Biofilm formation can help to mitigate the stress placed on organisms during biological treatment of high-salinity wastewaters, such as “produced water” resulting from oil and gas extraction. This study investigated the implementation of two different biofilm-based biological reactors, activated carbon as an adsorptive biofilm surface (Bio-GAC) and aerobic granular sludge (AGS), and a conventional activated sludge (CAS) reactor for the treatment of synthetic produced water (PW) under hypersaline conditions (85,000 mg/L NaCl). A mixture of benzyl alcohol, o-cresol, and phenol were used as a carbon source with concentrations of 100, 100, and 250 mg/L, respectively. The performance of Bio-GAC was higher than AGS, with overall removal efficiencies for aromatic compounds of 100% and 93%. The presence of catechol in all three reactors during the reaction cycle confirmed that biodegradation was occurring. The performance of CAS was significantly lower in terms of removal efficiency for aromatic compounds (73%) and resilience to high salinity. Scanning electron microscopy showed that biofilm-based biosystems establish stronger biofilm texture. Microbial community analysis showed that carbon source and biosystem type played a crucial role in selecting for microbiome structure. These findings show that biofilm reactors can be used to successfully biodegrade toxic organic contaminants in a high-salinity environment, and that the hybrid Bio-GAC process is particularly promising for treating PW.

Aerobic cometabolism is a viable method for treating groundwater contaminated with 1,4-dioxane. Although at least one biochemical pathway by which 1,4-dioxane is used as a sole source of carbon and energy has been elucidated, comparatively little is known about the products formed during cometabolic degradation. The objective of this study was to identify the main products formed during cometabolism of 1,4-dioxane by the mixed propanotrophic culture ENV487. During biodegradation of 14C-1,4-dioxane, soluble products accumulated that were concentrated by lyophilization and then separated into fractions using high-performance liquid chromatography. Formate accounted for 51% of the 14C-labeled compounds recovered, based on co-elution with authentic material. The identity of formate as the main product was confirmed using a formate dehydrogenase assay. Other products identified that represented at least 4% of the 14C products recovered included acetate, glycerate, glycolaldehyde, ethylene glycol, and glycolate. All these compounds are readily biodegradable in an aquifer environment. This is consistent with the expectation that the endpoint for aerobic cometabolism of 1,4-dioxane by propanotrophs in a mixed culture environment is carbon dioxide.

As source waters for many drinking water treatment plants are increasingly subject to intermittent blooms of cyanobacteria, utilities must adapt treatment methods to remove associated cyanotoxins. There is concern that treatment methods applied to remove dissolved extracellular toxins may damage whole cells, leading to the release of intracellular toxins and other secondary metabolites. The objective of this study was to determine whether sodium hypochlorite and potassium permanganate preoxidation treatments cause increased susceptibility of cyanobacterial cells to mechanical shear using a method that can be easily adapted by utilities. Bench-scale simulations examined Microcystis sp., Planktothrix sp., and Dolichospermum sp., which are three types of microcystin-producing cyanobacteria that are prominent in many bloom-impacted waters. We found that chlorine led to increased susceptibility to shear in Dolichospermum and permanganate led to increased susceptibility to shear in Planktothrix, each for shear rates of 750 s−1 (a typical rate for in-line mixers used in drinking water treatment). We found that shear does not cause immediate critical damage to cells, regardless of preoxidation conditions. However, shear appears to cause a stress response in cyanobacteria, indicating the possibility of delayed toxin release. The results of this study will help water treatment utilities to manage stressors within the treatment process that could lead to release of cellular compounds during cyanobacterial blooms. Additionally, utilities can adapt the applied method of intracellular phycocyanin analysis to independently evaluate real-time cell response to their treatment processes.

Chromium (Cr) contamination of groundwater from legacy industrial solid waste is a severe environmental problem, especially for marginalized communities dependent on groundwater as their only potable and irrigational resource. At one such site in Rania, India, alarming Cr concentrations (1–10 mg/L) relative to the World Health Organization (WHO) recommended 0.05 mg/L have been persistent for more than a decade. To mitigate this problem, sustained laboratory- to field-based interventions in the past led to the development of affordable methods for (1) rapid and accurate on-site measurement of Cr(VI) using a smartphone-based monitoring tool and (2) treatment of Cr(VI)-containing groundwater with ferrous sulfate amendment followed by slow sand filtration. In this contribution, these methods were scaled-up to a ∼14 L household filtration unit where Cr(VI) was first reductively precipitated as Fe(III)-Cr(III) oxyhydroxide particles in a specifically designed reactor. The particles were then removed by passing the suspension through an existing biosand filter (JalKalp), which also removed microbial contamination. The developed filter unit treated Cr-free groundwater spiked with variable Cr(VI) concentrations and Cr(VI)-contaminated groundwater sampled from the site with >99% efficiency. The toxicity characteristic leaching procedure confirmed that the generated sludge from these operations was nonhazardous. Subsequently, this filter and the smartphone-based monitoring tool were provided to an affected household to assess their performance and acceptability to the end user. With minimal training, the residents were able to operate the filter and systematically record Cr(VI) concentrations before and after filtration over 65 days of operation. JalKalp was able to limit Cr(VI) concentrations and other water quality parameters, except hardness and alkalinity, below the drinking water limit, and was operable without any electricity at a low cost of USD 0.057/100 L of purified water. This study serves as an example of how research outreach could not only provide translatable technical solutions to marginalized sections but also benefit from citizen science.

Heavy metal pollution has received increasing attention worldwide in recent decades. However, the characterization of heavy metal elements in coastal soils has been still poorly understood. In this study, eight metal elements Cd, Cr, Cu, Hg, Ni, Pb, Zn, and As were monitored in coastal soil samples, which were collected from Qingdao on the east coast of China, in 2019. The spatial distribution, pollution level, ecological, and health risks of heavy metals were then evaluated. The experimental results indicated that >50% of the sampling sites for Cd, Pb, Zn, and Hg exceeded the reference background values. In addition, the geoaccumulation index showed that 84%, 96%, and 92% of soil sample sites for Cd, Pb, and Hg were in pollution, respectively; both Cd and Hg had potential ecological risks with 50% and 22% in mild potential ecological risk, 37% (Cd) and 6% (Hg) in moderate potential ecological risk, and <10% the serious potential ecological risk, respectively. Furthermore, the averages of hazard index for all the elements were <1 indicated that the health risks for all eight heavy metals were in low level. Finally, compared with the data of 10 years ago, the concentrations, enrichments, and ecological risks of Pb increased fastest with 17%, 150%, and 17%, respectively. This indicates that with the rapid economic growth of Qingdao, the controlling of Pb in soil should be implemented with a high priority in the near future.

Under global climate change and resource crisis, the correlation and restriction between energy, water, and carbon emission are increasingly prominent, which has posed great challenges for the sustainable development of energy systems. This article develops a dual-interval stage-fuzzy credibility-constrained programming model for regional energy system management problems with energy–water nexus (EWN) and carbon emission reduction, in which uncertainties expressed as discrete intervals, probability distributions, and dual-interval fuzzy numbers can be addressed. It can provide a trade-off among economic cost, system risk, and environmental objective. Then, the hybrid programming method is applied to a case of Guangdong Province, China to verify its applicability, where a series of scenarios with respect to water resources and carbon emission constraints are explored and examined. The robust solutions of optimal strategies for electricity generation, capacity expansion, water supply, and carbon capture are investigated and obtained. Results disclose that different scenarios associated with water resource availability and carbon emissions would deeply affect the EWN system planning: (1) Compared with low carbon emission standard, the proportion of renewable power generation under high carbon emission scenario would increase by [1.39, 1.68] %, [1.69, 2.35] %, and [1.49, 1.94] % in periods 1–3, respectively. (2) Scarce water availability scenario would restrict coal-fired power generation and simulate the development of renewable energy. These findings can be useful for decision makers to gain deep insights into energy system management in a sustainable way considering energy structure adjustment, multiple uncertainties, EWN, and carbon emission reduction.

A ruthenium (II) photosensitizer, [Ru(bpy)2(phen)][PF6]2 (RuPS), was synthesized and its structure was confirmed by UV–Vis and 1H NMR spectroscopy. Under visible light, RuPS could efficiently promote the degradation of tetracycline hydrochloride (TC·HCl) in the presence of oxygen (O2). Its degradation rate could reach 94.6% in 5 h under 20°C, 50 mW/cm2 of radiation intensity, 20 mg/L of TC·HCl, 5 mg/L of RuPS, and pH 10.0. Its degradation pathways were complex and involved both direct and indirect photolysis. For both pathways, the degradation rate of TC increased with the increase of pH value. In acidic environment, the degradation of TC mainly depended on the sensitization of photosensitizer. Under alkaline conditions, the photodegradation of TC itself played a major role as well. For the indirect photolysis, it involved the oxidative degradation of exited TC (TC*) by triplet oxygen (3O2) and the oxidative degradation of TC by singlet oxygen (1O2). 1O2 was mainly generated by RuPS under light. In conclusion, aerobic photodegradation under alkaline conditions was a feasible and convenient method to remove TC from water.

The incentive to reduce greenhouse gas (GHG) emissions has motivated the development of lignocellulosic biomass conversion technologies, especially those associated with the carbohydrate fraction. However, improving the overall biomass valorization necessitates using lignin and understanding the impact of different tree parts (leaves, bark, twigs/branchlets) on the deconstruction of lignin, cellulose, and hemicellulose toward value-added products. In this work, we explore the production of chemicals from a yellow poplar-based integrated biorefinery. Yellow poplar (Liriodendron tulipifera L.) is an ideal candidate as a second-generation biomass feedstock, given that it is relatively widespread in the eastern United States. Herein, we evaluate and compare how the different proportions of cellulose, hemicellulose (xylan), and lignin among leaves, bark, and twigs/branchlets of yellow poplar, both individually and as a composite mix, influence the life-cycle GHG model of a yellow poplar biorefinery. For example, the processing GHG emissions were reduced by 1,110 kg carbon dioxide (CO2)-eq, 654 kg CO2-eq, and 849 kg CO2-eq per metric ton of twigs/branchlets, leaves, and bark, respectively. Finally, a sensitivity analysis illustrates the robustness of this biorefinery to uncertainties of the feedstock xylan/glucan ratio and carbon content.

Excess waste tires in Puerto Rico pose health and fire hazards. A policy was proposed to switch 75% of paving materials to asphalt modified with recycled ground tire rubber (GTR). Recycling would mitigate the health risks and fire hazards while reducing the dependence on the export of waste tires for energy recovery. This study uses a lifecycle assessment (LCA) and two scopes to inform the policy from an environmental perspective. The pavement-level analysis compares the conventional and rubberized pavement pilot sections. The system-level analysis evaluates the consequences of the policy's tire diversion from tire-derived fuel (TDF) to GTR. In doing so, this study bridges the gap between the waste management LCAs (focused on processing and less on the use of recycled products) and pavement LCAs (which assess GTR in pavements but not potential waste stream reductions). The results of the pavement-level analysis indicated that GTR pavements present higher impacts than their conventional counterparts. The increased impacts of the GTR section are primarily due to the higher binder content, increased mixing energy, and the binder modification process. The system-level analysis revealed that paving in Puerto Rico can use 6–16% of annual waste tires. When TDF replaces environmentally intense kiln fuels (coal and petroleum coke), tire diversion into GTR is not environmentally beneficial. Conversely, when replaced fuels are more environmentally friendly (coal and natural gas), tire diversion to GTR may present benefits. With the use of greener fuels in the cement industry, GTR deployment may gain interest.

In this study, an advanced temperature-sensitive hydrogel with sewage sludge ash (SSA) was synthesized and employed as draw agent for forward osmosis (FO) desalination. The effects of the incineration temperature (700–1,000°C) of SSA obtention, particle size (20–300 meshes), and dosage (0–4.5 wt%) of SSA were investigated for optimally synthesizing the temperature-sensitive hydrogel to meet the requirement of FO. The resulting hydrogels were characterized in terms of crystal structure, surface morphology, surface functional groups, and lower critical solution temperature (LCST). It was shown that the dosage of SSA significantly influenced the swelling capacity (in different concentrations of NaCl solution) and deswelling property of hydrogels, whereas the other two factors only affected the swelling of hydrogel, but had no effect on the deswelling. In addition, as a result of higher reticulated pore structure, and the hydrogen-bonding interaction between the chemical surface of SSA and monomers of hydrogels, the best production D2.5H as a draw agent generated high average water flux of 2.22 LMH in FO desalination with 2,000 ppm NaCl as feed solution. Furthermore, despite a little higher LCST with the comparison of D0H (blank sample without SSA), the D2.5H as a draw agent can still maintain the prominent temperature-sensitive performance in that, most of the water can be recovered in 10 min of 60°C water bath, and the average water fluxes of FO with even three times regenerated hydrogels were similar to that with the initial.