Algal Biofilm Growth Research Articles

Efficacy and mechanisms of rotating algal biofilm system in remediation of soy sauce wastewater

This study investigated the efficacy of the rotating algal biofilm (RAB) for treating soy sauce wastewater (SW) and its related treatment mechanisms. The RAB system demonstrated superior nutrient removal (chemical oxygen demand, ammonium nitrogen, total nitrogen, and phosphorus for 92 %, 94 %, 91 %, and 82 %, respectively) and biofilm productivity (14 g m−2 d–1) at optimized 5-day harvest time and 2-day hydraulic retention time. This was mainly attributed to the synergistic interactions within the algae-fungi (Apiotrichum)-bacteria (Acinetobacter and Rhizobia) consortium, which effectively assimilated certain extracellular polymeric substances into biomass to enhance algal biofilm growth. Increased algal productivity notably improved protein and essential amino acid contents in the biomass, suggesting a potential for animal feed applications. This study not only demonstrates a sustainable approach for managing SW but also provides insight into the nutrient removal and biomass conversion, offering a viable strategy for large-scale applications in nutrient recovery and wastewater treatment.

Chlorococcum sp. and mixotrophic algal biofilm growth in horizontal and vertical–oriented surfaces using wastewater and synthetic substrate

Chlorococcum sp. and mixotrophic algal biofilm growth in horizontal and vertical–oriented surfaces using wastewater and synthetic substrate

Examining the dependence of macroplastic fragmentation on coastal processes (Chesapeake Bay, Maryland)

Plastic debris in the coastal environment is subject to complex and poorly characterized weathering processes. To better understand how key environmental factors affect plastic degradation in a coastal zone, we conducted an in situ experiment. We deployed strips of high density polyethylene (HDPE) and polystyrene (PS) in paired coastal areas of contrasting conditions (hydrodynamic activity: erosional or depositional; water depths: subtidal or intertidal). Strips were collected after environmental exposures at 4, 8, and 43 weeks and analyzed for change in mass, algal biofilm growth, and imaged by petrographic and electron microscopy (SEM-EDS). Significant surface erosion was evident on both polymers, and was more rapid and more extensive with PS. Degradation of PS was responsive to intensity of hydrodynamic activity, and was greater at intertidal depths, highlighting the critical role played by photo-oxidation in the coastal zone, and suggesting that algal biofilms may slow degradation by playing a photo-protective role.

Improving the performance of activated sludge process with integrated algal biofilm for domestic wastewater treatment: System behavior during the start-up phase

This study aims to enhance nutrient removal in an existing activated sludge process based decentralized wastewater treatment system by introducing illumination and algal biofilms in the aeration chamber. The aeration tank (AT) has been modified with the addition of blue light-emitting diode (LED) lights and silicon carbide foam filters as supporting media for algal biofilm growth. The light intensity (varied between 100 and 200 W/180 m3) had shown a strong correlation with the chlorophyll concentration in the mixed liquor. The nitrogen removal has increased from 48 ± 9% to 63 ± 6% and P removal from 37 ± 12% to 70 ± 12% in the modified aeration tank using 200 W LEDs with 12:12 light: dark cycle. Decreasing the light period to 8-h had decreased the carbon and nutrient removal to 32 ± 11% and 45 ± 10% respectively. The influent C/N showed a strong association with carbon and nutrient removal.

A Novel System for Real-Time, In Situ Monitoring of CO2 Sequestration in Photoautotrophic Biofilms.

Climate change brought about by anthropogenic CO2 emissions has created a critical need for effective CO2 management solutions. Microalgae are well suited to contribute to efforts aimed at addressing this challenge, given their ability to rapidly sequester CO2 coupled with the commercial value of their biomass. Recently, microalgal biofilms have garnered significant attention over the more conventional suspended algal growth systems, since they allow for easier and cheaper biomass harvesting, among other key benefits. However, the path to cost-effectiveness and scaling up is hindered by a need for new tools and methodologies which can help evaluate, and in turn optimize, algal biofilm growth. Presented here is a novel system which facilitates the real-time in situ monitoring of algal biofilm CO2 sequestration. Utilizing a CO2-permeable membrane and a tube-within-a-tube design, the CO2 sequestration monitoring system (CSMS) was able to reliably detect slight changes in algal biofilm CO2 uptake brought about by light–dark cycling, light intensity shifts, and varying amounts of phototrophic biomass. This work presents an approach to advance our understanding of carbon flux in algal biofilms, and a base for potentially useful innovations to optimize, and eventually realize, algae biofilm-based CO2 sequestration.

Design and testing of an externally-coupled planar waveguide photobioreactor

Waveguides can be used to deliver light deep into algal photobioreactors, allowing the growth of algal biofilms with high areal yield. A current drawback of these reactors is their dependency upon artificial illumination. A more practical approach would be to use direct sunlight to illuminate the waveguide photobioreactor. In this paper a novel optical system is designed to grow algal biofilm using waveguides illuminated with external light using 3D-printed paraboloidal mirrors. It was found that the polygonal approximation of a compound parabolic trough was an effective mechanism for focusing external natural light, which could be constructed easily. It is also demonstrated that algae biofilm biomass productivity on the waveguide increases by a factor of 2.5 when operated in conjunction with mirrored troughs.

Lignocellulosic residue as bio-carrier for algal biofilm growth: Effects of carrier physicochemical proprieties and toxicity on algal biomass production and composition

Five types of lignocellulosic materials were applied as the bio-carriers for low-cost algal biofilm cultivation of three algal strains. The effects of bio-carrier physicochemical properties and toxicity on algal cells growth and attachment were investigated. Rougher and hydrophilic bio-carrier could yield more algal biomass than smoother and hydrophobic bio-carrier. Pine sawdust (diameter: 0.420–0.595 mm) performed the best when cultured Diplosphaera sp. (9.61 g·m−2·day−1) biofilm. Meanwhile, bio-carriers could be leached by the culture medium during cultivation, and their energy conversion proprieties could be improved due to the reduced ash contents and the decreased crystallinities. In addition, Chlorella vulgaris growth tests indicated that pine sawdust (15.45%) leachate promoted cell growth, whereas rick husk (15.48%) and sugarcane bagasse (13.19%) leachate inhibited cell growth. And bio-carriers leachates also modified the chemical compositions (lipid, protein and carbohydrate) of algal cells and increased the corresponding saturated fatty acids methyl ester content (from 48.71 to 55.58–57.08%).

A novel light source provided by photobacteria to improve the growth of microalgal biofilm

Attached microalgae cultivation for biomass/bioenergy production has been proposed these decades to avoid the energy-intensive harvest process. However, the external light could only propagate <200 μm in biofilm, which inhibits the growth of microalgae in deep layer. In this paper, the possibility of using inner light emitted by mix-cultured photobacteria for attached microalgae growth was investigated. The luminance of photobacteria gradually increased along with their growth. However, it would fade after approximately 14 h in one-time feed cultivation, which could be recovered by refreshing medium. By scattering photobacteria in the middle of microalgae, light emitted from photobacteria could be utilized for the photosynthesis of microalgae. It was found that the involvement of photobacteria could promote the algal biofilm growth from 9.6 mg to 11.5 mg under the natural condition for a 7-day cultivation, which needed to be further strengthened.

Algal biofilm ponds for polishing secondary effluent and resource recovery

In order to reduce the cost of microalgae harvesting, biofilm algal cultivations have received attention as a potential platform for algal biomass production and wastewater treatment. Two 50-L ponds containing vertically oriented geotextiles, cotton textiles, and polyethylene sheets were fed secondary effluent to examine the growth of algal biofilms. The removal of total phosphorus, PO43−-P and NO3−-N ranged from 52 to 97%, 59 to 93%, and 0 to 99%, respectively. The highest biomass productivity was 1.4 and 0.5 g m−2 day−1, and the lipid content of the attached biomass was quite low, 0.36 and 0.48%, in the cotton textile and polyethylene-baffled pond, respectively. The lipid content of the suspended biomass of the cotton textile and polyethylene pond was very low and similar (0.5%), but it increased to 13.8 and 3.4%, respectively, after a starvation period of 13 days.

Algae-based biofilm productivity utilizing dairy wastewater: effects of temperature and organic carbon concentration.

BackgroundBiofilm-based microalgal growth was determined as functions of organic chemical loading and water temperature utilizing dairy wastewater from a full-scale dairy farm. The dairy industry is a significant source of wastewater worldwide that could provide an inexpensive and nutrient rich feedstock for the cultivation of algae biomass for use in downstream processing of animal feed and aquaculture applications. Algal biomass was cultivated using a Rotating Algal Biofilm Reactor (RABR) system. The RABR is a biofilm-based technology that has been designed and used to remediate municipal wastewater and was applied to treat dairy wastewater through nutrient uptake, and simultaneously provide biomass for the production of renewable bioproducts.ResultsAerial algal biofilm growth rates in dairy wastewater at 7 and 27 °C temperatures were shown to be 4.55 ± 0.17 g/m2-day and 7.57 ± 1.12 g/m2-day ash free dry weight (AFDW), respectively. Analysis of Variance (ANOVA) calculations indicated that both an increase in temperature of the wastewater and an increase in the level of organic carbon, from 300 to 1200 mg L-1, contributed significantly to an increase in the rate of biomass growth in the system. However, ANOVA results indicated that the interaction of temperature and organic carbon content was not significantly related to the biofilm-based growth rate.ConclusionA microalgae-based biofilm reactor was successfully used to treat turbid dairy wastewater. Temperature and organic carbon concentration had a statistically significant effect on algae-based biofilm productivity and treatment of dairy wastewater. The relationships between temperature, TOC, and productivity developed in this study may be used in the design and assessment of wastewater remediation systems and biomass production systems utilizing algae-based biofilm reactors for treating dairy wastes.

Wastewater treatment and biofuel production through attached culture of Chlorella vulgaris in a porous substratum biofilm reactor

The feasibility of attached culture Chlorella vulgaris in a porous substratum biofilm reactor (PSBR) for simultaneous wastewater treatment and biofuel production was investigated. The characteristics, including algal biofilm growth, lipid yield, nutrient removal, and energy efficiency of the outdoor cultures, were investigated under the influence of both inoculum densities and the percent submerged area. A maximum biofilm productivity of 57.87 g m−2 d−1 with 81.9 % adhesion was achieved under optimal conditions (inoculum density of 18 g m−2 and the percent submerged area of 5.7 %). The lipid content and lipid yield were 38.56 % and 27.25 g m−2 d−1, respectively. Meanwhile, the algae removed 99.95 % ammonia, 96.05 % total nitrogen (TN), and 99.83 % total phosphorus (TP). Further, the energy life cycle for the PSBR was analyzed. The biomass productivity per unit irradiance was up to 4.6 g MJ−1 (photosynthetic efficiency of 10.65 %). The PSBR was considered to be economically feasible due to the net energy ratio of 1.3 (>1).

The effect of photon flux density on algal biofilm growth and internal fatty acid concentrations

Algal biofilm systems offer potential advantages over planktonic systems for growing, harvesting and processing algal biomass. To determine how feasible these systems can be, however, researchers must determine optimal biomass and lipid productivities. In this paper the effect of photon flux density (PFD) on algal biofilm biomass productivities, internal fatty acid concentrations, and overall fatty acid productivity was studied. It was determined that as PFD increased, algal biofilm biomass productivities significantly increased until they peaked i.e. at about 300μmol/m2/s, presumably due to light saturation. Increasing PFDs from 50 to 150μmol/m2/s produced statistically significant increases in fatty acid concentrations from 5% to 8%; however, increasing PFDs beyond that range did not enhance lipid accumulation. Because of significant increases in biomass productivity with increased PFD, there was also a significant increase in fatty acid productivity with increased PFD. Lastly, increasing PFD resulted in diminishing returns of biomass productivity, suggesting that photons are not being effectively utilized at higher light intensities. This finding has implications for photobioreactor design and operation with artificial lighting.

Novel waveguide reactor design for enhancing algal biofilm growth

Algal film photobioreactors have the potential to reduce dewatering costs and have a comparable productivity to raceway ponds. Current designs have focused on maximizing productivity and nutrient removal through material selection and design. However, fewer studies have focused on analyzing the effects of illumination and carbon dioxide (CO2) concentration on algal film growth. The transport of light in suspended photobioreactors is considered a serious problem due to cell shading, light scattering and non-uniform optical absorption. To enhance light delivery to algal biofilms, five different waveguide designs were developed Light emitting waveguides are capable of distributing a bright light source over a larger surface area. The light emission from these waveguide designs was characterized and the algal biofilm growth on waveguides was characterized in a parallel plate airlift reactor (17L). The light intensity and CO2 concentration were varied in a 32 factorial design experiment to determine if there were any interaction effects. Light emission from the waveguides could be altered by changing the tapper angle or by notching the surfaces. Algal film growth kinetics on the waveguides were overall non-linear, but had linear regions of growth. The waveguides achieved an algal biofilm surface area productivity of 2.8g/m2day and an aerial productivity of 33.6g/m2day. Algal film productivity displayed saturation kinetics with respect to light intensity and CO2 concentration, but the interaction effect of light and CO2 on productivity is likely non-linear. Algal film biomass per photon consumed decreased with increasing light intensity when the reactor was not CO2 limited. The results indicate the potential for algal biofilms to be grown on light emitting waveguides which opens up the opportunity to explore new algal film photobioreactor configurations.

The effect of light direction and suspended cell concentrations on algal biofilm growth rates.

Algae biofilms were grown in a semicontinuous flat plate biofilm photobioreactor to study the effects of light direction and suspended algal cell populations on algal biofilm growth. It was determined that, under the growth conditions and biofilm thicknesses studied, light direction had no effect on long-term algal biofilm growth (26 days); however, light direction did affect the concentration of suspended algal cells by influencing the photon flux density in the growth medium in the photobioreactors. This suspended algal cell population affected short-term (7 days) algae cell recruitment and algal biofilm growth, but additional studies showed that enhanced suspended algal cell populations did not affect biofilm growth rates over the long term (26 days). Studying profiles of light transmittance through biofilms as they grew showed that most of the light became attenuated by the biomass after just a few days of growth (88 % after 3 days). The estimated biofilm thicknesses after these few days of growth were approximately 150 μm. The light attenuation data suggests that, although the biofilms grew to 700-900 μm, under these light intensities, only the first few hundred micrometers of the biofilm is receiving enough light to be photosynthetically active. We postulate that this photosynthetically active layer of the biofilm grows adjacent to the light source, while the rest of the biofilm is in a stationary growth phase. The results of this study have implications for algal biofilm photobioreactor design and operation.

Development of a rotating algal biofilm growth system for attached microalgae growth with in situ biomass harvest

This work aimed to develop a rotating algal biofilm (RAB) cultivation system that can be widely adopted by microalgae producers for easy biomass harvest. Algal cells were grown on the surface of a material rotating between nutrient-rich liquid and CO2-rich gaseous phase. Scrapping biomass from the attached surface avoided the expensive harvest operations such as centrifugation. Among various attachment materials, cotton sheet resulted in best algal growth, durability, and cost effectiveness. A lab-scale RAB system was further optimized with harvest frequency, rotation speed, and CO2 levels. The algal biomass from the RAB system had a similar water content as that in centrifuged biomass. An open pond raceway retrofitted with a pilot-scale RAB system resulted in a much higher biomass productivity when compared to a control open pond. Collectively, the research shows that the RAB system is an efficient algal culture system for easy biomass harvest with enhanced biomass productivity.

Coupling hydraulic and biological measurements highlights the key influence of algal biofilm on infiltration basin performance

ABSTRACTInfiltration basins are increasingly used in urban areas for flood protection, groundwater recharge and storm water disposal. However, their operation is often affected by clogging, leading to degraded infiltration. The aim of this work was to evaluate the respective influences of sediment deposition and biofilm biomass on the deterioration of hydraulic performances in two infiltration basins used for groundwater recharge. Samples were collected by coring in the two basins. Grain size distribution (with and without organic matter), bacterial and algal biomasses, and microbial activity were measured at three depths from the soil surface (0–1 cm, 2–3 cm and 10–14 cm). In parallel, in situ single‐ring infiltration tests were performed before and after removal of the top layer (0–1 cm). The results showed considerably reduced permeability due to clogging of the top sedimentary layer in the two basins. The highest reduction of permeability was measured in the basin colonized by the largest algal biomass. The proportions of fine mineral particles (&lt;63 µm) were comparable in the two basins and could not explain their differences in saturated hydraulic conductivities. In addition, the relationships between biological and hydraulic parameters highlighted a threshold effect of algal biomass on the structure of the pore network, possibly explaining the decrease in infiltration. This original link between hydraulic and microbial characteristics suggests that algal biofilm growth had a major impact on the hydraulic performance of the infiltration basins. Copyright © 2013 John Wiley &amp; Sons, Ltd.

Decomposition during autumn foliage leaf-fall in wetlands situated along a biogeochemical gradient in Pennsylvania, USA

Autumn leaf fall represents an important allochthonous organic input to inland, aquatic ecosystems, particularly those situated in mixed hardwood forests. We evaluated factors that influence leaf decomposition in wetlands situated along a strong biogeochemical gradient spanning the ridge and valley region in the mid-Atlantic region in the United States. Leaf decomposition rates were estimated using mesh bags; at the same time, algal and invertebrate colonization on the leaf packs was measured. Leaf decomposition exhibited an exponential decline over the 35-day incubation period; rates were similar to those of previous studies (range 0.15–0.40 per day) and not significantly different (one-way ANOVA, F = 0.67, p = 0.526). Mean chlorophyll-a (mg/m2) on leaf packs increased among sampling dates and generally was 10-fold greater in the transition and valley wetlands (22.88 and 29.20 mg/m2) compared with the ridge (2.24 mg/m2) wetland (F = 14.78, p < 0.001). Invertebrate biomass on the leaf packs exhibited significant spatial variation among wetlands (one-way ANOVA, F = 32.1, df = 2, p = 0.0001). The ridge site supported significantly lower biomass compared with both transition and valley wetland sites. Shredders and collectors were dominant at the ridge site, while scrapers and predators were abundant in the transition and ridge wetlands; this provided strong evidence for the importance of algae as a food source in these benthic communities. Algal biofilm growth on leaves in these sites appears to reflect a unique trophic dynamic that may represent an important sink for recycled nutrients.

Tufa Deposition in Karst Streams Can Enhance the Food Supply of the Grazing CaddisflyMelampophylax mucoreus (Limnephilidae)

We studied the effect of carbonate depositions covering stone surfaces on the growth of larvae and the biomass of subsequent adults of the grazing limnephilid caddisfly Melampophylax mucoreus(Hagen, 1861) in a laboratory rearing experiment. M. mucoreus is mainly distributed in karst streams characterized by calcium carbonate precipitations (tufa). We reared larvae of M. mucoreus on stones covered by calcareous tufa crusts as well as on stones from which these crusts were experimentally removed to assess the influence on larval growth and the subsequent adult biomass. The rough surface of the covered stones provided a higher complexity of micro-habitats and supported algal growth compared to the smooth surface of stones without crusts. Larvae of M. mucoreus profited from the enhanced algal biofilm growth on the calcium carbonate precipitation indicated by faster larval growth and higher subsequent adult biomass. Biomass increase of larvae reared on stones covered by tufa crusts exhibited a faster biomass development (0.09 ± 0.015 mg/d) compared to the larvae reared on stones without crusts (0.06 ± 0.002 mg/d). Adult males (5.13 ± 0.25 mg) and females (7.64 ± 0.63 mg) were significantly heavier in the treatment with stones covered by tufa than their conspecifics from the treatment with uncovered stones (males: 4.26 ± 0.25 mg, p = 0.047; females: 4.96 ± 0.47 mg, p = 0.001). Additionally, males from the treatment with crust covered stones emerged significantly earlier (p = 0.003) than the males from the other treatment, whereas no significant difference was found for females. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Effects of water level regulation on algal biofilms in the River Murray, South Australia

The composition and growth of algal biofilms were monitored over 90 days at two littoral sites on the River Murray at Lock 1 (Blanchetown). Sites included the pool impounded by a 3 m weir, where water levels are relatively stable, and the tailwater, where levels fluctuate daily. Depth profiles of organic biomass above the sediment and biofilm composition were similar between sites. Algal biomass peaked in the zones of maximum light and sustained inundation. Biofilm composition was affected more by temporal environmental changes common to both sites than by differences between sites. Filamentous Cyanobacteria (Lyngbya) were prevalent early in succession, but by day 90 were replaced by filamentous Chlorophyta (Spirogyra). If river levels are managed to maintain diverse successional stages as resources for grazing invertebrates, the magnitude and duration of inundation in the littoral zone should exceed the desiccation tolerances of biofilm organisms. Copyright © 2000 John Wiley & Sons, Ltd.

A modeling study of carbon and light limitation in algal biofilms

In an effort to develop an understanding of the interaction of inorganic carbon and light limitation in algal biofilms, a mathematical model was developed, based on well-established mathematical descriptions of the biological, chemical, and physical processes involved. The results showed that the growth of algal biofilms is a very complex function of the inorganic carbon and light conditions, due to the interaction of inorganic carbon speciation with pH. These results are discussed in terms of the distribution of reaction rate through the biofilm and in terms of maximum potential growth rate for given bulk conditions.