Here, we evidenced the photo-induced degradation of mefenamic acid, a nonsteroidal anti-inflammatory drug, through the 254-nm light excitation of nitrite. The results demonstrated that the photodegradation of mefenamic acid was enhanced, and the mefenamic acid photodegradation rate significantly increased, from 0.00627 to 0.0350 min⁻¹ as the nitrite was increased from 0 to 0.5 mmol L⁻¹. The photodegradation rate increased from 0.0287 to 0.0512 min⁻¹ as the pH was elevated, from 5.0 to 10.0. The actual second-order rate constant for the reaction of mefenamic acid with ·OH was investigated to 1.079 × 10¹⁰ M⁻¹ s⁻¹ according to steady-state ·OH concentration of 3.5 × 10⁻¹⁴ mmol L⁻¹ and the contribution to the rate of ·OH of 67.1 %. The photoproducts were identified using HPLC/MS/MS, and possible nitrite-induced photodegradation pathways were proposed by hydroxylation, dehydrogenation, hydration, nitrosylation, and ketonized reactions. The toxicity of the phototransformation products was evaluated using the Microtox test, which revealed that the photoproducts were more toxic than mefenamic acid for the generation of nitrosation aromatic compounds.

In the present study, we investigated the concentrations of Ni, Fe, Pb, Cu, Co, Zn, Cd, Mn, and Cr in selected body tissues (liver, stomach, kidney, heart, lungs, and skeletal muscles) of two frog species: Rana tigrina and Euphlyctis cyanophlyctis captured from industrial wastewater of Sialkot city known worldwide for its tanning industry. The both frog species had darker appearance, distinctively different wet body weight, and snout-vent length. The results revealed that the heavy metal concentrations were high in the samples collected from industrial sites as compared to non-industrial sites. The different tissues of R. tigrina and E. cyanophlyctis exhibited little significant differences from two sites. The concentrations of heavy metals were more in tissues of R. tigrina as compared to E. cyanophlyctis. Mean concentration of Cd, Fe, Ni, Mn, Cu, and Cr was comparatively greater in R. tigrina, whereas Pb and Co were higher in E. cyanophlyctis. The concentration of Cu and Cd in the liver and kidney were relatively more in both species as compared to other organs. Further, the results indicated that frogs collected from industrial sites showed decreased body length and weight, and greater metal accumulation. The results will help the authorities for the conservation of these frog species which are under the influence of heavy metal contamination.

For the last 10 years, engineered nanomaterials (ENMs) have raised interest to industrials due to their properties. They are present in a large variety of products from cosmetics to building materials through food additives, and their value on the market was estimated to reach $3 trillion in 2014 (Technology Strategy Board 2009). TiO₂ NMs represent the second most important part of ENMs production worldwide (550–5500 t/year). However, a gap of knowledge remains regarding the fate and the effects of these, and consequently, impact and risk assessments are challenging. This is due to difficulties in not only characterizing NMs but also in selecting the NM properties which could contribute most to ecotoxicity and human toxicity. Characterizing NMs should thus rely on various analytical techniques in order to evaluate several properties and to crosscheck the results. The aims of this review are to understand the fate and effects of TiO₂ NMs in water, sediment, and soil and to determine which of their properties need to be characterized, to assess the analytical techniques available for their characterization, and to discuss the integration of specific properties in the Life Cycle Assessment and Risk Assessment calculations. This study underlines the need to take into account nano-specific properties in the modeling of their fate and effects. Among them, crystallinity, size, aggregation state, surface area, and particle number are most significant. This highlights the need for adapting ecotoxicological studies to NP-specific properties via new methods of measurement and new metrics for ecotoxicity thresholds.

In this study, monthly variations in biomass of ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) were analysed over a 1-year period by fluorescence in situ hybridization (FISH) at the full-scale Fusina WWTP. The nitrification capacity of the plant was also monitored using periodic respirometric batch tests and by an automated on-line titrimetric instrument (TITrimetric Automated ANalyser). The percentage of nitrifying bacteria in the plant was the highest in summer and was in the range of 10–15 % of the active biomass. The maximum nitrosation rate varied in the range 2.0–4.0 mg NH₄ g⁻¹ VSS h⁻¹ (0.048–0.096 kg TKN kg⁻¹ VSS day⁻¹): values obtained by laboratory measurements and the on-line instrument were similar and significantly correlated. The activity measurements provided a valuable tool for estimating the maximum total Kjeldahl nitrogen (TKN) loading possible at the plant and provided an early warning of whether the TKN was approaching its limiting value. The FISH analysis permitted determination of the nitrifying biomass present. The main operational parameter affecting both the population dynamics and the maximum nitrosation activity was mixed liquor volatile suspended solids (MLVSS) concentration and was negatively correlated with ammonia-oxidizing bacteria (AOB) (p = 0.029) and (NOB) (p = 0.01) abundances and positively correlated with maximum nitrosation rates (p = 0.035). Increases in concentrations led to decreases in nitrifying bacteria abundance, but their nitrosation activity was higher. These results demonstrate the importance of MLVSS concentration as key factor in the development and activity of nitrifying communities in wastewater treatment plants (WWTPs). Operational data on VSS and sludge volume index (SVI) values are also presented on 11-year basis observations.

Chromium (Cr) stress is one of the most adverse environmental factors that affect plant growth and food chain contamination. Fulvic acid (FA) is known to enhance the growth and production of crops, but the studies are scare regarding the application of FA on metal tolerance in plants. The effects of FA application on alleviating Cr phytotoxicity in wheat plants were investigated in a pot experiment conducted in sand- and soil-grown plants. Three Cr (0, 0.25, and 0.50 mM) treatments in the form of K₂Cr₂O₇ were applied in both soils with or without foliar application of 1.5 mg L⁻¹ FA. Plants were harvested after 4 months of treatments, and data regarding growth characteristics, biomass, photosynthetic pigments, and antioxidant enzymes were recorded. FA application increased plant biomass, photosynthetic pigments, and antioxidant enzymes while it decreased Cr uptake and accumulation in plants as compared with Cr treatments alone. We conclude that FA application contributes to decreased Cr concentrations in wheat grains and could be used as an amendment when aiming for decreased metal concentration in plants.

The present study was conducted to assess the impact of gibberellic acid on growth and yield of sunflower in hexavalent chromium [Cr(VI)]-contaminated soil in the presence as well as absence of pressmud. Seeds of sunflower were sown in potted soil amended with pressmud as an organic amendment and contaminated with different levels of Cr(VI) (12, 18, and 24 mg kg⁻¹) by using K₂Cr₂O₇ salt. Gibberellic acid (10⁻⁴ M) was applied at time of seedling emergence in the rhizosphere. The results showed that Cr(VI) stress significantly reduced the growth and yield of sunflower. However, application of gibberellic acid and pressmud reversed the toxic effects of Cr(VI) and improved the growth and yield of sunflower. Combined application of gibberellic acid and pressmud further improved growth and yield compared to their separate application in Cr(VI) stress. Moreover, gibberellic acid and pressmud decreased the uptake of Cr and stabilized it in the soil.

A mesophilic alkali-tolerant bacterial consortium belonging to the Bacillus genus was evaluated for its ability to biodegrade high free cyanide (CN⁻) concentration (up to 500 mg CN⁻/L), subsequent to the oxidation of the formed ammonium and nitrates in a continuous bioreactor system solely supplemented with whey waste. Furthermore, an optimisation study for successful cyanide biodegradation by this consortium was evaluated in batch bioreactors (BBs) using response surface methodology (RSM). The input variables, that is, pH, temperature and whey-waste concentration, were optimised using a numerical optimisation technique where the optimum conditions were found to be as follows: pH 9.88, temperature 33.60 °C and whey-waste concentration of 14.27 g/L, under which 206.53 mg CN⁻/L in 96 h can be biodegraded by the microbial species from an initial cyanide concentration of 500 mg CN⁻/L. Furthermore, using the optimised data, cyanide biodegradation in a continuous mode was evaluated in a dual-stage packed-bed bioreactor (PBB) connected in series to a pneumatic bioreactor system (PBS) used for simultaneous nitrification, including aerobic denitrification. The whey-supported Bacillus sp. culture was not inhibited by the free cyanide concentration of up to 500 mg CN⁻/L, with an overall degradation efficiency of ≥99 % with subsequent nitrification and aerobic denitrification of the formed ammonium and nitrates over a period of 80 days. This is the first study to report free cyanide biodegradation at concentrations of up to 500 mg CN⁻/L in a continuous system using whey waste as a microbial feedstock. The results showed that the process has the potential for the bioremediation of cyanide-containing wastewaters.

Increased application of titanium dioxide and zinc oxide nanoparticles (nano-TiO₂and nano-ZnO) raises concerns related to their environmental impacts. The effects that such nanoparticles have on environmental processes and the bacteria that carry them out are largely unknown. In this study, ammonia-oxidizing bacteria (AOB) enrichment cultures, grown from surface sediments taken from an estuary wetland in Fujian Province, China, were spiked with nano-TiO₂and nano-ZnO (with an average size of 32 and 43 nm, respectively) at predicted environmentally relevant concentrations (≤2 mg L⁻¹) to determine their impacts on ammonia oxidation and the mechanisms involved. Results showed that higher nano-TiO₂concentrations significantly inhibited ammonia oxidation in enrichment cultures. It is noteworthy that the average ammonia oxidation rate was significantly correlated to the Shannon index, the Simpson’s index, and AOB abundance. This suggested that ammonia oxidation inhibition primarily resulted from a reduction of AOB biodiversity and abundance. However, AOB biodiversity and abundance as well as the average ammonia oxidation rate were not inhibited by nano-ZnO at predicted environmentally relevant concentrations. Accordingly, an insignificant correlation was established between biodiversity and abundance of the AOB amoA gene and the average ammonia oxidation rate under nano-ZnO treatments. AOB present in samples belonged to the β-Proteobacteria class with an affinity close to Nitrosospira and Nitrosomonas genera. This suggested that identified impacts of nano-TiO₂and nano-ZnO on ammonia oxidation processes can be extrapolated to some extent to natural aquatic environments. Complex impacts on AOB may result from different nanomaterials present in aquatic environments at various ambient conditions. Further investigation on how and to what extent different nanomaterials influence AOB diversity and abundance and their subsequent ammonia oxidation processes is therefore required.

The study was planned to quantify the distribution of bacteria between bulk water and biofilm formed on different materials in an industrial scale cooling tower system of an oil refinery operating with clarified and chlorinated freshwater (CCW) or chlorinated tertiary effluent (TRW) as makeup water. The sessile and planktonic heterotrophic bacteria and Pseudomonas aeruginosa densities were significantly higher in the cooling tower supplied with clarified and chlorinated freshwater (CTCW) (p < 0.05). In the two towers, the biofilm density was higher on the surface of glass slides and stainless steel coupons than on the surface of carbon steel coupons. The average corrosion rates of carbon steel coupons (0.4–0.8 millimeters per year (mpy)) and densities of sessile (12–1.47 × 10³ colony-forming unit (CFU) cm⁻¹) and planktonic (0–2.36 × 10³ CFU mL⁻¹) microbiota remained below of the maximum values of reference used by water treatment companies as indicative of efficient microbial control. These data indicate that the strategies of the water treatment station (WTS) (free chlorine) and industrial wastewater treatment station (IWTS) followed by reverse electrodialysis system (RES) (free chlorine plus chloramine) were effective for the microbiological control of the two makeup water sources.

Mosquitoes transmit major communicable diseases such as dengue, malaria, filariasis, Japanese encephalitis, chikungunya, and so on. Vector control is important in epidemic disease situations as there is an urgent need to develop new and improved mosquito control methods that are economical and effective yet safe for non-targeted organisms. In the present study, silver nanoparticles (AgNPs) were synthesized from the aqueous leaf extract of neem plant (Azadirachta indica), and their effects on mosquito vectors (Aedes aegypti and Culex quinquefasciatus) were assessed. The synthesised AgNPs were characterized by UV–vis spectroscopy, scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FT-IR), and X-ray diffraction analysis (XRD). The nanoparticles have maximum absorption at 442 ± 1.5 nm with an average size of 41–60 nm. The XRD data showed six well-defined diffraction peaks, corresponding to a relative intensity of the crystal structure of metallic silver 36.42, 100.00, 53.70, 14.20, 16.05, and 6.79, respectively. The FT-IR data showed strong prominent peaks in different ranges, reflecting its complex nature. The mosquito larvae were exposed to varying concentrations of AgNPs synthesized from the neem leaves under investigation (0.07–25 mg/l) for 24 h; this revealed larvicidal activity of AgNPs with LC₅₀and LC₉₀values of 0.006 and 0.04 mg/l for A. aegypti, respectively. Further, the LC₅₀and LC₉₀values were also identified as 0.047 and 0.23 mg/l for Cx. quinquefasciatus, respectively. The result obtained from this study presents biosynthesized silver nanoparticle from A. indica as the biolarvicidal agent with the most potential for mosquito control.