Evaluation of Heavy Metal Removal from Wastewater in a Modified Packed Bed Biofilm Reactor

Azizi, Shohreh; Kamika, Ilunga; Tekere, Memory

doi:10.1371/journal.pone.0155462

Cited by 58 publications

(24 citation statements)

References 33 publications

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“…extracellular matrix (1). Biofilms are well-documented to provide bacterial cells protection from a variety of stresses, such as heavy metals, organic solvents, and antimicrobials (2)(3)(4). Biofilms of pathogenic bacteria allow these cells to tolerate higher concentrations of antibiotics (up to 1,000 times) than planktonic cells of the same species, leading to chronic infections and facilitating the development of multidrug-resistant strains, such as "superbugs" (2,5).…”

mentioning

confidence: 99%

Antibiotic Susceptibility of Escherichia coli Cells during Early-Stage Biofilm Formation

Lee

Carnicelli

et al. 2019

J Bacteriol

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Bacteria form complex multicellular structures on solid surfaces known as biofilms, which allow them to survive in harsh environments. A hallmark characteristic of mature biofilms is the high-level antibiotic tolerance (up to 1,000 times) compared with that of planktonic cells. Here, we report our new findings that biofilm cells are not always more tolerant to antibiotics than planktonic cells in the same culture. Specifically, Escherichia coli RP437 exhibited a dynamic change in antibiotic susceptibility during its early-stage biofilm formation. This phenomenon was not strain specific. Upon initial attachment, surface-associated cells became more sensitive to antibiotics than planktonic cells. By controlling the cell adhesion and cluster size using patterned E. coli biofilms, cells involved in the interaction between cell clusters during microcolony formation were found to be more susceptible to ampicillin than cells within clusters, suggesting a role of cell-cell interactions in biofilm-associated antibiotic tolerance. After this stage, biofilm cells became less susceptible to ampicillin and ofloxacin than planktonic cells. However, when the cells were detached by sonication, both antibiotics were more effective in killing the detached biofilm cells than the planktonic cells. Collectively, these results indicate that biofilm formation involves active cellular activities in adaption to the attached life form and interactions between cell clusters to build the complex structure of a biofilm, which can render these cells more susceptible to antibiotics. These findings shed new light on bacterial antibiotic susceptibility during biofilm formation and can guide the design of better antifouling surfaces, e.g., those with micron-scale topographic structures to interrupt cell-cell interactions. IMPORTANCE Mature biofilms are known for their high-level tolerance to antibiotics; however, antibiotic susceptibility of sessile cells during early-stage biofilm formation is not well understood. In this study, we aim to fill this knowledge gap by following bacterial antibiotic susceptibility during early-stage biofilm formation. We found that the attached cells have a dynamic change in antibiotic susceptibility, and during certain phases, they can be more sensitive to antibiotics than planktonic counterparts in the same culture. Using surface chemistry-controlled patterned biofilm formation, cell-surface and cell-cell interactions were found to affect the antibiotic susceptibility of attached cells. Collectively, these findings provide new insights into biofilm physiology and reveal how adaptation to the attached life form may influence antibiotic susceptibility of bacterial cells.

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confidence: 99%

Antibiotic Susceptibility of Escherichia coli Cells during Early-Stage Biofilm Formation

Lee

Carnicelli

et al. 2019

J Bacteriol

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“…The reported analytical values are the mean of five replicates. The particle size analysis was carried out by laser diffraction methods using the Malvern Mastersizer 2000 ® U.K. [23][24][25]. The reported analytical values are the mean of five replicates.…”

Section: Methodsmentioning

confidence: 99%

“…The reduction in solids increased with the digestion time (Figure 2A) For the first 24 h, increases for the MLSS were associated with the microorganisms' access to the remaining organic substances from the wastewater treatment system, after which there was a decline [25,26]. The rapid decrease in MLSS after 24 h was possibly due to the solubilized organic matter being consumed by micro-organisms for their growth [24,27]. Finally, the MLSS observed showed 87.40%, 88.15% and 88.31% decreases in their primary sludge value from the ASP, MBBR, and PBBR, respectively.…”

Section: Mlss Mlvss Svi Cod and Do Profiles In Batch Experimentsmentioning

confidence: 98%

Evaluation of the Digestibility of Attached and Suspended Growth Sludge in an Aerobic Digester for a Small Community

Azizi

Kamika

Tekere

2018

Water

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Abstract:The aerobic sludge digestion process for waste sludge generated from suspended biomass (i.e., activated sludge process, ASP) and attached biomass (i.e., moving bed bioreactor, MBBR and modified packed bed biofilm, PBBR) reactors in a residential complex were analyzed. The rate of digestion with respect to different sludge characteristics generated through these various treatment processes were examined; the results revealed that waste sludge from ASP took 16 days to achieve complete digestion while MBBR and PBBR took nine and seven days, respectively. The most important factors influencing the sludge digestion such as sludge volume index (SVI), mixed liquor suspended solid (MLSS), and mixed liquor volatile suspended solid (MLVSS) were examined. The ASP which had the highest initial MLSS and MLVS took a longer time for digestion. Aerobic sludge digestion in all the treatment reactors was studied under laboratory scale conditions in batch experimentation to evaluate sludge characteristics and the rate of digestion as well as through a continuous bench scale pilot system to optimize the process parameters. Removal efficiencies of volatile solids (VS) 90.71% in ASP, 84.27% in MBBR and 84.07% in PBBR in aerobic digestion during batch mode were also observed. The study revealed that the aerobic sludge digestion process utilized in curbing sludge is not feasible application for a small community due to very long digestion times and a large amount of space although Packed Bed Biofilm (PBBR) used the lowest time (seven days) compared to the other systems.

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“…High levels of heavy metals in raw sewage is one of the major concerns of WWTP management, it affects microbial activity in the system and impede biological wastewater process [AZIZI et al 2016]. In order to protect the purification process, Algerian standards were established in June 2009 setting limit values for the content of harmful substances other than domestic at the time of their discharge into a WWTP.…”

Section: Heavy Metals and Toxic Elementsmentioning

confidence: 99%

Irrigation with treated wastewaters and the protection of Hennaya groundwater – Tlemcen, Algeria

Bemmoussat

Adjim

Bensaoula

2019

Journal of Water and Land Development

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The Henaya Irrigated Perimeter (HIP) is an agricultural area irrigated by treated wastewater (TWW) of Ain El Hout treatment plant. Various analyses have shown that i) this water has low concentration of heavy metals and toxic elements, ii) the average values of the physicochemical parameters for 136 samples are satisfactory (29.2 mg O2∙dm−3 for chemical oxygen demands – COD, 13.14 mg O2∙dm−3 for biological oxygen demands – BOD, 14.2 mg∙dm−3 of suspended matter – SM, 1.82 mg∙dm−3 of N-NO3, 7.7 for pH and 927.74 μS∙cm−1 for electric conductivity – EC). Thirdly, it contains a high number of bacteria and nematodes (7200 CFU∙(100 dm3)−1 for faecal coliforms and 30 eggs∙dm−3 for intestinal Nematodes) which makes it dangerous for groundwater contamination.The objective in this work is to characterize the TWW and evaluate the impact of it use for irrigation on the quality of Hennaya groundwater. Before this, one has to prove that there is an amount of TWW that feeds the water table to show that there is a risk of pollution. We then estimated the aquifer minimum recharge value by TWW using the Thormthwaite method. The estimation has given 92 mm which is an important quantity. The results of the groundwater microbiological analyses reveal no sign of contamination. The cause is the efficiency of the degradation of pollutants of the Vadose zone. The soil purifying power Md of the HIP was evaluated by the Rehse method and gave values ranging from 2.1 to 12.7 which indicated a complete purification.

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Evaluation of Heavy Metal Removal from Wastewater in a Modified Packed Bed Biofilm Reactor

Cited by 58 publications

References 33 publications

Antibiotic Susceptibility of Escherichia coli Cells during Early-Stage Biofilm Formation

Antibiotic Susceptibility of Escherichia coli Cells during Early-Stage Biofilm Formation

Evaluation of the Digestibility of Attached and Suspended Growth Sludge in an Aerobic Digester for a Small Community

Irrigation with treated wastewaters and the protection of Hennaya groundwater – Tlemcen, Algeria

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