Vermistabilization of excess sludge employing Eisenia fetida: Earthworm histopathological alterations and phytotoxicity evaluation.

The aim of this work was to stabilize excess sludge (ES) coming from a wastewater treatment plant (WWTP) by vermistabilization and to evaluate ecotoxicological effects over the earthworm species Eisenia fetida. Three mixtures were made up in triplicate using different volume ratios of ES and soil (S) (100% ES, 70:30% ES:S and 30:70% ES:S in wet weight basis). Earthworms were added in order to compare vermicomposting vs. natural stabilization. The mixtures were monitored over 130 days through physical, chemical, pathological and biological analysis, following quality standards depicted in the US EPA 40 CFR Part 503, local regulations and background studies. Histopathological samples were processed as biomarkers of acute and chronic toxicity on earthworms, and germination assays were performed at the end of the experiment to assess phytotoxicity. In terms of pathogen depletion comparing initial and final values from each treatment, the mixtures with higher ES proportions (70 and 100%) with earthworms were the most efficient ones registering 64.8 and 75.5% of reduction of fecal coliforms (FC) respectively, while the lowest ES proportion with earthworms (30%) showed 54.7%. Final pathogens content in all the treatments with earthworms were significantly lower (ranged from 1360 to 1760 MPN g total solids-1) than the values registered in treatments without earthworms (ranged from 2400 to 4000 MPN g total solids-1) (p < 0.05). However, none of the treatments attained class A categorization (FC ≤ 1000 MPN g total solids-1) in terms of FC. Also, values of mean cocoon production and hatched juveniles along time were significantly higher in the treatments with 100 and 70% ES (p < 0.05), while the higher mean adult biomass was detected in the treatment with 30% ES. Volatile solids decrease ranged between 8.45 and 22.34% in treatments with earthworms and all values of specific oxygen uptake rate were below 1.5 mg O2 h -1 g total solids -1. There were not negative effects over behavior or reproduction of E. fetida adults, nor the presence of external and internal injuries. Final products from mixtures with earthworms presented a humus-like structure, were odorless and reached maturity values -presenting no phytotoxicity-with significant differences between germination index values of treatments with and without earthworms (p < 0.05). Vermistabilization is a successful eco-technology to sanitize excess sludge, acquiring an added-value material and contributing to its revalorization as organic amendments or fertilizers in soils within the circular economy framework and the United Nations' Sustainability Development Goals.

Model-Based Analysis of Lactuca sativa Root Growth under the Action of Herbicides in Milli-Channel Arrays with In Situ Imaging.

Extracting practical information from the large amounts of data gathered during the live imaging analysis of plant organs is a challenging issue. The present work investigates the use of the logistic growth model to analyze experimental data from root elongation assays performed in milli-fluidic devices with in situ imaging. Lactuca sativa was used as a bioindicator and was subjected to wide concentration ranges of four different herbicides: 2,4-D, atrazine, glyphosate, and paraquat. The model parameters were directly connected to standard indicators of toxicity and plant development, such as the LD50 and the absolute growth rate, respectively. In addition, it was found that realistic predictions of the maximum root length can be achieved about 60 h before the bioassay end point, which could significantly shorten the turnaround time. The combination of milli-fluidic devices, real-time imaging, and model-based data analysis becomes a powerful tool for environmental studies and ecotoxicity testing.

Earthworms to improve glyphosate degradation in biobeds.

In this work, earthworm effect on the efficiency of biobeds for glyphosate degradation was studied. Three biomixtures with and without the addition of earthworms (Eisenia fetida species) were evaluated. The initial concentration of glyphosate was 1000 mg/kg biomixture. Glyphosate and biological parameters were measured as a function of time. Earthworm survival, biomass, and reproduction were evaluated as well. All biomixtures that contain earthworms reached 90% of glyphosate degradation at 90 days in comparison with the biomixtures without earthworms that reached 80% approximately at the same time. Also, within the biomixtures that contained earthworms, glyphosate degradation rate was significantly higher in the one made up with soil and wheat stubble (Ws-E) showing excellent capacity for aminomethylphosphonic acid (AMPA) degradation, the main metabolite of glyphosate degradation. In addition, a study performed after the vermiremediation process showed that E. fetida can tolerate high glyphosate concentration without modifications in its life traits. It can be concluded that the use of E. fetida within the biobeds is an excellent combination to improve glyphosate and AMPA removal.

Milli-channel array for direct and quick reading of root elongation bioassays.

A novel platform to perform systematic analysis and direct reading of root elongation bioassays is presented. The device was designed to include multiplexed microenvironments for the germination and growth of individual seeds, which allows observation by the naked eye or by optical systems, notably cellphone cameras. Prototypes were fabricated by laser micromachining on a highly transparent material that is fully compatible with biological systems. The effectiveness of the milli-channel array was verified against the conventional system (Petri dish). Lactuca sativa was chosen as a model species and glyphosate as a typical toxic agent. All tests were run according to standardized procedures and data analysis was carried out through different statistical indicators such as the root elongation and germination indexes. Results attained in the milli-channel array were identical to those in Petri dish, with the remarkable benefit that several steps required in the conventional system were avoided, which enormously decreases the operation time and the possibility of experimental errors. Further advantages of the milli-channel array are also reported, such as the capability to achieve live imaging of plant organs growth through a simple experiment. The developed device has been proven to be effective, versatile, easy-to-use, and integrable to cellphones, which naturally provide facilities for data recording, analysis, and networking. These improvements open the route to novel applications of bioassays in the wide field of ecotoxicology and environmental studies.

Earthworms to assess the innocuousness of spent biomixtures employed for glyphosate degradation.

In this study, the innocuousness of different biomixtures employed for glyphosate degradation was tested through Eisenia fetida earthworms. Eight biomixtures were prepared with local materials: alfalfa straw (AS), wheat stubble (WS), river waste (RW) and two different soils (A and B). Each biomixture was divided into two equal portions: one without glyphosate application (control substrate) and the other was sprayed with a commercial glyphosate formulation of 1,000 mg glyphosate a.i. kg-1 biomixture (applied substrate). The bioassay started when all sprayed biomixtures reached high percentages of glyphosate degradation (spent biomixtures). Three parameters were studied: survival, adults and juveniles biomass and reproduction. The results allowed the identification of three biomixtures (AWS, BWS and BWSRW) for good maintenance and development of E. fetida. In addition, at the end of the bioassay two of the viable biomixtures (AWS and BWS) showed the highest performance of juvenile earthworms compared to a reference soil. The Principal Component Analysis (PCA) indicated that the biomixtures containing high silt and clay percentages and minor density renders higher values of earthworm growth and reproduction. Therefore, these innocuous biomixtures can be used as organic amendments or recycled materials for new treatments on biobeds.

Arsenic sorption onto titanium dioxide, granular ferric hydroxide and activated alumina: batch and dynamic studies.

The aim of this work was to evaluate and compare the efficiencies of three different adsorbents for arsenic (As) removal from water: titanium dioxide (TiO2), granular ferric hydroxide (GFH) and activated alumina (AA). Equilibrium experiments for dissolved arsenite and arsenate were carried out through batch tests. Freundlich and Langmuir isotherm models were adopted and their parameters were estimated by non-linear regressions. In addition, dynamic experiments were performed in mini fixed bed columns and breakthrough curves were obtained for each combination of sorbate/adsorbent. Experimental results obtained by column assays were compared with predictions of well-known breakthrough models (Bohart-Adams and Clark). Results indicate that As(V) is more easily adsorbed than As(III) for AA and GFH, while TiO2 has a similar behavior for both species. The titanium-based material is the most efficient adsorbent to carry out the process, followed by the GFH.

A novel approach to explain the inactivation mechanism of Escherichia coli employing a commercially available peracetic acid.

The chemical inactivation of Escherichia coli employing a commercial mixture of peracetic acid (PAA) was studied. For this purpose, experiments were carried out using dilutions of the unmodified mixture, and also the same mixture but altered with hydrogen peroxide (HP) previously inhibited. Also, these results were compared to those obtained before employing HP alone. It was found that the mixture is much more efficient than HP and PAA acting separately. Furthermore, it was found that PAA without HP is much more efficient than HP alone. A plausible explanation is presented. The homolysis of PAA would give rise to a chain reaction that generates a significant number of highly oxidizing radicals. An attacking scheme to bacteria in two stages is proposed, where the initial step, mainly caused by PAA, is very fast and eliminates some specific components of the bacteria that would otherwise inhibit the parallel action of HP. Thereafter, the emergence of a potentiating synergetic action of the second oxidant seems to be immediately unveiled.

Arsenic (III) oxidation of water applying a combination of hydrogen peroxide and UVC radiation.

Arsenic is toxic to both plants and animals and inorganic arsenicals are proven carcinogens in humans. The oxidation of As(III) to As(v) is desirable for enhancing the immobilization of arsenic and is required for most arsenic removal technologies. The main objective of this research is to apply an Advanced Oxidation Process that combines ultraviolet radiation and hydrogen peroxide (UVC/H(2)O(2)) for oxidizing aqueous solutions of As(III). For that purpose, a discontinuous photochemical reactor (laboratory scale) was built with two 40 W tubular germicidal lamps (λ = 253.7 nm) operating inside a recycling system. The study was made beginning with a concentration of 200 µg L(-1) of As(III), changing the H(2)O(2) concentration and the spectral fluence rate on the reactor windows. Based on references in the literature on the photolysis of hydrogen peroxide, arsenic oxidation and our experimental results, a complete reaction scheme, apt for reaction kinetics mathematical modelling, is proposed. In addition, the effectiveness of arsenic oxidation was evaluated using a raw groundwater sample. It is concluded that the photochemical treatment of As(III) using H(2)O(2) and UVC radiation is a simple and feasible technique for the oxidation of As(III) to As(v).