Slim Loukil

Anaerobic membrane bioreactor for the treatment of leachates from Jebel Chakir discharge in Tunisia

Landfill leachate (LFL) collected from the controlled discharge of Jebel Chakir in Tunisia was treated without any physical or chemical pretreatment in an anaerobic membrane bioreactor (AnMBR). The organic loading rate (OLR) in the AnMBR was gradually increased from 1 g COD l(-1)d(-1) to an average of 6.27 g COD l(-1)d(-1). At the highest OLR, the biogas production was more than 3 volumes of biogas per volume of the bioreactor. The volatile suspended solids (VSSs) reached a value of approximately 3 g l(-1) in the bioreactor. At stable conditions, the treatment efficiency was high with an average COD reduction of 90% and biogas yield of 0.46 l biogas per g COD removed.

Application of combined membrane biological reactor and electro-oxidation processes for the treatment of landfill leachates

Landfill leachate (LFL) is a very complex wastewater that poses considerable hazards to local communities and the environment. With this concern in mind, the present study was undertaken to investigate the performance of an aerobic membrane bioreactor treating raw LFL from Djebel Chekir (Tunisia) discharge. The LFL samples collected from this site were found to be highly loaded with organic matter, ammonia, salts, greases, phenols and hydrocarbons. Important removals of chemical oxygen demand (COD) and NH4+-N were attained after 44 days of treatment at optimum conditions for the membrane and with organic loading rates (OLR) of 1.9 and 2.7 grams COD per litter and day. This treatment allowed for an important detoxification of the landfill leachates and a significant elimination of the microorganisms. Electrochemical oxidation using Pi/Ti was applied as a post-treatment and after the biological process in order to reduce the residual ammonia and COD. At a pH value of 9, current density of 4 A dm(-2) and electrolysis time of 60 minutes, COD and ammonia nitrogen were reduced to 1,000 mg L(-1) and 27 mg L(-1), respectively. COD and NH4+-N removals were accompanied by significant detoxification.

Treatment of textile wastewater by submerged membrane bioreactor: In vitro bioassays for the assessment of stress response elicited by raw and reclaimed wastewater

The performance of a pilot-scale membrane bioreactor (MBR) system for the treatment of textile wastewater was investigated. The MBR was continuously operated for 7 months. Very high treatment efficiencies were achieved (color, 100%; chemical oxygen demand (COD), 98%; biochemical oxygen demand (BOD5), 96%; suspended solids (SS), 100%). Furthermore, the MBR treatment efficiency was analyzed from a toxicological-risk assessment point of view, via different In vitro bioassays using Caco-2 cells, a widely used cell model in toxicological studies. Results showed that MBR treatment significantly reduced the raw textile wastewater (RTWW) cytotoxicity on Caco-2 cells by 53% for a hydraulic retention time (HRT) of 2 days. Additionally, the RTWW-induced disruption in the barrier function (BF) of the Caco-2 cell monolayer was also significantly reduced after MBR treatment under a HRT of 2 days (no disruption of BF was observed). Moreover, the effect of RTWW and treated wastewater on stress response was investigated using different stress genes: AHSA1, HSPD1, HSPA1A, HSPA5 and HSPA8. The cell exposure to RTWW significantly increased the expression of all used stress genes; interestingly, the treated wastewater (HRT 2 days) did not show any significant modulation of the stress genes.

Anaerobic co-digestion of Tunisian green macroalgae Ulva rigida with sugar industry wastewater for biogas and methane production enhancement

Ulva rigida is a green macroalgae, abundantly available in the Mediterranean which offers a promising source for the production of valuable biomaterials, including methane. In this study, anaerobic digestion assays in a batch mode was performed to investigate the effects of various inocula as a mixture of fresh algae, bacteria, fungi and sediment collected from the coast of Sfax, on biogas production from Ulva rigida. The results revealed that the best inoculum to produce biogas and feed an anaerobic reactor is obtained through mixing decomposed macroalgae with anaerobic sludge and water, yielding into 408mL of biogas. The process was then investigated in a sequencing batch reactor (SBR) which led to an overall biogas production of 375mL with 40% of methane. Further co-digestion studies were performed in an anaerobic up-flow bioreactor using sugar wastewater as a co-substrate. A high biogas production yield of 114mL g-1 VSadded was obtained with 75% of methane. The co-digestion proposed in this work allowed the recovery of natural methane, providing a promising alternative to conventional anaerobic microbial fermentation using Tunisian green macroalgae. Finally, in order to identify the microbial diversity present in the reactor during anaerobic digestion of Ulva rigida, the prokaryotic diversity was investigated in this bioreactor by the denaturing gradient gel electrophoresis (DGGE) method targeting the 16S rRNA gene.

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.

Characterization and Toxicity Assessment of Wastewater from Rock Phosphate Processing in Tunisia

Phosphate ore processing wastewater (WWPP) from the Gafsa phosphate region of Tunisia was characterized. The WWPP had a very high turbidity, an almost neutral or slightly alkaline pH, and high salinity. The average chemical and biochemical oxygen demands (COD and BOD) met wastewater discharge standards, but the COD/BOD5 (4.34) significantly exceeded biodegradability values. Total nitrogen, residual phosphorus, and some others chemical constituents exceeded wastewater discharge standards. Microbiological enumeration showed that the effluents were very low in microflora. Untreated WWPP and diluted (WWPP/4) inhibited bioluminescence of Vibrio fischeri by 76 and 45%, respectively. The WWPP had a phytotoxicity rate of 20–70%, respectively, for alfalfa and tomato seeds. Adding the effluent to soil for 60 days reduced the residual phytotoxicity of the WWPP-irrigated soil to about 15 and 34%, respectively, for tomato and alfalfa seeds.ZusammenfassungAbwasser der Phosphatgesteinsverarbeitung in der Gafsa-Phosphatregion in Tunesien wurde charakterisiert. Das Abwasser hatte eine sehr hohe Trübung, nahezu neutrale bis schwach alkalische pH-Werte und eine hohe Salinität. Der durchschnittliche chemische und biochemische Sauerstoffbedarf (CSB und BSB5) entsprach den Abwasserableitungsstandards. Jedoch überstieg das Verhältnis CSB/BSB5 (4,34) signifikant die Werte für biologische Abbaubarkeit. Gesamtstickstoff, Phosphor und andere chemische Wasserinhaltsstoffe überschritten die Abwasserableitungsstandards. Zählungen der Mikroorganismen ergaben, dass die Besiedlung mit Mikroorganismen sehr gering war. Unbehandeltes Abwasser der Phosphatgesteinsverarbeitung hemmte die Biolumineszenz von Vibrio fischeri zu 75% und verdünntes (1:4) Abwasser der Phosphatgesteinsverarbeitung zu 45%. Das Abwasser der Phosphatgesteinsverarbeitung hatte eine Phytotoxizität von 20 bis 70% bei Samen von Alfagras und Tomaten. Die Wechselwirkung des Abwassers der Phosphatgesteinsverarbeitung mit Boden für 60 Tage verringerte die Phytotoxizität bei Tomaten- und Alfagrassamen auf 15% bzw. 34%, wenn der Boden mit Abwasser der Phosphatgesteinsverarbeitung bewässert wurde.ResumenSe caracterizó el agua residual proveniente del procesamiento de mineral fosfatado (WWPP) en la región Gafsa de Túnez. WWPP tenía una muy alta turbidez, un pH casi neutro o ligeramente alcalino y una alta salinidad. Las demandas química y bioquímica de oxígeno (COD y BOD), en promedio, cumplieron los estándares para agua de descarga pero COD/BOD5 (4,34) excedieron significativamente los valores de biodegradabilidad. El nitrógeno total, el fósforo residual y algunos otros constituyentes químicos excedieron los estándares para agua de descarga. El conteo microbiológico mostró que los efluentes tuvieron baja microflora. Tanto WWPP como su dilución (WWPP/4) inhibieron la bioluminiscencia de Vibrio fischeri en 76% y 45%, respectivamente. WWPP tiene una tasa de fitotoxicidad de 20 a 70% para semillas de alfalfa y de tomate, respectivamente. El agregado del efluente al suelo por 60 días redujo la fitotoxicidad residual del suelo irrigado con WWPP en 15% y 34% para semillas de tomate y de alfalfa, respectivamente.突尼斯磷矿加工废水及毒理特征研究了突尼斯Gafsa磷矿区矿石加工废水(WWPP)的特征。磷矿石加工废水以浊度高、中~微碱性和矿化度高为特征。磷矿石加工废水的平均化学需氧量(COD)和生物需氧量(BOD)都满足废水排放标准,但是它们的比值COD/BOD (4.34)却严重超出生物降解能力。磷矿石加工废水的总氮、残余磷和某些其它化学成分也超过废水排放标准。微生物枚举分析显示磷矿石加工废水的微生物群落数量非常少。未处理的和四倍稀释(WWPP/4)的磷矿加工废水对Vibrio fischeri荧光抑制分别达76%和45%。磷矿石废水对苜蓿(alfalfa)种子和番茄(tomato)种子的植物毒性分别为20%和70%。磷矿加工废水排放至土壤中60天后可减小磷矿加工废水灌溉土壤对苜蓿种子和番茄残种子植物毒性的15%和34%。