170 research outputs found
The start-up of an anammox reactor as the second step for the treatment of ammonium rich refinery (IGCC) wastewater with high C org /N ratio
No full textIn this study, the refinery wastewater produced by the integrated gasification combined cycle (IGCC) and pre-treated in a lab-scale partial nitritation chemostat was fed to a granular anammox reactor, in order to evaluate its feasibility as the final treatment step. The IGCC wastewater was characterized by high NH4-N concentration (540±82 mg L-1), high organic carbon to nitrogen ratio (Corg/N), and by the presence of toxic substances. A conservative exponential law was adopted to progressively replace the synthetic influent with the pre-treated IGCC wastewater, in order to avoid any stressful conditions which could hinder the process. An increase in specific anammox activity (SAA) up to 0.104 gNO2-N gVSS-1 d-1 was initially observed, suggesting that stimulation may occur if pre-treated IGCC wastewater dilution is sufficiently high. A system malfunction caused a worsening of process performance, which was partially restored: when only pre-treated IGCC wastewater was fed, the nitrogen removal efficiency and SAA were 71±3% and 0.045±0.002 gNO2-N gVSS-1 d-1, respectively, and the removal of organic matter due to denitrification was negligible. As to physical/morphological properties of anammox granules, they did not change significantly during the whole experimental campaign. Results showed that the anammox process can be successfully applied to treat complex industrial wastewaters with high Corg/N ratio, if a conservative start-up strategy is adopted and the preliminary partial nitritation step guarantees an efficient removal of readily degradable organic matter
Biological treatment of nitrogen rich refinery wastewater by partial nitritation (SHARON) process
No full textWastewater discharges containing high nitrogen levels can be toxic to aquatic life and cause eutrophication. In this study, the application of the SHARON (Single reactor for High activity Ammonium Removal Over Nitrite) process for the treatment of refinery wastewater (sour water) was evaluated, in view of its coupling with the ANAMMOX (ANaerobic AMMonium OXidation) process. A Continuous Flow Stirred Tank Reactor was initially fed with a synthetic medium, and the applied NH4-N concentration and wastewater/synthetic medium ratio were progressively increased up to 2000 mg(N)/L and 100%, respectively. Despite the high potential toxic effect of the real wastewater, overall SHARON performance did not decrease with the increasing real wastewater/synthetic medium ratio, and biomass showed progressive acclimation to the toxic compounds in the real wastewater, as demonstrated by toxicity assessments. NH4-N and dissolved organic carbon removal efficiency were around 50% and 65%, respectively. Moreover, the effluent was characterized by a NO2-N/NH4-N ratio of 0.9 +/- 0.01 and low nitrate concentration (<30 mg(N)/L), in line with the requirements for the subsequent treatment by the ANAMMOX process
Knowledge about Microplastic in Mediterranean Tributary River Ecosystems: Lack of Data and Research Needs on Such a Crucial Marine Pollution Source
No full textPlastic debris occurring in freshwater environments, which can either come from the surrounding terrestrial areas or transported from upstream, has been identified as one of the main sources and routes of plastic pollution in marine systems. The ocean is the final destination of land- based microplastic sources, but compared to marine environments, the occurrence and effects of microplastics in freshwater ecosystems remain largely unknown. A thorough examination of scientific literature on abundance, distribution patterns, and characteristics of microplastics in freshwater environments in Mediterranean tributary rivers has shown a substantial lack of information and the need to apply adequate and uniform measurement methods
The ANAMMOX process as the second step for the treatment of ammonium rich refinery wastewater with high Corg/N ratio
No full textThe combination of partial nitritation and anammox (anaerobic ammonium oxidation) has been mainly applied to the treatment of wastewaters with high ammonium concentration and low content of biodegradable organic carbon. So far, only few studies have focused on the application of partial nitritation-anammox process to the treatment of ammonium-rich wastewaters characterized also by a high organic carbon to nitrogen ratio (Corg/N), as well as by the presence of toxic substances: in this study, an anammox reactor was started-up and fed with the effluent from a partial nitritation reactor treating IGCC (Integrated Gasification Combined Cycle) wastewater, in order to evaluate its feasibility as an alternative to the currently applied chemical-physical-biological treatment.
A sequencing batch reactor was inoculated with granular anammox biomass and run at controlled temperature (35±0.5 °C) and pH (7.7±0.3). The synthetic influent containing NH4-N (up to 250 mg/L) and NO2-N (up to 330 mg/L) was progressively replaced by the IGCC wastewater, which had been pre-treated in the lab-scale partial nitritation reactor. When the reactor was fed with the synthetic medium at the target nitrogen loading rate (NLR, 0.350 gN/L·d), the observed NH4-N removal efficiency was 93±5%, and no nitrite was detected in the effluent. Good overall process performance was maintained as increasing amounts (up to 65%) of the effluent from the partial nitritation system were fed to the anammox reactor: NH4-N and NO2-N removal efficiencies were 98.9±1.0% and 96.6±2.1%, respectively, and nitrite specific removal rate peaked at 0.28 gNO2-N/gVSS∙d. On day 154, a nitrogen shock load was applied to evaluate anammox stability during start-up: despite system sensitivity to the sudden increase of nitrogen load, process performance was recovered and the percentage of IGCC wastewater in the influent could be raised to 100% with fairly good NH4-N and NO2-N removal efficiencies (85.7±5.8% and 88.2±2.3%, respectively). Anammox granules were compact (diameter, 636±20 m) and dense (86.5±3.4 gTSS/Lgran), with good settling properties. The total organic carbon (TOC) removal efficiency was low: since most of TOC (around 80±8%) had been removed in the preliminary partial nitritation step (results not shown), it can be assumed that the residual TOC entering the anammox reactor was slowly biodegradable, therefore heterotrophic denitrifiers did not compete with anammox biomass for nitrite.
The results indicate that anammox start-up can be successfully achieved and the process can be applied in combination with a preliminary partial nitritation step for the treatment of ammonium-rich IGCC wastewater, thus providing useful information also for the treatment of similar wastewaters with high Corg/N ratio and containing toxic substances
Partial nitritation of nitrogen-rich refinery wastewater (sour water) with different Ci/N molar ratios
No full textIn this study, a SHARON reactor was used to treat synthetic and real ammonium-rich refinery wastewater (sour water) with different inorganic carbon to nitrogen (Ci/N) molar ratios, in order to evaluate its possible implementation downstream of a steam stripping unit in a double-stage SHARON-ANAMMOX or SHARON-heterotrophic denitritation process. A synthetic influent containing NH4-N (2,000 mg/L) was initially fed to promote biomass acclimation, then real sour water containing also organic substrate, cyanides, sulphides and phenols was supplied. With both synthetic and real wastewater, the applied Ci/N molar ratio was progressively increased from 1 to 2 and the SHARON reactor produced an effluent suitable for further treatment by autotrophic ANAMMOX or heterotrophic denitritation, respectively. Acute toxicity assessments based on the specific measurement of nitritation activity confirmed that biomass acclimation to the toxic substances contained in the real wastewater occurred successfully. Moreover, high removal of organic matter (73%) suggested the absence of any competition between heterotrophic and autotrophic microorganisms. Controlling influent Ci/N molar ratio was shown to represent a key operating strategy to properly regulate SHARON performance, depending on the chosen downstream treatment, proving its actual feasibility under harsh operating conditions and providing useful indications for its implementation at full scale
Aerobic granular sludge reactors for the treatment of chlorinated aromatic and aliphatic compounds
No full textDue to their toxicity even at low concentration and their widespread use in several anthropic activities, chlorinated organic pollutants have been considered an environmental priority to deal with. Compared to non-chlorinated compounds, the presence of strong C-Cl bound in their molecular structure
makes them resistant to biological degradation and persistent in both water and soils. In this study, two
Granular sludge Sequencing Batch Reactors (GSBR) were run for the biological treatment of synthetic wastewater containing a mixture of 1,2,4-trichlorobenzene and 2,4-dichlorophenol (1,2,4-TCB and 2,4-DCP) and 1,2-dichloroethane (1,2-DCA), respectively, using readily biodegradable carbon sources as the primary (growth) substrates. For 1,2,4-TCB and 2,4-DCP degradation, GSBR-1 was operated as a Sequencing Batch Bubble Column (SBBC) reactor, while GSBR-2 was started-up and properly configured in order to minimize 1,2-DCA losses due to volatilization. Performance of both GSBRs in terms of 1,2,4-TCB, 2,4-DCP and 1,2-DCA removal efficiencies were evaluated throughout the research: toxic compounds were completely removed and granules were successfully maintained in the reactors. The treatment of a mixture of highly toxic 1,2,4-TCB and 2,4-DCP and the possibility to treat volatile chlorinated compounds by aerobic granules
are of novelty and will contribute in extending the potential applications of the aerobic granular sludge
technology
Partial nitritation of nitrogen rich refinery wastewater (sour water) with different IC/N molar ratios
No full textFor nitrogen rich streams, conventional biological treatment based on nitrification and denitrification usually lacks of efficiency and requires considerable amounts of an external carbon source to be supplied; on the other hand, physical-chemical processes are characterized by high operating costs. The possible application of partial nitritation SHARON (Single reactor for High activity Ammonium Removal Over Nitrite) coupled with autotrophic ANAMMOX (ANaerobic AMMonium OXidation) or heterotrophic denitrification via nitrite processes would represent a technical- and cost-effective technology: partial nitritation has been studied and commonly applied at full scale to treat anaerobic digester supernatant and landfill leachates, while only few studies focusing on the treatment of industrial wastewater containing toxic substances have been carried out so far.
In this study, a SHARON reactor was used to treat synthetic and real ammonium rich refinery wastewater (sour water): since availability of inorganic carbon (IC) determines the amount of NH4+-N being converted into NO2--N by partial nitritation, different influent IC/N (as HCO3-/NH4+-N) molar ratios were tested and SHARON feasibility as the preliminary treatment in a double stage SHARON-ANAMMOX or SHARON-Denitrification via nitrite process was assessed. In order to retain only ammonium oxidizing bacteria (AOB) in the system, the reactor was run at controlled temperature and operated as a chemostat (no biomass recirculation) at low hydraulic and solids retention time. A synthetic medium containing NH4+-N (2,000 mg/L) was initially fed to promote biomass acclimation, then real sour water containing also organic substrate, cyanides, sulphides and phenols was supplied. In both synthetic and real wastewater, the IC/N molar ratio was progressively increased from 1 to 2. Effluent from the SHARON reactor fed with the synthetic medium (influent IC/N molar ratio of 1) was suitable for subsequent treatment by ANAMMOX; increasing the IC/N molar ratio up to 2 enhanced NH4+-N conversion into nitrite, producing a final effluent suitable for denitrification via nitrite. Such positive results were confirmed with real sour water, despite the presence of highly toxic substances: the progressive increase of influent IC/N molar ratio from 1 to 2 enhanced NH4+-N removal efficiency (up to 97.20.1%) and its conversion into nitrite, always with low nitrate production, indicating stable nitritation. Acute toxicity assessments carried out on biomass drawn from the SHARON reactor confirmed that acclimation to toxic substances contained in the real wastewater was successfully achieved. Moreover, removal of organic matter indicated the growth of heterotrophic biomass without any competition with autotrophic microorganisms.
Results presented in this study proved that controlling influent IC/N molar ratio represents a key operating strategy to properly regulate SHARON performance: depending on the IC/N molar ratio, the SHARON reactor produced an effluent suitable for further treatment by either autotrophic ANAMMOX or heterotrophic denitrification via nitrit
Effects of different primary substrate concentrations on 2,4-dichlorophenol removal by aerobic granular sludge
No full textIn this study, the aerobic granular sludge technology was applied for the degradation of 2,4-
dichlorophenol (2,4-DCP, up to 30 mg/L), with sodium acetate (NaAc) as the primary (growth) substrate: since dosage of an external carbon source may represent a relevant cost at larger scale,
the effects of decreasing NaAc influent concentrations (from 800 to 400 mg/L) on process performance were evaluated, in order to reduce operating costs. High NaAc concentration in the influent, a key aspect during process start-up, was shown to play a minor role for granular sludge long term operation: both NaAc and 2,4-DCP were completely removed during the whole
experimental activity and the observed chloride release was found to be stoichiometric (indicating the complete mineralization of the toxic compound). The increase of the applied 2,4-DCP/NaAc
ratio from 0.025 to 0.075 also influenced microbial population dynamics, and probably forced granular biomass to enhance self aggregation as a defensive strategy against the toxic effects of 2,4-DCP: the increase of granules density (from 68±2 up to 124±6 gTSS/Lgran) was accompanied by
enhanced settling ability and better effluent quality. As shown by FISH, no inhibiting effects were observed on overall microbial activity and biodiversity of granular biomass at increasing 2,4-
DCP/NaAc ratios
SHARON process as preliminary treatment of refinery wastewater with high organic carbon-to-nitrogen ratio
No full textIn this study, a partial nitritation reactor (SHARON, Single reactor for High activity Ammonium Removal Over Nitrite) was used to treat ammonium-rich (up to 620 mg N/L) petrochemical wastewater produced by the integrated gasification combined cycle (IGCC) and characterized also by a high organic carbon-to-nitrogen ratio (C/N, up to 1.1 gC/gN). The reactor was initially fed with a synthetic influent containing only NH4-N as substrate, then a preliminary acute toxicity test was used to assess the potential inhibiting effect of IGCC wastewater on SHARON biomass: the observed IC10, IC50, and IC90 (14.9, 54.5, and 200 mL/L, respectively) suggested a prudential operating strategy based on the gradual replacement of the synthetic medium with the IGCC wastewater. As the synthetic influent was replaced by the IGCC wastewater, the resulting influent alkalinity-to-NH4-N ratio (expressed as inorganic carbon-to-nitrogen molar ratio, Cinorg/N) influenced process performance in terms of NH4-N removal efficiency. Despite the high influent C/N ratio, when the reactor was fed only with the IGCC wastewater, the ammonium removal efficiency was as high as 53 ± 10%, the corresponding effluent NO2-N/NH4-N ratio was 1.14 ± 0.42 and nitrate production was low. The presence of the organic substrate allowed the development of heterotrophic bacteria, as indicated by the high dissolved organic carbon removal efficiency (80 ± 8%) and the low effluent C/N ratio (0.20 ± 0.04). Such reactor performance made the effluent suitable for its subsequent treatment by anammox (ANaerobic AMMonium OXidation), providing useful information about the applicability of the SHARON process for the preliminary treatment of IGCC wastewater and similar ammonium-rich industrial wastewaters with high C/N ratio
Antiproliferative and antiviral activity of methanolic extracts from Sardinian Maltese Mushroom (Cynomorium coccineum L.)
No full textCynomorium coccineum is a non-photosynthetic plant that grows in Mediterranean countries and that is amply used in the traditional medicine. The aim of this study was to extend previous studies on the chemical and biological properties of C. coccineum, evaluating the potential antiviral and antiproliferative activity of the methanolic extract. The MTT assay was used for the in vitro cytotoxic studies against human cancer-derived cell lines, while both MTT and plaque reduction (PRT) methods were used to evaluate the potential inhibitory effect of the extract against a panel of mammal viruses. The results obtained showed no selective activity against any DNA and RNA virus but revealed an interesting antiproliferative activity against human leukaemia-derived cell lines
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