Biofilm Carrier Research Articles

Slow growers possess a high pollutant removal potential through granule formation for wastewater treatment

For the upgradation and building of wastewater treatment plants in limited areas, biological wastewater treatment processes with a high pollutant removal loading rate are required. Biofilm or membrane-based systems can achieve a high pollutant removal loading rate through high microbial biomass concentrations and/or activities. The sludge separation is the primary bottleneck for achieving high biomass concentrations inside the biological reactors. In addition, low growers including anaerobic ammonia oxidation bacteria and methanogens are usually easier to form granules and induce high nutrient removal loading rates. The possible granule formation mechanisms should be clarified through physical, chemical and biological aspects, including hydraulic control, microbial extracellular polymeric substances formation, biological energy utilization control, microbial interactions and also other microbial processes. In future, the possible mechanisms should be further clarified, and then high-efficient bioreactors, new microbial ecology control strategy and novel biofilm carriers should be developed for advancing biological wastewater treatment processes with high pollutant removal loading rates.

The impact of biofilm thickness-restraint and carrier type on attached growth system performance, solids characteristics and settleability

MBBR carrier type and physical properties have a significant effect on the solids production, detachment and subsequently the solids distribution size and settleability.

Enhancement of mainstream nitrogen removal via simultaneous partial nitrification, anammox and denitrification by the gel entrapment technique

A BSgel system was prepared by integrating the gel entrapment technique with a traditional biofilm carrier to realize the SNAD process under mainstream conditions.

Effects of coupling biofilm on the production of short-chain fatty acids (SCFAs) in sludge anaerobic fermentation

Short-chain fatty acids (SCFAs) could be recovered as valuable resources during sludge anaerobic fermentation. Addition of biofilm carriers might benefit the production of SCFAs by making microbial community more diverse or enriching functional microbial species. This study investigated the effects of three biofilm carriers, i.e. polyethylene (PE), polyurethane sponge (PUS), and granule-activated carbon (GAC), on the production of SCFAs during anaerobic fermentation of waste sludge. Experimental results revealed that the SCFAs production was improved at the presence of PE (2185.82 ± 61.73 mg/L) or PUS (1994.32 ± 110.99 mg/L), which were 1.4 and 1.27 times higher than that in the control test, respectively. The addition of GAC did not promote the SCFAs production, and furthermore, the concentration of SCFAs declined much faster than in other tests. High-throughput sequencing results showed that the microbial diversity in slurry was negatively related with the production of SCFAs. An increase in the relative abundance of SCFA consumers both in slurry and in biofilm might be an explanation for the effects of GAC. The findings suggest that the way a suitable biofilm carrier promotes the SCFAs production may be related with the enrichment of functional microbial species rather than a more diverse microbial community.

Degradation kinetics and COD fractioning of agricultural wastewaters from biogas plants applying biofilm respirometry

ABSTRACT Stormwater runoff from agricultural silo facilities can be heavily polluted and needs to be treated before discharged. This study investigates biological treatability and kinetic constants of characteristic silo runoffs, applying attached growth systems. For this, respirometry measurements, typically applied in the activated sludge systems (ASM) as a suspended growth, were modified by using adapted biofilm carriers. This allows a determination of degradation kinetic of the biofilm system and a COD fractioning at the same time, which are fundamental values for the design of a full-scale plant. The developed respirometry method was compared with the state-of-the-art method using suspended growth systems and domestic wastewater. Results are comparable with the parameter of the ASM. As stormwater runoff is usually a mixture from different pollution sources, various, typically occurring substrates are investigated regarding degradation kinetics and COD fractions. Wastewater polluted with digestion residue and solid manure showed similar COD fractions as domestic wastewater with an inert fraction Si of 5–6% and a comparatively low rapidly degradable fraction SS of 21–27%. However, wastewater from corn or whole crop silage showed significant better degradation efficiencies and kinetics with an Si of 2–3% and a rapidly degradable fraction of 56–57%. As COD concentrations up to 5000 mg L−1 for stormwater runoff and up to 60,000 mg L−1 for silage effluent can be expected, the results not only show the necessity but also prove the feasibility of biological treatment of stormwater runoff from silo works and provide design parameters for adapted treatment systems.

Bacterial enrichment in highly-selective acetate-fed bioreactors and its application in rapid biofilm formation

In this study, we systematically investigated the bacterial community dynamics in highly-selective (strong hydraulic selection pressure and high organic loading rate) bioreactors with acetate as the sole carbon source. 16S rRNA gene high-throughput sequencing and metagenomic sequencing results showed that phenolics-degrading bacteria (PDB), which were mainly Acinetobacter species, in the newly-formed aerobic granules could account for >70% of the total bacteria. Near full-length 16S rRNA gene sequences obtained by cloning suggest that the PDB are potentially novel species because they are distantly related to known Acinetobacter species. However, these PDB only temporarily appeared in the early stage of the granule formation and their abundance quickly decreased along the reactor operation. To retain these PDB, we demonstrated that the newly-formed aerobic granules could accelerate biofilm formation in moving bed biofilm reactors (MBBRs), and the biofilm carriers showed gradually-increased phenol degradation performance in the MBBRs. While, the bacterial community in biofilm significantly changed during the operation process of the MBBRs and the community structure became more complicated than that in the aerobic granules. Collectively, this study provides new insights into the microbial ecology of sludge granulation and biofilm formation process in the wastewater treatment systems for remediating phenolic matters.

Enhancement of Performance Robustness and Nitrogen Removal by Coupling Anammox with Denitrification in a Corncob-Dosed Reactor

Biofilm carriers play an important role in attached growth systems for wastewater treatment processes. In this study, to establish a more robust and efficient anammox system, corncobs were used as ...

Constructive use of filamentous fungi to remove pharmaceutical substances from wastewater

The removal efficiency of diclofenac and ketoprofen for five fungal strains was examined. The synergistic effect between selected fungal strains using synthetic wastewater media was studied using both individual and mixed strains. The mixed cultures had no additional effect in reducing diclofenac and ketoprofen. In contrary, fungi removed pharmaceutical substances faster when growing individually. The results showed that T. versicolor monoculture removed diclofenac completely (>99.9 %) in non-sterile municipal wastewater within three hours of incubation and continued to show complete reduction within 14 days using fungal biofilm carriers. The mechanism of removal was proposed based on the laccase enzyme production and biosorption study which revealed that T. versicolor could used in both processes. Additionally, this study demonstrated that T. versicolor could be stable in the biofilm carriers, and thus able to compete with other microorganisms in wastewater to be a promising candidate to remove diclofenac from municipal wastewater during the treatment process.

IMPROVED MOBILE BED BIOFILM REACTORS TO TREAT CELLULOSIC WASTEWATERS

The wastewater treatment sector is a very dynamic field, in continuous development. New technologies are developed, or the existing ones are improved [1]. An efficient biological treatment is based on solid small plastic pieces (biofilm carriers) on which different types of microorganisms attach, develop and grow. This technology is known as Moving Bed Biofilm Reactor (MBBR) technology [2]. The most common materials used for the biofilm carriers’ realization are based on high density polyethylene. This technology is not yet applied for the treatment of the cellulosic wastewaters, since cellulose is hard to be removed by using conventional microorganisms that are usually used in biological wastewater treatment. Some of the authors propose an improved material for carriers to be used in tertiary treatment for textile, paper-mill or tannery wastewaters [3]. The biofilm carriers are adapted for fungal activity. The selected fungal strains (White Root Fungi) capable of removing cellulose from wastewaters [4] will be immobilized on special biofilm carriers. The improved carrier is designed to be used in a MBBR and to favour fungal development in the presence of competing bacteria. Several laboratory experiments related to the fungal attachment on the improved carriers were realized and the results are presented in the paper.

Assessing the performance of modified waste cotton cloth (MWCC) installed in a biological contact reactor as a biofilm carrier used for domestic wastewater treatment

The current study examined the performance of modified waste cotton cloth (MWCC) in the removal of organic pollutants from domestic wastewater as an emerging technique for waste textile resource management and reuse. The MWCC biofilm carrier was self-made with discarded cotton cloths cut into smaller strips with 66 cm long and average weight of 2.4 g each. The surface of the non-modified waste cotton cloth (NM-WCC) was modified through the hydro-sulphuric acid (H2SO4) method to enhance the physical characteristics of the material such as hydrophilicity and biofilm attachment. The best filling rate of the carrier used for the experiment was 65% as determined by preliminary studies. Two self-made biological contact biofilm reactors: R1 (installed with NM-WCC) and R2 (fixed with MWCC), were used for the experiment. The experimental results showed that MWCC had higher removal efficacy of chemical oxygen demand, ammonia–nitrogen (NH4+–N) and total phosphorus (TP) at 98.34%, 85.44% and 60.20%, respectively. The hydraulic retention time decreased from 21 to 8 h on the 4th day. The scanning electron microscope was used to analyse the surface characteristics of the NM-WCC and MWCC. The water-holding capacity of the biofilm carriers was determined through the static immersion method and ASTM D1117-80 guiding principles. The water contact angle was estimated through the static process by adapting Young’s equation. The findings of this research could significantly contribute to the discovering of alternative innovative technological prospects of utilizing H2SO4 MWCC as an effective biofilm carrier in domestic wastewater treatment.

Comparison of active biofilm carriers and commercially available inoculum for activation of biofilters in marine recirculating aquaculture systems (RAS)

A recirculating aquaculture system (RAS) for rearing Atlantic salmon requires nitrifying microorganisms in the biofilter in order to be fully functional. These microorganisms play a crucial role in water quality improvement by removing ammonia, but the nitrifying population is time-consuming to establish in the biofilter due to their slow growth rates. An efficient biofilter activation strategy is therefore necessary for an improved and short maturation period of biofilters in new RAS. In this study, microbial growth cultures added two different inoculums for RAS were compared. The observed biofilm establishment on clean biofilm carriers and quantified nitrification in the cultures simulated activation of new RAS biofilters. The inoculums used in the experiments included commercial inoculum for marine RAS and transferred biofilm carriers from a marine RAS biofilter operated 1.5 years after activation. The growth experiments revealed that the enrichment cultures inoculated with biofilm carriers from RAS initiated nitrite and nitrate production from ammonia on day 4, which is much earlier than in enrichment cultures with commercial inoculum where nitrite and nitrate production were detectable on day 15 and 18, respectively. The concentration of nitrite and nitrate measured at the end of the experimental period was also substantially higher in enrichment cultures inoculated with biofilm carriers. These results were supported by microbial community analyses of the enrichment cultures, showing that the populations in cultures added biofilm carriers had the highest relative abundance of Nitrosococcus and Nitrospira. Overall, our study shows that biofilm carriers from an established RAS were applicable as inoculum for biofilter activation. However, more knowledge on optimized growth conditions for nitrifying bacteria in RAS could benefit the colonization efficiency and the enrichment of these microorganisms during biofilter activation. In addition, methodical screening for pathogenic bacteria or viruses is needed before biofilter material can be successfully transferred between RAS without risk for disease transfer.

An Enhanced System with Macrophytes and Polyurethane Sponge as an Eco-Technology for Restoring Eutrophic Water: A Pilot Test

Water eutrophication is one of the most serious environmental problems in urban lakes and ponds due to the excessive nutrients. To deal with this problem, the development of methods for supporting ecological rehabilitation has been undertaken. Meanwhile, the trophic interactions during rehabilitation also have been analyzed. In this study, a new technique was employed to solve the water eutrophication problems in an urban pond. To evaluate the water eutrophication at a pilot scale, an enhanced artificial floating-type biological treatment system (FBTS) composed of a floating bed, macrophyte, artificial biofilm carrier (polyurethane sponge) and aerator could be used as equipment for urban pond remediation. In addition, FBTS was employed to decrease the total nitrogen (TN), ammonia-nitrogen (NH3-N), total phosphorus (TP) and chemical oxygen demand (COD) in water. Meanwhile, the changes of water qualities were monitored in the remediation process, and differences in phytoplankton functional group diversity were also registered. Cyanobacteria would decrease after the removal of P, and the diatom assemblage composition changed. The dominant species Cyanophyta were transformed to co-existed with Bacillariophyta, Pyrrophyta and Chlorophyta due to the improvement of water quality. Consequently, this new FBTS could be a promising eco-technology for the removal of nitrogen and phosphorus from eutrophic water, and even could promote the phytoplankton succession.

Advanced Denitrification of Municipal Wastewater Achieved via Partial ANAMMOX in Anoxic MBBR

Anoxic MBBR is a process to achieve advanced denitrification from municipal wastewater. Here, anoxic MBBR was applied as a post-denitrification SBR to achieve advanced denitrification by partial anammox (anaerobic ammonium oxidation). During a 250-day operation, denitrification performance gradually improved and the total nitrogen concentration of the effluent was approximately 5 mg·L-1. The average nitrate, ammonia, and total inorganic nitrogen removal efficiencies were (97.7±2.9)%, (93.3±2.9)%, and (94.3±2.7)%, respectively, between day 211 and 250. The simultaneous removal of ammonia and nitrate was observed in the anoxic reactor. Analysis of the ammonia removal pathway revealed that assimilation and nitrification were poor in the anoxic MBBR. The anammox activity test and the denitrification performance showed that anammox occurred and played a not insignificant role in the anoxic MBBR. The results of real-time quantitative PCR showed that anammox bacteria enriched in anoxic MBBR, especially in the anoxic carrier biofilms, where the abundance of anammox bacteria increased from 4.37×107 copies·g-1 to 2.28×1010 copies·g-1. This study demonstrates that anoxic carrier biofilms may have potential applications in anammox bacterial enrichment to enhance denitrification from municipal wastewater.

Enhanced removal of nitrate and refractory organic pollutants from bio-treated coking wastewater using corncobs as carbon sources and biofilm carriers

The quality of the bio-treated coking wastewater (BTCW) is difficult to meet increasingly stringent coking wastewater discharge standards and future wastewater recycling needs. In this study, the pre-treatment process of BTCW was installed including the two up-flow fixed-bed bioreactors (UFBRs) which were separately filled with alkali-pretreated or no alkali-pretreated corncobs used as solid carbon sources as well as biofilm carriers. Results showed that this pre-treatment process could significantly improve the biodegradability of BTCW and increase the C/N ratio. Thus, over 90% of residual nitrate in BTCW were removed stably. Furthermore, GC-MS analysis confirmed that the typical refractory organic matters decreased significantly after UFBRs pre-treatment. High-throughput sequencing analysis using 16S rRNA demonstrated that dominant denitrifiers, fermentative bacteria and refractory-organic-pollutants-degrading bacteria co-existed inside the UFBRs system. Compared with no alkali-pretreated corncobs, alkali-pretreated corncobs provided more porous structure and much stable release of carbon to guarantee the growth and the quantity of the functional bacteria such as denitrifiers. This study indicated that the UFBRs filled with alkali-pretreated corncobs could be utilized as an effective alternative for the enhanced treatment of the BTCW.

Improving Wastewater Nitrogen Removal and Reducing Effluent NOx - -N by an Oxygen-Limited Process Consisting of a Sequencing Batch Reactor and a Sequencing Batch Biofilm Reactor

Abstract A series of reactors including a sequencing batch reactor (SBR) and a sequencing batch biofilm reactor (SBBR) were used for nitrogen removal. The aim of this study was simultaneous removal of NH4+-N and NOx–-N from synthetic wastewater. In the novel proposed method, the effluent from SBR was sequentially introduced into SBBR, which contained 0.030 m3 biofilm carriers, so the system operated under a paired sequence of aerobic-anoxic conditions. The effects of different carbon sources and aeration conditions were investigated. A low dissolved oxygen (DO) level in the biofilm depth of the fixed-bed process (SBBR) simulated the anoxic phase conditions. Accordingly, a portion of NH4+-N that was not converted to NO3–-N by the SBR process was converted to NO3–-N in the outer layer of the biofilm in the SBBR process. Further, simultaneous nitrification and denitrification (SND) was achieved in the SBBR where NO2–-N was converted to N2 directly, before NO3–-N conversion (partial nitrification). The level of mixed liquid suspended solids (MLSS) was 2740 mg/l at the start of the experiments. The required carbon source (C: N ratio of 4) was provided by adding an internal carbon source (through step feeding) or ethanol. Firstly, as part of the system (SBR and SBBR), SBR operated at a DO level of 1 mg/l while SBBR operated at a DO concentration of 0.3 mg/l during Run-1. During Run-2, the system operated at the low DO concentration of 0.3 mg/l. When the source of carbon was ethanol, the nitrogen removal rate (RN) was higher than the operation with an internal carbon source. When the reactors were operated at the same DO concentration of 0.3 mg/l, 99.1 % of the ammonium was removed. The NO3–-N produced during the aerobic SBR operation of the novel method was removed in SBBR reactor by 8.3 %. The concentrations of NO3--N and NO2–-N in the SBBR effluent were reduced to 2.5 and 5.5 mg/l, respectively. Also, the total nitrogen (TN) removal efficiency was 97.5 % by adding ethanol at the DO level of 0.3 mg/l. When C:N adjustment was carried out SND efficiency at C:N ratio of 6.5 reached to 99 %. The increasing nitrogen loading rate (NLR) to 0.554 kg N/m3 d decreased SND efficiency to 80.7 %.

Acetonitrile wastewater treatment enhanced by a hybrid membrane-aerated bioreactor containing aerated and non-aerated zones

Acetonitrile (ACN) is a very volatile, toxic and nitrogen-rich organic compound. To enhance ACN wastewater treatment, a novel hybrid membrane-aerated bioreactor (MAB) containing aerated and non-aerated zones was established. A polypropylene hollow fiber membrane module (HF) and a silicone rubber membrane module (SR) were separately used as the bubble-free aeration diffuser and the biofilm carrier, and the non-aerated zones of these two types of reactors were packed with ceramsite. When the influent ACN loading was 1.200 kg/m3·d, under aeration pressures of 20 kPa in the HF-MAB and 40 kPa in the SR-MAB, ACN removal loadings of 1.116 kg/m3·d and 1.004 kg/m3·d, respectively, were achieved, and the TN (total nitrogen) removal loadings were 0.267 kg/m3·d and 0.246 kg/m3·d, respectively. In the MABs, different stratified biofilm structures of the two zones and the diffusion and counter-diffusion of oxygen synergistically promoted ACN degradation, nitrification and denitrification.

Improved biofilm carriers for fungal exploitation in wastewater treatment

In Moving Bed Biofilm Reactors (MBBR) the biofilm grows protected within small plastic carriers (known as biofilm carriers), which are designed with high internal surface area. The biological wastewater treatment process consists of adding biofilm carriers in aerated or anoxic tanks to support biofilm attachment and growth. Some of the authors conceived, designed and realised an improved carrier (new shape and material) for fungal biofilm development. The improved biofilm carriers were tested in laboratory conditions and good results were obtained. This new biofilm carrier will be used to treat cellulosic (tannery and papermill) wastewaters and is grafted with cellulose fibers for the self-sustainability of the fungal biomass. This will facilitate substrate adhesion, due to biochemical capabilities of the selected strains, which involve secretion of extracellular enzymes, that can break down substrate by combined action of several degradative processes, such as demethylation, oxidative cleavage of the propane side chain, cleavage of ether bonds between monomers etc.

Biotechnologies used in wastewater treatment

One of the most efficient biological wastewater treatment process is based on the biofilm carriers’ utilization, on which the microorganisms attaches to form biofilm communities. The biological technology that uses artificial mobile supports is known as the Moving Bed Biofilm Reactor (MBBR) process. To have an efficient attachment of the biomass on the carriers, hydrophilic substrates are needed. To promote biofilm formation and development, the chemical nature of the biofilm carriers should be carefully selected. Most of the biofilm carriers are made from polyethylene. This material has hydrophobic properties. The authors propose a new material with more hydrophilic properties. Talcum is combined with polyethylene resulting a more hydrophilic material. The results regarding the biofilm adhesion on the new material are presented by the authors. Also, the paper presents a laboratory installation for wastewater treatment, on which can be compared different biological treatment processes.

Performance and microbial diversity of bioreactors using polycaprolactone and polyhydroxyalkanoate as carbon source and biofilm carrier in a closed recirculating aquaculture system

Nitrogen removal is essential for a successful management approach in a marine recirculating aquaculture system (RAS) through microbial remediation. In this study, two biodegradable polymers, polycaprolactone (PCL) and polyhydroxyalkanoate (PHA), were used as a carbon source and biofilm carrier for marine RAS wastewater treatment. Results showed that the use of an artificial saltwater nitrate (ASN) medium with seeded polymers had a high nitrogen removal efficiency regardless of flow rate, with a nitrate–nitrite removal efficiency of 95.4–98.9%. The TN removal efficiency was greater with PHA (95.1–95.3%) than PCL (86.1–90.1%). TP removal efficiency was greater with the use of PCL (64.1–67.3%) than PHA (48.2–52.5%). The use of marine aquaculture effluent showed an increased TN nutrient removal efficiency with PCL having a removal efficiency of 89%, with an increased TP removal efficiency using PHA (40.4%). Microbial community analysis demonstrated the complexity of microbial consortia within marine RAS. Two major classes identified in our study were Alphaproteobacteria (2–68%) and Flavobacteriia (0.5–58%). We identified Crocinitomix, Oceanicola, Meridianimaribacter, and Ruegeria as potential PCL degraders, while Winogradskyella, Muricauda, Marinobacter, and Alteromonas were identified as potential PHA degraders. The microbial communities responded to varying water chemistry differences and developed unique consortia based on biodegradable polymer types. Biodegradable plastics can be utilized in marine RAS to treat wastewater through microbial processes.

Optimized production of biomethane as an energy vector from low-solids biomass using novel magnetic biofilm carriers

Completely stirred tank reactors are the common type of bioreactors used for biogas production, however, efficient conversion of low-solids feedstocks to biomethane is restricted by the wash-out of microorganisms at short hydraulic retention times. Novel magnetic foam glass particles that can serve as biofilm carriers and retain active microbial biomass were investigated in high-rate biomethane production. A mesophilic completely stirred tank reactor containing 2% (w/w) magnetic carriers was operated at organic loading rates of 1.5 to 7.7 gVS L−1 d−1 feeding sugar beet silage, the hydraulic retention time was systematically decreased from 24.5 to 4.7 d. Magnetic foam glass particles clearly stabilized the methane production process, especially by supporting methanogenic microorganisms that presented 49% of the population living on the magnetic carriers. Even at an hydraulic retention time of 4.7 d, which is very low for completely stirred tank reactors, methane production remained stable at a high level of 2.2 L L−1 d−1 (organic loading rate 6.3 gVS L−1 d−1, methane yield 0.353 L gVS−1). Results suggest that magnetic foam glass particles are an attractive option for increasing the process stability and performance of anaerobic completely stirred tank reactors fed with low-solids feedstock, enabling high-rate production of energy from slurries and wastewaters representing waste materials in agriculture and industry.