Efficient and Sustainable Treatment of Tannery Wastewater by a Sequential Electrocoagulation-UV Photolytic Process

Tannery wastewater contains large amounts of pollutants that, if directly discharged into ecosystems, can generate an environmental hazard. The present investigation has focused the attention to the remediation of wastewater originated from tanned leather in Tunisia. The analysis revealed wastewater with a high level of chemical oxygen demand (COD) of 7376 mgO2/L. The performance in reduction of COD, via electrocoagulation (EC) or UV photolysis or, finally, operating electrocoagulation and photolysis in sequence was examined. The effect of voltage and reaction time on COD reduction, as well as the phytotoxicity were determined. Treated effluents were analysed by UV spectroscopy, extracting the organic components with solvents differing in polarity. A sequential EC and UV treatment of the tannery wastewater has been proven effective in the reduction of COD. These treatments combined afforded 94.1 % of COD reduction, whereas the single EC and UV treatments afforded respectively 85.7 and 55.9 %. The final COD value of 428.7 mg/L was found largely below the limit of 1000 mg/L for admission of wastewater in public sewerage network. Germination tests of Hordeum Vulgare seeds indicated reduced toxicity for the remediated water. Energy consumptions of 33.33 kWh/m3 and 314.28 kWh/m3 were determined for the EC process and for the same followed by UV treatment. Both those technologies are yet available and ready for scale-up

Application of a standard risk assessment scheme to a North Africa contaminated site (Sfax, Tunisia) - tier 1

Phosphorus is a critical element to agriculture, consequently global phosphate rock demand will remain rising to feed a growing world population. The beneficiation of phosphorous ore gives rise to several tons of a waste by-product [phosphogypsum (PG)] which valorisation is limited, within other reasons, by the risks posed to environment and human health. Although threatening, the accumulation in stacks is the only procedure so far practiced by several countries as a means to get rid of this industrial externality. As part of a NATO Science for Peace Project (SfP 983311) this study describes the application of an environmental risk assessment (ERA) framework, to assess the risks posed by a PG stack to the surrounding soils, in Sfax, Republic of Tunisia. The ERA followed a weight of evidence approach, supported by two lines of evidence (LoE): the chemical (ChemLoE) and the ecotoxicological (EcotoxLoE). Integrated risks point for risk values greater than 0.5 in soils collected in PG stack surrounding area. Soil salinization, has likely contributed to the exacerbation of risks, as well as to the lack of consistency between both LoEs. This study highlights the need of rethinking the weight given to each LoE in ERA, in areas where soil salinization is a reality.publishe

Interregional traceability of Tunisian olive oils to the provenance soil by multielemental fingerprinting and chemometrics

The aim of this study was to prove the usefulness of multielements as provenance markers of olive oils by evaluating their link with soil composition and their discriminatory power. Eleven elements in twenty-one olive oils and their paired soils from four Tunisian regions were characterized. Chemometrics have been implemented for ICP-MS data processing. Principal component analysis identified the predominant geochemical source of the elements in the oils based on their associations according to Goldschmidt’s rule. Although a clear correlation was not proven, correspondence was identified between the discriminating elements for both the soils and olive oils, which included Fe, Rb, Mg, and Pb. Linear discriminant analysis achieved classification and prediction rates of 92.1% and 87.3%, respectively. Our study substantiates the validity of multielements as markers of the olive oils’ provenance, and that an elemental fingerprinting approach can be successfully applied in the construction of a database of Tunisian olive oils

Speciation of Heavy metals by modified BCR sequential extraction in soils contaminated by phosphogypsum in Sfax, Tunisia

peer reviewe

Microplastics as an emerging hazard to terrestrial and marine ecosystems: Sources, Occurrence and Analytical Methods

Microplastics (MPs) with particles lower than 5mm in size, are crucial pollution of increasing ecotoxicological concern in the environments. Lately, studies on MPs have been documented globally due to increasing awareness of the potential risks for human health and for the environment. However due to limitations of different analytical methods and environmental assessment risk, MPs distribution and biological effects are still database topics. To clarify this gap, this study brings out a wide range of scientific literature related to MPs studies in different environmental compartments as well as sediments, oceans, coastlines, uptake and the health effect. The environmental and health risk related to microplastic contamination is still unclear

Comparison between several techniques of olive tree bark extraction (Tunisian Chemlali variety)

<p>In order to better understand the chemical composition of the olive tree bark of Tunisian chemlali variety (<i>Olea europaea cv. ‘Chemlali’</i>), this material was extracted by different ways. Compositions of extracts were used at best-selected conditions for each technique, and characterised using HPLC, LC/MS and GC–MS techniques. Analyses are conducted to an important variety of high carbon number compounds such as aliphatic compounds as nanocosane and heptacosane, and molecules with high value added tax (VAT) which can be classified as follows: diterpenes as phytol, triterpenes as squalene and also esters as Benzyl cinnamate. Hydrodistillation at high pressure seems to be a very common method to get a wide variety of compounds, the results are better than the ones obtained using supercritical fluid extraction and solvent extraction.</p

Rainwater harvesting potentials for drought mitigation in Tunisia: Water quality monitoring

Rainwater is extremely important for the arid regions of Tunisia for a better valorization of this water, the indigenous of these regions decided to build earthen cisterns (Majel and Fesquia) to collect rain water, to satisfy their needs and to have sufficient long-term water reserve in case of prolonged drought. Despite the difficulties faced to access the mountainous regions, a survey was conducted concerning all characteristics of earthen cisterns and their uses. 120 samples of water have been analyzed in the laboratory for their physicochemical parameters such as pH, EC, sodium, chloride, bicarbonate and microbiological quality parameters such as total coliforms, and Escherichia coli. It has been noted that the majority of people (62%) used rainwater as drinking water, for animal watering and as supplementary irrigation. In fact, physic-and chemical properties of, the rainwater samples collected are suitable for consumption according to WHO 2017 standards. However, the results of our microbiological indicator analyses suggested that rainwater stored in Majel and Fesquia are not suitable for human consumption without any treatment. Rainwater can be considered as potential source for non-potable uses, such as irrigation. The samples collected were categorized as suitable with regard of SAR belonged to the excellent to good class

Application of Sequential Combination of Electro-Coagulation/Electro-Oxidation and Adsorption for the Treatment of Hemodialysis Wastewater for Possible Reuse

Reusing hemodialysis wastewater (HWW) is more difficult due to its higher conductivity (salinity) and the need for an iterative RO or adsorption process. It can therefore be challenging and technologically laborious. In this context, this study aimed to investigate the possibility of treating HWW by combining electro-coagulation (EC) and electro-oxidation (EO) processes and adsorption as the best technologies to achieve efficient removal of dissolved micropollutants. In this work, the application of electro-coagulation/electro-oxidation processes using, respectively, aluminum and platinum electrodes combined with adsorption onto active carbon to treat HWW was studied. In the EC process, high removal of phosphate ions and chemical oxygen demand (COD) was observed. In the EO process, the COD removal performance, total nitrogen, and Mg were significant and reached 100, 83, and 89%, respectively, after 100 min of treatment. The estimated energies required to treat HWW by EC and/or EO were approximately 0.7 kWh/m3 and 0.05 kWh/m3, respectively. While the EO and EC processes used for COD removal from HWW showed almost similar performances, the EO process seems to consume less energy. Therefore, electrochemical removal of HWW can be successfully performed using the EO process and activated carbon (AC) for the complete removal of COD and the mineralization of pharmaceutical residues. The experimental results showed that the coupling of the three processes (EC–EO–AC) provides treated water that can be reused in agriculture due to its less sodium absorption ratio (SAR) value and might be an alternative method of wastewater treatment responding to the concept of green dialysis