Photo-oxidation of cork manufacturing wastewater

Several photo-activated processes have been investigated for oxidation of a cork manufacturing wastewater. A comparative activity study is made between different homogeneous (H2O2/UV-Vis and H2O2/Fe2+/UV-Vis) and heterogeneous (TiO2/UV-Vis and TiO2/H2O2/UV-Vis) systems, with degradation performances being evaluated in terms of total organic carbon (TOC) removal. Results obtained in a batch photo-reactor show that photo-catalysis with TiO2 is not suitable for this kind of wastewater while the H2O2/UV-Vis oxidation process, for which the effect of some operating conditions was investigated, allows to remove 39% of TOC after 4 h of operation (for C(H2O2)=0.59 M, pH=10 and T=35 degrees C). The combined photo-activated process, i.e., using both TiO2 and H2O2, yields an overall TOC decrease of 46% (for C(TiO2)=1.0 gl(-1)). The photo-Fenton process proved to be the most efficient, proceeds at a much higher oxidation rate and allows to achieve 66% mineralization in just 10 min of reaction time (for C(H2O2)=0.31 M, T=30 degrees C, Fe2+:H2O2=0.12 (mol) and pH=3.2).     

Application of the Fenton’s process in a bubble column reactor for hydroquinone degradation

The aim of this study was to assess the degradation and mineralization of hydroquinone (HQ) by the Fenton’s process in a bubble column reactor (BCR). The effect of the main operating variables, namely, air flow rate, effluent volume, hydrogen peroxide (H₂O₂) concentration, catalyst (Fe²⁺) dose, initial pH, and temperature, were assessed. For all air flow rates tested, no concentration gradients along the column were noticed, evidencing that a good mixing was reached in the BCR. For the best conditions tested ([H₂O₂] = 500 mg/L, [Fe²⁺] = 45 mg/L, T = 24 °C, Q _air = 2.5 mL/min, pH = 3.0, and V = 5 L), complete HQ degradation was reached, with ~ 39% of total organic carbon (TOC) removal, and an efficiency of the oxidant use—η _H2O2—of 0.39 (ratio between TOC removed per H₂O₂ consumed normalized by the theoretical stoichiometric value); moreover, a non-toxic effluent was generated. Under these conditions, the intermediates and final oxidation compounds identified and quantified were a few carboxylic acids, namely, maleic, pyruvic, and oxalic. As a strategy to improve the TOC removal, a gradual dosage of the optimal H₂O₂ concentration was implemented, being obtained ~ 55% of mineralization (with complete HQ degradation). Finally, the matrix effect was evaluated, for which a real wastewater was spiked with 100 mg/L of HQ; no reduction in terms of HQ degradation and mineralization was observed compared to the solution in distilled water.     

Synthetic olive mill wastewater treatment by Fenton’s process in batch and continuous reactors operation

Degradation of total phenol (TPh) and organic matter, (expressed as total organic carbon TOC), of a simulated olive mill wastewater was evaluated by the Fenton oxidation process under batch and continuous mode conditions. A mixture of six phenolic acids usually found in these agro-industrial wastewaters was used for this purpose. The study focused on the optimization of key operational parameters of the Fenton process in a batch reactor, namely Fe²⁺ dosage, hydrogen peroxide concentration, pH, and reaction temperature. On the assessment of the process efficiency, > 99% of TPh and > 56% of TOC removal were attained when [Fe²⁺] = 100 ppm, [H₂O₂] = 2.0 g/L, T = 30 °C, and initial pH = 5.0, after 300 min of reaction. Under those operational conditions, experiments on a continuous stirred-tank reactor (CSTR) were performed for different space-time values (τ). TOC and TPh removals of 47.5 and 96.9%, respectively, were reached at steady-state (for τ = 120 min). High removal of COD (> 75%) and BOD₅ (> 70%) was achieved for both batch and CSTR optimum conditions; analysis of the BOD₅/COD ratio also revealed an increase in the effluent’s biodegradability. Despite the high removal of lumped parameters, the treated effluent did not met the Portuguese legal limits for direct discharge of wastewaters into water bodies, which indicates that coupled chemical-biological process may be the best solution for real olive mill wastewater treatment.     

Inhibition of mitochondrial bioenergetics by carbaryl is only evident for higher concentrations -- Relevance for carbaryl toxicity mechanisms

Although pesticides have been useful in agriculture pest control, there is a considerable risk for human health and damage to ecosystems. Carbaryl is a carbamate often taken as a safe insecticide, although data on metabolic activities is still scarce, viz. mitochondrial toxicity. Therefore, it is the goal of this work to assay the compound on isolated mitochondria, a biochemical model already used with other pesticides. Mitochondria isolated from the livers of Wistar rats were assayed for bioenergetic parameters, namely mitochondrial respiration, membrane potential, membrane integrity and enzyme activities. For higher concentrations, it was observed that carbaryl has a depressive effect on mitochondrial respiration and on the generation of mitochondrial membrane potential, but with preservation of membrane integrity. A locus between Complex II and III appears particularly affected and the mitochondrial phosphorylation system relatively insensitive. Therefore, carbaryl inhibits mitochondrial respiration without affecting the phosphorylation complex. Carbaryl is toxic for mitochondria, although at concentrations higher as compared with other insecticide compounds. Mitochondrial toxicity should be excluded as one of the primary causes for carbaryl immediate toxicity, as concluded from the range of concentrations where carbaryl shows effective mitochondrial toxicity.     

An assessment of the chemical composition of precipitation and throughfall in rural-industrial gradient in wet subtropics (southern Brazil)

The chemical composition of bulk precipitation and throughfall were analyzed, during a 1-year period (2002), in rural-urban-industry gradients with similar forest cover (Eucalyptus spp.) in southern Brazil (Rio Grande and Porto Alegre cities). Values of pH varied from 5.0-5.1 in rural to 5.4-6.1 in industrial sites, and were intermediate in urban sites. The major ions in bulk precipitation were Na(+), Cl(-), [Formula: see text], [Formula: see text] and [Formula: see text], and concentrations increased in urban and industrial sites. Principal component analysis identified the local main anthropogenic sources. Estimated annual amounts of dry deposition were generally greater in both industrial and urban sites than in rural sites. Areas close to industrial activity showed greater S and N total deposition (10.4-10.9 and 20.2-30.6 kg/ha, respectively) than in urban (3.4-7.3 and 14.6-24.1 kg/ha) and in rural (1.7-2.6 and 8.9-12.1 kg/ha) sites. Annual deposition of Ca and P varied from 0.6 and 3.0 kg/ha in rural to 45.4 and 32.4 kg/ha in industrial sites, maximum values being observed closed to the phosphate fertilizer plant of Rio Grande. Deposition in urban and industrial sites may be balanced by the alkaline cations, as bulk precipitation pH varied from 5.4 to 6.1, and was greater than in rural sites (5.0-5.1).     

Macroalgae mitigation potential for fish aquaculture effluents: an approach coupling nitrogen uptake and metabolic pathways using Ulva rigida and Enteromorpha clathrata

Aquaculture effluents are rich in nitrogen compounds that may enhance local primary productivity, leading to the development of algae blooms. The goal of this study was to assess the potential use of naturally occurring green macroalgae (Ulva and Enteromorpha) as bioremediators for nitrogen-rich effluents from a fish aquaculture plant, by evaluating their respective uptake dynamics under controlled conditions. Ulva and Enteromorpha were incubated separately in aquaculture effluent from a local pilot station. Algae tissue and water samples were collected periodically along 4 h. For each sample, nitrate, nitrite, and ammonia concentrations were quantified in the effluent, while internal algae reserve pools and nitrate reductase activity (NRA) were determined within the algae tissues. Both macroalgae absorbed all dissolved inorganic nitrogen compounds in less than 1 h, favoring ammonia over nitrate. Ulva stored nitrate temporarily as an internal reserve and only used it after ammonia availability decreased, whereas Enteromorpha stored and metabolized ammonia and nitrate simultaneously. These distinct dynamics of ammonia and nitrate uptake supported an increase in NRA during the experiment. This study supports the hypothesis that Ulva or Enteromorpha can be used as bioremediators in aquaculture effluents to mitigate excess of dissolved inorganic nitrogen.     

Effects of a constructional intervention on airborne and deposited particulate matter in the Portuguese National Tile Museum, Lisbon

In the 1970s, a large ambulatory of the National Tile Museum, Lisbon, was closed with glass panes on both ground and first floor. Although this design was meant to protect the museum collection from ambient air pollutants, small openings between the glass panes remain, creating a semi-enclosed corridor. The effects of the glass panes on the indoor air quality were evaluated in a comparative study by monitoring the airborne particle concentration and the extent of particle deposition at the enclosed corridor as well as inside the museum building. Comparison of the indoor/outdoor ratio of airborne particle concentration demonstrated a high natural ventilation rate in the enclosed corridor as well as inside the museum building. PM₁₀ deposition velocities on vertical surfaces were estimated in the order of 3?×?10^?4 m s^?1 for both indoor locations. Also, the deposition rates of dark-coloured and black particles in specific were very similar at both indoor locations, causing visual degradation. The effectiveness of the glass panes in protecting the museum collection is discussed.     

Risk of exposure to Hg and pesticides residues in a traditional fishing community in the Amazon: a probabilistic approach based on dietary pattern

Exposure to mercury (Hg) and pesticides (o.p’DDT, p.p’DDT, o.p’DDE, and p.p’DDE) in the Amazon through eating fish is of concern due to the large participation of this food in the diet of traditional fishing communities. The aim of this study was to evaluate the estimated daily intake (EDI) and the incremental lifetime cancer risk associated with Hg and o.p’DDT, p.p’DDT, o.p’DDE, and p.p’DDE in an Amazonian community. The results showed that for Hg, the EDI from carnivorous and detritivorous fish had the highest values, while for pesticides, the EDI from detritivorous fish intake had the highest value. The incremental lifetime cancer risk was below the permitted limit. A recommendation for controlling the high risk of exposure includes the reduction of detritivorous fish ingestion and/or replacement with herbivorous fish, which had lower EDI. We highlight the importance of investigating the human dietary patterns when estimating risk of exposure to Hg and pesticides.