Pollution

Response of Water Chemistry and Young-of-Year Brook Trout to Channel and Watershed Liming in Streams Showing Lagging Recovery from Acidic Deposition Abstract Reductions in sulfur emissions have initiated chemical recovery of surface waters impacted by acidic deposition in the Adirondack region of New York State. However, acidified streams remain common in the region, which limits recovery of brook trout (Salvelinus fontinalis) populations. To investigate liming as a method to accelerate recovery of brook trout, the channels of two acidified streams were limed annually from 2012 to 2015, and an entire watershed of a third acidified tributary was limed by helicopter in 2013. Stream flow, water chemistry, and density of young-of-year (YOY) brook trout were measured in limed streams, an untreated acidified stream, and a buffered reference stream. Lime additions increased pH and acid-neutralizing capacity and decreased inorganic monomeric aluminum concentrations to less than 2.0 μmol/L, the minimum concentration at which in situ brook trout mortality has been documented. However, of the two channel-limed streams, only stream T8 showed a significant response (P < 0.01) in YOY density, increasing from a mean of 0.4 fish/m2 before liming to 2.7 fish/m2 after liming. No YOY brook trout response was observed in the stream within the limed watershed. Groundwater inputs to streams were identified by relative differences in temperature and concentrations of silica and sodium. YOY brook trout densities increased only in the channel-limed stream (T8) with suitable groundwater inputs for fall spawning and a summer nursery. Results suggest that targeted liming of acidified streams with the necessary groundwater habitat could be beneficial in accelerating recovery of brook trout populations.

The Chemistry of Sub-Alpine Streams in Mined Regions of the North Cascades Range Abstract One hundred and fifty years of mineral extraction throughout the mountainous Ruby Creek watershed, Washington has left a legacy of historical hard rock mines and placer claims and their wastes. We conducted a watershed-scale chemical analysis of these gold-bearing tributaries, accounting for seasonal variability in streamflow, to identify spatial and temporal changes in stream chemistry and attribute them to natural processes or mining activities. We used hierarchical cluster analysis (HCA) to group chemically similar water samples based on concentrations of 23 metals, pH, and conductivity and compared the chemistry of HCA-generated clusters of water samples using pairwise comparisons to find chemical patterns. Total concentrations of As, Ba, Ca, Mg, Na, Sb, and Se, dissolved concentrations of Fe, and conductivity increased as streamflow progressed from snowmelt-influenced to baseflow. High total concentrations of Al, Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb, Sb, V, and Zn during spring snowmelt and after rains were attributable to acid mine drainage at historical hard rock mines and prospect sites. Smaller-scale placer mining, by way of suction dredging and motorized gold panning, was associated with high concentrations of Al, Ba, Cd, Co, Fe, Mg, Mn, Mo, and Zn downstream. Stream biota may be adversely affected by exposure to Pb, which exceeded USEPA’s Aquatic Life Criteria, and exposure to particulate metals suspended in the water column.

Hybrid Carbon Nanochromium Composites Prepared from Chrome-Tanned Leather Shavings for Dye Adsorption Abstract Every year, the leather tanning industry produces substantial quantities of residues such as chrome-tanned leather shavings (CTLS), which contain considerable amounts of Cr(III) salts. The residues have no particular value and under natural conditions can transform into toxic Cr(VI) wastes. The objective of the present work is to evaluate the transformation of these residues into carbon adsorbents at low temperatures (< 600 °C), using ZnCl2 as an activating agent. The pyrolysis temperature and residence times were studied. The materials were characterized and qualified by Acid Black 210 (AB) adsorption. The results indicated that low amounts of chromium oxides (less than 2% of Cr), in the form of 50–200 nm particles, remained after the synthesis procedure. The deposited chromium oxides were present in (II), (III), and (IV) oxidation states. The low preparation temperatures employed prevented further chromium oxidation to Cr(VI). Maximum surface areas of 439 m2/g were obtained. The materials efficiently removed AB (maximum experimental adsorption capacity of 44.4 mg/g) by means of electrostatic interaction caused by the positively charged distribution of the carbons. The adsorption capacity was not affected by temperature, but pH had a mixed effect due to the combination of a shift in surface charge distribution and dye speciation. The results demonstrated that it is possible to obtain a value-added product, i.e., carbons modified with chromium nanoparticles for dye removal, from a hazardous residue of the tanning industry.

Optimization of Benzodiazepine Drugs Removal from Water by Heterogeneous Photocatalysis Using TiO 2 /Activated Carbon Composite Abstract Widely consumed benzodiazepine drugs are emerging contaminants, some of them being endocrine disruptors. Although many of these drugs remain in wastewater even after conventional treatment, innovative treatability studies are still sparse. The aim of this study was to investigate the efficiency of heterogeneous photocatalysis using synthesized composites based on TiO2 and activated carbon (TiO2/AC) as catalysts under sunlight-simulated irradiation. Different ratios and calcination temperatures were tested for the synthesis, and the composite with the best photocatalytic efficiency (based on methylene blue dye removal from water solution) was the one formed by 10% AC calcined at 400 °C (TiO2/AC10%). This composite was applied in heterogeneous photocatalysis to remove bromazepam, clonazepam, and diazepam at environmentally relevant concentrations (100 μg/L). Such treatment approach has not been reported in the literature to date. Independent variables such as catalyst concentration, pH, and sunlight-simulated irradiation were studied using design of experiments (DoE) to find conditions that provide maximum removal efficiency. TiO2/AC10% powder was characterized by SEM, XRD, BET, and diffuse reflectance. Under feasible optimized conditions, the efficiency of TiO2/AC10% to remove benzodiazepine drugs from water was > 97.5%, which is much higher than the removal obtained with commercial catalyst and all controls.

Pentachlorophenol Removal from Water by Soybean Peroxidase and Iron(II) Salts Concerted Action Abstract Soybean peroxidase (SBP) has been employed for the treatment of aqueous solutions containing pentachlorophenol (PCP) in the presence of hydrogen peroxide at pH range 5–7. Reaction carried out with 1 mg/L of PCP, 4 mg/L of H2O2, and 1.3 × 10−9 M of SBP showed a fast initial elimination of PCP (ca. 30% in 20 min), but the reaction does not go beyond the removal of 50% of the initial concentration of PCP. Modification in SBP and PCP amounts did not change the reaction profile and higher amounts of H2O2 were detrimental for the reaction. Addition of Fe(II) to the system resulted in an acceleration of the process to reach nearly complete PCP removal at pH 5 or 6; this is more probably due to a synergetic effect of the enzymatic process and Fenton reaction. However, experiments developed in tap water resulted in a lower PCP elimination, but this inconvenience can be partly overcome by leaving the tap water overnight in an open vessel before reaction.

Analysis of Changes of Particle Size Distribution and Biological Composition of Flocs in Wastewater During the Growth of Algae Abstract The process of growth of algae can be described using the images from microscopic analysis. The new approach to assessment of the growth dynamics of algae used the data of granulometric composition of liquid medium and the modified Avrami equation relating to the crystallisation process. This paper presents a comparison of both methods (granulometric and microscopic) for the analysis of the dynamics of changes in the growth of algae in wastewater. The experimental set-up consisted of four glass tanks filled with biologically treated sewage, in which algae grew. The cultivation of algae was carried out for 8 weeks. During this period, the granulometric analysis and microscopic observations of sewage were conducted. The study demonstrated that with increase in the size of flocs in treated sewage, biomass of algae was also increased. Therefore, the results obtained with the method of laser diffraction are in agreement with microscopic observation of flocs. Granulometric analysis could be, next to microscopic analysis, a method for the estimation of the dynamics of changes in the growth of algae in sewage. This knowledge will allow to selection of a suitable method of wastewater treatment and algal separation.

Ultrathin Support-Free Membrane with High Water Flux for Forward Osmosis Desalination Abstract In this work, an ultrathin polyamide (PA) membrane was fabricated via in situ removing polysulfone (PSF) substrate from the PSF-PA forward osmosis membrane for the first time. The physicochemical properties of the PA membranes were confirmed by means of surface morphology, chemistry analysis, and surface charge characterization. The performance of PA, PSF-PA, and physically combined PSF+PA membrane was compared in terms of water flux, reverse salt flux, and selectivity. The flux performance of these three membranes followed the order of PA>PSF-PA>PSF+PA membranes, and the possible mechanism for their performance was proposed. Compared with home-made PSF-PA and PSF+PA membranes, the ultrathin PA membrane had high water flux (i.e., 80.54 LMH) due to its low membrane resistance and minimized internal concentration polarization under same operation conditions (i.e., DI water feed solution, 1.0 M NaCl draw solution, and AL-FS orientation). This study would provide insights on the preparation and application of ultrathin PA membranes with high permeability in the context of global water/energy-related crisis.

Fate and Behavior of Bi 2 O 3 -BiVO 4 in Wastewater Treatment Plant Under an Aerobic System Abstract The use of engineered nanomaterials (ENMs) increases concerns relating to their fate, behavior, and toxicity due to their increased exposure to the environment. These ENMs end up in wastewater treatment plants (WWTPs), and the bacteria in these systems are sensitive to compounds such as heavy metals, which reduces the functionality of the WWTP. In this work, the fate and behavior of Bi2O3-BiVO4 in a WWTP using the OECD 303A guideline was studied. The Bi2O3-BiVO4 NPs were synthesized through a hydrothermal and impregnation method. X-ray diffraction showed monoclinic phases of both Bi2O3 and BiVO4 NPs. The effect of Bi2O3-BiVO4NPs was monitored using chemical oxygen demand (COD) and 5-day biological oxygen demand (BOD5). The COD and BOD5 for the sludge retention time where the NPs were added was > 70%. This showed that the NPs had no effect on the functionality of the treatment processes as it was further affirmed by the TPC measurements. Inductively coupled plasma–optical emission spectroscopy (ICP-OES) showed that the fate of the NPs was through the activated sludge than the effluent, whereby 90% of Bi and V were absorbed in the activated sludge and 10% in the effluent. The results indicate that the NPs have the potential to permeate through the environment segments through the wastewater sludge compared to the effluent. XRD analysis of the test sludge showed that the crystal phases of the heterojunction remained unchanged, and this could ascertain that the treatment conditions did not transform the NPs into toxic forms.

Degradation of Textile Dyes Employing Advanced Oxidative Processes: Kinetic, Equilibrium Modeling, and Toxicity Study of Seeds and Bacteria Abstract The textile industries’ production of effluents with a high content of organic matter and coloration is notorious, particularly as regards their effect on the aquatic environment. This occurs in the presence of dyes that inhibit light penetration, thus affecting the biodegradability of the medium. This study evaluates the advanced oxidative processes (AOP) for use in the degradation of the reactive red 195 and direct black 22 textile dyes using bench reactors. The photo-Fenton/sunlight process was efficient, achieving a degradation of over 99% for the chromophore groups after 150 min when utilizing [H2O2] = 60 mg L−1, [Fe] = 1 mg L−1, and a pH of between 3 and 4. The kinetic model into which the experimental data best fitted was the non-linear model which employs wavelength monitoring. The COD study indicated an organic matter conversion rate of 94.96%, with a good kinetic adjustment (R2= 0.9927. A mathematical model was proposed to estimate the degradation (%) according to the variables [H2O2], [Fe], pH, and λ. In addition, the present study evaluated the toxicity of the solution, both before and after the treatment, and was verified that the treated solution was toxic by using a concentration of 10% of Lactuca sativa and Syzygium aromaticum seeds. The toxicity analysis using microbiological techniques showed that, after the treatment, the percentage of inhibition was reduced considerably, dropping to 46.0% for the sample without dilution and inhibiting only 33.4% for SPT1%.

Dissipation of Acetaminophen, Atrazine, Carbamazepine, and Sulfamethoxazole in Water Mediated by Acorus gramineus and Canna hybrida ‘Orange Punch’ Abstract The pharmaceuticals acetaminophen, sulfamethoxazole, and carbamazepine, and herbicide atrazine are among the most highly manufactured compounds in the world and are frequently detected in the aquatic environment. Much uncertainty exists regarding the impacts of the pharmaceuticals on non-target aquatic resources, while more is known about atrazine. Reduction of residues of each chemical in surface water will reduce the exposures that organisms experience in the surface water environment, thus reducing unknown risks. This project evaluated the potential use of two aquatic plant species (Acorus gramineus and Canna hybrida ‘Orange Punch’) for reducing concentrations of the chemicals in water. Concentrations of each contaminant in solution were reduced in the presence of the plants after 14 days of exposure, in (acetaminophen 64–100%, atrazine 32–51%, carbamazepine 26–49%, sulfamethoxazole 41–60%). Results indicate that these plants have potential for reducing concentrations of these chemicals in surface water, but that plant- and chemical-specific properties prevent making generalizations regarding the extent and pathways for dissipation.