Porous asphalt (PA), porous concrete (PC), and permeable inter-locking pavers (PICP) with sub-surface layers consisting of different gravel sizes (63, 40, and 12 mm) commonly used in the bedding, base, and sub-base layers of permeable pavements were investigated for their ability to remove total suspended solids (TSS), total phosphorous (TP), and total nitrogen (TN). The investigation focused on the individual surface and sub-surface layers of the three permeable pavements to “treat” these pollutants and how the physical design of these layers influences their water quality treatment performance. This assessment was conducted with a laboratory study, but performances were also compared to data obtained from a field-scale study of pollutant removal in PA, PC, and PICP. Pollutant removal by a sub-surface layer and the particle size distribution of outflow are dependent on both the thickness of the layer and the gravel size. Superior performance in removing pollutants was found in PC’s surface layer compared to the surface layers of PA and PICP. The lab-scale pavements and the field-scale pavements have similar performance in removing pollutants for TSS (87–95 %) and TP (75–89 %) but not for TN (3–10 % for lab-scale and 2–40 % for field-scale pavements). A simple mathematical model based on these results was developed to provide estimates of performance in the field.

Hydrologically controlled moist-soil impoundment wetlands provide critical habitat for high densities of migratory bird populations. Nutrients exported from heavily used impoundments by prescribed seasonal drawdown of surface water may contribute to the eutrophication of aquatic ecosystems. To investigate the relative importance of nutrient export from managed impoundment habitats, we conducted a field study at Mattamuskeet National Wildlife Refuge in North Carolina, USA, which contains 1545 ha of impoundments that drain into hypereutrophic Lake Mattamuskeet. We found that prescribed hydrologic drawdowns of an impoundment exported roughly the same amount of nitrogen (N) as adjacent fertilized agricultural fields on a per-area basis and contributed approximately one fifth of total N load to Lake Mattamuskeet. The prescribed drawdown regime, designed to maximize waterfowl production in impoundments, may be exacerbating the degradation of habitat quality in the downstream lake as an unintended consequence. Few studies of wetland N dynamics have targeted impoundments managed to provide wildlife habitat, but a similar phenomenon may occur in some of the 36,000 ha of similarly managed moist-soil impoundments on National Wildlife Refuges in the southeastern USA, especially those hosting dense concentrations of waterfowl. We suggest an earlier seasonal drawdown could potentially mitigate impoundment N pollution and estimate it could reduce N export from our study impoundment by more than 70 %.

Escherichia coli (E. coli) contamination of groundwater (GW) and surface water (SW) occurs significantly through the subsurface from onsite wastewater treatment systems (OWTSs). However, E. coli transport in the subsurface remains inadequately characterized at the field scale, especially within the vadose zone. Therefore, the aim of this research is to investigate the impact of groundwater fluctuations (e.g., recharging, discharging conditions) and variable conditions in the vadose zone (e.g., pulses of E. coli flux) by characterizing E. coli fate and transport in a linked surface water-soil water-groundwater system (SW-SoW-GW). In particular, this study characterizes the impact of flow regimes on E. coli transport in the subsurface and evaluates the sensitivity of parameters that control the transport of E. coli in the SW-SoW-GW system. This study was conducted in Lake Granbury, which is an important water supply in north-central Texas providing water for over 250,000 people. Results showed that there was less removal of E. coli during groundwater recharge events as compared to GW discharge events. Also, groundwater and surface water systems largely control E. coli transport in the subsurface; however, temporal variability of E. coli can be explained by linking the SW-SoW-GW system. Moreover, sensitivity analysis revealed that saturated water content of the soil, total retention rate coefficient, and hydraulic conductivity are important parameters for E. coli transport in the subsurface.

In spite of extensive studies on multispecies toxigenic cyanobacterial blooms, they are still difficult to eliminate, and factors regulating their succession and toxin production remain still to discover. A 4-year study revealed periodical mass development of diazotrophic Nostocales such as Dolichospermum spp. (previously Anabaena), Aphanizomenon gracile and expansive Cuspidothrix (previously Aphanizomenon) issatschenkoi in a lake affected by perennial blooms of Planktothrix agardhii (Oscillatoriales). Compared to Oscillatoriales, Nostocales reached the highest total biomass (up to 16 mg L⁻¹) and contributed nearly 33–85 % to the total biomass of filamentous cyanobacteria at higher water temperatures (average values 17.5–22.6 °C) and higher ratio (11.8–14.1) of dissolved inorganic nitrogen to dissolved inorganic phosphorus (DIN/DIP). Species structure of Nostocales changed considerably from year to year as indicated by the Jaccard similarity index (0.33–0.78). Concentrations of intracellular anatoxin-a (ANTX) ranged from 0.03 to 2.19 μg L⁻¹ of the lake water, whilst extracellular toxin reached up to 0.55 μg L⁻¹. The highest positive correlations were found between the intracellular ANTX and the biomass of Dolichospermum spp. (R ² = 0.73) and C. issatschenkoi (R ² = 0.43–0.65). Our study suggests that ANTX production by Dolichospermum depended mainly on water temperature, whereas that by C. issatschenkoi was related to water conductivity and DIN/DIP ratio. P-PO₄ concentrations also seemed to be important. The relatively short-term mass development of neurotoxic Nostocales is an additional threat to shallow, highly eutrophic water bodies continuously affected by Oscillatoriales blooms and may be controlled mainly by the DIN/DIP ratio. ANTX should be considered as a pollutant of freshwaters.

Contamination due to improper disposal of oilfield drilling waste is a serious environmental problem all over the world. This study used bench-scale experimental columns to investigate the effectiveness of combining soil vapor extraction (SVE) with bioremediation (bioaugmentation plus biostimulation) in treating drilling waste from onshore oil wells. The drilling waste used in this study was heavily contaminated with a total petroleum hydrocarbon (TPH) concentration of 2.5 × 10⁴ mg/kg. After 154 h of SVE operation, the TPH concentrations decreased by 4.7–23.6 %, and continuous SVE operation did not significantly reduce the concentration of residual contaminants. Then, microbial consortium and inorganic nutrients (urea and K₂HPO₄) were employed further to enhance bioremediation, and after 216 h of bioremediation and SVE, 70 % of the residual TPH was removed. Bioremediation enhanced the overall pollutant removal efficiency by fully degrading low volatile compounds and transforming them into more volatile compounds which were extracted by SVE. Results from GC-MS analysis corroborated TPH concentration data showing the occurrence of biotransformation during SVE and bioremediation treatment. Overall, this study demonstrates that SVE combined with bioremediation is an effective technique for handling petroleum drilling waste.

Use of heavy metal-tolerant bacteria for bioremediation is an environmentally safe and economical approach. Selected chromium-tolerant bacteria were tested in a greenhouse experiment. Different sets of pots were contaminated with three rates of Cr, i.e., 20, 30, and 40 ppm, using K₂Cr₂O₇ and incubated for 1 month. Helianthus annuus (sunflower) seeds of Hysun-33 variety were inoculated with already screened Cr-tolerant bacteria (SS1, SS3, and SS6) along with un-inoculated seeds as control. Completely randomized design was used and two plants per pot were maintained after thinning. At harvesting, fresh as well as dry shoot and root weights were measured. Shoot and root samples were analyzed for Cr contents. The maximum increase in dry shoot and root weight (58 and 63%) was obtained by SS6 followed by SS1 (48 and 42%) and SS3 (37 and 47%) over control at various Cr concentrations. Cr accumulation in shoot and root was also enhanced by all the bacteria compared to control. Regarding the extent of total Cr uptake, SS6 enhanced Cr accumulation up to 107–171%, SS1 99.3–135%, and SS3 91–138% at 20, 30, and 40 ppm Cr, respectively. It is concluded from the study that there was a decreasing trend in growth with the increase of Cr concentration. All the bacteria improved growth and Cr accumulation significantly over control; however, SS6 found best among all Cr-tolerant bacteria. These bacteria can effectively be used for crop improvement and bioremediation.

The aim of this 2-year study was to examine the temporal changes in the concentration of microbiological indicators of water contamination and selected physicochemical parameters within the Białka river and its selected tributaries in the vicinity of the largest ski station in Białka Tatrzańska. The study involved 24 series of sampling in eight sites throughout the Białka river and on its selected tributaries. Temperature, pH, and electrical conductivity (EC₂₅ °C) were measured onsite. The microbiological assays included the numbers of mesophilic and psychrophilic bacteria, Staphylococcus spp. and Salmonella spp., as well as coliforms, thermotolerant (fecal) coliforms, Escherichia coli, Enterococcus faecalis, and sulfate-reducing Clostridium. The chemical analyses were conducted to determine the concentration of NH₄ ⁺, NO₂ ⁻, NO₃ ⁻, and PO₄ ³⁻. The analyses showed that contrary to common opinion, waters of the Białka river are strongly polluted in some sections. Seasonal variation in the prevalence of microbial indicators of fecal pollution was found, and the largest numbers of microorganisms were observed in winter ski season, followed by summer holidays. Similar seasonal pattern was observed in the examined chemical parameters. There was also very strong spatial variation within the tested microbial and chemical parameters, indicating the presence of pollution hotspots in the course of the Białka river. The employed principal component analysis revealed the presence of two main pollution sources, mainly affecting the quality of river water, i.e., fecal contamination of human origin and the natural source in the form of surface runoff and soil leaching. These factors, depending on the location of the sampling site, occurred in different configurations.

Acid rain caused a severe loss on agricultural productivity, aggravating the challenge for achieving sustainable food production to feed the increasing globe population. To clarify the mechanism on adaptation of rice root to acid rain, we studied the root morphology and growth regulated by nutrient absorption under hydroponic conditions. Our results show that acid rain (pH 5.0 or 3.5) increased the density of root hair and root volume by increasing concentrations of K⁺, Na⁺, and Ca²⁺ in rice roots, and the root dry weight was increased. However, strong acid rain (pH 2.5) decreased the root length, surface area, volume, and number of root tips by decreasing the concentrations of K⁺, Na⁺, and Mg²⁺ in rice root, and fresh and dry weight were both decreased. After a 5-day recovery, the root morphology of rice seedlings treated with acid rain (pH 5.0 or 3.5) was recovered to the control levels, and the concentrations of K⁺, Na⁺, Ca²⁺, and Mg²⁺ also had no difference from the control (p < 0.05). However, the root growth treated with strong acid rain (pH 2.5) was still lower than the control because the inhibition on root activity and hydrolytic activity of plasma membrane H⁺-ATPase might have exceeded the self-regulating capacity of rice seedlings, and the absorption of mineral nutrient could not sustain the growth. Hence, we concluded that the adaption of root morphology of rice seedlings to acid rain was related to regulation of mineral nutrient absorption in rice root.

Rhodamine B (RhB) is one of synthetic dyes with good stability. Treatment of wastewater containing synthetic dyes has attracted much attention. Heterogeneous activation of peroxymonosulfate (PMS) has been found to be a promising wastewater treatment technology through the activation with metal oxides for the generation of sulfate radicals. In this study, α-MnO₂ was prepared by a simple hydrothermal method and used as the catalyst to activate PMS. The degradation of RhB was studied by the α-MnO₂/PMS system. It was found that the prepared α-MnO₂ exhibited high catalytic activity on the activation of PMS for the degradation of RhB. The degradation of RhB could be well described by the first-order kinetic model. Influences of PMS concentration and α-MnO₂ dose on the degradation of RhB were examined. The chemical oxygen demand (COD) was determined to evaluate the mineralization capability of the α-MnO₂/PMS system. The stability of α-MnO₂ was also investigated through reusability experiments. Quenching tests of radicals were applied to differentiate the contribution of major reactive species for the degradation of RhB by the α-MnO₂/PMS system.

Hexavalent chromium (VI) in wastewater is a great risk to human health and to the quality of water sources. However, adapted microorganisms can rapidly reduce this chemical species to the trivalent form (III) and make it less active. Our objective was to evaluate the capacity of bacterial isolates for Cr (VI) reduction in nutrient medium and in effluent and to compare indigenous microorganisms with those isolated from wastewater contaminated with Cr (VI). Cr (VI) reduction was also tested with different sources of carbon, nitrogen, and phosphorus at two temperatures (10 and 30 °C). Initially, the resistant microorganisms were isolated from the solution with 100 mg L⁻¹ of Cr (VI). Subsequently, we evaluated the effectiveness of the isolates in reducing Cr (VI) I in culture medium under temperature-controlled conditions, with concentrations of 10 and 100 mg L⁻¹ of Cr (VI). In the subsequent step, we studied the isolates and autochthonous microorganism efficiency to reduce Cr (VI) present in contaminated effluent, with the addition of nutrients and at different temperatures (10 and 30 °C). In the culture medium containing 10 mg L⁻¹ of Cr (VI), isolates were reduced by 100 % in 48 h. When tested against 100 mg L⁻¹ of Cr (VI), the decrease was 70 and 40 % at 120 h of incubation of the isolates 6 and 11, respectively. In the effluent, there was no significant reduction without nutritional biostimulation. When carbon and phosphorus were applied, isolates 6, 11, and indigenous microorganisms reduced 100 % of the Cr (VI) in 72 h. Nitrogen was not limited in terms of effluent characteristics. At 10 °C incubation temperature, Cr (VI) was completely reduced but slower compared to incubation at 30 °C. The results demonstrate that nutritional biostimulation aided by bioremediation is an excellent tool for reducing hexavalent chromium in wastewater.