Pilot study on microbial treatment of high concentration chromium wastewater from cold rolling mills

The microbial treatment of wastewater containing a high concentration of chromium from cold rolling mills was carried out as a pilot study. The pilot-scale equipment, technological process and results are described in this paper. Two kinds of wastewater with a high concentration of chromium were tested ： one from a color coating line ; the other from a silicon steel line. The removal effect of Cr^6＋ , T-Cr and chemical oxygen demand （COD） in wastewater was studied. The results showed that this microbial treatment technology could be used to treat the above two kinds of chromium-containing wastewater. The average concentrations of Cr^6＋ in the color coating line effluent and the silicon steel line effluent were 0.02 mg/L and 0.04 mg/L respectively, and the average concentrations of T-Cr in the effluents were 0.71 mg/L and 0.74 mg/L respectively. Both were lower than the Sewage Discharge Standard （Cr^6＋ 〈 0.5 mg/L,T-Cr 〈 1.5 mg/L）. Furthermore, up to 60% of the COD was removed from chromate wastewater containing a high concentration COD （ 〉 3 g/L）. The removal rate of COD was lower than 25% for chromate wastewater containing a low concentration COD （ 〈 3 g/L）. Adding a flocculating agent was one of the effective ways of improving the COD removal rate from chromium-containing wastewater.

Characteristics of microbial community involved in early biofilms formation under the influence of wastewater treatment plant effluent

Effluents from wastewater treatment plants（WWTPs） containing microorganisms and residual nutrients can influence the biofilm formation. Although the process and mechanism of bacterial biofilm formation have been well characterized, little is known about the characteristics and interaction of bacteria, archaea and eukaryotes in the early colonization, especially under the influence of WWTP effluent. The aim of this study was to characterize the important bacterial, archaeal and eukaryotic species in the early stage of biofilm formation downstream of the WWTP outlet. Water and biofilm samples were collected 24 and 48 hr after the deposition of bio-cords in the stream. Illumina Miseq sequencing of the 16 S and 18 S rDNA showed that, among the three domains, the bacterial biofilm community had the largest alpha and beta diversity. The early bacterial colonizers appeared to be ＂biofilm-specific＂, with only a few dominant operational taxonomic units（OTUs） shared between the biofilm and the ambient water environment. Alpha-proteobacteria and Ciliophora tended to dominate the bacterial and eukaryotic communities, respectively, of the early biofilm already at 24 hr, whereas archaea played only a minor role during the early stage of colonization. The network analysis showed that the three domains of microbial community connected highly during the early colonization and it might be a characteristic of the microbial communities in the biofilm formation process where co-occurrence relationships could drive coexistence and diversity maintenance within the microbial communities.

Construction and application of the Synechocystis sp.PCC6803-ftnA in microbial contamination control in a coupled cultivation and wastewater treatment

Inspired by iron fertilization experiments in HNLC（high-nitrate, low-chlorophyll） sea areas,we proposed the use of iron-rich engineered microalgae for microbial contaminant control in iron-free culture media. Based on the genome sequence and natural transformation system of Synechocystis sp. PCC6803, ftn A（encoding ferritin） was selected as our target gene and was cloned into wild-type Synechocystis sp. PCC6803. Tests at the molecular level confirmed the successful construction of the engineered Synechocystis sp. PCC6803-ftn A. After Fe3＋-EDTA pulsing, the intracellular iron content of Synechocystis sp. PCC6803-ftn A was significantly enhanced, and the algae was used in the microbial contamination control system. In the coupled Synechocystis sp. PCC6803-ftn A production and municipal wastewater（MW, including Scenedesmus obliquus and Bacillus） treatment, Synechocystis sp. PCC6803-ftn A accounted for all of the microbial activity and significantly increased from 70% of the microbial community to 95%.These results revealed that while the stored iron in the Synechocystis sp. PCC6803-ftn A cells was used for growth and reproduction of this microalga in the MW, the growth of other microbes was inhibited because of the iron limitation, and these results provide a new method for microbial contamination control during a coupling process.

Performance and recent improvement in microbial fuel cells for simultaneous carbon and nitrogen removal: A review

Microbial fuel cells（MFCs） have become a promising technology for wastewater treatment accompanying electricity generation. Carbon and nitrogen removal can be achieved by utilizing the electron transfer between the anode and cathode in an MFC. However,large-scale power production and high removal efficiency must be achieved at a low cost to make MFCs practical and economically competitive in the future. This article reviews the principles, feasibility and bottlenecks of MFCs for simultaneous carbon and nitrogen removal, the recent advances and prospective strategies for performance improvement, as well as the involved microbes and electron transfer mechanisms.

A full-scale integrated-bioreactor with two zones treating odours from sludge thickening tank and dewatering house： performance and microbial characteristics

A full-scale integrated-bioreactor consisting of a suspended zone and an immobilized zone was employed to treat the ordours emitted from a wastewater treatment plant. The inlet concentrations of H,S and NH3 were 1.6-38.6 mg.m-3 and 0.1 6.7 mg.m-3 respectively, while the steady-state outlet concentrations were reduced to 0-2.8mg.m - for H2S and 0-0.5mg.m for NH3. BothH2SandNH3 were eliminated effectively by the integrated-bioreactor. The removal efficiencies of H2S and NH3 differed between the two zones. Four species of microorganisms related to the degradation of H2S and NH3 were isolated. The characteristics and distributions of the microbes in the bioreactor depended on the inlet concentration of substrates and the micro-environmental conditions in the individual zones. Product analysis indicated that most of the H2S was oxidized into sulfate in the immobilized zone but was dissolved into the liquid phase in the suspended zone. A large amount of NH3 was converted into nitrate and nitrite by nitration in the suspended zone, whereas only a small amount of NH3 was transferred to the aqueous phase mainly by absorption or chemical neutralization in the immobilized zone. Different microbial populations dominated the individual zones, and the major biodegradation products varied accordingly.

Performance assessment and microbial diversity of two pilot scale multi-stage sub-surface flow constructed wetland systems

This study assessed the performance and diversity of microbial communities in multi-stage sub-surface flow constructed wetland systems（CWs）. Our aim was to assess the impact of configuration on treatment performance and microbial diversity in the systems. Results indicate that at loading rates up to 100 g BOD5/（m2·day）, similar treatment performances can be achieved using either a 3 or 4 stage configuration. In the case of phosphorus（P）, the impact of configuration was less obvious and a minimum of 80% P removal can be expected for loadings up to 10 g P/（m2·day） based on the performance results obtained within the first16 months of operation. Microbial analysis showed an increased bacterial diversity in stage four compared to the first stage. These results indicate that the design and configuration of multi-stage constructed wetland systems may have an impact on the treatment performance and the composition of the microbial community in the systems, and such knowledge can be used to improve their design and performance.

Novel microbial fuel cell design to operate with different wastewaters simultaneously

A novel single cathode chamber and multiple anode chamber microbial fuel cell design（MAC-MFC）was developed by incorporating multiple anode chambers into a single unit and its performance was checked.During 60 days of operation,performance of MAC-MFC was assessed and compared with standard single anode/cathode chamber microbial fuel cell（SC-MFC）.The tests showed that MAC-MFC generated stable and higher power outputs compared with SC-MFC and each anode chamber contributed efficiently.Further,MAC-MFCs were incorporated with different wastewaters in different anode chambers and their behavior in MFC performance was observed.MAC-MFC efficiently treated multiple wastewaters simultaneously at low cost and small space,which claims its candidature for future possible scale-up applications.

On the use of ferroelectric material LiNbO3 as novel photocatalyst in wastewater-fed microbial fuel cells

In this work, the use of lithium niobate （LiNbO3）, a ferroelectric and photocatalyst material, is investi- gated as a new type of cathode catalyst for wastewater-fed single-chamber microbial fuel cells （MFCs）. Carbon cloth electrodes coated with LiNbO3 were studied with and without UV-vis irradiation to assess its photocatalytic behavior in these devices. The synthesized phase of LiNbO3 was characterized by X- ray diffraction, differential scanning calorimetry, particle size distribution, and transmission electron microscopy analyses. The MFC containing a LiNbO3-based cathode exhibited a maximum open circuit potential and power output of 400 mV and 131 mW/m^3, respectively, under irradiation. This cathode configuration also achieved the maximum chemical oxygen demand removal of 84% after 120 h of MFC operation. These results show that ferroelectric materials such as LiNbO3 could be used as cathode cat- alysts in MFC devices. As a complementary analysis, the removal of the heavy metals detected in the wastewater was also monitored.

Digestion performance and microbial community in full-scale methane fermentation of stillage from sweet potato-shochu production

Sweet potato shochu is a traditional Japanese spirit produced mainly in the South Kyushu area in Japan. The amount of stillage reaches approximately 8 x 105 tons per year. Wastewater mainly containing stillage from the production of sweet potato-shochu was treated thermophilically in a fullscale treatment plant using fixed-bed reactors （8 reactors ×283 m3）. Following the addition of Ni2＋ and Co2＋, the reactors have been stably operated for six years at a high chemical oxygen demand （COD） loading rate of 14 kg/（m3.day）. Analysis of coenzyme content and microbial communities indicated that similar microbial communities were present in the liquid phase and on the fiber carders installed in reactors. Bacteria in the phyla Firmieutes as well as Bacteroidetes were dominant bacteria, and Methanosarcina thermophila as well as Methanothermobacter crinale were dominant methanogens in the reactors. This study reveals that stillage from sweet potato-shochu production can be treated effectively in a full-scale fixed-bed reactor under thermophilic conditions with the help of Ni2~ and Co2＋. The high diversity of bacterial community and the coexistence of both aceticlastic and hydrogenotrophic methanogens contributed to the excellent fermentation performance.

Preparation and characterization of a novel microorganism embedding material for simultaneous nitrification and denitrification

A novel microorganism embedding material was prepared to enhance the biological nitrogen removal through simultaneous nitrification and denitrification. Polyvinyl alcohol （PVA）, sodium alginate （SA） and cyclodextrin （CD） were used to compose gel bead with embedded activated sludge. The effects of temperature, CD addition and concentrations of PYA and SA on nitrogen removal were evaluated. Results show that the gel bead with CD addition at 30℃contributed to the highest nitrogen removal efficiency and nitrogen removal rate of 85.4% and 2.08 mg·（L·h）^-1, respectively. Meanwhile, negligible NO3^- and NO2^- were observed, proving the occurrence of simultaneous nitrification and denitrification. The High-Throughput Sequencing confirms that the microbial community mainly contained Comamonadaceae in the proportion of 61.3%. Overall, CD increased gel bead＇s porosity and resulted in the high specific endogenous respiration rate and high nitrogen removal efficiency, which is a favorable additional agent to the traditional embedding material.