1,721,087 research outputs found
Evaluation of Chlorella vulgaris and Scenedesmus obliquus growth on pretreated organic solid waste digestate
Full text linkIn this research Scenedesmus obliquus and Chlorella vulgaris growth was tested on digestate sludge obtained from the anaerobic co-digestion treatment of the organic fraction of municipal solid waste (OFMSW) together with waste activated sludge (WAS). Digestate was diluted 1:10 and tested in three batch experimental conditions: with no pre-treatments (noPT), after centrifugation (AC) and after filtration (AUF), in order to evaluate microalgae limiting growth factors. The best growth was obtained by C. vulgaris on digestate AC compared to S. obliquus, reaching 479 ± 31 cell million ml−1 and 131 ± 12 cell million ml−1 respectively. Ammonia removal evaluated in C. vulgaris and S. obliquus cultures was 99.2% ± 0.3 and 98.146% ± 0.008 in AC condition, respectively. Considering that AUF showed similar microalgae growth values, the digestate pretreatment for microalgae growth, could be limited to centrifugation
Phytotoxicity of "green" stabilised micro-iron used for groundwater remediation
Full text linkTreatment with granular, micro- (mFe), and nano-sized (nFe) iron showed to remove several inorganic and organic pollutants. Recently, there has been a turnaround from nFe to mFe: mFe is cheaper than nFe (i.e. 10 €/kg for mFe compared to 100 €/kg) forming less agglomerates. We reported about the potential environmental impacts of mFe considering phytotoxicity effects on four types of iron powders: A (? 600 μm particle size (ps)), B and C (? 250 μm ps) and D (? 50 μm ps). Three macrophytes (Lepidium sativum, Sinapis alba and Sorghum saccharatum) were investigated (OECD, 2006) (seed germination, seedling elongation, germination index and biomass inhibition) exposing organisms to 20 g/L of each mFe stabilised in 2 g/L of Guar gum (GG) in deionized water (GGmFe), spiked with Cd (CdCl2) (1-100 mg/L). Considering real concentrations, preliminary results indicated: i) no adverse effects on L. sativum and S. saccharatrum versus all GGmFe; S. alba showed toxicity versus C and D GGmFe; ii) biostimulation was observed in S. saccharatum versus all GGmFe and L. sativum only versus C GGmFe; iv) mFe seemed to reduce Cd effects in all sample, but with a different efficiency: C > D > A = B; v) the presence of GG seemed to increase bioavailability of Cd
Influence of storage methods, refrigeration or freezing, on the toxicity of wastewater samples to oyster embryos
Full text linkOne of the main concerns in wastewater whole effluent assessment is the sampling phase and the sample chain of custody before any toxicity evaluation. The major problem is related to establishing the correct method for sample storage in order to perform toxicity bioassays. The toxicity of some domestic and glass factory industrial wastewater samples stored both by refrigeration at 4 ± 1°C for no more than three days, and freezing at -18 ± 1°C for no more than one month was compared via the embryo larval development bioassay with the oyster Crassostrea gigas. The results showed no significant differences between the toxicities of refrigerated and frozen wastewater samples. The wastewater classification, according to a score based on four toxicity classes, showed that the preservation methods did not alter the toxicity classification of the samples. In particular, it was demonstrated that the samples considered as 'not acutely toxic' after refrigeration were also found to have this classification after freezing
Effects of mineral amendments on trace elements leaching from pre-treated marine sediment after simulated rainfall events
Full text linkBauxite extraction by-products (red mud) were used to evaluate their potential ability to stabilize trace elements from dredged and aerated/humidified marine sediment. The investigated by-products were: bauxaline®(BX) that is a press-filtered red mud; bauxsol™(BS) that is a press-filtered red mud previously washed with excess of seawater, and gypsum neutralized bauxaline® (GBX). These materials were separately mixed to dredged composted sediment sample considering 5% and 20% sediment: stabilizer ratios. For pilot experiments, rainfall events were regularly simulated for 3 months. Concentrations of As, Mo, Cd, Cr, Zn, Cu, and Ni were analyzed in collected leachates as well as toxicity. Results showed that Cd, Mo, Zn, and Cu were efficiently stabilized in the solid matrix when 20% of BX, BS, and GBX was applied. Consequently, toxicity of leachates was lower than for the untreated sediment, meaning that contaminants mobility was reduced. A 5% GBX was also efficient for Mo, Zn and Cu stabilization. In all scenarios, As stabilization was not improved. Compared to all other monitored elements, Mo mobility seemed to depend upon temperature-humidity conditions during pilot experiments suggesting the need of further investigations
Performance assessment of AS-SBR and UF-MBR for hotel wastewater treatment
No full textA large number of tourist structures in Venice (Italy) have small sized on-site treatment systems for their wastewater. Due to its historical characteristics, the city has no public sewerage system and untreated hotel wastewater represents a serious hazard for its lagoon environment. This study focused on the wastewater facilities installed in two hotels adopting an Activated Sludge Sequencing Batch Reactor (AS-SBR) and an Ultra-Filtration Membrane Biological Reactor (UF-MBR). Their performance was checked in terms of both traditional physico-chemical and ecotoxicological parameters, the importance of which has recently been recognised by EU regulatory dispositions and OSPAR indications. Acute and sub-chronic endpoints were both considered on a whole effluent toxicity basis by means of Vibrio fischeri and Crassostrea gigas, respectively. The two months monitoring survey evidenced that the UF-MBR was more efficient than the AS-SBR in providing high-quality discharges under both chemical and ecotoxicological viewpoints
Modificazioni degli ambienti di risorgiva Friulani come cause dello sviluppo anomalo di insetti Simulidi
No full textEvaporation and air-stripping to assess and reduce ethanolamines toxicity in oily wastewater
No full textToxicity from industrial oily wastewater remains a problem even after conventional activated sludge treatment process, because of the persistence of some toxicant compounds. This work verified the removal efficiency of organic and inorganic pollutants and the effects of evaporation and air-stripping techniques on oily wastewater toxicity reduction. In a lab-scale plant, a vacuum evaporation procedure at three different temperatures and an air-stripping stage were tested on oily wastewater. Toxicity reduction/removal was observed at each treatment step via Microtox® bioassay. A case study monitoring real scale evaporation was also done in a full-size wastewater treatment plant (WWTP). To implement part of a general project of toxicity reduction evaluation, additional investigations took into account the monoethanolamine (MEA), diethanolamine (DEA) and triethanolamine (TEA) role in toxicity definition after the evaporation phase, both as pure substances and mixtures. Only MEA and TEA appeared to contribute towards effluent toxicity
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