Transfer of functional microorganism: Regulation of N-acyl-homoserine lactones on the microbial community in aniline-degrading sequencing batch biofilm reactor.

Due to the inhibition of nitrification from aniline toxicity, exogenous N-acyl-homoserine lactones (AHLs) addition was attempted to enhance nitrogen removal in this work. Two sequencing batch biofilm reactors (SBBRs): S1 (the control) and S2 (C6-HSL and 3-oxo-C8-HSL dosing) were used to treat aniline wastewater. The NH4+-N and TN removal rates of S2 were 42.50% and 26.99% higher than S1 in the aerobic phase, respectively. It revealed the nitrogen removal performance of S2 much better than S1. High-throughput sequencing results indicated that many nitrifiers and denitrifiers of S2, such as Nitrosomonas and Thauera, transferred from sludge to biofilm significantly and built closer relationships each other. Overall, main nitrogen removal was contributed by biofilm rather than sludge with the regulation of AHLs. A mild and collaborative environment of biofilms for microorganisms enhanced nitrogen removal. The work provided a new idea for reconciling the contradiction between nitrification and denitrification in aniline wastewater treatment.

Research on modified blast furnace dust in demulsification: The synergistic effect of ferric oxide, hydrophobic carbon, and polysilicate.

Current treatment processes for the cold rolling emulsion wastewater were in the dilemma that the cost was so high while the efficiency was not satisfied in China. In this work, a novel material with high-performance demulsification was obtained and used to treat the emulsion wastewater efficiently by modifying blast furnace dust (BFD), a steel industry waste. Firstly, the BFD was characterized by various analytical techniques and the results suggested that hydrophobic functional groups, positively charged iron oxide, and polysilicon in the BFD were contributed to removing stable oil droplets. Therefore, the BFD modification was conducted accordingly by optimizing the proportion and reaction conditions of these three components. The study demonstrated that the removal rate of oil and CODcr reached 75.21% and 81.23% under the conditions of the carbon type of GWF-HAC-R90, the carbon content of 14.86%, and the n(Fe)/n(Si) of 1.55, respectively. Based on this, the effects of pH, demulsifier dosage, and average agitation rate were investigated. The emulsion components before and after demulsification were analyzed by GC-MS, and the demulsification mechanism was expounded combined with kinetics. Results showed that the Fe2O3 with positive charge played a dominant role in emulsions with mainly anionic surfactants, while hydrophobic carbon structures and polysilicate acted as the auxiliaries. Besides, comprehensive analysis and characterization results suggested that the demulsification effect was a combination of the synergic processes: 1) electrostatic interaction developed by the anionic surfactant oil droplets and the positively charged the BFD particles; 2) hydrophobic association among the oil droplet with nonionic surfactant and amphiphilic carbon-iron complexes; 3) adsorption bridging between the surfactant oil droplets and polysilicate. The results of comparative tests in treating the actual cold-rolling emulsion wastewater showed the MBFD could bring about significant technical, economic benefits and achieve utilization of metallurgical solid wastes.Implications: Blast furnace dust (BFD) is an industrial solid waste obtained by dry de-dusting from blast furnace gas during the blast furnace ironmaking process. The main components of BFD are iron oxide and carbon, and also contain small amounts of different recoverable non-ferrous metals zinc, secret, indium and lead, which have recovery value. In this study, we enhanced the three parts of BFD and used to demulsification. In this study, the BFD was modified in three aspects (hydrophobic functional groups, positively charged iron oxide, and polysilicon) to achieve the secondary utilization of waste in emulsion wastewater treatment. And investigated the effect of reaction conditions on the demulsification effect with modified blast furnace dust (MBFD). Furthermore, the GC-MS analyzes combined with kinetics interpret the demulsification mechanism with the MBFD as a secondary resource. Finally, the comparative tests in treating the actual cold-rolling emulsion wastewater showed the MBFD could bring about significant technical and economic benefits and achieve utilization of metallurgical solid wastes.

Study on the biogas potential of anaerobic digestion of coffee husks wastes in Ethiopia.

The poorly controlled discharge of coffee husks in Ethiopia causes severe environmental pollution and is a waste of resources. The volatile solid and carbon content in coffee husks waste indicates that it is rich in organic matter and has huge potential to produce biogas. This study investigated the feasibility of coffee husks to produce biomass through anaerobic digestion, based on temperature, initial pH, inoculum/substrate (I/S) ratio and carbon/nitrogen (C/N) ratio. The study demonstrated that the maximum production of biogas and methane reached 3359.6 ml and 2127.30 ml, respectively, under the conditions of mesophilic temperature (35±1°C), an initial pH of 7, an I/S ratio of 0.75 and a C/N ratio of 30. Based on this result, the effects of trace elements (Fe2+, Ni2+, Co2+) on biogas production and methane content were also explored. Compared with the group with no addition of trace elements, the experiment adding trace elements had significant enhancement effects on the production of biogas and methane, in which Fe2+ played a leading role (p<0.05). Fe2+ promoted the hydrolysis and acidification of coffee husks, resulting in the production of a series of intermediates such as volatile fatty acids and the other kinds of dissolved organic matter. Furthermore, the cooperation of Ni2+, Co2+ and Fe2+ enhanced the activity of the enzyme system in methanogens, promoting methane production. The results in this paper show that coffee husks have clear biogas potential through anaerobic digestion, and its effective utilization could fulfill the dual purpose of solid waste reclamation and local environmental protection in Ethiopia.

Effects of dissolved oxygen concentrations on a bioaugmented sequencing batch rector treating aniline-laden wastewater: Reactor performance, microbial dynamics and functional genes.

This work compared the efficiencies and internal reasons for aniline removal in a bioaugmented sequencing batch reactor at elevated dissolved oxygen (DO) concentrations. Nearly complete aniline removal was achieved while medium DO of 2.65 mg/L was optimal for subsequent nitrogen removal via heterotrophic nitrification-aerobic denitrification. Apart from the highest bacterial diversity richness, favorable DO condition largely enriched putatively aniline degrader, nitrifiers and denitrifiers. Further evidence from qPCR confirmed that moderate DO significantly stimulated the functional genes including aniline degrading gene tad, nitrifying genes amoA, hao, and denitrifying genes nirS and napA, respectively. This study indicates that the significant enrichment of key microorganisms and effective functional genes under optimal DO is the inner mechanism for reliable aniline degradation and subsequent nitrogen removal in the activated sludge reactor.