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The growing concern about antibiotic-resistant microorganisms has focused on the sludge from wastewater treatment plants (WWTPs) as a potential hotspot for their development and spread. To this end, it seems relevant to analyze the changes on the microbiota as a consequence of the antibiotics that wastewater may contain. This study aims at determining whether the presence of sulfamethoxazole (SMX), even in relatively low concentrations, modifies the microbial activities and the enzymatic expression of an activated sludge under aerobic heterotrophic conditions. For that purpose, we applied a metaproteomic approach in combination with genomic and transformation product analyses. SMX was biotransformed, and the metabolite 2,4(1H,3H)-pteridinedione-SMX (PtO-SMX) from the pterin-conjugation pathway was detected at all concentrations tested. Metaproteomics showed that SMX at 50–2000 μg/L slightly affected the microbial community structure, which was confirmed by DNA metabarcoding. Interestingly, an enhanced activity of the genus Corynebacteriumand specifically of five enzymes involved in its central carbon metabolism was found at increased SMX concentrations. Our results suggest a role of Corynebacteriumgenus on SMX risks mitigation in our bioreactors.

The presence of organic micropollutants in water and sediments motivates investigation of their biotransformation at environmentally low concentrations, usually in the range of μg L–1. Many are biotransformed by cometabolic mechanisms; however, there is scarce information concerning their direct metabolization in this concentration range. Threshold concentrations for microbial assimilation have been reported in both pure and mixed cultures from different origins. The literature suggests a range value for bacterial growth of 1–100 μg L–1for isolated aerobic heterotrophs in the presence of a single substrate. We aimed to investigate, as a model case, the threshold level for sulfamethoxazole (SMX) metabolization in pure cultures of Microbacteriumstrain BR1. Previous research with this strain has covered the milligram L–1range. In this study, acclimated cultures were exposed to concentrations from 0.1 to 25 μg L–1of 14C-labeled SMX, and the 14C–CO2produced was trapped and quantified over 24 h. Interestingly, SMX removal was rapid, with 98% removed within 2 h. In contrast, mineralization was slower, with a consistent percentage of 60.0 ± 0.7% found at all concentrations. Mineralization rates increased with rising concentrations. Therefore, this study shows that bacteria are capable of the direct metabolization of organic micropollutants at extremely low concentrations (sub μg L–1).

Novel wastewater treatment plants (WWTPs), which are based on a partial nitritation-anammox (PN-anammox) process, enable higher chemical oxygen demand (COD) recovery to produce biogas and lower treatment costs. In this study, rotating belt filters (RBFs) were examined in different configurations to identify the opportunities for RBFs to be included in novel WWTP configurations. RBFs enable recovery of 22–37% of the influent COD and removal of 34–56% of hydrophobic organic micropollutants (OMPs). However, the effluent was not suitable for treatment in a PN-anammox process due to its high COD. Chemically enhanced settling (CES) enabled these limitations to be overcome and caused an increase in OMP removal to 73–94%. However, a dose of 300 mg L−1of ferric chloride was required to produce a suitable effluent for a PN-anammox reactor. The combination of RBFs and CES not only produced effluents suitable for treatment in PN-anammox units but also decreased the alkalinity consumption and the required chemical dose 3-fold to achieve comparable COD recovery and OMP removal. The methane yield of the combined sludges that were produced (184 L(N) CH4per kg CODinfluent) was 75% higher than that obtained from a conventional wastewater treatment (105 L(N) CH4per kg CODinfluent), and the electricity requirements decreased from 0.54 to 0.41 kWh m−3of treated wastewater. The energetic calculations showed that a WWTP incorporating this combined treatment could attain energy autarky with 29% lower operational costs than that of a conventional treatment (0.022 vs.0.031 € m−3) as long as a minimum alkalinity-to-ammonium ratio of 1–1.25 g IC to g NH4+-N was ensured in the effluent of the combined treatment.

Traditional wastewater treatment plants (WWTPs) are electrical consumers, with a usual high demand in the range of 0.3 to 0.6 kW h per m3of wastewater treated. Their digesters are commonly oversized, and consequently operated at low organic loading rates (OLRs). This provides a great opportunity for anaerobic co-digestion (AcoD) as an interesting technology to increase methane productivity and electrical self-production in WWTPs. However, there is a quite limited implementation of AcoD in full-scale plants, since the transition from mono- to co-digestion and further AcoD optimisation are crucial and delicate steps that could lead to the inhibition of the process if not thoroughly controlled. In this study, a methodology based on an optimum control strategy is explained in detail and it was applied to safely and optimally steer the transition from mono- to co-digestion and to maximize methane production during AcoD. A lab-scale anaerobic digester of 14 L mimicking the full-scale one (3500 m3) was operated 30 days in advance to anticipate and, if needed, correct any operational destabilization that might occur. As a result, the treatment of sewage sludge with two co-substrates (coming from a pig slaughterhouse and from a frying industry), which accounted for just 11% of the feeding flowrate, at a hydraulic retention time of 20 days allowed the increase of the OLR and the methane production by 2-fold and 3-fold, respectively, increasing the self-produced electricity from 25% to 75% of the total demand of the WWTP. The diagnosis indicators proved to be accurate to make decisions concerning waste blending and the strategy of increasing the OLR. Besides, the proposed control system provides the steps to ensure a safe transition from anaerobic mono- to co-digestion and further optimisation in full-scale plants.

Operation of wastewater treatment plants can be subjected to economic, energetic and/or environmental objectives, besides the compliance with effluent limits. As trade-offs between different objectives are frequently unavoidable, model based analysis can assist in decision making and give further insight on the effect of the operating conditions. Furthermore, as new wastewater treatment technologies have appeared in the latest years, model-based analysis is needed to ascertain what the advantages of the new technologies are. We demonstrate here how to assess and operate an innovative WWTP according to different objectives with case-study based on a real innovative pilot plant. The plant features the use of denitrifying anaerobic methane oxidation (DAMO) bacteria to deplete methane from digestate. Furthermore, given the slow growth rate of the system and the tendency to create complex syntrophic environments, the use of a model becomes a keystone to operate these reactors.

Chilean hazelnuts (Gevuina avellana Mol)and mosqueta rose (Rosa aff. RubiginosaL.) meals were extracted with methanol, ethanol, acidified water, acetone, butanol, diethyl ether and ethyl acetate. Ethanol and methanol extracted the highest amount of soluble substances from both seed meals. The highest concentration of total polyphenols was found in the ethanolic extracts, although that of acetone from R. rubiginosapresented similar values. The antioxidant activity of the extracts evaluated by the β-carotene assay and with as hydrogen radical scavenging ability showed that the activity of the butanol and methanol extracts from G. avellanawas comparable to those of synthetic antioxidants butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT). The 2,2,-diphenyl-1-picrylhydrazyl radical (DPPH) radical scavenging activity of the G. avellanamethanol, ethanol and water extracts was 2–3 times lower than those of BHT and BHA, respectively. The activity of R. rubiginosaextracts ranged from that of BHT for the water extracts to 80% inhibition in respect to control achieved with the ethanol extracts.

Wastewaters from fish-canning industries have a high concentration of organic polluting substances (10–50 g chemical oxygen demand L-1[COD]) and, in some cases, a high content of sea salts (Cl-: 8–19 g L-1, Na+: 5–12 g L-1, SO2-4: 0.6–2.7 g L-1). The presence of high sodium ion concentrations in wastewaters with high organic content traditionally is considered as a very negative factor for their anaerobic treatment. In fact, both the presence of Na+and SO2-4, transformed into H2S during the anaerobic degradation process, may cause toxicity and inhibition on the methanogenic process.
This work deals with the operation and treatment efficiency of two lab-scale mesophilic and thermophilic anaerobic filters (MAF and TAF, respectively). So that the adaptation of anaerobic sludge to high saline concentrations is attained, a prolonged start-up period of about nine months was necessary. After this, a stable operation and similar treatment efficiencies were reached, even when organic loading rate (OLR) as high as 9 kg COD m-3d-1(TAF) or 24 kg COD m-3d-1(MAF) were applied at chloride concentration of 13 g L-1. At these conditions, the COD removal reached 73% (TAF) and 64% (MAF), and the COD methanized reached 69% (TAF) and 66% (MAF). The sulphate in the influent was removed practically completely, leading to a H2S concentration in the biogas between 3–4%.
In spite of the lower specific activity of sludge from MAF (0.21 g COD g-1volatile suspended solids [VSS] d-1) than from TAF (0.66), the MAF reached a higher OLR than TAF. This fact can be explained because of the higher retention of sludge into MAF (72 g VSS L-1) than TAF (10 g VSS L-1). Two practical conclusions may be derived from this work: the thermophilic operation needs the use of a packing material with a higher capacity to retain biomass and the mesophilic operation requires a more frequent detachment of biomass from the support in order to avoid clogging problems.

Summary The efficiency of a biological bleaching process on a highly contaminated iron oxides kaolin was analyzed. The bio-bleaching method consists of two steps: first, the fermentation of a chemically-defined medium byAspergillus niger leads to a spent liquor which, in a second step, is employed as leaching agent for kaolin. In the leaching process 43% of iron oxides was removed when the kaolin was treated at 60°C for 5 h and the whiteness index was increased to 67%. Extracellular enzymes were not responsible for leaching, which is basically due to organic acids produced during the fermentation.

Summary The fungusPhanerochaete chrysoporium BKM-F-1767 was able to degrade high concentrations ofp-cresol (up to 150 mg L-1) provided that glucose was added as a carbon and energy source and conditions favourable to ligninolytic enzyme activities were used, i.e. a nitrogen-limited medium. The fungus also simultaneously degradedp-cresol (50 mg L-1) and phenol (50 mg L-1) in a mixture at similar rates. Kinetics ofp-cresol biodegradation were almost identical whether the compound was tested individually or in a mixture with phenol.

The effect of different antibiotics at several concentrations of ampicillin (0–250 mg/L),benzylpenicillin (0–250 mg/L), novobiocine (0–150 mg/L), oxytetracycline (0–250 mg/L), and chloramphenicol (0–50 mg/L) on a stabilized nitrifying sludge was evaluated under aerated and lithoautotrophic conditions. No effect resulting from the presence of antibiotics on the biomass and nitrate production was noticed. The specific growth rate and volumetric nitrification rate average values for the controls were 8.28 × 10−3/h−1and 2.74 × 10−3g/L·h, respectively. Similar rate values were found when different kinds of antibiotic and concentrations were tested. These results may be explained by the nature of the floc or the instability of the antibiotics.

Bleaching of kaolin with a high content of iron oxides by means of three organic acids (citric, gluconic and oxalic) was studied. The first two release small quantities of iron oxides from the kaolin, which means they will not be adequate for large-scale processes. Oxalic acid is capable of dissolving all the leachable iron in kaolin, reaching a whiteness index of 80%, thus making the kaolin suitable for its basic industrial applications. ©1997 SCI

Enzymatic hydrolytic treatments to enhance the oil extractability from soy and sunflower seeds (low and high oil content, respectively) were performed at a range of experimental conditions (moisture content, particle size, incubation time, pH and agitation). Light microscopy and scanning electron microscopy showed the microstructural changes caused by the enzymatic attack. The extent of the cell wall degradation, closely related to the oil extractability, was observed to be dependent on the operational conditions under which the enzymatic treatment was carried out. Additionally, the effects of the enzymatic treatment on the seed structure were compared with those caused by thermal and mechanical treatments. © 1998 Society of Chemical Industry.

In this research the influence of substrate structure on the kinetics of the enzymatic hydrolysis of starch by glucoamylase was evaluated. For this purpose, two substrates of different form and molecular weight were used. In one case, the kinetics of the hydrolysis corresponds to a typical Michaelis-Menten behavior; in the other, a decrease of the hydrolysis rate occurred once a determined substrate concentration was surpassed. The structural differences between the starches, which caused important differences on the rheological properties of their solutions, justify the observed differences in their behavior. Branching of the substrate exerts two opposite effects on the hydrolysis rate because it allows the increase of the number of available points for the enzymatic attack, although the branching increases the steric hindrances and, consequently, the mass transfer resistances. The balance between these two effects is clearly dependent on the substrate concentration.

The role of heterotrophic and nitrifying microorganisms in the (co-)metabolic biotransformation of 10 pharmaceutically active compounds (PhACs) was investigated. To this aim, biotransformation assays were performed with heterotrophic and nitrifying sludge developed separately in a two-stage full-scale activated sludge system. Each stage was operated at different inflow wastewater characteristics and sludge retention times (on average 8 d and 35 d). The biotransformation capacity of each sludge was evaluated in the absence of primary substrate and in the presence of acetate and ammonium, to independently elucidate the co-metabolic role of heterotrophs and nitrifiers present in both sludges. Trimethoprim, diclofenac and carbamazepine were recalcitrant (removal < 5% after 1 d; biotransformation rate < 50 µg/g VSS·d) under all the tested conditions. High concentrations of caffeine, acetaminophen and iopromide were quickly biotransformed (> 80% after 1 d; > 800 µg/g VSS·d) in the absence of primary substrates. The heterotrophic sludge only showed a co-metabolic effect towards erythromycin, which increased its biotransformation rate between 43% and 53% when acetate and ammonium were supplied. In contrast, when stimulated, nitrifiers and slow-growing heterotrophs present in the nitrifying sludge co-metabolically biotransformed acetaminophen, ibuprofen and naproxen to a significant extent. Sulfamethoxazole was recalcitrant, except when the nitrifying sludge was fed with acetate (> 800 µg/g VSS·d), suggesting that slow-growing heterotrophs co-metabolically biotransformed it. This study provides evidence that biotransformation of PhACs depends on several metabolic activities, as the heterotrophic activity of the nitrifying sludge, which are not only determined by the SRT but also by the feeding composition.

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