Degradation of 17α-ethinylestradiol by Enterobacter tabaci Isolate and Kinetic Characterization Abstract In the present study, the degradability of 17α-ethinylestradiol (EE2) by isolated bacterial strains from the activated sludge of the wastewater treatment plant of a factory manufacturing contraceptive pills was investigated. The strain with more degradation capacity of EE2 (strain S1) was identified as Enterobacter tabaci based on its morphology and analysis of the 16S rRNA sequence. The isolated strains were used in the form of pure (containing the identified bacterial strain) and mixed (containing the two isolated bacterial strains) cultures for degradation of EE2 as the sole carbon and energy source. The added substrate (0–4 mg L−1) was metabolized almost completely within 4 d at 30 °C. EE2 was used as the growth substrate by the bacterial cultures, since the biomass concentration was obviously increased. EE2 biodegradation was kinetically investigated according to the kinetic data obtained by fitted appropriate models (the Monod model and the allosteric sigmoidal model were used for the pure and the mixed bacterial cultures, respectively). The first-order kinetic rate constant ( \( \frac{q_m}{K_s} \) ) for EE2 utilization by the pure culture was noticeably higher than the value obtained by the mixed culture, probably due to preference of the isolated bacterial strain to estrogenic compounds as the growth substrate by producing specific enzymes. By comparing the degradation and also the growth kinetic parameters, it was concluded that the pure bacterial culture had better efficiency in degradation of EE2. Graphical Abstract Isolation and characterization of an EE2 degrading culture from the activated sludge of the wastewater treatment plant

Removal of Malachite Green Dye from Aqueous Solutions Using Zeolitic Imidazole Framework-8 Abstract Adsorption of malachite green (MG) using zeolitic imidazole framework-8 (ZIF-8) as a novel adsorbent was investigated in the current study. The effect of pH (3 to 11), contact time (15 to 120 min), ZIF-8 dosage (0.01 to 0.09 g/L), and competitive compounds (NaCl and NH4Cl) was studied on the adsorption of MG (25 to 200 mg/L) alongside the sonocatalyst process at 30 kHz for 60 min. Moreover, isotherm and kinetic models were investigated. Optimum conditions were obtained at pH=7, catalyst dosage=0.05 g/L, MG concentration=25 mg/L and contact time=90 min, with a removal efficiency of MG up to 95%. Experimental data were well fitted on the Freundlich and pseudo-second order model. Maximum adsorption capacity was found to be 224.14 mg/g. The effect of competitive compounds was insignificant. This study demonstrated that the sonocatalyst process in combination with ZIF-8 is a promising and efficient method for adsorption of MG from aqueous solutions.

Hydrogeologic Behavior of a Complex and Mature Karst Aquifer System under Drought Condition Abstract This paper aims, using classic hydrogeologic techniques, Time Series Analysis, Principal Component Analysis, Standardized Precipitation Index, and MRC methods to better understand the hydrogeological, and hydraulic characteristics of a mature karst aquifer system, and to analyze its behavior under drought conditions. The study area is the karst aquifer system of Aggitis (AAS), Northern East Greece, characterized by a mountainous terrain consisting of highly fissured and karstified Falakro marbles of Mesozoic age. AAS catchment extends 63.4 km2 and exhibits a duality of conduit and/or diffuse flow model. AAS is drained by the permanent large Maaras spring with a mean annual value of 4.656 m3/s. The dominant chemical type is Ca-HCO3. PCA and hydrochemical analysis were effectively used in combination to interpret the main hydrogeochemical mechanisms controlling karst water quality. A combined methodology provides a useful and effective tool for assessing the characteristic behavior of karst springs under drought conditions. It enables also, to gain insight into the prevailing processes in a karst aquifer system. The statistical analysis of hydrological data revealed the karst system is mainly recharged by diffuse infiltration.

A Multi-criteria Decision Analysis of Co-substrate Selection to Improve Biowaste Composting: a Mathematical Model Applied to Colombia Abstract Several physicochemical properties of biowaste can limit its composting. The incorporation of bulking agents (BA) and amendment materials (AM) is the most frequently applied operational approach to overcome such substrate limitations. This work proposes a decision model to optimally select bulking agents and amendment materials by applying a multicriteria analysis. The main objective of this study was to present a methodology to rank the co-substrates needed to compost biowaste. To accomplish this aim, an integrated hierarchy-based model was used that accounted for technical and environmental criteria. In particular, Analytical Hierarchy Process (AHP) and the Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) were used to rank the potential co-substrates. The co-substrate ranking that was achieved with AHP and TOPSIS was then complemented by a cost analysis. The results of this study demonstrated the importance and the significant weight of the technical criteria, such as nutrients, porosity and biodegradability. The methodology was applied to a small town in Colombia that operates a biowaste composting facility. The results of the application of the tool in the above case study revealed that the most suitable materials for biowaste composting were sugarcane filter cake and star grass.

Community Synergism: Degradation of Triazine Dye Reactive Black 1 by Mixed Bacterial Cultures KND_PR under Microaerophilic and Aerobic Conditions Abstract Mixed bacterial cultures KND_PR comprising five bacterial species, namely Lysinibacillus sp. BAB-4931, Raoultella sp. BAB-4932, Enterococcus sp. BAB-4933, Citrobacter sp. BAB-4934 and Lysinibacillus sp. BAB-4935, were originally developed from contaminated soil near Pirana, Ahmedabad, India. KND_PR have an astonishing ability to degrade Reactive Black 1 (RB1) under both microaerophilic and aerobic conditions within 8 and 12 h, respectively. Mixed bacterial cultures KND_PR showed azoaromatic degradation efficiency up to 1500 mg/L of dye concentration and were able to tolerate salt up to 25 g/L. KND_PR can degrade twenty-five structurally different complex dyes that indicate its catabolic versatility. During azoaromatic degradation, it was observed that under microaerophilic condition KND_PR first followed symmetric cleavage of the azo bond by azoreductase, whereas, under aerobic condition, asymmetric cleavage of RB1 took place via lignin peroxidase. Metabolic pathways for RB1 degradation by KND_PR has been postulated with enzymatic and bioanalytical techniques, which showed the significant conversion of parent dye into low molecular weight aliphatic compound. These results were further confirmed by observing significant results of phytotoxicity experiments with model plants under microaerophilic and aerobic conditions. The foregoing results indicate that the enriched mixed bacterial cultures can efficiently degrade dye under microaerophilic and aerobic conditions within a short time period, which exhibited the usefulness of mixed bacterial cultures KND_PR to tackle the problems associated with dye contaminated wastewater.

Sanitary Landfill Leachate Treatment with Double Chamber Anaerobic Reactor in Series with Constructed Wetland Abstract A treatment system composed of a double-chamber anaerobic (DCA) reactor in conjunction with a constructed wetland (CW) of horizontal sub-surface flow, for the treatment of leachates generated in the municipal sanitary landfill of a typical mid-sized city was investigated. The aim of this work was to assess the capability of the system to remove pollutants such as organic load, nutrients and solids. The system was evaluated at hydraulic retention times (HRT) of 7.97, 5.31 and 2.88 days. The highest removal efficiencies for the system were obtained at HRT of 7.97 days and were 89% and 91% for TCOD and BOD, respectively. In the case of NO3−, NO2−, NH4+ and Total Kjeldahl Nitrogen (TKN), their removal rates were estimated at 88%, 93%, 93% and 85%, respectively; whilst for TS, TVS and TTSS they were 88%, 86% and 90%, respectively, again at HRT of 7.97 d. Efficiencies of 78%, 83% and 77% were obtained respectively for TCOD, BOD and TKN in DCA reactor at HRT of 1.5 d. Typha domingensis was identified as a species capable of adapting to the physicochemical conditions of the leachate, exhibiting an average growth of 196 cm. In leachate there were found low concentrations of heavy metals, being aluminum the metal with the highest concentrations (between 3.31–10.09 mg/L). Results show that it is feasible to implement the DCA reactor in series with a constructed wetland for the treatment of sanitary landfill leachates. Therefore, this system can be replicated for the treatment of leachates with similar conditions.

Modelling of Maximum Daily Water Temperature for Streams: Optimally Pruned Extreme Learning Machine (OPELM) versus Radial Basis Function Neural Networks (RBFNN) Abstract This study proposed two data-driven models, namely the optimally pruned extreme learning machine (OPELM) and the radial basis functions neural networks (RBFNN) to predict maximum daily water temperature in streams. Air temperature (Ta), flow discharge (Q) and the day of the year (DOY) were used as predictors. Four indicators, including the coefficient of correlation (R), the Willmott index of agreement (d), the root mean squared error (RMSE), and the mean absolute error (MAE) were used in evaluating the performances of different models. The present study was conducted according to four different scenarios. First, the OPELM and RBFNN models were developed and validated for each station separately. For the three other scenarios, the models were developed using data from one station and validated for the two other stations separately. Modelling results showed that in the proposed models Ta and Q may not be sufficiently informative and the addition of DOY significantly contributes to better capturing the seasonal pattern of the maximum daily water temperature in streams. Generally, OPELM models outperformed RBFNN models, and overall, the modelling results indicated that the OPELM models developed in this study can be effectively used for predicting maximum water temperature in streams.

Assessment of Total Amount of Surface Sediment in Urban Environment Using Data on Solid Matter Content in Snow-Dirt Sludge Abstract The aim of the study is the development of a method of quantitative assessment of the total and size-fractionated amount of urban surface deposited sediment. The method utilises the feature of snow cover to accumulate the surface sediment. Snow-dirt sludge formed as a result of snow, and surface deposited sediment mixing on roads and other urban surfaces accumulates sediment over the winter period. In regions with long winter, the snow-dirt sludge lifecycle presents a delayed runoff event. Testing of the method was conducted in Ekaterinburg, Russia, a city situated in a cold region with long winter. Specimens of snow-dirt sludge and urban surface deposited sediment were collected in winter and summer 2017, respectively. Proportions of concentrations of dust, fine sand and coarse fractions in snow-dirt sludge were compared with the same proportion in surface deposited sediment sampled in the summer season. The average concentration of solid phase material in the snow-dirt sludge was 25 ± 9 g/L of melted water. The dust fraction <0.1 mm contributed 44% to the total concentration of the solid phase. The average mass concentrations of coarse fraction, fine sand and dust in summer samples of surface deposited sediment were in proportion 31%:31%:38%, respectively. A total amount of urban surface deposited sediment of approximately 320,000 tons (3.2 kg/m2 per unit residential area) was estimated in Ekaterinburg, of which about 120,000 tons was the dust fraction. Obtained quantitative assessments of sediment deposition on urban surfaces characterise the sedimentation as important environmental process in contemporary urban areas.

Statistical Analysis of Flow Structures around a Circular Cylinder Abstract The turbulent flow characteristics around a partially submerged vertical circular cylinder mounted on a flat rigid surface have been studied experimentally in a laboratory flume to examine the turbulence characteristics, joint probability density function and the associated ejection-sweep cycles of Reynolds shear stresses. The results show the signatures of the recirculation zone and a thin shear layer between the recirculating flow behind the cylinder and the flow at the outer region. It is also noticed that at the upstream side of the cylinder, the correlation term \( \overline{u^{\prime }w^{\prime }} \) is prominent, whereas in the wake region behind the cylinder, the correlation term \( \overline{u^{\prime }v^{\prime }} \) is dominant. It is found that the contribution of stress fraction to total shear stress is more substantial at the upstream side of the cylinder compared to that at the reattachment region for uv-plane in the bottom wall region, signifying the reverse phenomenon observed for uw-plane at the same locations. Stratification of the intermittent nature of the energy dissipation within the entire flow depth at the upstream side of the cylinder is observed, while no distinct stratification of the intermittent nature of turbulence occurs at the wake region of the cylinder which creates a strong turbulent mixing. Results of the present study may be helpful for the better design of bridge pier and coastal structures.

Impacts of Dem Source, Resolution and Area Threshold Values on SWAT Generated Stream Network and Streamflow in Two Distinct Nepalese Catchments Abstract This study explores the relationship of Digital Elevation Model (DEM) resolution and flow accumulation threshold value to watershed characteristics and streamflow in two Nepalese catchments, Kaligandaki and Bagmati basin. DEMs from three different sources: ASTER Global DEM v2, SRTM v4.1, and Contour of Nepal, with resolutions of 30 m, 90 m, and 250 m were used. Automatic watershed delineation in SWAT was used to derive the stream network, and basin and flow characteristics at different DEM scenarios. It is found that DEM source and resolution influence basin characteristics and stream network morphology. The assumption that SWAT model performance improves with an increase in DEM resolution did not hold true. All the models were equally efficient in predicting the runoff. The model performance for both basins was similar regardless of the origin of the DEM. NSE and R2 varied in the range 0.726–0.781 and 0.772–0.81, respectively, for Kaligandaki basin. Similarly, for Bagmati basin, NSE and R2 varied in the range 0.772–0.837 and 0.779–0.839, respectively. The drainage density and simulated flow got better when the threshold area was decreased. However, the model ceased to improve any further after the optimum value of the threshold area. Our results indicate that DEM of higher resolution (30 m or finer) needs to be used to model the catchment in SWAT accurately and appropriate threshold area needs to be used for best model performance based on the temporal sensitivity of the runoff.