COD removal from expanded granular sludge bed effluent using a moving bed biofilm reactor and their microbial community analysis

The microbiome of two strategies for ammonia removal with the sequencing batch moving bed biofilm reactor treating cheese production wastewater

IMPORTANCE

Cheese production facilities must abide by sewage discharge bylaws that prevent overloading municipal water resource recovery facilities, eutrophication, and toxicity to aquatic life. Compact treatment systems can permit on-site treatment of cheese production wastewater; however, competition between heterotrophs and nitrifiers impedes the implementation of the sequencing batch moving bed biofilm reactor (SB-MBBR) for nitrification from high-carbon wastewaters. This study demonstrates that a single SB-MBBR is not feasible for nitrification when operated with anerobic and aerobic cycling for carbon and phosphorous removal from cheese production wastewater, as nitrification does not occur in a single reactor. Thus, two reactors in series are recommended to achieve nitrification from cheese production wastewater in SB-MBBRs. These findings can be applied to pilot and full-scale SB-MBBR operations. By demonstrating the potential to implement partial nitrification in the SB-MBBR system, this study presents the possibility of implementing partial nitrification in the SB-MBBR, resulting in the potential for more sustainable treatment of nitrogen from cheese production wastewater.

Role of Biofilms in Waste Water Treatment

Biofilm cells have a different physiology than planktonic cells, which has been the focus of most research. Biofilms are complex biostructures that form on any surface that comes into contact with water on a regular basis. They are dynamic, structurally complex systems having characteristics of multicellular animals and multiple ecosystems. The three themes covered in this review are biofilm ecology, biofilm reactor technology and design, and biofilm modeling. Membrane-supported biofilm reactors, moving bed biofilm reactors, granular sludge, and integrated fixed-film activated sludge processes are all examples of biofilm reactors used for water treatment. Biofilm control and/or beneficial application in membrane processes are improving. Biofilm models have become critical tools for biofilm foundational research as well as biofilm reactor architecture and design. At the same time, the differences between biofilm modeling and biofilm reactor modeling methods are acknowledged.

Characterization of a novel micro-pressure double-cycle reactor for low temperature municipal wastewater treatment

To solve the deterioration of effluent caused by low temperature in urban sewage treatment plant in cold areas, a new type of reactor was proposed, the biochemical environmental and low-temperature operating characteristics of the reactor were studied. Through analysis of flow simulation and dissolved oxygen (DO) distribution when the aeration rate was 0.6 m³/h, it showed that there were many different DO environments in the reactor at the same time, which provided favourable conditions for various biochemical reactions. The operation test showed that the average effluent removal rate of COD, TN, NH₄⁺-N and TP was 92.53%, 74.57%, 89.61% and 96.04%, respectively. And there were a variety of functional bacteria related to nitrogen and phosphorus removal in the system, most of them with strong adaptability at low temperatures. Among the dominant microorganisms, Flavobacterium and Rhodobacter were related to denitrification, Aeromonas and Thiothrix were related to phosphorous removal. Denitrifying phosphorus removal was the main way of phosphorus removal. Picrust2 results showed that the reactor operated well at low temperature, and the regional difference distribution of nitrification genes further confirmed the existence of functional zones in the reactor. The results showed that the Micro-pressure Double-cycle reactor worked well at low temperature, which provided a new idea and way for the upgrading of urban sewage treatment plants in cold areas.

Enhanced biological phosphorus and nitrogen removal by high-concentration powder carriers: extracellular polymeric substance, microbial communities, and metabolic pathways

In this study, diatomite, activated carbon, and iron-carbon (Fe-C) were used as biological carriers for the integrated fixed-film activated sludge process. Biomass, pollutant removal efficiency, and extracellular polymer were tested, and the effect of nitrogen and phosphorus removal, enzyme activity, and microbial diversity were studied after the sludge retention time was changed. The mechanism of carrier enriching microorganism and promoting pollutant degradation was studied. The results showed that the addition of these three carriers contributed to the enrichment of nitrifying bacteria in the system, and the NH₄⁺-N removal efficiency was above 98%. Diatomite and Fe-C could improve pollutant removal by increasing the activity of the electron transfer system. The abundance of denitrogenation-related reductases and the enzymes synthesizing poly-β-hydroxybutyrate was increased in activated carbon. The addition of Fe-C increased the abundance of denitrifying phosphate-accumulating organisms by approximately 25% and the removal efficiency of total phosphorus by 12.61-14.88% at the end of the long-term operation.

Promoted removal of phosphate by layered double hydroxides combined with bacteria: Application of novel carriers in biofilm reactor

Layered double hydroxides (LDHs) were used as carriers for the microbial consortium in sequencing biofilm batch reactor (SBBR) without inoculation to promote the removal of phosphate. The adsorption capacity of [Zn-Al]-LDH was significantly better than that of [Mg-Al]-LDH. The pollutants removal performance and behavior of microorganisms in LDH-SBBRs were also investigated. LDH-SBBRs showed improved removal efficiencies of COD, phosphate and TP with a low C/N ratio. Microscopic images show that biofilm formed rapidly in LDH-SBBRs. SEM-EDS detected abundant carbon and phosphorus, implying that biomass and phosphorus accumulate on LDH carriers. The microbial compositions of the three SBBRs indicate that the LDHs carriers improved the biodiversity of biofilm in the bioreactors. Synergistic effects of adsorption and biodegradation between well-structured LDHs and microorganisms led to an improved phosphate removal performance of LDH-SBBR. The results also demonstrate that [Zn-Al]-LDH carrier is the best for improving SBBR phosphate removal.

Accelerated anaerobic biodecolorization of sulfonated azo dyes by magnetite nanoparticles as potential electron transfer mediators

Anaerobic decolorization of azo dyes has been evidenced to be an economical and effective pretreatment method, but its generally limited by the low decolorization efficiency, especially for biodecolorization sulfonated azo dyes. In this study, magnetite nanoparticles (MNPs) as a conductive material, was coupled into anaerobic system for enhancing decolorization of sulfonated azo dyes, i.e., methyl orange (MO), with technology feasibility and system stability emphasized. The results showed that the anaerobic decolorization capacity was significantly enhanced with addition of MNPs (at dose of 1 g/L), where the efficiencies of MO decolorization and aromatic amines formation were as high as 97.28 ± 0.78 % and 99.44 ± 0.25%, respectively. In addition, both electron transport system activity and sludge conductivity were also significantly improved, suggesting that a direct extracellular electron transfer had been successfully established via MNPs as RMs. Under continuous-flow experiments, addition of MNPs not only improved anaerobic system resistance environmental stress (e.g., high MO concentration, low hydraulic retention time and low co-substance concentration) but also accelerated sludge granulation. The relative abundance of functional species related to dissimilatory iron reduction and MO biodegradation were also enriched under MNPs stimulation. The observed long-term stable performance suggests the full-scale application potential of this coupled system for treatment of wastewater containing sulfonated azo dyes.

Effect of Benzophenone-3 on performance, structure and microbial metabolism in an EGSB system

Benzophenone-3 is an organic compound widely used as a UV filter, which has been reported as water pollutant and is connected with endocrine disruption in humans and animals. Expanded granular sludge beds (EGSB) are a form of an anaerobic digestion system, which has been successfully evaluated for wastewater treatment, and the removal of different compounds, however little is known about the effect of compounds as Benzophenone-3 in the performance of EGSB systems. In this study, we evaluate the effect of BP-3 on the performance, microbial structure and metabolism of EGSB reactors. For this purpose, biogas production, removal efficiencies of BP-3 and DQO were monitored. Changes in bacteria and archaea microbial structure were investigated using PCR-DGGE, and the effect on anaerobic metabolism was evaluated by measuring the expression of mcrA and ACAs genes through qRT-PCR. The systems remained stable and efficient throughout the operation stages, with CH4 percentages greater than 55% and COD and BP-3 removal percentages greater than 90%. The presence of different concentrations of Benzophenone-3 influenced the organization of microbial communities, especially archaea. However, this did not affect the stability and performance of the EGSB systems.

Kinetic effects of anaerobic staging and aeration rates on sequencing batch moving bed biofilm reactors: Carbon, nitrogen, and phosphorus treatment of cheese production wastewater

The food and beverage industry produces wastewaters containing high concentrations of organic carbon and nutrients, which when discharged leads to eutrophication and algal blooms. Given recent stringencies in effluent regulations, industries are required to treat their wastewater on-site. There is a critical need for compact, high-rate, cost-effective wastewater technologies to treat industrial wastewaters, such as the sequencing batch moving bed biofilm reactor. The aim of this study is to investigate the potential and evaluate the performance of the sequencing batch moving bed biofilm reactor cycling between anaerobic and aerobic stages to treat high-strength food and beverage wastewaters. Specifically, this study focuses on the effects of anaerobic staging times and enhanced aeration on the removal of carbon, nitrogen, and phosphorous from cheese production wastewaters. Increasing anaerobic staging times was found to improve the removal rates of carbon beyond previously reported moving bed biofilm reactor results. Increasing the anaerobic stage however decreased the total nitrogen removal, with organic nitrogen undergoing ammonification during the anaerobic stage. This study demonstrates an optimum anaerobic staging time of 138 min; with a carbon removal rate of 31.1 g-sCOD·m^-2d^-1 and a nitrogen removal rate of 1.3 g-N·m^-2d^-1. Enhanced aeration was found to be detrimental to phosphorous removal, where a moderate aeration rate demonstrated a net total phosphorous removal of approximately 22 mg-P·l^-1 with the phosphorous-content of the suspended solids being approximately 4%. Finally, the sequencing batch moving bed biofilm reactor shows potential for on-site treatment of carbon, nitrogen, and phosphorous from cheese production wastewater.

Culture-independent study of bacterial communities in tropical river sediment

Ubiquitous microbial communities in river sediments actively govern organic matter decomposition, nutrient recycling, and remediation of toxic compounds. In this study, prokaryotic diversity in two major rivers in central Thailand, the Chao Phraya (CP) and the Tha Chin (TC) distributary was investigated. Significant differences in sediment physicochemical properties, particularly silt content, were noted between the two rivers. Tagged 16S rRNA sequencing on a 454 platform showed that the sediment microbiomes were dominated by Gammaproteobacteria and sulfur/sulfate reducing Deltaproteobacteria, represented by orders Desulfobacteriales and Desulfluromonadales together with organic degraders Betaproteobacteria (orders Burkholderiales and Rhodocyclales) together with the co-existence of Bacteroidetes predominated by Sphingobacteriales. Enrichment of specific bacterial orders was found in the clayey CP and silt-rich TC sediments, including various genera with known metabolic capability on decomposition of organic matter and xenobiotic compounds. The data represent one of the pioneered works revealing heterogeneity of bacteria in river sediments in the tropics.

An experimental model of COD abatement in MBBR based on biofilm growth dynamic and on substrates' removal kinetics

In this study, the performance of a lab-scale Moving Bed Biofilm Reactor (MBBR) under different operating conditions was analysed. Moreover, the dependence of the reaction rates both from the concentration and biodegradability of substrates and from the biofilm surface density, by means of several batch kinetic tests, was investigated. The reactor controls exhibited an increasing COD (Chemical Oxygen Demand) removal, reaching maximum yields (close to 90%) for influent loadings of up to12.5 gCOD/m(2)d. From this value, the pilot plant performance decreased to yields of only about 55% for influent loadings greater than 16 gCOD/m(2)d. In response to the influent loading increase, the biofilm surface density exhibited a logistic growing trend until reaching a maximum amount of total attached solids of about 9.5 g/m(2). The kinetic test results indicated that the COD removal rates for rapidly biodegradable, rapidly hydrolysable and slowly biodegradable substrates were not affected by the organic matter concentrations. Instead, first-order kinetics were detected with respect to biofilm surface density. The experimental results permitted the formulation of a mathematical model to predict the MBBR organic matter removal efficiency. The validity of the model was successfully tested in the lab-scale plant.

Survey of Microbial Diversity in Flood Areas during Thailand 2011 Flood Crisis Using High-Throughput Tagged Amplicon Pyrosequencing

The Thailand flood crisis in 2011 was one of the largest recorded floods in modern history, causing enormous damage to the economy and ecological habitats of the country. In this study, bacterial and fungal diversity in sediments and waters collected from ten flood areas in Bangkok and its suburbs, covering residential and agricultural areas, were analyzed using high-throughput 454 pyrosequencing of 16S rRNA gene and internal transcribed spacer sequences. Analysis of microbial community showed differences in taxa distribution in water and sediment with variations in the diversity of saprophytic microbes and sulfate/nitrate reducers among sampling locations, suggesting differences in microbial activity in the habitats. Overall, Proteobacteria represented a major bacterial group in waters, while this group co-existed with Firmicutes, Bacteroidetes, and Actinobacteria in sediments. Anaeromyxobacter, Steroidobacter, and Geobacter were the dominant bacterial genera in sediments, while Sulfuricurvum, Thiovirga, and Hydrogenophaga predominated in waters. For fungi in sediments, Ascomycota, Glomeromycota, and Basidiomycota, particularly in genera Philipsia, Rozella, and Acaulospora, were most frequently detected. Chytridiomycota and Ascomycota were the major fungal phyla, and Rhizophlyctis and Mortierella were the most frequently detected fungal genera in water. Diversity of sulfate-reducing bacteria, related to odor problems, was further investigated using analysis of the dsrB gene which indicated the presence of sulfate-reducing bacteria of families Desulfobacteraceae, Desulfobulbaceae, Syntrobacteraceae, and Desulfoarculaceae in the flood sediments. The work provides an insight into the diversity and function of microbes related to biological processes in flood areas.

Accelerated start-up of moving bed biofilm reactor by using a novel suspended carrier with porous surface

A novel suspended carrier with porous surface was firstly prepared by coating a sponge on the inside and outside of a hard polyethylene ring. Herein the effects of the sponge thickness (0, 2, 4, 6 mm) and pore size (17, 45, 85 pores per inch, ppi) on the performance of the start-up stage in moving bed biofilm reactor (MBBR) were investigated. The results indicated that the home-made carrier with the sponge thickness of 4 mm and the pore size of 45 ppi, defined as SC4-45, showed the best performance, which obtained high biomass concentration of 2,136.6 mg/L, oxygen uptake rate for COD of 150.1 mg O2/h and oxygen uptake rate for NH4(+)-N of 17.4 mg O2/h. The DGGE profiles of the biofilms obtained in SC4-45 and a commercial carrier showed a similar community as the Dice similarity coefficients between two samples was 0.72. Furthermore, 16S rRNA gene sequence analysis reveals dominance of Sphaerotilus sp. and Aeromonas sp. in the community of both samples. Moreover, for the MBBR based on SC4-45, COD and NH4(+)-N removal rates reached 99.5 ± 1.1 and 93.6 ± 2.3 % at the end of the start-up stage, much higher than those of the commercial carrier, 74.9 ± 2.7 and 40.0 ± 1.8 %, respectively. These indicated the novel carrier obtained a quick start-up.