Moving Bed Bioreactor Research Articles

Reuse of plastic waste as bio-carriers for domestic wastewater treatment – An approach towards circular economy

With the rapid growth of economic development, the circular economy has been raised in many internationalenvironmental and socio-economic conferences and forums nowadays. The recycling of plastic waste was oneof those aspects. This paper studied the potential of directly reusing plastic bottle caps as bio-carriers in movingbed bioreactors without further waste processing. As the caps had lower surface areas than the commercial carriers, total bacteria communities on the commercial carriers (K3) were 3-4 times higher than those on the bottle caps at different counting magnitudes. Nevertheless, the bottle caps could accommodate similar nitrogen-based bacteria (ammonia-oxidizing bacteria - AOB and nitrite-oxidizing bacteria - NOB density), which promotes well for the nitrification and denitrification processes. The COD and N-NH4 removal efficiencies were 92% and 86% on average, respectively. The high pollutant removal capacity reveals the very promising potential of bottle caps as bio-carriers for domestic wastewater treatment, promoting waste reduction and treatment expenses and presenting an excellent example of economic circular.

Combined treatment of domestic wastewater with landfill leachate using aerobic moving bed bioreactor (AeMBBR)

In this study, the treatment of landfill leachate (LFL) and domestic wastewater using an aerobic moving bed biofilm reactor (AeMBBR) was investigated. AeMBBR was filled with 30 % (v:v) biocarrier material (Kaldnes K1). The effect of different hydraulic retention times (HRTs) (6- 24 h) at a constant dissolved oxygen (DO) of 3.2 mg/L was investigated for system optimization. AeMBBR was successfully operated for LFL and domestic wastewater treatment corresponding to 94 %, and 78 % ammonium nitrogen (NH4-N) and total organic carbon (TOC) removals, respectively. Additionally, Proteobacteria (66%) have been identified as the predominant culture in the biofilm layer, which plays an important role in the co-treatment of domestic wastewater and LFL. Considering the results obtained; it was found that a significant amount of NH4-N was successfully removed.

Investigation of the performance of the combined moving bed bioreactor-membrane bioreactor (MBBR-MBR) for textile wastewater treatment

The present study focused on the investigation of the performance of a Moving Bed Bioreactor coupled with a Membrane Bioreactor (MBBR-MBR) on a small scale for textile wastewater treatment. The parameters examined in this study included the removal efficiency of chemical oxygen demand (COD), biochemical oxygen demand (BOD), total suspended solids (TSS), turbidity, color, and heavy metals (HM). The two reactors were operated consecutively and maintained aerobic conditions. The idea is to reduce the pollutant load significantly through the activity of microorganism attached to the biofilm covered carriers in MBBR and successive membrane filtration. The system demonstrated a favorable outcome even in a smaller hydraulic retention time (HRT) of 1 day, which presents a significant advantage in terms of cost and space saving. The removal effectiveness of COD attained a maximum of 92 %, BOD reached a maximum of 95 %, and the color removal performance obtained a removal efficiency of 87 %. Furthermore, the treatment showed remarkable efficiency in removing up to 100 % of TSS and 96 % of turbidity. Additionally, an evaluation was conducted on the elimination of heavy metals, including Zinc (Zn), Lead (Pb), Chromium (Cr), and Iron (Fe). The efficacy of removing these HMs was found to exceed 85 %. All these favorable outcomes contribute to the improvement of effluent quality, mitigation of contamination hazards, and fouling reduction.

Computational modelling to advise and inform optimization for aeration and nutrient-dosing in wastewater treatment: Case study from pulp and paper mill in south-central Sweden

Sweden's pulp and paper sector accounts for a significant proportion of national energy usage, besides generating wastewater that causes eutrophication of nearby sinks. In this paper, the possibility of optimizing biological wastewater treatment at the Stora Enso Skoghall mill south of the city of Karlstad in central Sweden, with respect to electricity usage and the addition of nutrients, has been investigated. A computational model of the treatment process was developed, based on process data obtained from the said mill, and nine different scenarios were compared subsequently, with energy use, environmental impacts and operational expenses, as criteria. The most energy-efficient and cost-effective alternative was a combination of measures such as lowering the oxygen level in the MBBR (Moving Bed Bio-Reactor) from 3 mg/l to 2 mg/l and using the Hyperclassic aerator in the aerated lagoon. This arrangement yielded a 48.5 % reduction in operational expenses, and a 60 % decrease in the energy use, vis-à-vis the reference case, without affecting the efficiency of the treatment process. This also uncovered an opportunity to mitigate the annual global warming and eutrophication impacts, by approximately 100 tons CO2-eq. and 140 kg PO43−-eq. respectively. All attempts to optimise the use of resources and decrease the anthropogenic environmental footprint ought to be made to come closer to the targets set by the United Nations' sustainable development goals (SDGs). The authors' conclusion predicated on the results of the modelling and analysis done in this study is that the potential of seemingly small process modifications, such as lowering the oxygen level in the MBBR, and applying a more optimal dosage of nutrient salts, must not be overlooked by wastewater treatment plants in general (and those in pulp and paper mills in particular).

STP design calculation for 100 KLD SBR (Sequential batch reactor)

Sewage treatment aims to remove the contaminants from different municipal sources in order to prevent pollution of aquatic bodies. There are numerous sewage treatment systems available in the market, including ASP (Activated Sludge Process), MBBR (Moving Bed Bioreactor), MBR (Membrane Bioreactor), etc. One of them, the SBR (Sequential Batch Reactor), is a remarkable technology that may be used in large-scale treatment plants due to its simple maintenance. Sequential batch reactors (SBR) are reactors or basins in which the biological treatment of waste water is carried out in a series of four steps, namely filling, aeration, settling (clarification) and decanting. One of the newest solutions for treating municipal sewage is the sequential batch reactor (SBR). In this research designing study, a thorough design computation for a sewage treatment system with a 100 KLD capacity was elucidated. In this study, two important aspects of design calculation such as units available in the SBR scheme and Equipment’s available in the SBR scheme. Thus, the simple calculation makes it easier for any design engineers to construct their sewage treatment plant or system.

The Efficiency of Moving Bed Bioreactor Carrier (MBBRC) Hybrid with Algae and Bacterial Strains for Ammonia Removal in the Rosetta Branch of the River Nile

The Efficiency of Moving Bed Bioreactor Carrier (MBBRC) Hybrid with Algae and Bacterial Strains for Ammonia Removal in the Rosetta Branch of the River Nile

Non-potable water reuse and the public health risks from protozoa and helminths: a case study from a city with a semi-arid climate.

The study estimated the risk due to Cryptosporidium, Giardia, and Ascaris, associated with non-potable water reuse in the city of Jaipur, India. The study first determined the exposure dose of Cryptosporidium, Giardia, and Ascaris based on various wastewater treatment technologies for various scenarios of reuse for six wastewater treatment plants (WWTPs) in the city. The exposure scenarios considered were (1) garden irrigation; (2) working and lounging in the garden; and (3) consumption of crops irrigated with recycled water. The estimated annual risk of infection varied between 8.57 × 10-7 and 1.0 for protozoa and helminths, respectively. The order of treatment processes, in decreasing order of annual risk of infection, was found to be: moving-bed bioreactor (MBBR) technology > activated sludge process (ASP) technology > sequencing batch reactor (SBR) technology. The estimated annual risk was found to be in this order: Ascaris > Giardia > Cryptosporidium. The study also estimated the maximum allowable concentration (Cmax) of pathogen in the effluent for a benchmark value of annual infection of risk equal to 1:10,000, the acceptable level of risk used for drinking water. The estimated Cmax values were found to be 6.54 × 10-5, 1.37 × 10-5, and 2.89 × 10-6 (oo) cysts/mL for Cryptosporidium, Giardia, and Ascaris, respectively.

Process optimization of a moving bed bioreactor undergoing simultaneous nitrification and denitrification for wastewater in the absence of organic carbon

ABSTRACT Moving bed bioreactors are efficient for the removal of nitrogen effluents by simultaneous nitrification and denitrification (SND), which is particularly challenging for effluents with low C/N ratio due to insufficient carbon available for denitrification. The addition of external organic carbon in such cases increases treatment costs. Endogenous degradation of biomass offers a cost-effective and persistent source of carbon. Internal carbon leads to low denitrification rates and optimizing the biomass content leads to a sustainable solution for treating such effluents. The present study aims to optimize the process of SND using endogenous carbon by investigating the effect of operational parameters like dissolved oxygen, influent ammonium (NH4–N) loading, hydraulic retention time (HRT) and carrier filling ratio (CFR). The synthetic wastewater used in the study does not inherently contain any organic carbon, thus indicating the responsible carbon for denitrification to be of internal origin. Using a novel carrier for multispecies biofilm development, initial NH4–N concentration variation showed an insignificant effect on SND efficiency. At higher loading, nitrite accumulation due to incomplete denitrification was observed. The effect of CFR was investigated in a range of 20–35%, beyond which non-homogeneous mixing was caused in the reactor. Under controlled DO and temperature of about 5 mg/L and 28 ± 2°C, respectively, an optimum filling ratio of 35% was finalised, resulting in an SND efficiency of 97.9% at 22 h HRT for high influent NH4–N concentration of 500 mg/L. Bacteriological species identification revealed the coexistence of nitrogen-fixing, aerobic nitrifying and anaerobic denitrifying bacteria in the biofilm growing on the biocarrier. Mechanism of SND occurring in aerobic moving bed bioreactors: Laboratory-scale aerobic Moving Bed Bioreactor setup for a continuous study evaluating the influence of operational parameters on SND Occurrence of aerobic and anoxic zones in biofilm grown on the surface of novel carriers due to diffusional gradient of dissolved oxygen

Advanced treatment of toluene emissions with a cutting-edge algal bacterial photo-bioreactor: Performance assessment in a circular economy perspective

A novel approach for the treatment of VOCs (by using toluene used as a model compound) and the simultaneous conversion of carbon dioxide into valuable biomass has been investigated by using a combination of an activated sludge moving bed bioreactor (MBBR) and an algal photo-bioreactor (PBR).The first unit (MBBR, R1) promoted toluene removal up to 99.9 % for inlet load (IL) of 119.91 g m−3 d−1. The CO2 resulting from the degradation of toluene was then fixed in PBR (R2), with a fixation rate up to 95.8 %. The CO2 uptake was promoted by algae, with average production of algal biomass in Stage VI of 1.3 g L−1 d−1. In the contest of the circular economy, alternative sources of nutrients have been assessed, using synthetic urban wastewater (UWW) and dairy wastewater (DWW) for liquid renewal. The produced biomass with DWW showed a high lipid content, with a maximum productivity of 450.25 mg of lipids L−1 d−1. The solution proposed may be thus regarded as a sustainable and profitable strategy for VOCs treatment in a circular economy perspective.

Comparison on biological nutrient removal and microbial community between full-scale anaerobic/anoxic/aerobic process and its upgrading processes

A comparative study was conducted for the anaerobic/anoxic/aerobic (AAO) process and its two upgrading processes, five-stage Bardenpho and AAO coupling moving bed bioreactors (AAO + MBBR), using long-term operation data of six full-scale wastewater treatment plants. The three processes all had good COD and phosphorus removal performance. The reinforcing effects of carriers on nitrification were moderate at full-scale applications, while the Bardenpho was advantageous in nitrogen removal. The AAO + MBBR and Bardenpho processes both had higher microbial richness and diversity than the AAO. The AAO + MBBR favored bacteria to degrade complex organics (Ottowia and Mycobacterium) and to form biofilms (Novosphingobium), and preferentially enriched denitrifying phosphorus-accumulating bacteria (DPB) (norank_o__Run-SP154) with the highest anoxic to aerobic phosphorus uptake rates of 65.3 % − 83.9 %. The Bardenpho enriched bacteria tolerant to varied environments (Norank_f__Blastocatellaceae, norank_o__Saccharimonadales, and norank_o__SBR103), and was more suitable for the upgrading of the AAO because of its excellent pollutant removal performance and flexible operation mode.

Performance evaluation of moving bed bioreactor for simultaneous nitrification denitrification and phosphorus removal from simulated fertilizer industry wastewater.

With increasing demand for agricultural production, chemical fertilizers are now being intensively manufactured and used to provide readily available nutrients in larger quantities, which often leach out and contaminate the groundwater source. At the same time, effluents from fertilizer plants also pollute water bodies, when disposed of without proper treatment. The present study evaluates nitrogen and phosphorus removal efficiencies in a single-stage aerobic moving bed bioreactor (MBBR) from diammonium phosphate(DAP)-spiked wastewater containing no organic carbon. To date, no similar study has been undertaken that treats fertilizer plant effluent or agricultural runoff without the aid of external carbon, where organic carbon ishypothesized to be supplied from endogenous degradation of biomass. Both denitrification and phosphorus removal occurs in the anoxic zones of deeper layers of the biofilm. The present investigation demonstrates the feasibility of the processes with the requirement of a two-stage MBBR for effective simultaneous nitrification, denitrification, and phosphorus removal (SNDPr) together with a polishing technology to bring down the phosphorus concentration within limits. A novel bio-carrier designed for efficient SND was used in the study, with a carrier filling ratio of 35% that supported the formation of deep biofilms creating anoxic zones in the inner surface. Identification of the bacterial species reflects the occurrence of simultaneous nitrification, denitrification, and phosphorous removal (SNDPr) in the reactor. A maximum ammonium nitrogen removal efficiency of 98% was recorded with 95% total nitrogen removal, 69% phosphorus removal, and 85% SND efficiency, indicating the applicability of the process with a tertiary phosphorus removal unit to lower the nutrient concentration of effluents prior to disposal.

Development of a Simplistic Mathematical Model for Simultaneous Nitrification and Denitrification in Moving Bed Bioreactor

Development of a Simplistic Mathematical Model for Simultaneous Nitrification and Denitrification in Moving Bed Bioreactor

Food-based sizing criteria of bead filters with floating media in serial treatment with moving bed bioreactors

The bead filter and moving bed biological reactor (MBBR) are two common technologies used in tandem to remove solids and ammonia from recirculating aquaculture systems. While the sizing of these two technologies is well understood when designed separately, the same sizing guidelines lead to inefficiencies when the two are used together. This is primarily due to the sizing by part design philosophy not considering processes that occur in multiple system components. In response, the authors have reviewed and amended sizing recommendation to avoid unnecessary oversizing. This analysis presents three cases to examine how sizing by parts can lead to system inefficiencies and to lay out a better design approach. Case 1 utilizes the bead filter as a solids capture device, ignoring the impact of the system’s recirculating flow rate and bead filter’s nitrification capacity. Case 2 uses the bead filter’s volume to determine the system’s recirculating flow rate without considering the bead filter’s nitrification capacity. In Case 3 the bead filter’s nitrification capacity is utilized in sizing the moving bed reactor placed in series after the bead filter. In summary, the high-rate floating bead filters (Ω=2888 m3 day −1 m−3 media) should be utilized to remove solids prior to a moving bed reactor and the nitrification capacity of the floating bead filter should be consideration in the MBBR sizing. This will produce a more cost-effective design and result in a balanced design free of transport limitations.

Effects of media length on biofilms and nitrification in moving bed biofilm reactors

Biofilms grown on free-floating plastic media are increasingly being used to cultivate biofilms in integrated fixed film activated sludge (IFAS) and moving bed bioreactor (MBBR) systems for wastewater treatment with the common goal of increasing nitrogen removal. Fundamental principles of fluid dynamics dictate that the length of internal media channels affects fluid velocities and shear forces across biofilm surfaces, which in turn should affect rates of mass transfer and biofilm growth and activity, but little is known about media length effects on water quality and biofilm characteristics. It was hypothesized that length affects biofilm thickness, microbial populations and their activities, and system performance. Nitrification rates and biofilm characteristics were monitored in parallel continuous flow, bench-scale MBBRs systems with media length as a controlled variable. Longer media produced biofilms with approximately twice the thickness and twice the mass per unit area than did media with one-third their length. Based on calculated head losses, the combined effects of length and constriction of internal channels led to an estimated 77% reduction in fluid velocity through the longer media relative to the shorter media. Longer media demonstrated more rapid development of nitrite oxidizing bacteria (NOB) activity than the shorter media over much of the study, as indicated by measurements of nitrite and nitrate, but AOB activity was similar in the two media. Both biomass and NOB activity were concentrated toward media ends, while ammonia oxidizing bacteria (AOB) activity was uniformly distributed across the media, based on testing of sectioned media. 16s rRNA amplicon sequencing indicated the presence of several putative heterotrophic nitrifying families, particularly Xanthomonadaceae, Comamonadadeae and Microbacteriaceae, as well as the autotrophic Bradyrhizobiacea (which includes the NOB Nitrobacter) were common on both media throughout the study. The short media enriched for Nitrosomonadaceae, which includes the AOB genus Nitrosomonas, while minimal autotrophic AOBs were found in the long media biofilm. These results provide insights to the design of media for improved performance, particularly with respect to nitrite versus nitrate production, which may be useful to improve nitrification and for energy saving processes for nitrogen removal such as deammonification. The research also provides fundamental insights regarding the effects of media geometry on biofilm structure and function, which advances our understanding of environmental factors affecting biofilm development.

Effect of biocarrier material on nitrification performance during start-up in freshwater RAS

Biofilters are key components in recirculating aquaculture systems (RAS). For ensuring cost-efficient function of biofilters, characteristics of biocarriers such as shape, material, surface area, density, longevity, and price needs to be evaluated. In this study, we compared otherwise identical biocarriers made of polyethylene (PE) against ones made of polypropylene (PP) and PP biocarriers with three different levels of pigment (carbon black) addition (without added pigment, semi-pigmented, fully-pigmented). The four types of biocarriers were tested in 12 parallel moving bed bioreactors under identical conditions receiving water from a semi-commercial freshwater RAS with rainbow trout. Measurements of total ammonium nitrogen (TAN) and nitrite-nitrogen (NO2--N) removal rates and nitrification kinetics were carried out by spiking events with NH4Cl or NaNO2 two, four, and six weeks after start-up. The results showed all biofilters removed TAN only after two weeks of operation, and that biofilters with PP biocarriers had a shorter maturation time, reaching their maximum TAN removal rate at week 4, while PE biofilters reached equal maximum at week 6. Biofilters with PE had generally lower NO2--N removal rates and first-order reaction constants than PP biofilters. Pigmentation level had a minor effect on TAN and NO2--N removal rates and kinetics, as fully pigmented biocarriers initially were found to have lower removal rates and first order constants for TAN and NO2--N than semi-pigmented or biocarriers without added pigment. Overall, the results suggest that PE is inferior biocarrier material than PP, due to the longer start-up period and nitrite accumulation, which might be related to the differences in the surface characteristics between these two materials. Furthermore, the results indicate that pigment addition does not provide any extra benefit for nitrification.

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.

Performance evaluation of 1 MLD MBBR type sewage treatment plant

Sewage treatment system considered to be an inevitable step to handle the burgeoning water scarcity in the recent years. In this study a 1 MLD (Million Litres per Day) sewage treatment plant was selected and evaluated its performance efficiency for a period of 8 Weeks (02.10.2021 to 20.11.2021). The adapted treatment technology was Moving bed Bioreactor (MBBR) which is an attached biological growth method. This technology totally driven by MBBR Carrier media, which provides an enormous surface area for the microbial attachment. The treatment system has the following units such as Bar screen chamber, Grit Chamber, Oil & Grease Chamber, Equalization Tank, Anoxic Tank, MBBR Tank, Settling Tank, Filter Feed Tank, Pressure Sand Filter (PSF), Activated Carbon Filter (ACF), Chlorine dosing and Treated Water Tank. Water samples were collected from different treatment units for 10 days and analysed for the major water quality parameters such as Biochemical oxygen demand (BOD), Chemical oxygen demand (COD), Total Kjeldhals Nitrogen (TKN) and Total suspended solids (TSS). The analysis showed that all treated water parameters meet the State Pollution board standards. Also the results were very much useful to prepare a Standard Operating Procedure (SOP) which helps in hindrance free Operation and Maintenance of the system.

Investigating the Molecular Mechanism of Optimized Bio Denitrification by Thiobacillus denitrificans in the Presence of Metal Nanostructures in Bioreactor

Nitrate contamination of groundwater and surface water has become a serious problem. Zero-capacity iron (Fe0) nanoparticles are of great interest for the purification of toxic compounds from water. The aim of this study was to synthesis and optimize starch-coated “St” and carbon quantum dot-coated “CQD” Fe0 nanoparticles (St-Fe0 and CQD-Fe0) and investigate their role in bio denitrification and expression of nirS, narH and recA genes using the q-PCR technique. This study has a non-treatment control. The structural and morphological characteristics of nanoparticles were determined by XRD, TEM, FE-SEM and FTIR. Two important operating parameters including temperature (̊C) and nanoparticles concentration (g l−1) influencing the bio denitrification process of Thiobacillus denitrificans in the presence of nanoparticles were optimized by the response surface method (RSM). The FTIR spectrum confirmed the formation of CQD-Fe0 bonds. The average diameter of CQD-Fe0 nanoparticles was in the range of 29.31 to 38.32 nm. Denitrification in the presence of St-Fe0 and CQD-Fe0, with increasing temperature (35 C°) and nanoparticle concentration (1 g l−1), was 71.42% and 73.43%, respectively. After determining the optimal conditions, bio denitrification in the presence of nanoparticles at different concentrations of nitrate was investigated in a moving bed bioreactor. According to the results, in the discontinuous conditions, bio denitrification efficacy of Thiobacillus denitrificans in the presence of St-Fe0 and CQD-Fe0 nanoparticles was 80.10% and 79.83%, respectively. While in the bioreactor, denitrification efficacy in the presence of St-Fe0 and CQD-Fe0 was increased to 94.07% and 95%, respectively. In other words, bio denitrification of microorganisms in the moving bed bioreactor in the presence of CQD-Fe0 was higher compared to St-Fe0. The results of this study showed that the expression of all three genes nirS, narH and recA in cells treated with St-Fe0 and CQD-Fe0 significantly increased compared to the control group, which indicates the high impact of these nanoparticles, especially CQD-Fe0 on bio denitrification of this microorganism.

Life cycle cost analysis of wastewater treatment technologies

With the ever-increasing population, volumes of wastewater treatment are a major concern in our country. The Activated Sludge Process (ASP), Biological Filtration and Oxygenated Reactor (BIOFOR), Upflow Anaerobic Sludge Blanket (UASB), and Moving Bed Bio Reactor (MBBR) are all monetarily investigated in the present study using the Life Cycle Cost Assessment (LCCA) tool. In this study, life cycle costing is done using the present value method, which involves discounting the costs for a 20-year economic life. The costs of treating wastewater per million litres per day (MLD) of wastewater treatment technology are obtained from the literature. Moreover, this study takes into account the capital, annual operation, energy, salvage, and replacement costs to compare the life cycle costs of ASP, UASB, BIOFOR, and MBBR to make the best guess of an economical technology. The LCCA demonstrates that the MBBR has the highest costs of treatment, resulting in the highest Life Cycle Cost (LCC). BIOFOR has the largest energy requirement making LCC the second-highest among the technologies. In India, ASP is one of the most widely used technologies, whose LCC is the third most advanced of the four technologies. Because of its lower energy and operating costs, UASB has the lowest LCC.

Synergistic effect of chitosan-based sludge aggregates CS@NGS inoculum accelerated the start-up of biofilm reactor treating aquaculture effluent: Insights into performance, microbial characteristics, and functional genes

The moving bed bioreactor (MBBR) process has drawn more attention as a promising biological wastewater treatment process. Nevertheless, achieving quick start-up and microbial biofilm formation remains a significant challenge. Consequently, the present study investigated a novel chitosan-based natural sludge (CS@NGS) seeding strategy for the accelerated start-up of MBBR. Three identical bioreactors were employed; the first bioreactor was without sludge seed as the control (BR1), the second was inoculated only with sludge (BR2), and the third was inoculated with CS@NGS according to the proposed seeding method (BR3). All bioreactors were utilised to treat simulated recirculating aquaculture systems (RAS) effluent. Resultantly, the CS@NGS shortened the start-up period from over twenty to seven days due to the enhanced initial microbial adhesion and biofilm formation. Under optimal conditions, the ammonium removal in BR3 approached 100%, which was relatively higher than BR2 (96.35 ± 1.12%) and BR1 (92.56 ± 2.17%). Moreover, a low nitrite accumulation was exhibited in the effluents, approximately ≤0.03 mg L−1. The process performance correlated positively with core bacteria from the genera Nakamurella, Hyphomicrobium, Nitrospira, Paenarthrobacter, Rhodococcus, and Stenotrophobacter. The quantitative polymerase chain reaction (qPCR) results demonstrated that the CS@NGS enhanced the expressions of amoA, nxrB, nirK, nirS, narG, and napA nitrogen metabolism-related functional genes to varying degrees. The present study findings can assist the rapid start-up of aquaculture biofilters utilised to solve high nitrite and ammonia accumulation in recirculated water from industrial RAS.