Biofilm Carrier Research Articles

The influence of carrier material on the dominance of polyphosphate-accumulating organism metabolism in the biofilm-based biological phosphorus removal process

This study reveals that the type of carrier material affects the stoichiometry of the anaerobic conversion and the metabolism in cultures enriched with polyphosphate-accumulating organisms (PAOs) and helps increase the biological phosphorus removal performance. PAO-enriched biofilms were cultivated in two identical lab-scale sequencing batch reactors containing different carrier types: a typical moving bed bioreactor carrier (MBBR) and a novel carbon-based moving carrier type (CBMC) coated by activated carbon particles. The experiments were conducted at various influent PO43- concentrations (14, 17, 20 mg-PO43--P/L) and two aeration periods (220 and 460 min) under similar operating conditions. The results showed that due to the particular characteristics of the highly porous CBMC carriers, biomass adhesion increased by approximately 15 % compared to the MBBR carriers. It was also found that the CBMC carrier biofilm relied more on intracellularly stored polyphosphate than glycogen (which could be used by glycogen accumulating organisms (GAO)) as a source of energy for anaerobic uptake of organic substrates, which resulted in a greater dominance of PAO metabolism within the biofilm, especially at lower P concentrations. Conversely, a microbial community with mixed PAO-GAO metabolism was observed within the MBBR carrier biofilm, which changed to PAO dominated metabolism with increasing P concentration. Therefore, a higher specific PO43- uptake rate was obtained for the CBMC reactor (0.072–0.082 P-mol/C-mol.h), indicating a significant enhancement in the range of 13.1–19.6 % compared to the MBBR reactor, depending on the influent P concentration. In addition, better resistance of the CBMC biofilm to prolonged aeration corroborated that although the highly porous structure of the CBMC carriers was effective in achieving a higher P-removal efficiency by 13.5 %, the carrier material still played the major role in PAO metabolism dominance.

Synthesis and application of magnetic PS@Fe3O4 microparticles for improving nitrogen removal in wastewater treatment process

This paper aims to improve the biological nitrogen removal performance by using magnetic polystyrene composite microparticles (PS@Fe3O4). Three types of PS@Fe3O4 with different surface morphologies were prepared by in-situ emulsion polymerization. Then, the optimum was creatively used as a biofilm carrier to form magnetic activated sludge (MAS) in lab-scale reactors. Compared to the conventional activated sludge, the utilization of PS@Fe3O4 accelerated the sludge settling velocity to 0.76 m/h. In addition, the ammonium nitrogen removal, total nitrogen removal and simultaneous nitrification and denitrification improved by 7.08%, 24.27% and 19.53%, respectively. The dissolved oxygen concentration and pH were observed to reveal the effect of PS@Fe3O4 on the nitrogen removal process. Based on microbial community analysis, there were more nitrifying and denitrifying bacteria in the MAS. Therefore, the novel developed PS@Fe3O4 can be a promising utilization material as a biofilm carrier for biological wastewater treatment.

Startup strategies for mainstream anammox polishing in moving bed biofilm reactors

AbstractThis study evaluated startup strategies for mainstream polishing anammox moving bed biofilm reactors (MBBRs) without anammox bacterial (AMX) biomass inoculation. Two types of startups were tested: anammox only (no external carbon addition) and partial denitrification/anammox (PdNA) with glycerol addition. Reactors were started with either virgin carriers or carriers with a preliminary biofilm from a mainstream aerobic integrated fixed‐film activated sludge (IFAS) process. Three pilot‐scale startups were completed under the following conditions: anammox‐only with preliminary biofilm carriers, PdNA with preliminary biofilm carriers, and PdNA with virgin carriers. AMX presence was confirmed via quantitative polymerase chain reaction (qPCR) after 57, 57, and 77 days, respectively. Prior to AMX detection, average influent concentrations of ammonia and nitrite ranged from 1.7–2.7 mg/L and 0.98–1.8 mg/L, respectively. This study demonstrated that AMX can be grown on carriers without AMX seeding under mainstream conditions (temperature 17–29°C, low ammonia and nitrite), regardless of whether nitrite came from upstream or partial denitrification within the reactor. This study also showed that using preliminary biofilm carriers can decrease startup time by approximately 1 month. These results address critical questions for moving mainstream anammox processes to full‐scale implementation, and suggest that PdNA MBBRs are feasible and sustainable for full‐scale ammonia, nitrate, and nitrite polishing to meet stringent total nitrogen requirements.Practitioner Points This research will help utilities develop methods for starting up mainstream anammox MBBRs without the barrier of anammox biomass seeding. Preliminary biofilm carriers accelerated startup time in a PdNA MBBR, but a virgin carrier reactor started up in a similar timeframe, contrary to expectations. Also, contrary to expectations, high concentrations of ammonia and nitrite are not necessary for startup of an anammox or PdNA MBBR.

Experimental investigation of biofilm carriers of varying shapes, sizes, and materials for wastewater treatment in fixed bed biofilm reactor: a qualitative study of biocarrier performance

AbstractBACKGROUNDBiofilm carriers were introduced in the early 1990s mainly to abate chemical oxygen demand (COD). However, studies have continued investigating few biocarriers repeatedly, without studying a large number of carriers in a single study under similar conditions.RESULTSThe current study investigated the performance of nine synthetic and eight natural biofilm carriers for 7 days of palm oil mill effluent (POME) treatment in terms of COD removal. A fixed bed biofilm reactor (FBBR) was 100% packed with biocarriers and operated at 35 °C. Performance based on the 7th day COD removal could be ranked in the following order: green ammonia absorption stone (91%), K1 micro (88%), coral sand (87.8%), volcanic stone (86.6%), Micro Media (85.5%), 1.6 cm BioBall (85%), pebble (82.4%), porous ceramic ring (82.3), K1 (82.1%), non‐porous ceramic ring (80.9%), brown ammonia absorption stone (78.6%), biological filter (77.7%), Ultra Media (76.8%), blue media (69.3%), 3.0 cm BioBall (68.8%), 2.5 cm BioBall (66.5%), and loofah sponge (63%).CONCLUSIONThe smallest carrier, K1 micro, yielded the highest COD removal (88%) on day 7 among the other synthetic carriers, while green ammonia absorption stones provided the highest quality effluent from day 1 (3565 mg COD L−1) to day 7 (780 mg COD L−1) and delivered the shortest start‐up compared with all natural and synthetic carriers. The discussion revealed that all carrier functionalities (i.e., scale, shape, surface pores, roughness, material, surface area, porosity, and durability) play a key role in deciding carrier quality. The current study also introduced ‘carrier efficiency limit’, which refers to the carrier's capacity to entrap biomass and immobilize microorganisms. © 2022 Society of Chemical Industry (SCI).

Bio-electrical stimulation process on degradation of Phenanthrene from aqueous solution using a novel anode modified with carbon cloth: Operational performance, microbial activity and energy

Phenanthrene as the hazardous PAHs-component are extensively detected in industrial wastewater. However, the impacts of bioelectrostimulation process on Phenanthrene degradation in aerobic reactors remained unclear. Here, a novel bioelectrostimulation process equipped with carbon cloth as electrodes was developed to investigate the removal efficiency of Phenanthrene and ATPase enzyme activity in the synthetic wastewater. The results obtained from the present study indicated that a complete Phenanthrene degradation (100%) can be achieved using microbial electrostimulation systems steel mesh coated with carbon cloth (MES-CC) as anode under optimal operational conditions (electrical current: 4 mA, HA concentration: 15 mg L−1) within 18 h. The conductive carbon cloth provides a biofilm carrier to easily transfer the electrons between electrodes and microbial communities. In addition, the highest ATPase enzyme activity (5176 U) was observed when the aerobic MES-CC reactors were operated with electrical current 4 mA. Furthermore, the COD removal efficiency in MES-CC increased from 49% to 96% when the C: N ratio decreased from 20 to 5. The highest value of Vmax in MES-CC for suspended and attached growth were determined to be 2.87 and 0.54 g COD g−1 biomass. Overall, the results demonstrated that MES equipped with carbon cloth and continuous electrical current mode has good potential for efficient Phenanthrene wastewater treatment.

Polyhydroxyalkanoate Pellets as Novel Immobilization Medium for Phenol Biodegradation by Activated Sludge

Biofilm enhances the performances of biological wastewater treatment systems. This study aimed to investigate the feasibility of using biodegradable polyhydroxyalkanoate (PHA) pellets as novel biofilm carrier for phenol biodegradation. Two identical laboratory-scale reactors were operated with fill, react, settle, draw and idle periods in the ratio of 2:12:2:1:7 for a 24-h cycle. One reactor was supplemented with 2% (v/v) of PHA pellet and operated as sequencing batch biofilm reactor (SBBR), whereas the other reactor was operated as sequencing batch reactor (SBR) and used as the control reactor. The performances of SBBR and SBR in degrading phenol were studied at three phases with the introduction of 300, 500 and 1000 mg L-1 phenol, respectively. The removal of phenol was found best described using zero-order kinetics, with R2 > 0.97. At all phases, the phenol removal rate during react period for SBBR (7.30 ± 0.55 to 9.33 ± 1.06 mg L-1 min-1) was found higher compared to those for SBR (4.28 ± 0.66 to 8.35 ± 0.68 mg L-1 min-1), with significance difference observed at low phenol concentration. Whereas for chemical oxygen demand biodegradation kinetics, SBRR exhibited significantly higher rate compared to SBR at all phases. From the scanning electron microscopy image, the attachment of activated sludge onto PHA pellet was observed. The results indicated the potential of PHA serving as alternative biofilm carrier in biofilm process.

A New Device for In Situ Dental Biofilm Collection Additively Manufactured by Direct Metal Laser Sintering and Vat Photopolymerization.

Dental biofilms are complex medical biofilms that cause caries, the most prevalent disease of humankind. They are typically collected using handcrafted intraoral devices with mounted carriers for biofilm growth. As the geometry of handcrafted devices is not standardized, the shear forces acting on the biofilms and the access to salivary nutrients differ between carriers. The resulting variability in biofilm growth renders the comparison of different treatment modalities difficult. The aim of the present work was to design and validate an additively manufactured intraoral device with a dental bar produced by direct metal laser sintering and vat photopolymerized inserts with standardized geometry for the mounting of biofilm carriers. Additive manufacturing reduced the production time and cost, guaranteed an accurate fit of the devices and facilitated the handling of carriers without disturbing the biofilm. Biofilm growth was robust, with increasing thickness over time and moderate inter- and intraindividual variation (coefficients of variance 0.48-0.87). The biofilms showed the typical architecture and composition of dental biofilms, as evidenced by confocal microscopy and 16S rRNA gene sequencing. Deeper inserts offering increased protection from shear tended to increase the biofilm thickness, whereas prolonged exposure to sucrose during growth increased the biofilm volume but not the thickness. Ratiometric pH imaging revealed considerable pH variation between participants and also inside single biofilms. Intraoral devices for biofilm collection constitute a new application for medical additive manufacturing and offer the best possible basis for studying the influence of different treatment modalities on biofilm growth, composition, and virulence. The Clinical Trial Registration number is: 1-10-72-193-20.

Impact of the restraint of biofilm volume and thickness on the performance and microbial composition in anaerobic moving-bed biofilm reactors (AnMBBRs)

The effect of limiting biofilm volume using carriers with maximum thickness control on the performance and microbial community composition was investigated in anaerobic moving-bed biofilm reactors (AnMBBRs). Three parallel, continuous AnMBBRs (4 L) were operated (288 d, 24/36 °C) to treat the soluble fraction of a wastewater from a food-manufacturing facility. Two different biofilm carriers controlling maximum biofilm thickness at 200 and 1000 µm (AnoxK™Z-200 and Z-1000) were used in the three reactors, targeting the same projected surface area for biofilm growth (410 m2/reactor): R200 (Z-200), R1000 (Z-1000) and RMix (both Z-200 and Z-1000). The composition of the bacterial (16S rRNA V1-V3) and methanogenic (mcrA gene) communities was analysed using amplicon sequencing. Under relatively constant organic loads (3.6–4.2 gSCOD/Ld, 34–39 gSCOD/m2d, hydraulic retention time=7.7–8 h), R200 presented lower soluble chemical oxygen demand (SCOD) removals (51–60%) than the other reactors (R100 = 91–93%, RMix = 86–91%), likely due to a limited amount of active protected biofilm volume. Lower SCOD removals were associated with higher concentrations of volatile fatty acids in the effluent (R200 =400–800 mgCOD/L; R1000 and RMix<200 mgCOD/L) and lower methane production (R200 =0.66; R1000 =0.72; RMix=0.73 gCH4-COD/gSCODremoved). The Z-200 carriers contained a different fermentative/acidogenic bacterial community abundant in representatives of the families Christensenellaceae, Anaerovoracaceae and Synergistaceae, and led to less amount of biofilm biomass growth, albeit more active than that of carriers allowing for thicker biofilms (Z-1000). In contrast, methanogenic populations were less sensitive to biofilm thickness restraint by these carriers. This study shows for the first time that limiting biofilm volume in MBBR carriers can impact the performance and bacterial community in AnMBBR biofilms.

Recent Advances in Functional Materials for Wastewater Treatment: From Materials to Technological Innovations

The growing concerns about climate changes and environmental pollution have galvanized considerable research efforts in recent years to develop effective and innovative remediation technologies for contaminated soils and water caused by industrial and domestic activities. In this context, the establishment of effective treatment methods for wastewater has been critically important and urgent, since water pollution can take place on a very large scale (e.g., oceanic oil spills) and have massive impacts on ecosystems and human lives. Functional materials play a central role in the advancement of these technologies due to their highly tunable properties and functions. This article focuses on reviewing the recent progress in the application of various functional materials for wastewater treatment. Our literature survey is first concentrated on new modification methods and outcomes for a range of functional materials which have been actively investigated in recent years, including biofilm carriers, sand filters, biomass, biopolymers, and functional inorganic materials. Apart from the development of modified functional materials, our literature survey also covers the technological applications of superhydrophilic/superhydrophobic meshes, hybrid membranes, and reusable sponges in oil–water separation. These devices have gained significantly enhanced performance by using new functional materials as the key components (e.g., coating materials), and are therefore highly useful for treatment of oily wastewater, such as contaminated water collected from an oil spill site or oil–water emulsions resulting from industrial pollution. Based on our state-of-the-art literature review, future directions in the development and application of functional materials for wastewater treatment are suggested.

Biofilm growth characterization and treatment performance in a single stage partial nitritation/anammox process with a biofilm carrier

Biofilm carriers can avoid microorganism washout while maintaining a high amount of biomass, but are also associated with a long biofilm formation period and biofilm aging. A single stage partial nitritation/anammox process (single stage PN/A) reactor was setup to study the biofilm growth characterization and treatment performance under an NLR of 0.53 to 0.90 gN/L/d over one year. Biofilm growth was divided into three stages: the formation stage, maturation stage and aging stage. The initial biofilm was observed at day 84. A nitrogen removal efficiency of 83.4% was achieved at an NLR of 0.90 gN/L/d during the mature biofilm stage. Starvation, nitrogen gas accumulation and hydroxyapatite formation resulted in biofilm aging. After mechanical stirring treatment, biofilm reactivation was achieved by biofilm re-formation within one month. There is clear potential for phosphorus recovery, as indicated by the 5.24% - 6.29% phosphorus content in the biofilm (similar to the 5%-7% phosphorus content in enhanced biological phosphate removal sludge). The AnAOB genera abundance in the biofilm maintained at a high level of 18.25%-32.31%, while the abundance of AnAOB increased from the initial 4.10% to 13.78% after mechanical stirring treatment in the suspended sludge ensured biofilm reactivation. The results of this study clearly show that mechanical stirring treatment can be used to achieve the biofilm reactivation as the biofilm fills with the hollow cylindrical carrier. This study has potential as a useful reference for the realization of the wide application of the biofilm single stage PN/A process in the future.

A composite Fe–C/layered double oxides (Fe–C/LDO) carrier fabrication and application for enhanced removal of nitrate and phosphate from polluted water with a low carbon/nitrogen ratio

In this study, a multifunctional biofilm carrier (Fe–C/LDO) integrating Fe–C micro-electrolysis with Mg–Al layered double oxides (LDO) was developed and applied in a biofilter aimed to remove nitrogen and phosphorus simultaneously from slightly polluted water with a low carbon/nitrogen (C/N) ratio. Four types of carriers were prepared under different conditions and their performance in nitrate reduction and phosphorus removal were compared. Results showed that the composite Fe–C/LDO carrier prepared with polyethylene glycol as the pore-forming agent demonstrated the highest nitrate reduction rate and phosphorate adsorption capacity (2.09 mg PO43--P·g−1). A biofilter packed with the Fe–C/LDO carrier was investigated under heterotrophic conditions (C/N = 4.13) and complete autotrophic conditions (C/N = 0) during a long-term operation. Good removal of NH4+-N (96–98%), TN (92–96%) and PO43--P (50–58%) were achieved in the biofilter under both heterotrophic and autotrophic conditions. High throughput pyrosequencing analysis revealed that a large population of autotrophic denitrifying bacteria Thiobacillus and Thioalkalispira were enriched in the biofilm. Metagenomic analysis was performed to analyze functional genes related to nitrogen metabolism and carbon cycle, and it confirmed the presence of a whole denitrification and Calvin-Benson-Bassham carbon fixation pathway in biofilm. Finally, the possible mechanisms for nitrogen and phosphorus removal in the biofilter were proposed. The Fe–C/LDO carrier not only enriched abundant autotrophic denitrifying bacteria, but also provided numerous Fe–C galvanic cells for nitrate reduction through micro-electrolysis. In addition, the Mg–Al LDO in combination with iron hydroxides generated during micro-electrolysis may contribute greatly to phosphorus removal. Biofilter packed with the multifunctional Fe–C/LDO carrier could be a promising technology for simultaneous nitrogen and phosphorus removal from slightly polluted water.

Life cycle assessment of urban uses of biochar and case study in Uppsala, Sweden

Biochar is a material derived from biomass pyrolysis that is used in urban applications. The environmental impacts of new biochar products have however not been assessed. Here, the life cycle assessments of 5 biochar products (tree planting, green roofs, landscaping soil, charcrete, and biofilm carrier) were performed for 7 biochar supply-chains in 2 energy contexts. The biochar products were benchmarked against reference products and oxidative use of biochar for steel production. Biochar demand was then estimated, using dynamic material flow analysis, for a new city district in Uppsala, Sweden. In a decarbonised energy system and with high biochar stability, all biochar products showed better climate performance than the reference products, and most applications outperformed biomass use for decarbonising steel production. The climate benefits of using biochar ranged from − 1.4 to − 0.11 tonne CO2-eq tonne−1 biochar in a decarbonised energy system. In other environmental impact categories, biochar products had either higher or lower impacts than the reference products, depending on biochar supply chain and material substituted, with trade-offs between sectors and impact categories. However, several use-phase effects of biochar were not included in the assessment due to knowledge limitations. In Uppsala’s new district, estimated biochar demand was around 1700 m3 year−1 during the 25 years of construction. By 2100, 23% of this biochar accumulated in landfill, raising questions about end-of-life management of biochar-containing products. Overall, in a post-fossil economy, biochar can be a carbon dioxide removal technology with benefits, but biochar applications must be designed to maximise co-benefits.

Research and Application of Supersaturated Dissolved Oxygen Technology Combined with Magnetization Technology in the Improvement of Water Quality: Taking the South-to-North Water Diversion Project of China as a Pilot Project

Supersaturated dissolved oxygen and magnetization (SDOXM) technology is a composite technology that combines supersaturated dissolved oxygen with water magnetization technologies. Compared with conventional water purification technology, the advantages introduced by such technology include obvious and efficient improvement in purified water quality without adding any chemicals, removing sludge and changing the original function of the river. In this study, taking the Middle-Route (MR) of the South-to-North Water Diversion Project of China (SNWDPC) as a pilot project, the effects of the SDOXM composite process on microbial activity, phytoplankton community structure, and removal efficiency of the main nutritional indexes in the canal of the MR were evaluated. Aiming at static and flowing water bodies, this study was divided into two parts: static and dynamic experiments (two groups: a group with artificial aquatic plants and another group without artificial aquatic plants). The performance of the SDOXM system was assessed by monitoring the organic matter removal as well as the relative light unit (RLU) of ATP, changes in the community structure of phytoplankton, and the effects of artificial aquatic plants as a biofilm carrier on organic matter removal and microbial activity. During the study period, SDOXM technology was able to increase the concentration of dissolved oxygen (DO) in water and maintained the state of supersaturation for more than three days. The removal effect of organic matter from water was obvious. The community structure of phytoplankton changed from the Bacillariophyta-Cyanophyta type to the Bacillariophyta-Cyanobacteria type. Finally, the introduction of artificial aquatic plants has contributed to the improvement in water quality. Therefore, SDOXM technology can be used as a new water quality improvement technology to enhance the self-restoration ability of a river natural ecology.

Microbial composition and nitrogen removal pathways in a novel sequencing batch reactor integrated with semi-fixed biofilm carrier: evidence from a pilot study for low- and high-strength sewage treatment.

The sequencing batch reactor (SBR) activated sludge process is a well-established technology for sewage treatment. One of the drawbacks of SBRs, however, total nitrogen (TN) removals is insufficient. By means of introducing four improvements, including semi-fixed biofilm carrier, sludge elevation mixing and change for the mode of influent and effluent, compliant standard for TN discharge was obtained in this novel SBR configuration during low- and high-strength sewage load. To illustrate the microbial compositions and functions of the attached biofilm on semi-fixed carrier and the suspended aggregates, as well as the nitrogen removal pathway, high throughput 16S rRNA gene amplicon sequencing, PICRUSt2 algorithm, and KEGG database were applied. The results revealed that (i) the microbial communities from suspended aggregates and biofilm samples were significantly different from each other; (ii) during low-strength sewage loads, TN removal was mainly by nitrification-denitrification. The suspended aggregates was responsible for denitrification, while the biofilm was focused on ammonium oxidation; (iii) during high-strength sewage loads, function of nitrate reductase from suspended aggregates was faded, and anammox and N assimilation by biofilm became dominant. Meanwhile, TN removal referring to the formation of L-glutamine via assimilation was the main pathway.

Microalgae-assisted fixed-film activated sludge MFC for landfill leachate treatment and energy recovery

The sustainability and innovation of a novel leachate treatment technology is a matter of vital significance. Bio-electrochemical-driven wastewater and leachate treatment methods, particularly MFC, and their improvements have attracted scientists’ attention recently. This study developed a new MFC system, which consisted of an anodic chamber, a cathode chamber with fixed biofilm carriers and a low-cost sheet of carbon felt between them as a membrane-like separator. The study was conducted to evaluate the capacity of MFC coupled with integrated fixed-film activated sludge (IFAS), to enhance the efficiency of the treatment and the amount of energy produced. Three MFC systems with different cathode processes were compared, namely, conventional activated sludge (MFC-AS), MFC-IFAS, and microalgae coupled MFC-IFAS (MFC-IFAS/MA). The experimental results revealed that MFC-IFAS/MA produced higher power density and nitrogen removal than the other two systems. The average removals of COD, NH4+-N, and total nitrogen (TN) were, 69.9%, 84.2% and 60.5% for MFC-AS, 84.3%, 79.2% and 71.6% for MFC-IFAS; and 82.0%, 90.3% and 88.6% for MFC-IFAS/MA. MFC-IFAS/MA demonstrated its superior electrochemical behaviors and nitrogen removal and this behavior was referring to the dual effect of fixed-biofilm and microalgae assimilation. This study investigated for the first time the symbiosis between microalgae and IFAS in an MFC reactor, which may open a new prospect for MFC application.

Simultaneous Heterotrophic Nitrification and Aerobic Denitrification of Water after Sludge Dewatering in Two Sequential Moving Bed Biofilm Reactors (MBBR).

Water after sludge dewatering, also known as reject water from anaerobic digestion, is recycled back to the main wastewater treatment inlet in the wastewater treatment plant Porsgrunn, Norway, causing periodic process disturbance due to high ammonium of 568 (±76.7) mg/L and total chemical oxygen demand (tCOD) of 2825 (±526) mg/L. The main aim of this study was the simultaneous treatment of reject water ammonium and COD using two pilot-scale sequential moving bed biofilm reactors (MBBR) implemented in the main wastewater treatment stream. The two pilot MBBRs each had a working volume of 67.4 L. The biofilm carriers used had a protected surface area of 650 m2/m3 with a 60% filling ratio. The results indicate that the combined ammonia removal efficiency (ARE) in both reactors was 65.9%, while the nitrite accumulation rate (NAR) and nitrate production rate (NPR) were 80.2 and 19.8%, respectively. Over 28% of the reject water’s tCOD was removed in both reactors. The heterotrophic nitrification and oxygen tolerant aerobic denitrification were the key biological mechanisms found for the ammonium removal in both reactors. The dominant bacterial family in both reactors was Alcaligenaceae, capable of simultaneous heterotrophic nitrification and denitrification. Moreover, microbial families that were found with equal potential for application of simultaneous heterotrophic nitrification and aerobic denitrification including Cloacamonaceae, Alcaligenaceae, Comamonadaceae, Microbacteriaceae, and Anaerolinaceae.

Biofilm and Chronic Typhoid Carriers with Special Reference to Bacteriophage Therapy

Biofilm and Chronic Typhoid Carriers with Special Reference to Bacteriophage Therapy

Iron carriers promote biofilm formation and p-nitrophenol degradation

Vertical baffled biofilm reactors (VBBR) equipped with Plastic-carriers and Fe-carriers were employed to explore the effect of biofilm carriers on biofilm formation and p-nitrophenol (PNP) degradation. The results showed that Fe-carriers enhanced biofilm formation and PNP degradation. The maximum thickness of biofilm grown on the Fe-carriers was 1.5-fold higher than that on the Plastic-carriers. The Fe-VBBR reached a maximum rate of PNP removal at 13.02 μM L−1 h−1 with less sodium acetate addition (3 mM), while the maximum rate of PNP removal was 11.53 μM L−1 h−1 with more sodium acetate addition (6 mM) in the Plastic-based VBBR. High-throughput sequencing suggested that the Fe-VBBR had a higher biodiversity of the bacterial community in evenness, and the Achromobacter genus and Xanthobacteraceae family were as main PNP degraders. Kyoto Encyclopedia of Genes and Genomes (KEGG) Orthology analysis suggested more abundances of iron uptake genes were expressed to transport iron into the cytoplasm under an iron-limited condition in two VBBRs, and the metabolic pathway of PNP degradation went through 4-nitrocatechol and 1,2,4-benzenetriol. Our results provide a new insight for iron enhancing biofilm formation and PNP degradation.

Mathematical Model Development and 3D Printing of Cylindrically Shaped Biofilm Carrier Media from Recycled Plastic Waste for Wastewater Treatment

Wastewater management and purification remain one of the greatest problems of mankind. The biological wastewater treatment technique uses a biofilm media carrier where microorganisms attach themselves to the surface. This biofilter is usually made from virgin plastic pellets and can also be produced from recycled waste plastic and used in wastewater treatment. The need to treat water using low-cost carrier media has led to finding alternative sources of materials for biofilter manufacturing. Therefore, this work is centered on the recycling of waste plastic to make filaments which are then used for 3D printing of a high specific surface area (SSA) less clogging biofilm carrier through the parametric redesign. In the current study, the polypropylene material was recycled to make a 2.85 mm diameter filament compatible with the Ultimaker S3. Moreover, analytical models and governing equations were developed for the design of the K3 Kaldnes and MB3 media. Empirical surface area (SA), specific surface area, and volume of the respective carriers were determined using the model developed. SolidWorks was used to design and evaluate the same parameters which were then compared to model results. The errors in SSA obtained from the model with respect to the SolidWorks results for both the K3 Kaldnes and MB3 media were 0.34% and 0.76% respectively. With these small error margins, the model can serve as a tool and guideline for the designing of cylindrically shaped carriers. By transforming plastics into biofilters, waste plastics are mopped up reducing pollutions. Consequently, the deployment of such biofilters will enhance efficient wastewater treatment for a cleaner environment and the wellbeing of human race.

Negative food dilution and positive biofilm carrier effects of microplastic ingestion by D. magna cause tipping points at the population level

Ingestion of microplastics by aquatic organisms is often harmful due to the dilution of their regular food with low-calorie microplastic particles, but can also be beneficial if nutritious biofilms are present on the microplastic surface. This begs the question: is ingestion of microplastic harmful or beneficial and can the net effect of the two mechanisms be quantified? Here, we quantified these harmful and beneficial effects on Daphnia magna, using dose-response tests with clean and biofouled microplastic respectively, and determined the trade-off between these counteracting effects. A population model was developed to calculate the isoclines for zero population growth, separating the regime where adverse food dilution dominated from that where the beneficial biofilm vector mechanism dominated. Our results show that the organisms grew better when exposed to biofouled microplastic compared to pristine microplastic. Very good model predictions (R2 = 0.868–0.991) of the effects of biofouled microplastic were obtained based on literature parameter values, with optimization required only for the two sub-model parameters driving the dose-effect relationships for pristine microplastic. These results contradict previous sudies were only pristine microplastic were used and demonstrate that the ruling paradigm of unambiguously adverse microplastic effects is not ecologically justifiable.