Marco S. Lucas

Removal of COD from olive mill wastewater by Fenton's reagent: kinetic study.

This work describes the application of Fentons reagent (H(2)O(2)/Fe(2+)) to the removal of chemical oxygen demand (COD) from olive mill wastewater (OMW) in a laboratory-scale batch reactor. The effect of different operational conditions, namely, hydrogen peroxide and ferrous ion concentrations, temperature and initial pH were evaluated. ORP, pH and dissolved oxygen were on-line monitored. Working with an initial pH equal to 3.5, a temperature of 30 degrees C, a molar ratio H(2)O(2)/Fe(2+)=15 and a weight ratio R=H(2)O(2)/COD=1.75 makes possible a COD conversion of 70%. A kinetic study was carried out using a modified pseudo-first-order model. The experiments performed at different temperatures allowed the calculation of the Arrhenius equation parameters and the global activation energy for the pseudo-first-order reaction (28.2 kJ/mol).

Mature landfill leachate treatment by coagulation/flocculation combined with Fenton and solar photo-Fenton processes

This work reports the treatment of a mature landfill leachate through the application of chemical-based treatment processes in order to achieve the discharge legal limits into natural water courses. Firstly, the effect of coagulation/flocculation with different chemicals was studied, evaluating the role of different initial pH and chemicals concentration. Afterwards, the efficiency of two different advanced oxidation processes for leachate remediation was assessed. Fenton and solar photo-Fenton processes were applied alone and in combination with a coagulation/flocculation pre-treatment. This physicochemical conditioning step, with 2 g L(-1) of FeCl3 · 6H2O at pH 5, allowed removing 63% of COD, 80% of turbidity and 74% of total polyphenols. Combining the coagulation/flocculation pre-treatment with Fenton reagent, it was possible to reach 89% of COD removal in 96 h. Moreover, coagulation/flocculation combined with solar photo-Fenton revealed higher DOC (75%) reductions than single solar photo-Fenton (54%). In the combined treatment (coagulation/flocculation and solar photo-Fenton), it was reached a DOC reduction of 50% after the chemical oxidation, with 110 kJ L(-1) of accumulated UV energy and a H2O2 consumption of 116 mM. Toxicity and biodegradability assays were performed to evaluate possible variations along the oxidation processes. After the combined treatment, the leachate under study presented non-toxicity but biodegradability increased.

Microbiological and physicochemical characterization of olive mill wastewaters from a continuous olive mill in Northeastern Portugal

The microbiological and physicochemical characterization of samples from the different wastewaters generated during oil extraction in a continuous olive mill was performed. The main aim was to determine which of the physicochemical parameters were the best fitted to correctly characterize these residual waters. High correlations were obtained for COD, DOC, K, P and N contents with the sampling points, allowing the distinction of olive washing waters (OWW) from olive centrifuge waters (OCW) and olive mill wastewaters (OMW). These parameters were sufficient for a rapid and less costly chemical characterization of these waters. Phenols and oil and grease contents, together with low pH and dissolved oxygen contents, and high organic loads, were the most toxic for microbial populations. Microbial characterization showed that fungi were well adapted to these stressing environmental characteristics and the reuse of OMW after aerobic treatment with microbial species isolated from the effluent is considered.

Ozonation kinetics of winery wastewater in a pilot-scale bubble column reactor

The degradation of organic substances present in winery wastewater was studied in a pilot-scale, bubble column ozonation reactor. A steady reduction of chemical oxygen demand (COD) was observed under the action of ozone at the natural pH of the wastewater (pH 4). At alkaline and neutral pH the degradation rate was accelerated by the formation of radical species from the decomposition of ozone. Furthermore, the reaction of hydrogen peroxide (formed from natural organic matter in the wastewater) and ozone enhances the oxidation capacity of the ozonation process. The monitoring of pH, redox potential (ORP), UV absorbance (254 nm), polyphenol content and ozone consumption was correlated with the oxidation of the organic species in the water. The ozonation of winery wastewater in the bubble column was analysed in terms of a mole balance coupled with ozonation kinetics modeled by the two-film theory of mass transfer and chemical reaction. It was determined that the ozonation reaction can develop both in and across different kinetic regimes: fast, moderate and slow, depending on the experimental conditions. The dynamic change of the rate coefficient estimated by the model was correlated with changes in the water composition and oxidant species.

Tertiary treatment of pulp mill wastewater by solar photo-Fenton.

This work reports on pulp mill wastewater (PMW) tertiary treatment by Fenton (Fe(2+)/H(2)O(2)) and solar photo-Fenton (Fe(2+)/H(2)O(2)/UV) processes in a pilot plant based on compound parabolic collectors (CPCs). Solar photo-Fenton reaction is much more efficient than the respective dark reaction under identical experimental conditions. It leads to DOC mineralisation, COD and total polyphenols (TP) removal higher than 90%. The solar photo-Fenton experiment with 5mg Fe L(-1) reaches 90% of DOC mineralisation with 31kJ L(-1) of UV energy and 50mM of H(2)O(2). The initial non-biodegradability of PMW, as shown by respirometry assays and BOD(5)/COD ratio, can be changed after a solar photo-Fenton treatment. Experiments with 20 and 50mg Fe L(-1) revealed that solar photo-Fenton can reach the same DOC degradation (90%), however, consuming less H(2)O(2) and time. Diluting the initial organic load to 50% also diminishes the dosage of H(2)O(2) and the necessary reaction time to achieve high DOC removals. Accordingly, solar photo-Fenton can be considered an alternative or complementary process to improve the performance of a biologic treatment and, subsequently, achieve legal limits on discharge into natural waters.

Solar Photochemical Treatment of Winery Wastewater in a CPC Reactor

Degradation of simulated winery wastewater was studied in a pilot-scale compound parabolic collector (CPC) solar reactor. Total organic carbon (TOC) reduction by heterogeneous photocatalysis (TiO(2)) and homogeneous photocatalysis with photo-Fenton was observed. The influence of TiO(2) concentration (200 or 500 mg/L) and also of combining TiO(2) with H(2)O(2) or Na(2)S(2)O(8) on heterogeneous photocatalysis was evaluated. Heterogeneous photocatalysis with TiO(2), TiO(2)/H(2)O(2) and TiO(2)/S(2)O(8)(2-) is revealed to be inefficient in removing TOC, originating TOC degradation of 10%, 11% and 25%, respectively, at best. However, photo-Fenton experiments led to 46% TOC degradation in simulated wastewater prepared with diluted wine (WV) and 93% in wastewater prepared with diluted grape juice (WG), and if ethanol is previously eliminated from mixed wine and grape juice wastewater (WW) by air stripping, it removes 96% of TOC. Furthermore, toxicity decreases during the photo-Fenton reaction very significantly from 48% to 28%. At the same time, total polyphenols decrease 92%, improving wastewater biodegradability.

Treatment of crystallized-fruit wastewater by UV-A LED photo-Fenton and coagulation-flocculation.

This work reports the treatment of crystallized-fruit effluents, characterized by a very low biodegradability (BOD5/COD <0.19), through the application of a UV-A LED photo-Fenton process. Firstly, a Box-Behnken design of Response Surface Methodology was applied to achieve the optimal conditions for the UV-A LED photo-Fenton process, trying to maximize the efficiency by saving chemicals and time. Under the optimal conditions ([H2O2] = 5459 mg/L; [Fe(3+)] = 286 mg/L; time >180 min), a COD removal of 45, 64 and 74% was achieved after 360 min, using an irradiance of 23, 70 and 85 W/m(2) respectively. Then a combination of UV-A LED photo-Fenton with coagulation-flocculation-decantation attained a higher COD removal (80%), as well as almost total removal of turbidity (99%) and total suspended solids (95%). Subsequent biodegradability of treated effluents increased, allowing the application of a biological treatment step after the photochemical/CFD with 85 W/m(2).

Winery wastewater treatment by combination of Cryptococcus laurentii and Fenton's reagent.

Winery wastewaters (WW) have high levels of organic matter, resulting in high COD and BOD and suspended solids. This paper studies the combination of biological and chemical processes in WW treatment. Among 10 yeast isolates, Filobasidium sp. (AGG 577) and Cryptococcus laurentii (AGG 726) were selected due to their superior performance in COD removal. During WW degradation, COD and total polyphenols (TPP) content removal of 89-90% for Filobasidium sp. and 90-93% for C. laurentii were obtained. However, despite similar degradation efficiency for both yeasts, COD kinetics and pH evolution during treatment reveals that C. laurentii presents a faster response than Filobasidium sp. The toxicity (inhibition of Vibrio fischeri luminescence) of C. laurentii treated WW decreases to an inhibition value below 2.5%. However, treated WW exceeds the legal limits, making necessary an additional treatment. In this case, the selection of Fentons reagent as a chemical final polish step process is a good compromise between efficiency and lower practical complexity. The best results for both COD and TPP removal were obtained with H2O2 initial concentration of 39.2mM and a H2O2:Fe(2+) molar ratio of 15:1. The combined C. laurentii - Fentons reagent treatment of WW achieved a total reduction of 98% and 96%, for COD and TPP, respectively.

Treatment of olive mill wastewater by a combined process: Fenton's reagent and chemical coagulation.

Olive mill wastewater (OMW) was exposed to Fenton treatment and subjected to post Fenton coagulation/flocculation using lime. Several tests were performed for different R = H2O2/COD ratios, from 0.25 to 3.0, promoting the gradual addition of H2O2 and Fe2 +, with the original condition of a pH = 3.5 and maintaining a constant relationship H2O2/Fe2 + = 15. A maximum reduction of COD of 96.8% was obtained using Fenton reagent with R = 3.0. In a second phase, the effluent which was neutralized with Ca(OH)2 reached a higher reduction of COD, achieving a final degradation value of 99.3%. Overall, the results show evidence of the potential value of applying the combined process tested.

Gallic acid photochemical oxidation as a model compound of winery wastewaters

Winery wastewaters (WW) are characterized by their high organic load and by the presence of non-biodegradable compounds such as phenolic compounds. This study was undertaken to evaluate the capacity of different Advanced Oxidation Processes (AOP) combined with several radiation sources to degrade the phenolic compound Gallic Acid (GA). A toxicological assessment was also carried out to evaluate the subproducts harmful effect generated during the most efficient AOP in the GA photoxidation. Through the course of the study it was verified that the UV radiation lamp TNN 15/32 showed the capacity to degrade 34.7% of GA, the UV radiation lamp TQ 150 achieved a value of 20.2% and the solar radiation presented only a value of 2.3% in 60 minutes. The combination of different advanced oxidation processes (Fentons reagent, ferrioxalate and heterogeneous photocatalysis) were evaluated with the previously studied sources of radiation. From the experiments conducted it was possible to suggest that the AOP in combination with Fe2 + + H2O2 + UV TNN 15/32 (photo-Fenton process) was the most efficient process thereby achieving the GA degradation value of 95.6% in 7.5 minutes and resulting in a total elimination of toxicity.