Biological Contact Oxidation Reactor Research Articles

Firmicutes and Bacteroidetes as the dominant microorganisms for ammonium nitrogen wastewater treatment with a low C/N ratio in BCOR

Improving nitrogen removal is a significant concern in the biological treatment of ammonium nitrogen (NH4+-N) wastewater with low chemical oxygen demand (COD)/NH4+-N (C/N) ratio, and microorganisms are the critical factor affecting nitrogen removal. In this study, a laboratory-scale biological contact oxidation reactor (BCOR) system was successfully started up (day 1 to day 47) and stabilized (day 48 to day 320). A 16S rRNA gene sequencing analysis showed that the phyla Firmicutes and Bacteroidetes were first observed as the dominant microorganisms in the BCOR for the ammonium nitrogen wastewater treatment with a low C/N ratio. The genera Bacteroides (phylum Bacteroidetes), Porphyromonas (phylum Bacteroidetes), Dialister (phylum Firmicutes), and Anaerococcus (phylum Firmicutes) also became the main microorganisms in this system for the first time. These microbial communities enabled the system to achieve an average ammonium nitrogen removal efficiency and total nitrogen removal efficiency of 95.8 % and 88.1 %, respectively, during the operational period. It indicated that these dominant microorganisms in the BCOR system played an essential role in improving the performance of biological nitrogen removal. This conclusion will play a critical role in promoting the microbial mechanism research and technology engineering application of the BCOR system for treating ammonium nitrogen wastewater with a low C/N ratio.

Bioaugmented biological contact oxidation reactor for treating simulated textile dyeing wastewater

In this study, modified polyamide fibers were used as biocarriers to enrich dense biofilms in a multi-stage biological contact oxidation reactor (MBCOR) in which partitioned wastewater treatment zone (WTZ) and bioaugmentation zone (BAZ) were established to enhance the removal of methyl orange (MO) and its metabolites while minimizing sludge yields. WTZ exhibited high biomass loading capacity (5.75 ± 0.31 g/g filler), achieving MO removal rate ranging from 68 % to 86 % under different aeration condition within 8 h in which the most dominant genus Chlorobium played an important role. In the BAZ, Pseudoxanthomonas was the dominant genus while carbon starvation stimulated the enrichment of chemoheterotrophy and aerobic_chemoheterotrophy genes thereby enhanced the microbial utilization of cell-released substrates, MO as well as its metabolic intermediates. These results revealed the mechanism bioaugmentation on MBCOR in effectively eliminating both MO and its metabolites.

Bioaugmentation treatment of coal chemical reverse osmosis concentrate in biological contact oxidation system coupled with ozone pretreatment

With the zero discharge requirements of coal chemical industry in China, reverse osmosis technology and fractional crystallization technology have been applied to recover water and valuable salts. Organic matter significantly inhibits salt crystallization, therefore it is urgent to remove organic matter from coal chemical reverse osmosis concentrate (CCROC) efficiently and economically. Common biological systems have the bottlenecks of long start-up period and poor pollutants removal efficiency due to the inhibition of toxic compounds and high salinity to the microorganisms. In this work, a self-prepared halotolerant bacteria preparation (HBP, mixture of screened Bacillus, Pseudomonas, and Halomonas with strong degrading capacity of CCROC) was inoculated into different biochemical systems (activated sludge and biological contact oxidation in sequencing batch reactor) to try to enhance the pollutants removal of extremely refractory CCROC (BOD5/COD of 0.05). The results showed that HBP increased the total organic carbon (TOC) removal efficiency from 8% to 15% in activated sludge system. In addition, biological contact oxidation reactor (BCOR) could better retain the HBP, leading to a higher TOC removal efficiency (20%). Typically, the inoculation of HBP without activated sludge in BCOR contributed to the highest TOC removal (28%). The class Bacilli (genus Bacillus) was dominant during the start-up and stable period of this bioaugmented treatment process. To further increase the pollutants removal, ozone oxidation pretreatment was conducted prior to biological treatment to break the ring structures. The total TOC removal increased to 42% under the combined treatment, while the dominant classes in biofilms shifted to Actinobacteria, Gammaproteobacteria, Alphaproteobacteria, and Bacteroidia. This study provided an effective approach for CCROC treatment with industrial application potentials.

Responses of the microbial community and the production of extracellular polymeric substances to sulfamethazine shocks in a novel two-stage biological contact oxidation system.

The biological contact oxidation reactor is an effective technology for the treatment of antibiotic wastewater, but there has been little research investigating its performance on the sulfamethazine wastewater treatment. In this study, a novel two-stage biological contact oxidation reactor was used for the first time to explore the impact of sulfamethazine (SMZ) on the performance, microbial community, extracellular polymeric substances (EPS), and antibiotic-resistant genes (ARGs). The chemical oxygen demand (COD) and ammonia nitrogen (-N) removal efficiencies kept stable at 86.93% and 83.97% with 0.1-1 mg/L SMZ addition and were inhibited at 3 mg/L SMZ. The presence of SMZ could affect the production and chemical composition of EPS in the biofilm, especially for the pronounced increase in TB-PN yield in response against the threat of SMZ. Metagenomics sequencing demonstrated that SMZ could impact on the microbial community, a high abundance of Candidatus_Promineofilum, unclassified_c__Anaerolineae, and unclassified_c__Betaproteobacteria were positively correlated to SMZ, especially for Candidatus_Promineofilum. Candidatus_Promineofilum not only had the ability of EPS secretion, but also was significantly associated with the primary SMZ resistance genes of sul1 and sul2, which developed resistance against SMZ pressure through the mechanism of targeted gene changes, further provided a useful and easy-implement technology for sulfamethazine wastewater treatment.

Mixotrophic denitrification processes in basalt fiber bio-carriers drive effective treatment of low carbon/nitrogen lithium slurry wastewater

Lithium battery slurry wastewater was successfully treatedby using basalt fiber (BF) bio-carriers in a biological contact oxidation reactor. This resulted in a significant reduction of COD (93.3 ± 0.5 %) and total nitrogen (77.4 ± 1.0 %) at 12 h of HRT and dissolved oxygen (DO) of 0–1 mg/L. The modified Stover-Kincannon model indicated that the total nitrogen removal rate was 4.462 kg/m3/d in R-BF while the substrate maximum specific reaction rate (qmax) in the Monod model was 0.323 mg-N/mgVSS/d. A stable internal environment was established within the bio-nest. Metataxonomic analysis revealed the presence of denitrification and decarbonization bacteria, combined heterotrophic nitrification-aerobic denitrification bacteria, nitrite-oxidizing bacteria, and ammonia-oxidizing bacteria. Functional analysis displayed changes related to (aerobic)chemoheterotrophy, nitrogen respiration, nitrate reduction, respiration/denitrification of nitrite, and nitrate in R-BF. The study proposes a novel approach to achieve denitrification for the treatment of lithium slurry wastewater at low C/N conditions.

Performance and microbial characteristics of a novel pilot-scale tubing biological contact oxidation reactor for rural drinking water

Drinking water treatment under rural conditions often require compactness and portability. To address this, the present study developed a pilot-scale helical tubular biological contact oxidation (BCO) reactor filled with annular porous biofilm carriers (fillers). To determine the drinking water treatment efficiency and microbial characteristics, the system was investigated for 212 days at (24.1 ± 3.4) °C under different flow rates (1.86 L · h−1, 3.72 L · h−1, and 7.2 L · h−1) to treat simulated rural drinking water. The results show that (62.7 ± 9.3) % of ammonium (NH4+-N) and (19.5 ± 5.4) % of UV254 absorbance were removed by the BCO reactor after entering the stable operation period. It is shown that shorter hydraulic retention time (HRT) weakened the removals of tryptophan-like substances and fulvic acid according to the three-dimension fluorescence excitation emission matrix spectroscopy, with the removal ratios decreased from 90% to 0% when the HRT declined from 16.8 h to 4.2 h. Despite operating at regular room temperature ((24.1 ± 3.4) °C), the drinking water BCO reactor underwent a long start-up period (5.5 months) to reach a steady state in terms of biofilm concentration and pollutant removal performance. Genus Xanthobacter and Methylobacterium might significantly contribute to the removal of NOM in the BCO reactor, while genus Pedomicrobium and Bradyrhizobium were speculated to be responsible for nitrogen conversion. The present study provides new insights into the application of BCO reactors for ammonium and NOM removal from rural drinking water.

Application of basalt fibers in a biological contact oxidation reactor for the treatment of landfill leachate

Landfill leachate often has high nitrogen concentration that results in an imbalance of carbon to nitrogen ratio, ultimately affecting the bioremediation potential of the system. This problem may be solved by retrofitting a bio-carrier in a reactor that particularly helps microbial communities to drive the nitrogen cycle. In this study, basalt fiber (BF) was used as a bio-carrier in a conventional biological contact oxidation reactor for the remediation of landfill leachate. The physicochemical parameters namely chemical oxygen demand (COD), ammonium-nitrogen (NH4+-N), total nitrogen (TN), and total phosphorus (TP) were assessed and compared with a control reactor comprising combination fillers to evaluate the system’s performance. The potential role of microorganisms in the remediation process was elucidated by microscopic morphology and microbial community structure analyses via 16S amplicon sequencing. The results showed that the surface of BF promotes the adhesion and proliferation of microorganisms. The abundant microbial genera were potentially involved in the nitrogen cycle such as dokdonella, saccharibacteria general incertae sedis, and Nitrospira. When the hydraulic retention time was 10 h and the dissolved oxygen was 1–2 mg/L, the nitrogen removal efficiency was the highest. Accordingly, the adsorption equilibrium of heavy metals was achieved in a short time which could be attributed to the sorption on biomass. This study concludes that BF application could help alleviate current problems of complex wastewater treatment having low denitrification abilities as a low cost solution.

Treatment of high-load organic wastewater by novel basalt fiber carrier media

The carrier medium plays a key role in improving existing remediation potential of conventional biological contact oxidation reactors. In this study, a biological contact oxidation reactor was constructed using basalt fiber (R-BF) as a biological carrier. The bioreactor performance was investigated in terms of reduction in chemical oxygen demand (COD), ammonium nitrogen (NH4+-N), and total nitrogen (TN) at organic loadings rate of 15.243 kg/m3·d and nitrogen loading rate of 1.068 kg/m3·d. We found that COD, NH4+-N, and TN were reduced to 99.1%, 97.9%, and 97.8%, respectively. Within the R-BF, a bio-nest was developed which had abundant pores and channels and supported successful movement of nutrients, resulting in high biological activity (55.78%). The microbial communities within the bio-nest were diverse and rich and sludge production during operation was minimal. This makes BF a promising application for wastewater treatment. This research might be useful in the construction of integrated bioreactors that can operate under high organic and nitrogen loadings rates with reduced energy consumption, i.e. 75% in this study.

Electrolysis-sulfate-reducing up-flow sludge bed-biological contact oxidation reactor for Norfloxacin removal from wastewater with high sulfate content

This study investigated the treatment of 100-mg/L Norfloxacin (NOR) wastewater containing high concentrations of sulfate through a combination of electrolysis, sulfate-reducing up-flow sludge bed (SRUSB), and biological contact oxidation reactor (BCOR) treatments. Results revealed that after 62 h, the reaction system had processed over 97% of the NOR. Additionally, electrolysis with sodium sulfate as the electrolyte transformed 87.8% of the NOR but only 33.5% of the total organic carbon (TOC). In the SRUSB, the TOC and SO42− contents were simultaneously reduced by 87.4% and 95.6%, respectively, providing a stable environment to the BCOR. In the BCOR, 36.3% and 85.9% of the NOR and TOC were degraded. High-performance liquid chromatography-tandem mass spectrometry analysis identified three possible degradation pathways under the attack of –OH during electrolysis, including defluorination, piperazinyl ring transformation, and quinolone ring transformation. Furthermore, the Illumina HiSeq sequencing results demonstrated that the sulfate-reducing bacteria (represented by Desulfobacter and Desulfobulbus) in the SRUSB and the sulfate-oxidizing bacteria (mainly consisting of Gammaproteobacteria and Alphaproteobacteria) in the BCOR played important roles in carbon chain oxidation and benzene ring opening and thoroughly degraded the electrolysis products. Thus, this method effectively overcomes the incomplete degradation and low removal efficiency issues associated with single electrolysis or biological methods in traditional processes.

Micro-Polluted Water Treatment by Biological Contact Oxidation Process: Aeration Mode and Bacteria Community Analysis

Traditional biological contact oxidation (BCO) process was modified; influent, stirring, aeration, sedimentation, and effluent were carried out alternately in the same BCO reactor to realize anaero...

Biodegradation of saline phenolic wastewater in a biological contact oxidation reactor with immobilized cells of Oceanimonas sp.

To develop a method to treat saline phenolic wastewater in a biological contact oxidation reactor (BCOR) with immobilized cells of a marine microorganism, Oceanimonas sp., isolated from seawater. Cells were immobilized on fibre carriers in the BCOR. Saline wastewater with phenol at 1.5g/l and NaCl at 6% (w/v) was treated. In continuous assays, 99% removal of phenol was achieved and a kinetic model for the phenol degradation is presented based on Monod's equation. The BOCR system using immobilized cells of Oceanimonas efficiently treats saline phenolic wastewaters without having decrease the salinity of the wastewater.

Behaviour of fouling-related components in an enhanced membrane bioreactor using marine activated sludge

This paper presents an experimental study on behaviour of fouling-related components during saline wastewater treatments in an enhanced mesoporous membrane bioreactor (MBR) system integrated with a biological contact oxidation reactor (BCOR). By monitoring the transmembrane pressure, the MBR system without BCOR assistance was observed to get membrane fouling easier during saline wastewater treatments. Typically, the concentration of total EPS gradually increased in the MBR system over the operation time, while no significant change in its concentration was observed in the BCOR-MBR system. The concentration of total SMP in the MBR system reached high levels earlier than the BCOR-MBR system, causing a significant membrane fouling. Besides, unlike a simple MBR system, the BCOR-MBR system produced more soluble microbial by-product-like components (simple) instead of fulvic acid-like or humic acid-like components (complex) during the saline wastewater treatments, resulting in higher resistance to a membrane fouling.

Bioaugmentation of biological contact oxidation reactor (BCOR) with phenol-degrading bacteria for coal gasification wastewater (CGW) treatment

This study was conducted to evaluate the performance of the biological contact oxidation reactor (BCOR) treating coal gasification wastewater (CGW) after augmented with phenol degrading bacteria (PDB). The PDB were isolated with phenol, 4-methyl phenol, 3,5-dimethyl phenol and resorcinol as carbon resources. Much of the refractory phenolic compounds were converted into easily-biodegradable compounds in spite of low TOC removal. The bioaugmentation with PDB significantly enhanced the removal of COD, total phenols (TP) and NH3-N, with efficiencies from 58% to 78%, 66% to 80%, and 5% to 25%, respectively. In addition, the augmented BCOR exhibited strong recovery capability in TP and COD removal while recovery of NH3-N removal needed longer time. Microbial community analysis revealed that the PDB presented as dominant populations in the bacteria consortia, which in turn determined the overall performance of the system.

Dissolved organic matter in digested piggery wastewater from combined treatment process

ABSTRACT The temporal and spatial variation of dissolved organic matter in the processes of hydrolytic acidification and biological contact oxidation during post-treatment of digested piggery wastewater were characterized systematically by means of ion chromatography, fluorescence spectra, and ultraviolet spectra in this study. The highest removal efficiencies of chemical oxygen demand and nitrogen have been achieved when the 1/3 effluent of biological contact oxidation reactor was backflow into the reactor of hydrolytic acidification. It was found that the concentrations of total organic acids were 283.6 mg/L at the first 2 h of hydrolytic reaction and 305.5 mg/L at the beginning of recirculation between the two reactors and then decreased to around 200 mg/L and keep stable. The results of synchronous and three-dimensional excitation–emission matrix fluorescence spectroscopy revealed that the protein-like fluorescence peaks were identified in the hydrolytic acidification reactor and their intensities increased gradually along with hydrolytic time increasing. Moreover, the fulvic acid-like fluorescence peaks in biological contact oxidation reactor were observed, and the intensity increased gradually. The synchronous intensity of 277 nm wavelength was significantly correlated with the total organic acids concentration. Variation of SUVA254 and E 253/E 203 during the hydrolytic acidification process indicated that concentrations of aromatic and unsaturated compounds slightly increase and those aromatic compounds are not stable. However, SUVA254 and E 253/E 203 decreased rapidly in the biological contact oxidation reactor, which suggested that easily degradable organic matters had been consumed rapidly.

Study on Treatment of Dye Wastewater by UASB-Biological Contact Oxidation Process

A continuously fed stainless steel anaerobic UASB and biological contact oxidation reactor were used in sequence for the experimentation. Dye wastewater which initial COD was 2850mg/L, the COD remove ratio reached to 72% by UASB, COD remove ratio reached to 99% by Biological Contact Oxidation pond. NV (Volume loading) of UASB reached to 1.83 kg COD/ (m3•d), NV of Biological Contact Oxidation pond reached to 1.12 kg COD/ (m3•d). Considering the development of UASB and biological contact oxidation，a dye wastewater treatment process was proposed.