Influence of metronidazole on activated sludge activity.

Metronidazole is potentially carcinogenic to humans and it has been detected in wastewaters. The Wastewater Treatment Plants using biological processes have been highly impacted by the emergent compounds of recalcitrant type, and the knowledge about that issue is quite relevant. Therefore, this paper was focused on how metronidazole influences the kinetics and metabolic behaviour of nitrification and heterotrophic activity on activated sludge in batch cultures. Eight concentrations of metronidazole in the range of 5-100 mg/L were evaluated, in the presence of 2109 ± 129 mg VSS/L. The increment of initial metronidazole concentration caused a decline on COD and ammonium removal efficiencies, nitrate production yields, as well as in the substrate-specific consumption rates. Metronidazole (MDZ) had a greater impact on heterotrophic activity than nitrifying activity; also, it had a greater inhibitory effect on nitrite oxidation than ammonium oxidation. The activated sludge was not able to biotransform metronidazole; however, the azole compound significantly affected the physiology of it. The inhibition of ammonium oxidation was non-competitive (qmax = 120 mg NH4+-N consumed/gVSS-d, and Ki = 41.5 mg MDZ/L) and the initial metronidazole concentration that inhibited 50% of nitrifying activity (IC50) was 43 mg MDZ/L.

Copper removal from wastewater by a chitosan-based biodegradable composite.

This work demonstrates that a biodegradable chitosan-based biocomposite packed in mini-reactors successfully removes copper ions from aqueous solutions. The chitosan is obtained by deacetylation of biological chitin, which is extracted from shrimp wastes by lactic acid fermentation. The polysaccharide is embedded in a biodegradable prepolymer matrix before extrusion to produce porous cylindrical pellets of 2 × 80 mm. The highest copper ion removal is 62.5 mg Cu2+ per g of the biodegradable adsorbent. Additionally, the adsorption capacity of the material, below its saturation, allows several cycles of reuse with a hydraulic retention time reduction of 1 h. This chitosan-based material is advantageous when compared with other approaches using non-biodegradable materials or costly commercial adsorbents for removing heavy metal ions in wastewater effluents as well as a filter component in water purification devices.