Biological treatment of fish processing wastewater: A case study from Sfax City (Southeastern Tunisia)

The present work presents a study of the biological treatment of fish processing wastewater at salt concentration of 55 g/L. Wastewater was treated by both continuous stirred-tank reactor (CSTR) and membrane bioreactor (MBR) during 50 and 100 days, respectively. These biological processes involved salt-tolerant bacteria from natural hypersaline environments at different organic loading rates (OLRs). The phylogenetic analysis of the corresponding excised DGGE bands has demonstrated that the taxonomic affiliation of the most dominant species includes Halomonadaceae and Flavobacteriaceae families of the Proteobacteria (Gamma-proteobacteria class) and the Bacteroidetes phyla, respectively. The results of MBR were better than those of CSTR in the removal of total organic carbon with efficiencies from 97.9% to 98.6%. Nevertheless, salinity with increasing OLR aggravates fouling that requires more cleaning for a membrane in MBR while leads to deterioration of sludge settleability and effluent quality in CSTR.     

Cadmium in blood of Tunisian men and risk of bladder cancer: interactions with arsenic exposure and smoking

Prior investigations identified an association between low-level blood arsenic (As) and bladder cancer risk among Tunisian men but questions remain regarding confounding by cadmium (Cd), a well-established bladder carcinogen. A case–control study of Tunisian men was re-examined to assess the levels of cadmium in blood and reparse the association between the simultaneous exposure to these metals and bladder cancer risk. Levels of blood Cd were significantly twice higher among cases than in controls (P?<?0.05) and were positively correlated with smoking and age. Additionally, analysis of metal levels among non-smokers according to the region of residence showed very high blood Cd and As levels for the coastal regions of Sfax and central Tunisia. After controlling for potential confounders, for low blood As levels (<0.67 μg/L), the OR for blood Cd was 4.10 (95 % CI 1.64–10.81), while for higher levels (>0.67 μg/L), it was reduced to 2.10 (CI, 1.06–4.17). Adjustment for Cd exposure did not alter the risk associated to As exposure. This study is the first to report the relationship between Cd exposure and risk of bladder cancer occurrence in interaction with smoking and As exposure. Smoking is shown to be the main exposure source to Cd in the Tunisian population but also environmental pollution seems to be responsible of Cd exposure among non-smokers. Exposure assessment studies encompassing a wider population are needed.     

Remazol Brilliant Blue R decolourization by the laccase from Trametes trogii

The decolourization of the recalcitrant dye RBBR by the culture filtrate of Trametes trogii and its isolated laccase was investigated. Both filtrates from Cu-induced cultures as well as purified laccase decolourized the dye RBBR. The purified laccase decolourized the dye down to 97% of 100 mg l(-1) initial concentration of RBBR when only 0.2U ml(-1) of laccase was used in the reaction mixture. The effects of different physicochemical parameters were tested and optimal decolourization rates occurred at pH 5 and at a temperature of 50 degrees C. Decolourization of RBBR occurred in the presence of metal ions which could be found in textile industry effluents. Of all the metal ions tested, FeCl2 was the most inhibiting for the decolourization. HBT was shown to have no effect on the decolourization of RBBR at low concentration, while at a concentration of 5 mM it slightly inhibited decolourization. The presence of aromatic compounds was found to be inhibiting for the decolourization at a concentration of 10 mM, but not at 0.1 mM, while at 1 mM only ortho-diphenols were inhibiting. Probing the effect of methanol it was found that higher concentrations caused a decrease in the decolourization rate of RBBR. The effect of laccase inhibitors on the decolourization of RBBR was tested with L-cysteine, SDS and EDTA. It was demonstrated that L-cysteine was the most inhibiting substrate for the decolourization while SDS was only inhibiting at 10 mM concentration and ETDA was not inhibiting at all tested concentrations.     

Prediction of pollutant dispersion in turbulent two-phase flows

With a growing awareness of water pollution problems, in recent years there has been a considerable increased effort in developing and applying numerical models to predict accurately the contaminant distributions, particularly in free surface flows. This numerical study presents a predictive hydrodynamic model in order to explore the dispersion phenomenon of a pollutant injected from time-dependent sources in a turbulent free surface flow. More precisely, we study the impact of pulsation on the dispersion of an injected material. The air/water interface was modeled with the volume of fluid method and sharpness of the free surface was assured by means of Geo-Reconstruct scheme. The numerical results showed that the pulsation played a dominant role at the early stage of the pollutant transport. It was also observed that the pulsation affected the distribution of the injected material especially near the front and that a major swirling action was developed compared to the constant-rate-injection case.     

Effect of phosphogypsum addition in the composting process on the physico-chemical proprieties and the microbial diversity of the resulting compost tea

Environmental Science and Pollution Research - Phosphoric acid production and olive oil production are among the most important economical sectors in Tunisia. However, they generate huge amounts of...     

Biological treatment of fish processing wastewater: A case study from Sfax City (Southeastern Tunisia)

The present work presents a study of the biological treatment of fish processing wastewa at salt concentration of 55 g/L. Wastewater was treated by both continuous stirred-ta reactor(CSTR) and membrane bioreactor(MBR) during 50 and 100 days, respectively. Th biological processes involved salt-tolerant bacteria from natural hypersaline environme at different organic loading rates(OLRs). The phylogenetic analysis of the correspond excised DGGE bands has demonstrated that the taxonomic affiliation of the most domin species includes Halomonadaceae and Flavobacteriaceae families of the Proteobacteria(Gamm proteobacteria class) and the Bacteroidetes phyla, respectively. The results of MBR w better than those of CSTR in the removal of total organic carbon with efficiencies from 97 to 98.6%. Nevertheless, salinity with increasing OLR aggravates fouling that requires m cleaning for a membrane in MBR while leads to deterioration of sludge settleability a effluent quality in CSTR.     

Trace metal quantification in bladder biopsies from tumoral lesions of Tunisian cancer and controls subjects

The incidence of bladder tumors has been dramatically increasing since the 1970s, possibly as a consequence of ongoing environmental pollution. Previous studies have provided some evidence of an association between cancer and exposure to carcinogenic metals. In order to examine the association between levels of toxic metals in patients with bladder tumors and controls, the amounts of arsenic, cadmium, chromium, and nickel were measured in tumoral lesions and adjacent normal part of the bladder mucosa excised for carcinoma and compared with those in the bladder mucosa of volunteer subjects operated for non-neoplastic diseases. The quantification of metals in tissue was assessed by atomic absorption spectroscopy. In tumoral tissues of the excised bladder mucosa, content of Cr and Ni was significantly low compared to that of adjacent normal tissues and control tissues while that of As and Cd in normal tissues adjacent to the tumor were significantly elevated compared to controls. Though the sample size was small, the present study shows that concentrations of metals such as Cd, Cr, As, and Ni in bladder tissue may be used as a biomarker of exposure. On the basis of the results obtained in this study, high amounts of As and Cd in adjacent normal parts of the bladders with carcinomas compared to controls would strongly suggest possible, individual or synergistic, effects of these pollutants on enzymatic systems, priming an oncogenic pathway.     

Low-level arsenic exposure is associated with bladder cancer risk and cigarette smoking: a case–control study among men in Tunisia

Although exposure to high levels of arsenic is associated with excess bladder cancer risk, lower exposures generally are not. This study represents the first biomonitoring of arsenic exposure in Tunisia and focuses on a possible association with bladder cancer risk. In this context, 124 male bladder cancer cases and 220 controls were recruited and blood samples were analyzed to determine the concentration of As. The study subjects were stratified into median groups based on concentrations of arsenic in their blood. Blood arsenic (B-As) was significantly two to threefold higher in bladder cancer cases than in controls (p?<?0.05). The arsenic concentrations were significantly higher among both smokers and workers in construction. However, neither drinking water nor seafood was found to be incriminated as exposure sources. The adjusted risk ratios for B-As concentration categories 0.1–0.67 and ≥0.67 μg/L were 0.18 (95% CI?=?0.014–2.95) and 2.44 (95% CI?=?1.11–5.35), respectively. Arsenic levels were not found to be associated with tumor grade or stage. The considerable risk in the category of highest cumulative exposure argues for an association between bladder cancer risk and low-level arsenic exposure. Future investigations with larger samples and using techniques that allow the distinction of the different arsenic species should better elucidate this association. Furthermore, the modulation of arsenic level according to the histological grade may be of potential to be used as a diagnostic marker of the disease process and its possible relationship etiologically.