Novel insights into the co-metabolism of pyridine with different carbon substrates: Performance, metabolism pathway and microbial community.

Pyridine is a widely employed nitrogen-containing heterocyclic organic, and the discharge of pyridine wastewater poses substantial environmental challenges due to its recalcitrance and toxicity. Co-metabolic degradation emerged as a promising solution. In this study, readily degradable glucose and the structurally analogous phenol were used as co-metabolic substrates respectively, and the corresponding mechanisms were thoroughly explored. To treat 400 mg/L pyridine, all reactors achieved remarkably high removal efficiencies, surpassing 98.5%. And the co-metabolism reactors had much better pyridine-N removal performance. Batch experiments revealed that glucose supplementation bolstered nitrogen assimilation, thereby promoting the breakdown of pyridine, and resulting in the highest pyridine removal rate and pyridine-N removal efficiency. The high abundance of Saccharibacteria (15.54%) and the enrichment of GLU and glnA substantiated this finding. On the contrary, phenol delayed pyridine oxidation, potentially due to its higher affinity for phenol hydroxylase. Nevertheless, phenol proved valuable as a carbon source for denitrification, augmenting the elimination of pyridine-N. This was underscored by the abundant Thauera (30.77%) and Parcubacteria (7.21%) and the enriched denitrification enzymes (narH, narG, norB, norC, and nosZ, etc.). This study demonstrated that co-metabolic degradation can bolster the simultaneous conversion of pyridine and pyridine-N, and shed light on the underling mechanism.

Electro-Fenton treatment of mature landfill leachate in a continuous flow reactor.

The treatment of mature landfill leachate by EF-Fere (also called Fered-Fenton) method was carried out in a continuous stirred tank reactor (CSTR) using Ti/RuO(2)-IrO(2)-SnO(2)-TiO(2) mesh anodes and Ti mesh cathodes. The effects of important parameters, including initial pH, inter-electrode gap, H(2)O(2) to Fe(2+) molar ratio, H(2)O(2) dosage and hydraulic retention time, on COD removal were investigated. The results showed that the complete mixing condition was fulfilled in the electrochemical reactor employed in this study and COD removal followed a modified pseudo-first order kinetic model. The COD removal efficiency increased with the decrease of H(2)O(2) to Fe(2+) molar ratio and hydraulic retention time. There existed an optimal inter-electrode gap or H(2)O(2) dosage so that the highest COD removal was achieved. Nearly the same COD removal was obtained at initial pH 3 and 5, but the steady state was quickly achieved at initial pH 3. The organic pollutants in the leachate were analyzed through a gas chromatography coupled with mass spectrometry (GC-MS) system. About 73 organics were detected in the leachate, and 52 of which were completely removed after EF-Fere process.

Application of experimental design methodology to the decolorization of Orange II using low iron concentration of photoelectro-Fenton process.

The influence of different variables in the photoelectro-Fenton process for the decolorization of Orange II was investigated using an experimental design methodology. The variables considered in this study include electrical current, Fe(3+) concentration, H(2)O(2) concentration and initial pH. Response factors were decolorization efficiencies after 30, 90 and 120 min of reaction time, for an initial dye concentration of 100 mg/L. The positive and negative effects of variables and the interaction between variables on color removal were determined. The response surface methodology models were derived based on the decolorization efficiency results and the response surface plots were developed accordingly.

Evaluation of electro-oxidation of biologically treated landfill leachate using response surface methodology.

Box-Behnken statistical experiment design and response surface methodology were used to investigate electrochemical oxidation of mature landfill leachate pretreated by sequencing batch reactor (SBR). Titanium coated with ruthenium dioxide (RuO(2)) and iridium dioxide (IrO(2)) was used as the anode in this study. The variables included current density, inter-electrode gap and reaction time. Response factors were ammonia nitrogen removal efficiency and COD removal efficiency. The response surface methodology models were derived based on the results. The predicted values calculated with the model equations were very close to the experimental values and the models were highly significant. The organic components before and after electrochemical oxidation were determined by GC-MS.