Membrane bioreactor (MBR) has been proven to be an efficient technology capable of treating various industrial effluents. However, the evaluation of its performances in the case of olive mill wastewater (OMW) over a conventional activated sludge (CAS) have not been determined yet. The present study aims to compare OMW treatment in two laboratory scale pilots: an external ceramic MBR and CAS starting with an acclimation step in both reactors by raising OMW concentration progressively. After the acclimation step, the reactors received OMW at 2 gCOD/L with respect to an organic loading rate of 0.2 and 0.3 kgCOD/kgMLVSS/d for MBR and CAS, respectively. Biomass acclimation occurred successfully in both systems; however, the MBR tolerated more OMW toxicity than CAS as the MBR always maintained an effluent with a better quality. At a stable state, a higher reduction of 95% chemical oxygen demand (COD) was obtained with MBR compared to CAS (86%), but both succeeded in polyphenols removal (80%). Moreover, a higher MLSS elimination from the MBR treated water (97%) was measured against 88% for CAS. Therefore, CAS was suitable for OMW treatment and MBR could be proposed as an alternative to CAS when a better quality of treated water is required.

The Olive Mill Wastewater (OMWW) biodegradation in an external ceramic membrane bioreactor (MBR) was investigated with a starting acclimation step with a Ultrafiltration (UF) membrane (150 kDa) and no sludge discharge in order to develop a specific biomass adapted to OMWW biodegradation. After acclimation step, UF was replaced by an Microfiltration (MF) membrane (0.1 µm). Sludge Retention Time (SRT) was set around 25 days and Food to Microorganisms ratio (F/M) was fixed at 0.2 kgCOD kgMLVSS-1 d-1. At stable state, removal of the main phenolic compounds (hydroxytyrosol and tyrosol) and Chemical Oxygen Demand (COD) were successfully reached (95% both). Considered as a predominant fouling factor, but never quantified in MBR treated OMWW, Soluble Microbial Products (SMP) proteins, polysaccharides and humic substances concentrations were determined (80, 110 and 360 mg L-1 respectively). At the same time, fouling was easily managed due to favourable hydraulic conditions of external ceramic MBR. Therefore, OMWW could be efficiently and durably treated by an MF MBR process under adapted operating parameters.

The performance of a biomass adapted to Oncological Ward Wastewater (OWW) in a membrane bioreactor (MBR) was compared with that of a municipal WWTP, on the removal of pharmaceutical molecules and more specifically on their overall resistance and purifying ability in the presence of pharmaceutical cocktails. Sorption and biotransformation mechanisms on two antineoplastics, one antibiotic and a painkiller were evaluated. Sludge acclimated to OWW allowed for a 34% increase in the removal rate and in the minimum inhibition concentration. The percentage of the amounts of specific pharmaceutical compounds removed by biotransformation or by sorption were measured. These results are positive, as they show that the observed removal of pharmaceutical molecules by biomass acclimated to OWW can mostly be attributed to developed biotransformation, unlike the biomass from the municipal WWTP for which sorption is sometimes the only removal mechanism. The biotransformation kinetic and the solid-water distribution coefficients in this study show good agreement with literature data, even for much higher pharmaceutical concentrations in OWW.

Discharges of care, analyses and research activities from hospital wards are the source of the specificity of hospital effluents because they contain, among others, drug residues, detergents and disinfectants. Even if hospitals represent a small fraction of the total drug load discharged into the environment, below 10% for drugs, the characterization of this specific effluent shows that global pollution is 2–3 times more concentrated than urban wastewater. Moreover this ratio increases to 150 times for some micropollutants. Activated sludge acclimation in 2 membrane bioreactor (MBR) configurations (external and external submerged) to effluents from an oncological ward will be studied monitoring the performances on conventional pollution parameters (chemical oxygen demand, ammonium, total suspended solids etc.). The performances of drug degradation are compared with the data of the literature and with degradation tests in batch reactor with no acclimated biomass from a municipal wastewater treatment plant. The results are achieved for effluents with a high concentration of drug molecules, up to 6.82mgL−1 for ifosfamide. The treatment allows the development of enhanced purification efficiencies on drug molecules and confirms the choice of a MBR process to treat this effluent, although the simultaneous presence of the various compounds leads to a complex biological response. Indeed, 5-FU was eliminated almost systematically over 90%. Sulfamethoxazole and codeine can be significantly eliminated biologically, respectively to 79 and 95%. IF and CP removal in the reactor appeared more moderate since it does not exceed 40% but membrane fouling led to higher removals of both molecules.

This study is a first kinetic approach about the compost liquor treatment by activated sludge. This industrial wastewater is highly loaded in organic and nitrogen compounds (COD≈12,000 mg L(-1) and NH(4)(+)-N≈4,000 mg L(-1)). The possibility of its treatment in an urban WWTP is studied measuring ammonia oxidation rate with non-acclimated sludge to the industrial effluent. Compost liquor appears as an inhibitor substrate. The ammonia oxidation rate can be modelled by the Haldane model: U(MAX)=0.180 d(-1), K(S)=12.0 mgN.L(-1) and K(I)=26.0 mgN.L(-1). The ammonia oxidation rate also follows for a synthetic substrate which has the same pollutant load as the real substrate. In this case, the ammonia oxidation rate can be modelled by the Monod model: U(MAX)=0.073 d(-1) and K(S)=4.3 mgN.L(-1). This result confirms that the ammonia oxidising bacteria are inhibited by the real wastewater. The following-up of nitrate production shows also the inhibition of nitrite oxidising bacteria. The compost liquor treatment seems not possible in an urban WWTP (<50,000 p.e.). That's why a specific WWTP is recommended and an acclimation step of activated sludge is essential.

An external ceramic membrane bioreactor was used to carry out an experimental study of process stability and fouling aspects for olive mill wastewater (OMW) treatment. Three diluted OMW solutions were used to continuously feed the reactor. An acclimated biomass was employed and the process stability was followed on the basis of the permeate quality and some operating parameters (pressure, temperature, mass flow and dissolved oxygen). Several backpulse combinations were tested to determine the best filtration and backwash time. It appeared that a short backpulse duration was sufficient and that the behaviour, in terms of the permeate flux versus time, stabilized. In terms of increased permeate flux, the effect of the backpulsing depended on the nature of the solution. This improvement was limited, but, in the long‐term, backpulsing makes it possible to maintain a constant permeate flux over a period of several days.

Although microorganism respiration inhibition by sodium azide (NaN3) is used in some studies to identify activated sludge adsorption capacity, little is known about the effect of this compound on the suspension properties. In this study we have investigated the effect of NaN3 addition on both volumetric oxygen mass transfer coefficient and rheology of activated sludge (AS) suspensions in a 1.9 L bioreactor. The rheological properties (shear thinning one) of AS suspensions with and without NaN3 addition are measured in situ (triphasic conditions). It appears that NaN3 addition leads to a deflocculation of AS suspensions and thus a decrease in apparent viscosity. A small amount of suspended solids was added in order to obtain identical apparent viscosities (under 1.2 or 46.3 s−1) for AS suspensions with and without NaN3 addition. KLa values were then measured in both respiring and non-respiring suspensions for different air flow rates (2, 3 or 4 L/min) and under low or high mechanical shear rate (1.2 or 46.3 s−1). Results show that under high mechanical shear rate, the respiration state for a given air flow rate does not impact the KLa values. On the contrary, under low mechanical shear rate, NaN3 addition induces an increase of KLa values in comparison with those obtained with the respiring biomass. This effect, for a same apparent viscosity, is attributed to the deflocculation observed in the presence of NaN3. Indeed, AS with and without NaN3 addition used for the KLa measurements induce a modification of the floc internal structure, corresponding to smaller floc size in the case of NaN3 addition.

The synthetic hormone 17α-ethinylestradiol (EE2) is an endocrine disrupter of great concern with insufficient removal in wastewater treatment plants (WWTP) and subsequent impacts on the aquatic environment. In this paper, membrane bioreactor (MBR) technology was compared with conventional activated sludge (CAS) systems. Contrary to previous studies on MBRs, continuous purification was combined with the determination of sorption and biodegradation parameters. In addition, EE2 removal was studied in two different MBR configurations. Continuous purification with AS acclimated in the MBR (MLVSS of 9gL−1 and a 50-d SRT) resulted in the stabilization of the EE2 removal at a plateau of 65% (initial load of 1.8mgEE2gMLVSS−1d−1). In contrast, CAS resulted in EE2 accumulation in the permeate. During batch kinetics, CAS was shown to remove EE2 only through sorption (87% removal of EE2) whereas AS acclimated to the MBR process developed biodegradation abilities towards the synthetic hormone (7% removal of EE2). Therefore, the membrane process combined with AS was shown to be essential to improve EE2 removal (with the autotrophic activity as the key factor). In addition, either the external or the external-immersed configuration can be applied, due to similar performance with respect to EE2 removal.

The aim of this paper was to determine the effect of two different membrane bioreactor (MBR) configurations (external/immersed) on sludge structure and microbial activity. Sludge structure was deduced from rheological measurements. The high shear stress induced by the recirculation pump in the external MBR was shown to result in decreasing viscosity due to activated sludge (AS) deflocculation. Besides, soluble microbial products (SMP) release was higher in the external MBR (5mgCODgMLVSS−1) than in the immersed configuration (2mgCODgMLVSS−1). Microbial activity was followed from respirometry tests by focusing on the distinction between heterotrophs and autotrophs. An easier autotrophic microbe development was then observed in the immersed MBR compared to the external one. However, the external MBR was shown to allow better heterotrophic microbe development.

The synthetic hormone 17α-ethinylestradiol (EE2) is primarily removed in wastewater treatment plants (WWTPs) by sorption, and nitrifying biomass has been shown to be responsible for EE2 biodegradation. Membrane bioreactor (MBR) technology was chosen to develop a community of autotrophic, nitrifying micro-organisms and determine kinetic parameters for EE2 biodegradation. Biological inhibition by azide was applied to differentiate sorption from biodegradation. Activated sludge (AS) was acclimated in the MBR to a substrate specific to autotrophic biomass and resulted in an increase in nitrifying activity. Acclimated AS was used to successfully biodegrade EE2 (11% increase in EE2 removal), and the overall removal of EE2 was determined to be 99% (sorption+biodegradation). AS used directly from a WWTP without acclimation removed EE2 only through sorption (88% removal of EE2). Therefore, higher nitrifying activity developed by acclimating AS allowed almost complete removal of EE2.