Multistage treatment system for raw leachate from sanitary landfill combining biological nitrification-denitrification/solar photo-Fenton/biological processes, at a scale close to industrial--biodegradability enhancement and evolution profile of trace pollutants.

A multistage treatment system, at a scale close to the industrial, was designed for the treatment of a mature raw landfill leachate, including: a) an activated sludge biological oxidation (ASBO), under aerobic and anoxic conditions; b) a solar photo-Fenton process, enhancing the bio-treated leachate biodegradability, with and without sludge removal after acidification; and c) a final polishing step, with further ASBO. The raw leachate was characterized by a high concentration of humic substances (HS) (1211 mg CHS/L), representing 39% of the dissolved organic carbon (DOC) content, and a high nitrogen content, mainly in the form of ammonium nitrogen (>3.8 g NH4(+)-N/L). In the first biological oxidation step, a 95% removal of total nitrogen and a 39% mineralization in terms of DOC were achieved, remaining only the recalcitrant fraction, mainly attributed to HS (57% of DOC). Under aerobic conditions, the highest nitrification rate obtained was 8.2 mg NH4(+)-N/h/g of volatile suspended solids (VSS), and under anoxic conditions, the maximum denitrification rate obtained was 5.8 mg (NO2(-)-N + NO3(-)-N)/h/g VSS, with a C/N consumption ratio of 2.4 mg CH3OH/mg (NO2(-)-N + NO3(-)-N). The precipitation of humic acids (37% of HS) after acidification of the bio-treated leachate corresponds to a 96% DOC abatement. The amount of UV energy and H2O2 consumption during the photo-Fenton reaction was 30% higher in the experiment without sludge removal and, consequently, the reaction velocity was 30% lower. The phototreatment process led to the depletion of HS >80%, of low-molecular-weight carboxylate anions >70% and other organic micropollutants, thus resulting in a total biodegradability increase of >70%. The second biological oxidation allowed to obtain a final treated leachate in compliance with legal discharge limits regarding water bodies (with the exception of sulfate ions), considering the experiment without sludge. Finally, the high efficiency of the overall treatment process was further reinforced by the total removal percentages attained for the identified organic trace contaminants (>90%).

Co-composting of poultry manure with low quantities of carbon-rich materials.

To study the feasibility of co-composting poultry manure with low quantities of high-value, carbon-rich materials experiments to characterize three pilot-scale piles were carried out. The piles comprised poultry manure (pile 1), poultry manure and straw (pile 2) and poultry manure and sawdust (pile 3), using wood chips as bulking agent. Pile 1 presented the highest losses of organic matter and nitrogen contents (> or = 92.9% and 92.0%, respectively). Although a thermophilic phase (temperature > 40 degrees C) was not verified for this pile, the final compost was stable (class IV) and free of pathogen indicator micro-organisms but it was the most phytotoxic, and presented a humic and fulvic acids ratio (HA/FA) that was less than 1. In contrast, piles 2 and 3 sustained thermophilic phases and produced stable (class V) and mature (HA/FA > 1) composts. Pile 2 showed the lowest loss in nitrogen content (88.9%) and produced the final compost with the highest C/N ratio (14.7) and the lowest value of electrical conductivity (3.9 mS cm(-1)). This study showed that it is possible to reduce the costs of poultry manure composting, namely the costs associated with the use of carbon-rich materials, given that the final co-composts presented parameters within the range of those recommended by the Second Draft Proposal for compost quality.

Selenite resistant rhizobacteria stimulate SeO(3) (2-) phytoextraction by Brassica juncea in bioaugmented water-filtering artificial beds.

BACKGROUND, AIM, AND SCOPE: Selenium is a trace metalloid of global environmental concern. The boundary among its essentiality, deficiency, and toxicity is narrow and mainly depends on the chemical forms and concentrations in which this element occurs. Different plant species-including Brassica juncea-have been shown to play a significant role in Se removal from soil as well as water bodies. Furthermore, the interactions between such plants, showing natural capabilities of metal uptake and their rhizospheric microbial communities, might be exploited to increase both Se scavenging and vegetable biomass production in order to improve the whole phytoextraction efficiency. The aim of the present study was to evaluate the capability of selenite removal of B. juncea grown in hydroponic conditions on artificially spiked effluents. To optimize phytoextraction efficiency, interactions between B. juncea and rhizobacteria were designedly elicited. MATERIALS AND METHODS: Firstly, B. juncea was grown on water-filtering agriperlite beds in the presence of three different selenite concentrations, namely, 0.2, 1.0, and 2.0 mM. Plant growth was measured after 3 and 6 weeks of incubation in order to establish the selenite concentration at which the best plant biomass production could be obtained. Afterwards, water-filtering agriperlite beds were inoculated either with a selenium-acclimated microbial community deriving from the rhizosphere of B. juncea grown, erstwhile, in a selenite-amended soil or with axenic cultures of two bacterial strains, vicelike Bacillus mycoides SeITE01 and Stenotrophomonas maltophilia SeITE02, previously isolated and described for their high resistance to selenite. These latter were seeded separately or as a dual consortium. Selenite was amended at a final concentration of 1.0 mM. Total Se content in plant tissues (both shoots and roots), plant biomass production, and persistence of bioaugmented microbial inocula during the experimental time were monitored. Moreover, parameters such as bioconcentration factor (BF) and phytoextraction efficiency (PE) were determined at the end of the testing run to evaluate the effects of the different bioaugmentation strategies adopted on selenite phytoextraction efficiency of B. juncea. RESULTS: A general but significant increase in capacity to extract and transport selenium to the epigeous plant compartments was recorded in B. juncea grown in beds augmented with microbial inocula, except for the treatment with B. mycoides SeITE01 alone. Nevertheless, a severe decrease in vegetable biomass production was observed after all microbial treatments with the exception of the plants that had received only S. maltophilia SeITE02. Actually, an increase in selenium phytoextraction efficiency up to 65% was observed in B. juncea, when this bacterial strain was inoculated. DISCUSSION: Emendation of B. juncea grown in water-filtering beds with a Se(IV)-acclimated microbial community caused a higher Se uptake along with a reduction of plant biomass yield with respect to plants grown without addition of the same bacterial inoculum. The increase of selenium BF in shoots suggests that the Se(IV)-acclimated microbial community not only elicited the plant capacity to absorb selenite, but also did improve the capacity to transport the metalloid to the epigeous compartments. On the other hand, the reduction in plant biomass yield might be related exactly to this improved capability of B. juncea to accumulate selenium at concentrations that are actually toxic for plants. Differently, addition of two selenite-resistant bacterial strains, namely, S. maltophilia SeITE02 and B. mycoides SEITE01, had weaker effects on plant biomass production when compared to those recorded in the presence of the Se(IV)-adapted microbial community. In particular, inoculation of water-filtering beds with the SeITE02 strain alone was the sole strategy resulting in a positive effect on both plant biomass production in stressful conditions and the capacity of shoots to accumulate selenium. In fact, its putative ability of reducing Se(IV) to organo-Se compounds significantly enhanced either selenium absorption by the plants or active metalloid translocation to epigeous parts. CONCLUSIONS: Bioaugmentation with the bacterial strain S. malthophila SeITE02 is suggested to elicit selenite phytoextraction efficiency in B. juncea. RECOMMENDATIONS: Manipulation of synergistic interactions between plants having phytoextraction capabilities and their associated rhizobacteria may enhance already consolidated treatment processes aimed to detoxify selenite laden wastewater.