Olive mill wastewater treatment using natural adsorbents: phytotoxicity on durum wheat (Triticum turgidum L. var. durum) and white bean (Phaseolus vulgaris L.) seed germination.

This research was undertaken to optimize the phenolic compound removal from Olive Mill Wastewater (OMW) by sawdust and red clay as natural adsorbents. Fractional factorial experimental design at 25-1 was used in order to optimize the experimental conditions for high removal efficiency. Statistics ANOVA analysis, Fisher's test, and Student's test suggested that the adsorbent dose has the most significant influence on polyphenol removal for both adsorbents. The maximum removal of polyphenols by sawdust reached 49.6% at 60 °C by using 60 g/L of adsorbent dose, pH 2, reaction time of 24 h, and agitation speed of 80 rpm. Whereas, for red clay, 48.08% of polyphenols removal was observed under the same conditions for sawdust except the temperature of 25 °C instead of 60 °C. In addition, the thermodynamic parameters suggested spontaneous process for both adsorbents, endothermic for the sawdust and exothermic for red clay. Furthermore, the phytotoxicity effect of OMW on durum wheat (Triticum turgidum L. var. durum) and white bean (Phaseolus vulgaris L.) seed germination was investigated. The obtained results showed that the untreated OMW inhibited the seed germination of T. turgidum and P. vulgaris seeds. OMW treatment with red clay followed by dilution (95% water) resulted in 87 and 30% germination of P. vulgaris and T. turgidum, respectively. While, the treatment of OMW with sawdust and dilution at 95% resulted in 51 and 26% germination of P. vulgaris and T. turgidum, respectively.

Assessment of the impact of diluted and pretreated olive mill wastewater on the treatment efficiency by infiltration-percolation using natural bio-adsorbents.

The current study was carried out to treat the olive mill wastewater (OMW) via infiltration percolation process, using low-cost natural adsorbents that could improve the ability of the system to enhance the disposal rate of elimination of pollutant from the OMW. The experimental pilot was composed of three PVC (polyvinyl chloride) columns with 10 cm in diameter and 110-cm height equipped with lateral air entries. Each column was filled with four layers of 10 cm of a mixture of sand (70%), charcoal (20%) and sawdust (10%) respectively. These layers were alternated by four permeable layers of 10 cm of Pouzzolane. To assess the effect of the pretreatment on the efficiency of the system, three types of OMW were used: raw OMW, diluted OMW with domestic wastewater at 1/1(v/v) ratio and OMW pretreated with lime. For the column feed with raw OMW, an average removal of total COD (41%), dissolved COD (54%), NH4-N (40.25%), NO3- (15.76%), total phosphorus (55.63%) and orthophosphate (50.84%) was recorded. The results showed that the column feed with diluted OMW with domestic wastewater was the most efficient one with a removal rate that reached 93.2% of total COD, 86.2% of dissolved COD, 92% of polyphenol, 92% of orthophosphate (OP), 97.2% of total phosphorus (TP) and 81% of NH4-N. The pretreatment of OMW with lime gave the lowest removal rate for all the parameters: total COD (34%), dissolved COD (50%), NH4-N (30%), NO3- (- 21%), total phosphorus (15.19%) and orthophosphate (9.04%). This study demonstrated that the dilution is a way to optimize the efficiency of the system of infiltration-percolation in treating the OMW.

Flagellar Phenotypes Impact on Bacterial Transport and Deposition Behavior in Porous Media: Case of Salmonella enterica Serovar Typhimurium.

Bacterial contamination of groundwater has always been an ecological problem worthy of attention. In this study, Salmonella enterica serovar Typhimurium with different flagellar phenotypes mainly characterized during host-pathogen interaction were analyzed for their transport and deposition behavior in porous media. Column transport experiments and a modified mobile-immobile model were applicated on different strains with flagellar motility (wild-type) or without motility (ΔmotAB), without flagella (ΔflgKL), methylated and unmethylated flagellin (ΔfliB), and different flagella phases (fliCON, fljBON). Results showed that flagella motility could promote bacterial transport and deposition due to their biological advantages of moving and attaching to surfaces. We also found that the presence of non-motile flagella improved bacterial adhesion according to a higher retention rate of the ΔmotAB strain compared to the ΔflgKL strain. This indicated that bacteria flagella and motility both had promoting effects on bacterial deposition in sandy porous media. Flagella phases influenced the bacterial movement; the fliCON strain went faster through the column than the fljBON strain. Moreover, flagella methylation was found to favor bacterial transport and deposition. Overall, flagellar modifications affect Salmonella enterica serovar Typhimurium transport and deposition behavior in different ways in environmental conditions.

Transport and retention of bacteria through a filtration system consisting of sands and geotextiles.

Water-saturated column experiments were conducted to study the effect of nonwoven geotextiles on bacteria transport and deposition through two sandy porous media with grain sizes 1.05 and 3.25 mm. The breakthrough curves (BTCs) of tracer for the all porous media exhibited an asymmetrical shape with a substantial tailing, indicating that non-equilibrium and dispersive flow patterns in these porous media. The mass recovery of the bacteria from the effluent (Meff) increased with grain size. The retention profiles (RPs) exhibited hyper-exponential behavior, especially in the finer sand. The presence of the geotextiles increased bacteria retention rate. For a given geotextile, greater retention was observed in the surrounding region close to the geotextile. Moreover, the retention of bacteria became more significant in the geotextile with a lower porosity. Results demonstrated that model simulations of bacteria transport and fate need to accurately account for both observed BTC and RP behaviors and also the geotextile placement can impact mechanisms of retention.

Bacteria transport and deposition in an unsaturated aggregated porous medium with dual porosity.

Bacterial transport and deposition play an important role in the assessment and prediction of subsurface pollution risks. Bacteria transport experiments were performed under unsaturated flow conditions in an aggregated porous medium at the laboratory column scale, to investigate how the inter- and intra-aggregated pore space of this medium could affect transport and deposition under unsaturated flow conditions, where inter- and intra-pore spaces are not fully activated. The results obtained through experimental observations and numerical simulations showed that some intra- and inter-pore space of this medium was excluded from bacteria transport and retention, as confirmed by the non-uniform transport of bacteria pathways in the aggregated porous media under unsaturated flow conditions. Capillary energy was higher the than other forces acting at bacteria air-water-solid interfaces. If this energy should contribute in increasing bacteria deposition under unsaturated conditions, similar to what has been reported for sandy media, similar overall retention of E. coli and R. rhodochrous was obtained under unsaturated flow conditions, suggesting that capillary energy was not the driving force for bacteria deposition.

DLVO, hydrophobic, capillary and hydrodynamic forces acting on bacteria at solid-air-water interfaces: Their relative impact on bacteria deposition mechanisms in unsaturated porous media.

Experimental and modeling studies were performed to investigate bacteria deposition behavior in unsaturated porous media. The coupled effect of different forces, acting on bacteria at solid-air-water interfaces and their relative importance on bacteria deposition mechanisms was explored by calculating Derjaguin-Landau-Verwey-Overbeek (DLVO) and non-DLVO interactions such as hydrophobic, capillary and hydrodynamic forces. Negatively charged non-motile bacteria and quartz sands were used in packed column experiments. The breakthrough curves and retention profiles of bacteria were simulated using the modified Mobile-IMmobile (MIM) model, to identify physico-chemical attachment or physical straining mechanisms involved in bacteria retention. These results indicated that both mechanisms might occur in both sand. However, the attachment was found to be a reversible process, because attachment coefficients were similar to those of detachment. DLVO calculations supported these results: the primary minimum did not exist, suggesting no permanent retention of bacteria to solid-water and air-water interfaces. Calculated hydrodynamic and resisting torques predicted that bacteria detachment in the secondary minimum might occur. The capillary potential energy was greater than DLVO, hydrophobic and hydrodynamic potential energies, suggesting that film straining by capillary forces might largely govern bacteria deposition under unsaturated conditions.

Bacteria cell properties and grain size impact on bacteria transport and deposition in porous media.

The simultaneous role of bacteria cell properties and porous media grain size on bacteria transport and deposition behavior was investigated in this study. Transport column experiments and numerical HYDRUS-1D simulations of three bacteria with different cell properties (Escherichia coli, Klebsiella oxytoca, and Rhodococcus rhodochrous) were carried out on two sandy media with different grain sizes, under saturated steady state flow conditions. Each bacterium was characterized by cell size and shape, cell motility, electrophoretic mobility, zeta potential, hydrophobicity and potential of interaction with the sand surface. Cell characteristics affected bacteria transport behavior in the fine sand, but similar bacteria breakthroughs and retardation factors observed in the coarse sand, indicated that bacteria transport was more depended on grain size than on bacteria cell properties. Retention decreased with increasing hydrophobicity and increased with increasing electrophoretic mobility of bacteria for both sand. The increasing sand grain size resulted in a decrease of bacteria retention, except for the motile E. coli, indicating that retention of this strain was more dependent on cell motility than on the sand grain size. Bacteria deposition coefficients obtained from numerical simulations of the retention profiles indicated that straining was an important mechanism affecting bacteria deposition of E. coli and Klebsiella sp., in the fine sand, but the attachment had the same importance as straining for R. rhodochrous. The results obtained in the coarse sand did not permit to discriminate the predominant mechanism of bacteria deposition and the relative implication of bacteria cell properties of this process.

Modeling of an aerobic bioprocess based on gas exchange and dynamics: a novel approach.

Monitoring of the biological degradation of a substrate by microorganisms is a key issue, especially in the soil bioremediation area. Respiration measurement is the easiest way to obtain online information on the biological activity. Nevertheless, it is indirectly related to substrate consumption and microbial growth. To be able to link these phenomena, a robust and descriptive model has been developed. Both biological and gas/liquid transfer dynamics must be taken into account to link the online measurement with the actual biological respiration. For that, experimental evolution of the respiratory ouotient (RQ) during a biodegradation has been compared against general biodegradation knowledge. To obtain a reliable model, practical and structural sensitivity analyses have been conducted. The model can describe the evolution of both online measurable and non-measurable states. It also gives a new definition of the apparent RQ, measured in the gas phase, compared to the actual biological RQ.