Physico-Chemical and Microbiological Control of the Composting Process of the Organic Fraction of Municipal Solid Waste: A Pilot-Scale Experience.

The aim of this work was to carry out a pilot experiment to monitor OFMSW (organic fraction of municipal solid waste) composting processes using different types of installations (automatic reactor, aerated static pile and turned pile). To carry out the process, pruning waste was used as structuring material (SM), in a 1:1 and 1:2, v:v, OFMSW:SM ratio. Monitoring was carried out through the control of physico-chemical and microbiological parameters, such as temperature, pH, humidity, Rottegrade, Solvita tests, the presence of Salmonella sp. and Escherichia coli, total coliform, and Enterococcus sp. concentrations. After carrying out the tests, it can be affirmed that the three types of installations used worked correctly in terms of the monitoring of physico-chemical parameters, giving rise to a compost of sufficient stability and maturity to be applied on agricultural soil. In all cases the bacterial concentrations in the final compost were lower than those detected in the mixture of initial components for its preparation, thus complying with the requirements established in RD 506/2013 and RD 999/2017RD on fertilizer products. However, it cannot be affirmed that one of the three types of installation used produces a greater bacterial inactivation than the others. When composting with different types of facilities, it is of interest to optimize the irrigation and aeration system in order to have a better control of the process and to study the possible temperature gradients in the piles to ensure good sanitization without the risk of bacterial proliferation a posteriori. Finally, the different initial mixtures of OFMSW and SM used in this study did not have a significant influence on the functioning of the composting process or on the microbiological quality during the process. The irrigation water can provide a bacterial contribution that can lead to increases in concentration during the composting process. This study is part of the Life-NADAPTA project (LIFE16 IPC/ES/000001), an integrated strategy for adaptation to Climate Change in Navarra, where NILSA participates in water action and collaborates in agricultural action, which includes among its objectives the development of new soil amendments from different organic waste.

Photoactivation and photoregeneration of TiO2/PAC mixture applied in suspension in water treatments: approach to a real application.

The process TiO2/PAC/UV-vis has been under study and compared with the isolated treatments of adsorption and photocatalysis determining possible synergies between adsorption and photocatalysis of target antibiotics: amoxicillin, enrofloxacin, sulfadiazine, and trimethoprim. The characterization of the TiO2/PAC mixture was carried out via FESEM and FTIR. Moreover, a kinetic study has been performed. The effect of UV-vis radiation and the type of matrix was analyzed in TiO2/PAC/UV-vis process. The performance of this treatment has been monitored during three cycles, evaluating also the regeneration of TiO2/PAC mixture by UV-vis light. TiO2/PAC/UV-vis process allowed the removal of the antibiotics in the range 90-100% (an average removal of 93% of the initial concentration) after 60 min of treatment. However, only amoxicillin showed a significant synergy applying TiO2/PAC/UV-vis process. Regarding matrix effect, no influence of the matrix type (ultrapure water or treated wastewater) was observed. Since PAC tends to be deactivated gradually, the TiO2/PAC/UV-vis process performance decreases after each cycle in a 15% average. Finally, regeneration via UV-vis light started to be effective after a total of 4 h of regeneration.

Comparative adsorption of ciprofloxacin on sugarcane bagasse from Ecuador and on commercial powdered activated carbon.

This work examined the adsorption capacity of sugarcane bagasse (SB) for the removal of ciprofloxacin (CPX) from water using batch experiments and a fixed bed column and compared its adsorption performance with a powdered activated commercial carbon (PAC). Both adsorbents achieved a similar percentage removal of about 78% with doses of 3 g L-1 of SB and 0.3 g L-1 of PAC (20 mg L-1 initial CPX concentration at 30 °C). The maximum removal was obtained at a pH between 6 and 8. SB adsorption isotherms were fitted to the Langmuir, BET and Freundlich models showing a maximum adsorption capacity of 13.6 mg g-1. The kinetic data for both SB and PAC fitted the pseudo second-order model (R2 = 0.99). The adsorption process was faster on the SB (65% of elimination in the first 5 min) than on the PAC. The study of the adsorbent properties shows that SB is a macroporous solid with a specific surface area 250 times smaller than PAC. The thermodynamic results show that SB adsorption was physical and exothermic. The main suggested interactions between CPX and SB are electrostatic attraction, hydrogen bonding and dipole-dipole interactions. The experiments carried out in a fixed bed show that the adsorption capacity at breakthrough increases with the bed height. The adsorption capacity at saturation time was 9.47 mg g-1 at a flow rate of 3 mL min-1, a bed height of 14 cm, and a diameter of 1.5 cm. The experimental data were fitted to the Bohart-Adams model (R2 = 0.98). These results highlight the capacity of sugarcane bagasse to adsorb ciprofloxacin from water, illustrating its potential as a low-cost adsorbent.

Antibiotics removal from aquatic environments: adsorption of enrofloxacin, trimethoprim, sulfadiazine, and amoxicillin on vegetal powdered activated carbon.

This study addresses the growing concern about the high levels of antibiotics in water, outlining an alternative for their removal. The adsorption of four representative antibiotics from commonly used families (fluoroquinolones, ß-lactams, trimethoprim, and sulfonamides) was performed over vegetal powdered activated carbon. The evolution of the adsorption was studied during 60 min for different initial antibiotic concentrations, not only individually but also simultaneously to determine competitive adsorption. Moreover, this research studied the adsorption isotherms and kinetics of the process, as well as the pH influence; FTIR of the activated carbon before and after adsorption was carried out. Trimethoprim and sulfadiazine showed more affinity for the adsorbent than amoxicillin and enrofloxacin. This trend might be attributed to their structure, capable of stablishing stronger π-π interactions with the adsorbent, which showed high affinity for the active sites of the adsorbent via FTIR. In addition, the sorption isotherms of trimethoprim followed a Langmuir type isotherm, amoxicillin followed a Freundlich type isotherm, and enrofloxacin and sulfadiazine followed both. The antibiotics followed pseudo-second-order kinetics. Sulfadiazine and amoxicillin gave better performances in acidic conditions. By contrast, the sorption of trimethoprim was favored in basic environments. Variations of pH had a negligible effect on the removal of enrofloxacin.

Study of Evolution of Microbiological Properties in Sewage Sludge-Amended Soils: A Pilot Experience.

Large amounts of sewage sludge are generated in urban wastewater treatment plants and used as fertilizer in agriculture due to its characteristics. They can contain contaminants such as heavy metals and pathogenic microorganisms. The objective of this research work is to study, in real conditions, the evolution of microbial concentration in agricultural soils fertilized by biologically treated sewage sludge. The sludge (6.25 tons Ha-1) was applied in two agricultural soils with different textures and crops. A microbiological (total coliforms, Escherichia coli, Staphylococcus aureus, Enterococcus sp., Pseudomonas sp., Salmonella sp. and total mesophylls) and physical-chemical characterization of the sludge, soils and irrigation water were carried out. The evolution of these parameters during sowing, growth and harvesting of crops was studied. Initially, sewage sludge had a higher concentration of microorganisms than soils. Irrigation water also contained microorganisms, fewer than sewage sludge amendment but not negligible. After amendment, there were no differences in the microbiological evolution in the two types of soil. In general, bacterial concentrations after crop harvest were lower than bacterial concentrations detected before sewage sludge amendment. Consequently, the application of sludge from water treatment processes did not worsen the microbiological quality of agricultural soil in this study at real conditions.

Identification of free-living amoebas and amoeba-resistant bacteria accumulated in Dreissena polymorpha.

To identify the free-living amoeba (FLA) and amoeba-resistant bacteria (ARB) accumulated in zebra mussels and in the water in which they are found, mussels were collected at two locations in the Ebro river basin (North East Spain). FLAs and bacteria were isolated from mussel extracts and from natural water. PCR techniques were used to identify the FLAs and endosymbiont bacteria (Legionella, Mycobacterium, Pseudomonas and cyanobacteria), and to detect Giardia and Cryptosporidium. The most frequently found FLAs were Naegleria spp. The presence of Legionella, Mycobacterium and Pseudomonas inside the FLA was demonstrated, and in some cases both Legionella and Pseudomonas were found together. Differences between FLAs and ARB identified inside the mussels and in the water were detected. In addition, Escherichia coli, Clostridium perfringens, Salmonella spp. and Enterococcus spp. were accumulated in mussels in concentrations unconnected with those found in water. The results show the ability of the zebra mussel to act as a reservoir of potentially pathogenic FLAs, which are associated with potentially pathogenic ARB, although the lack of association between microorganisms inside the mussels and in the water suggests that they are not useful for monitoring microbiological contamination at a specific time.

Electrochemical oxidation of butyl paraben on boron doped diamond in environmental matrices and comparison with sulfate radical-AOP.

The electrochemical oxidation (EO) of butyl paraben (BP) over boron-doped diamond (BDD) anode was studied in this work. Emphasis was put on degradation performance in various actual water matrices, including secondary treated wastewater (WW), bottled water (BW), surface water (SW), ultrapure water (UW), and ultrapure water spiked with humic acid (HA). Experiments were performed utilizing 0.1 M Na2SO4 as the electrolyte. Interestingly, matrix complexity was found to favor BP degradation, i.e. in the order WW ~ BW > SW > UW, thus implying some kind of synergy between the water matrix constituents, the reactive oxygen species (ROS) and the anode surface. The occurrence of chloride in water matrices favors reaction presumably due to the formation of chlorine-based oxidative species, and this can partially offset the need to work at increased current densities in the case of chlorine-free electrolytes. No pH effect in the range 3-8 on degradation was recorded. EO oxidation was also compared with a sulfate radical process using carbon black as activator of sodium persulfate. The matrix effect was, in this case, detrimental (i.e. UW > BW > WW), pinpointing the different behavior of different processes in similar environments.

Seeking the reuse of effluents and sludge from conventional wastewater treatment plants: Analysis of the presence of intestinal protozoa and nematode eggs.

Some of the microorganisms present in urban wastewater, which include intestinal protozoa and nematodes, can be pathogenic. Their (oo)cyst and egg transmissible stages are very resistant to environmental stresses and disinfectants and they are therefore difficult to remove. Thus, they can constitute a health risk if water or sludge obtained in the purification of wastewater is reused for agricultural purposes. In this context, the presence of intestinal protozoa and nematodes were studied in influents, effluents and sludge from five wastewater treatment plants (WWTPs) in the north of Spain by optical microscopy and PCR techniques. The removal efficiency of different wastewater treatments was also compared. The presence of protozoa has increased among the population discharging waste to WWTPs in recent years. Cryptosporidium spp., Giardia duodenalis, Entamoeba spp. and nematodes were detected in all of the WWTPs. Indeed, this is the first report of Entamoeba histolytica and Entamoeba moshkovskii in Spanish WWTPs. The water treatments studied showed different removal efficiencies for each species of intestinal protozoa, with the aerated lagoons providing the best results. (Oo)cysts were also detected in sludge even after aerobic digestion and dehydration. To avoid risks, (oo)cyst viability should be analysed whenever the sludge is to be used as a fertilizer. This study reinforces the necessity of establishing legal limits on the presence of protozoa in WWTP effluents and sludges, especially if reuse is planned. Further studies are necessary for a better understanding of the presence and behaviour of intestinal parasites.

Performance comparison of commercial TiO2: separation and reuse for bacterial photo-inactivation and emerging pollutants photo-degradation.

This research aims to compare the disinfection and degradation effectiveness in water of a commercial suspension of nano-TiO2 (TiO2Levenger) with the standard TiO2Degussa P25. Photo-inactivation and photo-degradation experiments were conducted with UVA-vis light. Concerning the disinfection, the effects of TiO2 dose (0-2 g/l), water matrix, bacterium type (Gram-positive or Gram-negative), and bacterial regrowth after the photo-treatments were studied for each catalyst. The experimental results show that Enterococcus sp. (Gram-positive) was more resistant to the photo-treatments than Escherichia coli (Gram-negative) for both catalyst; however, postirradiation trends showed similar behavior for both bacteria, favoring regrowth for short-treated cells and decay for longer-treated ones. Caffeine was selected as a model substance of pharmaceuticals and personal care products. In terms of caffeine removal, the effects of TiO2 dose (0-2 g/l) and water matrix were analyzed. Besides, the comparison between mechanical coagulation-flocculation-decantation and simple decantation of TiO2 was carried out. The results show that simple decantation allowed the recovery of 97.5% of TiO2 Degussa P25 and TiO2 Levenger within 1 day of simple decantation, while applying the proposed mechanical coagulation-flocculation decantation 99.7% of recovery of both catalysts was achieved in 2 hours. Finally, the subsequent reuse of both catalysts was proved with little loss of efficiency in terms of photo-disinfection during the four cycles. Nevertheless, the standard TiO2 Degussa P25 photo-degradation efficiency of caffeine decreases considerably as compared to commercial suspension of TiO2 Levenger concerning the reutilization.

Electrochemical advanced oxidation processes for Staphylococcus aureus disinfection in municipal WWTP effluents.

This paper presents the Staphylococcus aureus inactivation in a simulated wastewater treatment plant effluent by different electrochemical techniques, including the photo-electro-Fenton process. S. aureus, dissolved organic carbon (DOC), total oxidants and H2O2 concentrations, as well as pH, were monitored during the assays. An electrolytic cell, including a UVA lamp, a gas diffusion electrode (GDE) as cathode and an IrO2 anode, was used to conduct the experiments under galvanostatic conditions (20 mA). Low inactivation (-0.4) and low DOC removal were achieved within 120 min when applying the GDE-IrO2 system, in which bacteria disinfection was caused by the generated H2O2. When light was combined with GDE-IrO2, the process efficiency noticeably increased (-3.7 log inactivation) due to the synergistic effect between UVA and H2O2. Introducing iron (5 mg L-1 Fe2+) into the system also produced higher disinfection and DOC mineralization. The electro-Fenton process (GDE-IrO2+Fe2+) led to a bacterial reduction of -0.9 log units and DOC reduction of 14%, while with the photo-electro-Fenton process (GDE-IrO2+UVA + Fe2+) -5.2 units of bacteria and 26% of DOC were removed. Increasing the current intensity (20 mA, 30 mA and 40 mA) in the photo-electro-Fenton system increased H2O2 production and, consequently, augmented the bacterial inactivation (-5.2 log, -6.2 log and -6.5 log, respectively). However, mineralization extent slightly increased or remained practically the same. When comparing the influence of Fe2+ and Fe3+ on photo-electro-Fenton, similar S. aureus inactivation was observed, while DOC removal was higher with Fe2+ (31%) than with Fe3+ (19%). Finally, by testing the system with a Ti anode, the direct anodic oxidation contribution of the IrO2 anode was identified as negligible.

Synergistic effect of the presence of suspended and dissolved matter on the removal of cyanide from coking wastewater by TiO2 photocatalysis.

This study assesses the influence of the presence of suspended and dissolved matter on the efficiency of TiO2 photocatalysis for the removal of cyanide from coking wastewater. Photocatalytic processes were carried out at basic pH (pH 9) with titanium dioxide (1 g/L), artificial radiation (290-800 nm) and during different time periods (20-100 min). The first assays applied in aqueous solutions achieved promising results in terms of removing cyanide. The maximum cyanide removal obtained in coking wastewater was 89% after 80 min of irradiation in the presence of suspended and dissolved matter. The presence of suspended matter composed of coal improves the efficiency of the photocatalytic process due to the synergistic effect between carbon and TiO2. The absence of dissolved matter also improves the process due to the minimization of the hydroxyl radical scavenging effect produced by carbonate and bicarbonate ions. On the other hand, the presence of certain species in the real matrix such as silicon increases the activity of the titanium dioxide catalyst. In consequence, the improvement achieved by the photocatalytic process for the removal of cyanide in the absence of dissolved matter is counteracted.

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.

Sediment quality evolution (2001-2011) in the Ebro River basin (Spain).

Spatio-temporal variations in sediment quality (20 sample sites) of the Ebro River basin between 2001 and 2011 have been assessed. The self-organizing map classified the sediment samples according to similarities in their chemical compositions. Its powerful visualization tools helped establish the main pollution contribution on each sample. Most of the samples showed low values of the mean-probable effect concentration quotient through time. However, six samples presented several quality issues related to some trace elements or polycyclic aromatic hydrocarbons. Finally, geoaccumulation index values calculated using estimates of background trace element concentrations suggested anthropogenic influences in more than half of the samples.

Potential risk assessment of trace elements and PAHs in sediment samples of the Ebro River basin (Spain).

This study was carried out in order to assess potential toxicity of hazardous pollutants (8 trace elements and 8 polycyclic aromatic hydrocarbons) in 20 sediment samples of the Ebro River basin (Spain) sampled in 2009. Mean-probable effect concentration quotient (m-PECQ) was found to range from 0.03 to 0.79. Two sites were classified as high priority sites in order to take future remediation actions due to their high m-PECQ value (>0.5). Worst-case scenario in equilibrium partitioning approach showed that acid volatile sulfide (AVS) content was greater than total trace element concentration in all samples. However, 4 sediments were classified as degraded due to the high AVS content measured (>50 mmol/kg). Principal component analysis classified the samples according to similar chemical characteristics and revealed that industrial activities are the main source of pollution of the basin.

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.

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.

Sequential solar photo-fenton-biological system for the treatment of winery wastewaters.

In this study, winery wastewaters are considered for degradation using heterogeneous photo-Fenton as a preliminary step before biotreatment. The heterogeneous photo-Fenton process assisted by solar light is able to partially degrade the organic matter present in winery wastewaters. When an initial hydrogen peroxide concentration of 0.1 M is used over 24 h of treatment, a degradation yield of organic matter (measured as TOC) of around 50% is reached. The later treatment (activated sludge process) allows the elimination of 90% of the initial TOC present in pretreated winery wastewaters without producing nondesired side-effects, such as the bulking phenomenon, which is usually detected when this treatment is used alone. The final effluent contains a concentration of organic matter (measured as COD) of 128 mg O2/L. The coupled system comprising the heterogeneous photo-Fenton process and biological treatment based on activated sludge in simple stage is a real alternative for the treatment of winery wastewater.