Fathi Aloui

Detrimental effects of high molecular-mass polyphenols on olive mill wastewater biotreatment

Research was undertaken to investigate whether low, medium or high molecular-mass polyphenolics were the most problematic compounds for olive mill wastewater (OMW) biotreatments. For this reason, three polyphenolic fractions were isolated by ultrafiltration of crude OMW and characterized by GC/MS and gel filtration analysis. When P. chrysosporium was cultivated in the presence of F1 polyphenolic fraction (F1 60 kDa) was observed. Lignin peroxidase (LiP) was detected as traces for the F1 fraction and undetected in the case of F3 one. Moreover, increasing the molecular-mass of aromatics led to decreases in levels of depolymerization and COD removal by P. chrysosporium cultures. The use of a lignin peroxidase induction medium has a positive effect on the high molecular-mass fraction decolorization and a high degree of decolorization paralleled the appearance of LiP activity in the extracellular fluid. By comparison to the synthetic medium used, LiP production was delayed in the presence of F1 fraction but strongly inhibited (80% loss) in the presence of F3 fraction. The F1 fraction was well degraded aerobically by P. putida DSM3932 (pWWO) and A. eutrophus DSM 4057 (pJP3) or an activated sludge consortium while F3 resisted degradation by the OMW-acclimated activated sludge. Moreover, continuous anaerobic biomethanization experiments conducted in parallel with the different fractions showed that at the same hydraulic retention time (26 days), the F1 fraction was bioconverted into methane at high yield while F3 fraction was poorly biodegraded.

Physicochemical treatments of anionic surfactants wastewater: Effect on aerobic biodegradability.

The effect of different physicochemical treatments on the aerobic biodegradability of an industrial wastewater resulting from a cosmetic industry has been investigated. This industrial wastewater contains 11423 and 3148mgL(-1) of chemical oxygen demand (COD) and anionic surfactants, respectively. The concentration of COD and anionic surfactants were followed throughout the diverse physicochemical treatments and biodegradation experiments. Different pretreatments of this industrial wastewater using chemical flocculation process with lime and aluminium sulphate (alum), and also advanced oxidation process (electro-coagulation (Fe and Al) and electro-Fenton) led to important COD and anionic surfactants removals. The best results were obtained using electro-Fenton process, exceeding 98 and 80% of anionic surfactants and COD removals, respectively. The biological treatment by an isolated strain Citrobacter braakii of the surfactant wastewater, as well as the pretreated wastewater by the various physicochemical processes used in this study showed that the best results were obtained with electro-Fenton pretreated wastewater. The characterization of the treated surfactant wastewater by the integrated process (electro-coagulation or electro-Fenton)-biological showed that it respects Tunisian discharge standards.

Electrochemical oxidation post-treatment of landfill leachates treated with membrane bioreactor

Integration of membrane bioreactor (MBR) with electrochemical process was investigated as treatment of stabilized landfill leachates, collected from Djebel Chekir (Tunisia). Results showed that at optimum conditions for the membrane and with organic loading rates of 1.9 and 2.7g COD L(-1)d(-1), MBR treated effluent is still colouring and contains high COD and ammonia concentrations. In order to reduce these high pollutant concentrations, electrochemical oxidation process using Ti/Pt, graphite and PbO(2) electrodes, was tested as effluent post-treatment. Ti/Pt electrodes showed the best performance. COD, ammonia and colours removals were affected by the current density (J) and treatment time (t). At optimal operational conditions (t=1h, J=4Adm(-2)), the final COD and total kjeldahl nitrogen concentrations (TKN) were 1000 and 86mgL(-1), respectively. The final treated wastewater COD, TKN, colours, pH meet the discharge standards in the sewer. The combination of MBR treatment process with electrochemical oxidation can be a technical suitable solution for stabilized landfill leachates treatment with an efficient reduction of different parameters, essentially COD (85%), TKN (94%), and colour(436) (99%).

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.

Isolation and Characterization of Hydrocarbon-Degrading Yeast Strains from Petroleum Contaminated Industrial Wastewater.

Two yeast strains are enriched and isolated from industrial refinery wastewater. These strains were observed for their ability to utilize several classes of petroleum hydrocarbons substrates, such as n-alkanes and aromatic hydrocarbons as a sole carbon source. Phylogenetic analysis based on the D1/D2 variable domain and the ITS-region sequences indicated that strains HC1 and HC4 were members of the genera Candida and Trichosporon, respectively. The mechanism of hydrocarbon uptaking by yeast, Candida, and Trichosporon has been studied by means of the kinetic analysis of hydrocarbons-degrading yeasts growth and substrate assimilation. Biodegradation capacity and biomass quantity were daily measured during twelve days by gravimetric analysis and gas chromatography coupled with mass spectrometry techniques. Removal of n-alkanes indicated a strong ability of hydrocarbon biodegradation by the isolated yeast strains. These two strains grew on long-chain n-alkane, diesel oil, and crude oil but failed to grow on short-chain n-alkane and aromatic hydrocarbons. Growth measurement attributes of the isolates, using n-hexadecane, diesel oil, and crude oil as substrates, showed that strain HC1 had better degradation for hydrocarbon substrates than strain HC4. In conclusion, these yeast strains can be useful for the bioremediation process and decreasing petroleum pollution in wastewater contaminated with petroleum hydrocarbons.

PERFORMANCE OF BIOLOGICAL TREATMENT OF HIGH‐LEVEL AMMONIA LANDFILL LEACHATE

Abstract The biological treatment efficiency of landfill leachate (LFL) from a Tunisian site collection was investigated in this study. The raw effluent was highly charged with organic matter (more than 25 g l−1 of chemical oxygen demand (COD)), ammonia (1.7 g l−1) and salts (20 g l−1). With the presence of heavy metals, phenols and hydrocarbons, LFL exhibited high toxicity to organisms since it totally inhibited the bioluminescence of Vibrio fischeri and the germination of Lepidium sativum seeds. The biological oxygen demand (BOD5)/COD ratio of 0.5 indicates that the effluent can be biologically treated. Sludge from a wastewater treatment plant was acclimatized to the effluent in continuous batches. During the acclimatization phase, the consortia demonstrated a good ability to remove organic matter and toxicity in spite of an increase of introduced load reaching 3.2 g of COD 1.d. Consequently, the biodegradation experiments were carried out in a stirred tank reactor (STR) at organic loading rate (OLR) ranging from 0.5 to 5.4 g l−1 per day. The hydraulic retention time was decreased from 50 days to 4.6 days. The process seemed to be efficient to eliminate organics and ammonia. The COD removal efficiency reached a maximum of 80% for a loading rate of 5.4 g l−1 per day. The values of N‐NH4 + became less than those recommended by standards requested for rejection in public canalizations. During the treatment process, the biomass was increased from 0.8 g l−1 at the start‐up of the process to 3 g l−1. On the other hand, results of toxicity examinations showed that the treatment was efficient to provide detoxification of the effluent indicating a good adaptability of the consortia in spite of the presence of problematic compounds. The increase of the loading rate up to 6 g l−1 was responsible for the perturbation of the system and caused an accumulation of residual COD and toxicity.

A comparative study of the industrial discharges effect on the anaerobic treatment of domestic wastewater in both experimental and pilot‐plant scales

The aim of this study was to compare the effect of industrial discharges on the anaerobic treatment of domestic wastewater in both laboratory and pilot‐plant scales at mesophilic conditions. The laboratory experiment results have shown the low process efficiency of anaerobic treatment of DW by the use of an adapted or a non‐adapted methanogenic inoculum. These experiments performed in batch digesters were further confirmed by scaling up to a pilot‐plant anaerobic membrane bioreactor (MBR). The treatment inefficiency in both laboratory and pilot‐plant experiments could be related to the presence of toxic compounds due to the wastewater contamination by industrial discharges. The toxic character of DW was proved by the phytotoxicity and microtoxicity tests. Indeed, the luminescence inhibition percentages started at an average of 21% in the morning and reached more than 84% in the late afternoon. Moreover, the toxicity results have shown a direct relation with methanization results. Indeed, when the average microtoxicity increased to 73%, the average germination index value and the methanization efficiency expressed as the average methane percentage in the produced biogas decreased to 0% and 14.5%, respectively.

Olive mill wastewater sludge from evaporation ponds: evolution of physico-chemical parameters during storage and composting process.

The evolution of analytical parameters of olive mill waste water sludge stored in evaporation ponds was investigated after one year and two years of storage. It was observed that some of the phenolic monomer compounds resisted removal and the fraction of water soluble phenols was only slightly polymerised. Co-composting of the sludge was carried out with yard trimming as bulking agent ratio and poultry manure to balance the C/N. Three turned piles with three proportions of 35%, 65% and 80% of olive mill waste water sludge were prepared. Co-composting of the sludge was possible in all the cases. Best results were obtained, however, at a proportion of 35% which permitted a shorter composting time, a higher degree of nitrification and a higher rate of total phenols decreasing. A high polymerisation of the fraction of water soluble phenols was observed at the end of composting in all the piles.

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%。