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Constructed wetlands (CWs) have increasingly been developed worldwide for stormwater and wastewater treatment. In this context, CWs have been seen as an economically attractive, energy-efficient way of providing high standards of wastewater treatment. In the present study, a CWS has specifically been designed and operated for domestic wastewater treatment. The removal efficiency of basic pollutants was evaluated in the CWs under free water surface (FWS) and horizontal subsurface flow conditions, employing two native species: Paspalum paniculatum and Thalia geniculata. The experimental results showed that the retention time throughout the treatments varied from 6.5 to 7.5 days; while temperatures of approximately 26°C were observed to reduce the load of pollutants. The experimental tests were highly effective for the wastewater treatment since the removal efficiencies of biological oxygen demand (BOD), chemical oxygen demand (COD), total suspended solids, total nitrogen, and total phosphorus were found to be in the range of 79%-94%. The experimental data were statistically analyzed by the ANOVA approach and Tukey´s test. The treatments showed highly significant statistical differences (P<0.05). From the operating cost standpoint, the current native vegetation was proven to be satisfactory for wastewater treatment in tropical regions of Mexico.

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Constructed wetlands (CW) are efficient wastewater treatment technologies with low energy consumption. A constructed wetland with horizontal sub-surface flow was designed at a pilot scale involving Thalia geniculate as vegetation, with a wastewater loading rate of 204±66 L/day, using gravel as inert medium with a porosity and density of n= 56.3 ± 3.5 and 1666.7 ± 119.3 kg/m3, respectively. The reactor allows the biological treatment of 0.85 ± 0.05 and 0.66 ± 0.05 m3 of wastewater, with 4.2 days as a hydraulic retention time, favoring the removal of 85% of the average values of BOD with a k of-0.43 days-1. The pollutant analysis showed a pH value of 7.5 ± 0.1 in the reactor. The temperature (30.44 to 28.32°C), the electrical conductivity (4010 to 2922 μS/cm), the turbidity (144 to 17 UTN) and the bacterial biomass (30000 to 2646 mg/kg) decreased substantially from inlet to oulet across the reactor. The efficiency of the wastewater treatment in the CW is notable, nevertheless, keeping the appropiate hydraulic retention time is important in order to fully comply with the maximum permissible limits of 30 mg/L established in the Mexican environmental legislation (NOM-001-SEMARNAT-1996).

The anodization of titanium has been an excellent option for protecting titanium and its alloys from corrosive environments such as acids and chloride systems, by generating a homogenous oxide layer. The objective of the current investigation was to evaluate the electrochemical corrosion behavior of alloys Ti-6Al-2Sn-4Zr-2Mo and Ti-6Al-4V anodized in 1M H2SO4 and H3PO4 solutions at a current density of 2.5 × 10–3 A/cm2. The anodization’s electrochemical characterization was achieved in NaCl and H2SO4 at 3.5% wt. electrolytes. Scanning electron microscopy (SEM) was employed to determine the anodized thickness and morphology. Cyclic potentiodynamic polarization (CPP) and electrochemical impedance spectroscopy (EIS), based on ASTM G61-86 and G106-15 Standards, were the electrochemical techniques mainly employed. The anodized samples presented a change in Ecorr values and a higher passivation zone. The EIS plot showed a higher resistance for samples anodized in H3PO4 and Ti-6Al-2Sn-4Zr-2Mo.