María P. Ormad

Evaluation of trihalomethane formation potential in function of oxidation processes used during the drinking water production process.

The presence of natural organic matter (NOM) in both surface and groundwater supplies produces toxic by-products, mainly trihalomethanes (THMs), during oxidation steps in drinking water production. This research work shows the efficiency of different advanced oxidation processes (AOPs) based on ozone for the degradation of precursors of trihalomethanes in aqueous solutions. Completed treatments comprised different preoxidation processes (chlorination and AOP: O(3), O(3)/H(2)O(2), O(3)/TiO(2) and O(3)/H(2)O(2)/TiO(2)), adsorption with PAC (optional operation), coagulation-flocculation and final postchlorination applied to synthetic samples which were prepared by dilution of the soluble fraction of a humic solution. A direct chlorination of synthetic humic samples which display dissolved organic carbon close to 3 mg l(-1) produced a THM concentration of around 1600 microg CCl(3)l(-1) (measured as THMFP). Comparisons between the trihalomethane formation potential of initial synthetic samples and samples treated by prechlorination and coagulation-flocculation-decantation show that the main factor responsible for THM reduction is the coagulation-flocculation process since a decrease of 90% is achieved. Considering the various completed treatments studied, the most recommendable include preoxidation by ozonation, adsorption by PAC, coagulation-flocculation using aluminium sulphate followed by decantation and final postchlorination.

Bactericidal Effectiveness of O3, O3/H2O2 and O3/TiO2 on Clostridium perfringens

The purpose of this research is to evaluate the bactericidal capacity of different Advanced Oxidation Treatments (AOTs) based on ozone: ozone, ozone/hydrogen peroxide and ozone/titanium dioxide on a wild strain of Clostridium perfringens, a fecal bacterial indicator in drinking water. The dose of ozone consumed ranges from 0.6 mg L−1 min−1 to 5.13 mg L−1 min−1 depending on the process and on the sample. In the treatments combined with O3, H2O2 dose utilized is 0.04 mM and TiO2 dose, 1 g L−1. In order to evaluate the influence of natural organic matter and suspension solids over the disinfection rate, treatments are performed with two types of water – natural water from Ebro River (Zaragoza, Spain) and NaCl solution 0.9%. To achieve 4 log units of inactivation, 3.6 mg O3 L−1 is necessary in O3 treatment, 4.25 mg O3 L−1 in O3/TiO2 system and 2.7 mg O3 L−1 in O3/H2O2 after processing the natural water. In NaCl solution, to get the same inactivation, 0.42 mg O3 L−1 is necessary in O3 treatment, 1.15 mg O3 L−1 in O3/TiO2 system and 0.06 mg O3 L−1 in O3/H2O2 process. Even though the three treatments studied have a high bactericidal activity due to the number of surviving bacteria decreases to non-detectable levels, O3/H2O2 is the most effective system for eliminating C. perfringens cells in a lower contact time, followed by O3 and finally O3/TiO2 system.

Photocatalytic Degradation of Pesticides in Natural Water: Effect of Hydrogen Peroxide

The aim of this paper is to evaluate the effectiveness of photocatalytic treatment with titanium dioxide in the degradation of 44 organic pesticides analyzed systematically in the Ebro river basin (Spain). The effect of the addition of hydrogen peroxide in this treatment is studied, and a monitoring of effectiveness of photocatalytic processes is carried out by measurements of physical-chemical parameters of water. The application of photocatalytic treatment with 1 g L−1 of TiO2 during 30 minutes achieves an average degradation of the studied pesticides of 48%. Chlorine demand, toxicity, and dissolved organic carbon (DOC) concentration of water are reduced. If hydrogen peroxide is added with a concentration of 10 mM, the average degradation of pesticides increases up to 57%, although chlorine demand and toxicity of water increase while DOC concentration remains unchanged with this treatment. The application of either photocatalytic treatments does not produce variations in the physical-chemical parameters of water, such as pH, conductivity, colour, dissolved oxygen, and hardness. The pesticides which are best degraded by photocatalytic treatments are parathion methyl, chlorpyrifos, α-endosulphan, 3,4-dichloroaniline, 4-isopropylaniline, and dicofol while the worst degraded are HCHs, endosulphan-sulphate, heptachlors epoxide, and 4,4′-dichlorobenzophenone.

Freshwater sediment quality in Spain

This study was carried out to evaluate sediment pollution related to trace elements such as Cd, Cu, Ni, Pb, Zn, Hg, As and Cr and eight polycyclic aromatic hydrocarbons (PAHs) in 127 sites located in 85 rivers in Spain. Sediment samples were classified according to similar chemical characteristics by means of statistical multivariate techniques (principal component analysis, PCA) and artificial neural networks such as self-organizing maps (SOM). Sediment sample classification provided by PCA was not as useful as the one provided by the SOM, revealing itself as a powerful tool to be incorporated in the first steps of sediment quality assessments. The use of sediment quality guidelines such as the mean-probable effects concentration quotient (m-PECQ) predicted sediment quality and gave an overall view of sediment pollution throughout Spain. Most of the samples (118 out of 127) showed m-PECQ values below 0.5 highlighting their relative low potential risk to cause adverse effects on the benthic fauna. However, some samples presented m-PECQ values higher than 0.5 suggesting a clear potential risk to these fauna. Besides, unusual high concentrations of trace elements and PAHs were related to the human activities carried out near each sampling point.

Identification of pathogen bacteria and protozoa in treated urban wastewaters discharged in the Ebro River (Spain): water reuse possibilities

The aim of this research work is to identify the presence of pathogens, bacteria and protozoa, in different treated urban wastewaters and to relate biological pollution with the processes used in wastewater treatment plants. A study of the possibilities for water reuse is carried out taking into account bacterial and parasite composition. The analysed bacteria and protozoa are: Enterococcus faecalis, Pseudomonas aeruginosa, Staphylococcus aureus, Clostridium perfringens (spore), Salmonella spp., Legionella spp., helminths eggs, Giardia, Cryptosporidium spp. and free-living amoebae (FLA). The selected municipal wastewater treatment plants (MWTPs) are located in Navarra (Spain) and the main difference between them is the use of natural lagoons as tertiary treatment in some plants. The results concerning bacteriological identification showed contamination of mainly faecal origin, and the use of natural lagoons as tertiary treatment in some MWTPs produced an important disinfection effect. Moreover, pathogen parasites such as Giardia and Cryptosporidium were not detected in the samples studied although FLA were identified in all cases.

Potential Toxicity of Polycyclic Aromatic Hydrocarbons and Organochlorine Pesticides in Sediments from the Ebro River Basin in Spain

This study was carried out to estimate the potential toxicity of 8 Polycyclic Aromatic Hydrocarbons (PAHs) and 5 organochlorine pesticides (OCPs) in sediments in the Ebro River Basin (20 sampling points) according to different methodologies. Detection limit (DL) concentrations were used for compounds reported below the DL (worst-case scenario). The majority of PAH concentrations were found to be below their method detection limit. DL concentrations for OCPs were above the threshold values set by one guideline. In such cases, no toxicity assessment was carried out. It should be noted that no sediment is expected to cause adverse effects on the benthic species living in these sediments according to the methodologies applied.

Combined photo-fenton-SBR processes for the treatment of wastewater from the citrus processing industry.

In this study, the photo-Fenton process was combined with a sequencing batch reactor (SBR) for the treatment of synthetic samples of citrus wastewater (CWW). An experimental design based on the surface response methodology was applied to assess the individual and combined effects of several operating parameters (CODinitial, Fe3(+) concentration and H2O2 concentration) on the photo-Fenton treatment efficiency (DOC removal) with the aim of optimizing the process. The experimental results obtained under optimal conditions for CWW with high CODinitial (10000 mgO2/L) showed a partial degradation of organic matter of around of 61% (measured as DOC). Thereafter, the photo-Fenton effluent was neutralized and clarified before being subjected to the SBR reactor. The results show degradation yields up to 93% of the initial DOC removal without producing undesired side effects, using a hydraulic retention time (HRT) of 1.59 d. The final effluent contained a concentration of organic matter (measured as COD) of 120 mg O2/L.

Treatment of Wastewater Coming from Painting Processes: Application of Conventional and Advanced Oxidation Technologies

The process of car body painting is one of the manufacturing processes that may involve the use of organic solvents for surface treatments. As a result of this process, wastewaters containing raw materials and auxiliary products used during the cleaning step are produced. The main objective of this study is to find an appropriate purification technique to eliminate or reduce the contamination present in this kind of wastewater. Different treatments were investigated: ozonation, ozonation combined with hydrogen peroxide, photo-Fenton treatment, and coagulation- flocculation.

Bioaccumulation of pathogenic bacteria and amoeba by zebra mussels and their presence in watercourses.

Dreissena polymorpha (the zebra mussel) has been invading freshwater bodies in Europe since the beginning of the nineteenth century. Filter-feeding organisms can accumulate and concentrate both chemical and biological contaminants in their tissues. Therefore, zebra mussels are recognized as indicators of freshwater quality. In this work, the capacity of the zebra mussel to accumulate human pathogenic bacteria and protozoa has been evaluated and the sanitary risk associated with their presence in surface water has also been assessed. The results show a good correlation between the pathogenic bacteria concentration in zebra mussels and in watercourses. Zebra mussels could therefore be used as an indicator of biological contamination. The bacteria (Escherichia coli, Enterococcus spp., Pseudomonas spp., and Salmonella spp.) and parasites (Cryptosporidium oocysts and free-living amoebae) detected in these mussels reflect a potential sanitary risk in water.

Inactivation of Enterococcus sp. by Conventional and Advanced Oxidation Processes in Synthetic Treated Urban Wastewater

The aim of this research work was to evaluate the disinfection efficiency of several techniques on the inactivation of the bacteria Enterococcus sp. inoculated in synthetic treated urban wastewater. Different types and doses of reagents and times of exposure were studied. The compared treatments include chlorination, ozone-based treatments in the absence and presence of H2O2 and UVA-visible irradiation-based processes with TiO2 and H2O2. Different combinations of chlorine doses and times of contact inactivated all the bacteria (-7.5 log units). Ozone and O3/H2O2 also achieved high disinfection levels (-6 log units), showing similar inactivation curves. However, the studied phototreatments were less efficient.