. Planktonic cells are hidden under a surrogate concentration of extracellular polymeric substances which is often associated with fouling. Membrane fouling rate is directly proportional to amount of free planktonic cells suspended in sludge. Several influent bacterial genera are enriched in the water phase of membrane bioreactor sludge. Removing these may mitigate fouling.

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Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

J = \frac{TMP}{μ (R_{m} + R_{c})}

Section: Methodsmentioning

confidence: 99%

\frac{d ω}{italicdt} = (J ‐ J_{italicLIM} (1 ‐ e^{‐ ω / ω_{italiccrit}})) C_{b}

In Equation (), C b is the bulk sludge concentration, J LIM is the limiting flux (m/s), whereas ω crit is the critical specific mass of cake (m/kg).…”