Toxic effects of linear alkylbenzene sulfonate on metabolic activity, growth rate, and microcolony formation of Nitrosomonas and Nitrosospira strains

Pilot-scale adsorption of pharmaceuticals from municipal wastewater effluent using low-cost magnetite-pine bark: Regeneration/enumeration of viable bacteria with a study on their biotoxicity

A low-cost and renewable magnetite-pine bark (MPB) sorbent was evaluated in continuous-flow systems for the removal of various pharmaceuticals from municipal wastewater effluent following membrane bioreactor (MBR) treatment. A 33-day small-scale column test (bed volume: 791 cm3) was conducted using duplicate columns of biochar (BC, Novocarbo) and activated carbon (AC, ColorSorb) as reference for two columns of BC and MPB in order to compare the efficiency of AC and MPB. After the small-scale column test, the pharmaceutical concentrations were generally below the detection limit. In the next stage, a four-month pilot-scale adsorption test was performed using a large column (bed volume: 21 L) filled with BC and MPB. A variety of compounds were removed after the pilot-scale column, including trimethoprim (99.7%), hydrochlorothiazide (81.8%), candesartan (26.0%), carbamazepine (86.1%), ketoprofen (89.4%), clindamycin (86.6%), oxazepam (91.3%), sulfadiazine (38.6%), sulfamethoxazole (58.3%), tramadol (88.9%), zopiclone (73.5%), venlafaxine (93.7%), furosemide (93.5%), fexofenadine (91.6%) and losartan (81.2%). The enumeration of viable bacteria in the pilot-scale column samples revealed that regenerating the BC-MPB bed with NaOH increased bacterial counts in the treated water due to the desorption of adsorbed bacteria from the bed. A biotoxicity study using the Nitrosomonas europaea bioreporter strain indicated that the wastewater was generally non-toxic to this nitrifying bacterium and regeneration of pilot-scale column samples caused short-time toxicity immediately after regeneration. The study confirms that MPB is efficient for the adsorption of pharmaceuticals and can be applied in column mode with a support material such as BC. Therefore, MPB is a viable alternative for AC for the remediation of pharmaceutical-contaminated wastewaters.

Quorum sensing mediated response mechanism of anammox consortia to anionic surfactant: Molecular simulation and molecular evidence

The widespread use of surfactants raise challenges to biological wastewater treatment. Anaerobic ammonium oxidation (anammox) process has the potential to treat wastewater containing anionic surfactants, but the response of anammox consortia at the molecular level under long-term exposure is unclear. Using high-throughput sequencing and gene quantification, combined with molecular docking, the effect of sodium dodecyl sulfonate (SDS) on anammox consortia were investigated. Levels of reactive oxygen species (ROS) might be lower than the threshold of oxidative damage, while the increase of lactate dehydrogenase (LDH) represented the cell membrane damage. Decreased abundance of functional genes (hdh, hzsA and nirS) indicated the decrease of the anammox bacterial abundance. Trace amounts of N-acyl homoserine lactone (AHL, C6-HSL, C8-HSL and C12-HSL) contained in influent could induce endogenous quorum sensing (QS), which could regulate the correlation between functional bacteria to optimize the microbial community and strengthen the resistance of anammox consortia to SDS. In addition, the proliferation of disinfectant resistance genes might increase the environmental pathogenicity of sewage discharge. This work highlights the potential response mechanism of anammox consortium to surfactants and provides a universal microbial-friendly bioenhancement strategy based on QS.

Soil amendments promoting nitrifying bacteria recovery faster than the denitrifying bacteria at post soil fumigation

Chloropicrin (CP) is a soil fumigant that not only reduces disease-causing pathogenic microbes but regrettably also those that benefit soil quality and crop health. However, we have few knowledge on rapidly restoring populations of beneficial microbes suppressed by CP fumigation. Here we used genetic sequencing technology to monitor changes in the recovery of soil bacteria in response to ammonium sulfate added to the soil following CP fumigation. The results showed that regardless of the N fertilizer addition rate, the accumulated NH4+-N in CP fumigated soil was rapidly consumed within 42 d. The rapid reduction in NH4+-N coincided with the observed recovery nitrogen-cycling microorganisms, especially the nitrification bacteria AOA and AOB that contributed to the formation of NH4+-N. Additionally, we further observed that the resilience index of nitrifying bacteria (AOB and AOA) was greater than the resilience index of denitrifying bacteria that contain the denitrification genes nirS, nirK and nosZ (0.12 to 0.55 vs. -0.27 to 0.073). These results revealed that N fertilizer stimulated the recovery of nitrifying bacteria more than denitrifying bacteria. Our research suggests that ammonium sulfate applied to CP fumigated soil could be used commercially to improve soil health as a result of an increase in beneficial microbes.

Characteristics of compounds with strong or weak nitrification inhibition in sewage

To clarify the characteristics of compounds with strong or weak nitrification inhibition in sewage, 64 organic compounds including compounds registered in Pollutant Release and Transfer Register (PRTR) were evaluated in terms of their chemical structures and molecular weights. Nineteen compounds showed strong nitrification inhibition by testing with Nitrosomonas europaea. Compounds with thioamide structures had the lowest median value of EC50 (0.017 mg/L), followed by those with alkyne structures (0.121 mg/L), chlorophenol structures (0.300 mg/L), and then azole structures (0.365 mg/L). In contrast, 33 of the 64 compounds showed weak nitrification inhibition at a concentration of 10 mg/L, 27 of which were categorized into three main groups: long-chain alcohol structures, alkyne structures with a phenyl group, and aromatic structures. Most compounds with strong nitrification inhibition had a low molecular weight (MW) from 50 to 200. Meanwhile, the proportion of compounds with weak nitrification inhibition tended to be greater with increasing MW and such compounds were predominant at higher molecular weights above 300. The correlations of results derived from tests of nitrification inhibition based on ISO 9509 and N. europaea showed that 24 out of 30 compounds provided results that were highly correlated between these tests (R = 0.85), while 4 compounds with chlorophenol structures and 2 compounds with alkyne structures showed weaker inhibition rates in the ISO 9509 test than in the N. europaea test. Our results indicate that the magnitude of nitrification inhibition depends on MW in addition to the chemical structure, which is helpful in the search for the cause of nitrification inhibition in wastewater treatment plants.

Effect of Cd(II) shock loading on performance, microbial enzymatic activity and microbial community in a sequencing batch reactor

The performance, microbial enzymatic activity and microbial community of a sequencing batch reactor (SBR) were explored under instantaneous Cd(II) shock loading. After a 24-h Cd(II) shock loading of 100 mg/L, the chemical oxygen demand and NH₄⁺-N removal efficiencies decreased significantly from 92.73% and 99.56% on day 22 to 32.73% and 43% on day 24, respectively, and then recovered to the normal values gradually. The specific oxygen utilization rate (SOUR), specific ammonia oxidation rate (SAOR), specific nitrite oxidation rate (SNOR), specific nitrite reduction rate (SNIRR) and specific nitrate reduction rate (SNRR) decreased by 64.81%, 73.28%, 77.77%, 56.84% and 52.46% on day 23 in comparison with the absence of Cd(II) shock loading, respectively, and they gradually returned to the normal levels. The changing trends of their associated microbial enzymatic activities including dehydrogenase, ammonia monooxygenase, nitrite oxidoreductase, nitrite reductase and nitrate reductase were in accordance with SOUR, SAOR, SNOR, SNIRR and SNRR, respectively. Cd(II) shock loading promoted the microbial reactive oxygen species production and lactate dehydrogenase release, indicating that instantaneous shock caused oxidative stress and damaged to cell membranes of the activated sludge. The microbial richness and diversity, and the relative abundance of Nitrosomonas and Thauera obviously decreased under the stress of Cd(II) shock loading. PICRUSt prediction showed that Cd (II) shock loading significantly affected Amino acid biosynthesis, Nucleoside and nucleotide biosynthesis. The present results are conducive to take adequate precautions to reduce the adverse effect on bioreactor performance in wastewater treatment systems.

Surfactant-enhanced mobilization of persistent organic pollutants: Potential for soil and sediment remediation and unintended consequences

This review aims to provide an overview of the sources and reactions of persistent organic pollutants (POPs) and surfactants in soil and sediments, the surfactant-enhanced solubilisation of POPs, and the unintended consequences of surfactant-induced remediation of soil and sediments contaminated with POPs. POPs include chemical compounds that are recalcitrant to natural degradation through photolytic, chemical, and biological processes in the environment. POPs are potentially toxic compounds mainly used in pesticides, solvents, pharmaceuticals, or industrial applications and pose a significant and persistent risk to the ecosystem and human health. Surfactants can serve as detergents, wetting and foaming compounds, emulsifiers, or dispersants, and have been used extensively to promote the solubilization of POPs and their subsequent removal from environmental matrices, including solid wastes, soil, and sediments. However, improper use of surfactants for remediation of POPs may lead to unintended consequences that include toxicity of surfactants to soil microorganisms and plants, and leaching of POPs, thereby resulting in groundwater contamination.

An Overview on the Treatment of Oil Pollutants in Soil Using Synthetic and Biological Surfactant Foam and Nanoparticles

Oil-contaminated soil is one of the most concerning problems due to its potential damage to human, animals, and the environment. Nanoparticles have effectively been used to degrade oil pollution in soil in the lab and in the field for a long time. In recent years, surfactant foam and nanoparticles have shown high removal of oil pollutants from contaminated soil. This review provides an overview on the remediation of oil pollutants in soil using nanoparticles, surfactant foams, and nanoparticle-stabilized surfactant foams. In particular, the fate and transport of oil compounds in the soil, the interaction of nanoparticles and surfactant foam, the removal mechanisms of nanoparticles and various surfactant foams, the effect of some factors (e.g., soil characteristics and amount, nanoparticle properties, surfactant concentration) on remediation efficiency, and some advantages and disadvantages of these methods are evaluated. Different nanoparticles and surfactant foam can be effectively utilized for treating oil compounds in contaminated soil. The treatment efficiency is dependent on many factors. Thus, optimizing these factors in each scenario is required to achieve a high remediation rate while not causing negative effects on humans, animals, and the environment. In the future, more research on the soil types, operating cost, posttreatment process, and recycling and reuse of surfactants and nanoparticles need to be conducted.

Multi stress system: Microplastics in freshwater and their effects on host microbiota

Microplastics are persistent and complex contaminants that have recently been found in freshwater systems, raising concerns about their presence in aquatic organisms. Plastics tend to be seen as an inert material; however, it is not well known if exposure to plastics for a prolonged time, in combination with organic chemicals, causes organism mortality. Ingestion of microplastics in combination with another pollutant may affect a host organism's fitness by altering the host microbiome. In this study, we investigated how microplastics interact with other pollutants in this multi-stress system, and whether they have a synergistic impact on the mortality of an aquatic organism and its microbiome. We used wild water boatmen Hemiptera (Corixidae) found at lake Erken located in east-central Sweden in a fully factorial two-way microcosm experiment designed with polystyrene microspheres and a commonly used detergent. The microplastic-detergent interaction is manifested as a significant increase in mortality compared to the other treatments at 48 h of exposure. The diversity of the microbial communities in the water was significantly affected by the combined treatment of microplastics and the detergent while the microbial communities in the host were affected by the treatments with microplastics and the detergent alone. Changes in relative abundance in Gammaproteobacteria (family Enterobacteriaceae), were observed in the perturbed treatments mostly associated with the presence of the detergent. This confirms that microplastics can interact with detergents having toxic effects on wild water boatmen. Furthermore, microplastics may impact wild organisms via changes in their microbial communities.

Nitrogen removal by Rhodococcus sp. SY24 under linear alkylbenzene sulphonate stress: Carbon source metabolism activity, kinetics, and optimum culture conditions

Artificial intervention combined with stress acclimation was used to screen a heterotrophic nitrifying-aerobic denitrifying (HN-AD) bacterial, strain Rhodococcus SY24, resistant to linear alkylbenzenesulfonic acid (LAS) stress. When LAS was<15 mg/L, strain SY24 performed better cell growth and carbon source metabolism activity. The maximum nitrification and denitrification rates of SY24 under LAS stress could reach 1.18 mg/L/h and 1.05 mg/L/h, respectively, which were 13.80 % and 8.81 % higher than those of the original strain CPZ24. Higher LAS tolerance was seen in the functional genes (amoA, nxrA, napA, narG, nirK, nirS, norB, and nosZ). Response surface modeling revealed that 2 mg/L LAS, sodium succinate as a carbon source, 190 rams, and carbon/nitrogen 11 were the ideal culture conditions for SY24 to nitrogen removal under the LAS environment. This study offered a new screening strategy for the functional species, and strain SY24 showed significant LAS tolerance and HN-AD potential.

Graywater treatment of emerging pollutant linear alkylbenzene sulfonate by adsorption with leather shave waste activated carbon

The purpose of this research is to evaluate the use of leather shave waste activated carbon (ACLW) as an alternative for the treatment of wastewater containing linear alkylbenzene sulfonate (LAS). Batch adsorption tests were carried out (pH effect, isotherms, kinetics). The activated carbon was tested for its life cycle by desorption with solvent and it was further evaluated as real wastewater treatment for bath graywater. Under the optimum pH of 2.5, kinetic studies showed a better correlation with the pseudo-second order model, with an activation energy of 27.5 kJ mol-1. Equilibrium isotherms correlated better with the double layer model, indicating hemi-micelle formation and performing a high-affinity isotherm. Adsorption was shown to be endothermic (∆H0 =  + 73.89 kJ mol-1), entropy driven (∆S0 =  + 0.46 kJ mol-1 K-1), and occurring spontaneously. The use of ethanol solution was effective for the regeneration of the adsorbent. Adsorption was applied in real wastewater, removing contaminants from bath graywater, especially anionic surfactants with up to 95% removal efficiency.

Surfactant-aided mycoremediation of soil contaminated with polycyclic aromatic hydrocarbons

Remediation of persistent polycyclic aromatic hydrocarbons (PAHs) contaminated soil has become a major challenge in recent years. Further, conventional application of bioaugmentation strategies for PAHs remediation require continuous supply of microbial specific nutrients, which makes these processes less feasible. Hence, the present study focused on PAHs remediation using surfactants along with wood assisted fungal system in a microcosm set up. In this study, in absence of surfactants, a saturation in PAHs degradation was noted in bioaugmentation with wood assisted fungal system (BAW) with 61 ± 1.25% degradation, followed by bioaugmentation with free fungi system (BAF) (54 ± 0.46%). However, with addition of 1500 mg/L of surface-active compounds (SAC), a maximum PAHs degradation in BAW (100%) and BAF (86 ± 1.30%) strategies were noted on 21st day. Irrespective of the strategies, presence of SAC and rhamnolipids enhanced PAHs degradation by increasing the enzymes production in Trametes hirsuta when compared to Triton x-100 and sodium dodecyl sulphate (SDS). Among the detected PAHs, 100% degradation within 17 days was noted for naphthalene and acenaphthene in SAC-supplemented BAW system. Further, ecotoxicity analysis established showed the LC50 of sediment soil at 26.5 ± 0.24%, which was reduced by an average of 71% after soil remediation. Hence, the current microcosm system proved that the application of SAC with BAW enhanced the PAHs remediation rate, which supports its application in real time soil remediation.

Tracking pollutants in a municipal sewage network impairing the operation of a wastewater treatment plant

This work provides a screening of organic contaminants and characterization of the dissolved organic matter in the sewer network until the municipal wastewater treatment plant (WWTP), identifying the network areas with a higher degree of contamination and their impact on the WWTP performance, particularly in the activated sludge reactor. Three monitoring campaigns were carried out at six selected locations of the sewage system (PVZ-1, PVZ-2, PS-F, PS-VC, CP-VC, and PS-T), influent (WWTP_INF) and effluent (WWTP_EFF) of the WWTP. Advanced analytical techniques were employed, namely excitation/emission matrix fluorescence-parallel factor analysis (EEM-PARAFAC), size exclusion chromatography with organic carbon detector (SEC-OCD), and liquid chromatography with high-resolution-mass spectrometric detection (LC-HRMS). EEM-PARAFAC showed higher fluorescence intensity for the protein-like component (C2), particularly at CP-VC (near seafood industries) associated with the presence of surfactants (~50 mg/L). SEC-OCD highlighted the WWTP efficiency in removing low molecular weight acids and neutrals. LC-HRMS tentatively identified 108 compounds of emerging concern (CEC) and similar detection patterns were obtained for all wastewater samples, except for PVZ-2 (lower detection), many of which occurred in the effluent. Eight CECs included on relevant Watch-Lists were detected in all WWTP_EFF samples. Furthermore, 111 surfactants were detected, the classes more frequently found being alcohol ethoxylates (AEOs), nonylphenol polyethoxylates (NPEOs) and linear alkylbenzene sulphonates (LAS). The continuous presence of LAS and NPEOs allied to surfactants concentrations in the WWTP_INF of 15-20 mg/L, with CP-VC location (linked with food industries) as an important contributor, explain the morphological changes in the activated sludge and high LAS content in the dewatered sludge, which may have impacted WWTP performance.

Synthesis, self-assembly and biolabeling of perylene diimide-tyrosine alkyl amide based amphiphiles: nanomolar detection of AOT surfactant

Perylene diimide-tyrosine alkyl amide based amphiphiles were synthesized and characterized. PDI 3a showed ‘beehive’ nanostructure and applied for biolabeling of MG-63 live cells. PDI 3b can be used for NIR detection of anionic surfactant.

Combined effect of nanoscale zero-valent iron and linear alkylbenzene sulfonate (LAS) to the freshwater algae Scenedesmus obliquus

With wide use of nanoparticles, co-exposure of aquatic organisms to nanoparticles and organic pollutants often takes place in the environment. However, the combined effects are still rarely understood. In this study, in order to study the interaction and biological effects of nanoscale zero-valent iron (nZVI) and linear alkylbenzene sulfonate (LAS), which acts as a typical surfactant, the freshwater algae Scenedesmus obliquus was exposed to nZVI and LAS individually and in combination for 96 h. According to the inhibition rate of the algae, the toxic effects were investigated by dose-response analysis. Then the combined effect of nZVI and LAS was evaluated using three evaluation models including toxicity unit (TU), additional index (AI), and mixture toxicity index (MTI). The results showed that the 96 h IC₅₀ of nZVI and LAS to Scenedesmus obliquus was 2.464 mmol L^-1 and 0.332 mmol L^-1, respectively. When nZVI coexisted with LAS at toxic ratio 1:1, the 96 h IC₅₀ value was 1.658 mmol L^-1 (shown with nZVI), and the partly additive effect of nZVI mixed with LAS was confirmed. However, when the toxic ratio of nZVI:LAS was 4:1, it showed synergistic effect. In addition, when nZVI mixed with LAS at toxic ratio 1:4, the joint effect is antagonistic effect. In addition, the content of chorophyll in Scenedesmus obliquus, especially the content of chlorophyll a, was decreased with the increase of mixture dose. However, the protein levels did not show significant changes at different mixture doses.

Antimicrobial and bacteriostatic activity of surfactants against B. subtilis for microbial cleaner formulation

Cleaning products containing live bacteria that form spores of Bacillus spp. as active substances are becoming increasingly common in probiotic cleaner formulation. The quality of cleaning performance for the production of probiotic cleaners does not only depend on the potential of the bacterial strains used, but also on the chemical components of the formulations. In this study, the surfactants and other additives were investigated as biocidal or bacteriostatic against B. subtilis, and the viability of B. subtilis was examined at different pH ranges for microbial cleaner formulation. As a result, it was discovered that the B. subtilis, which can be used in the microbial cleaner formulation, shows higher growth and viability at the neutral pH, and it passes into the death phase at pH 3. According to antagonistic activity results, the Gram-positive S. aureus and K. pneumoniae were the most sensitive bacteria while B. cereus was the most resistant bacteria. The anionic surfactants such as linear alkylbenzene sulfonic acid and sodium lauryl ether sulfate act as bacteriostatic on Bacillus spp. and do not cause cell death. In the view of these results, the usage of appropriate bacterial cultures and the correct stabilization of the formulations are also critical elements in the development of microbial cleaner formulations.

Linear anionic surfactant (SDBS) destabilized anammox process through sludge disaggregation and metabolic inhibition

The increase of emerging contaminants, such as surfactants, is one of the major challenges to biological wastewater treatment. However, the potential impact of linear alkylbenzene sulphonates (LAS), a major class of anionic surfactants, on anammox process is unclear. The long-term effects of sodium dodecyl benzene sulfonate (SDBS, as a model LAS) on reactor performance, microbial community and sludge properties were investigated in this study. The presence of 5 mg L^-1 SDBS promoted the release of extracellular microbial products from anammox granules and the wash-out of anammox population via effluent. Despite sludge disaggregation, the reactor performance was robust to the exposure of 5 mg L^-1 SDBS due to functional redundancy. With the further increase of SDBS to 10 mg L^-1, the metabolic activity of anammox biomass and the transcription and post-translation of hydrazine dehydrogenase were significantly decreased. The potential mechanism might be associated with the damage on cell membrane that induced the leakage of intracellular matrix. These results highlight the need to consider the potential risk of LAS to operation of anammox process in biological wastewater treatment plant.

Effects of aluminum oxide nanoparticles on the performance, extracellular polymeric substances, microbial community and enzymatic activity of sequencing batch reactor

The performance, pollutant removal rate, microbial community and enzymatic activity of a sequencing batch reactor (SBR) were investigated under oxide nanoparticles (Al₂O₃ NPs) stress. Al₂O₃ NPs at 0-50 mg/L showed no evident impact on the COD and NH₄ ⁺ removals of SBR. The oxygen-uptake rate, nitrifying rate and nitrite-reducing rate slightly diminished with the increase of Al₂O₃ NPs concentration. Compared with 0 mg/L Al₂O₃ NPs, the dehydrogenase activity declined by 23.52% at 50 mg/L Al₂O₃ NPs. The activities of ammonia monooxygenase, nitrite oxidoreductase and nitrite reductase decreased with the increase of Al₂O₃ NPs concentration from 0 to 50 mg/L Al₂O₃ NPs. However, the nitrate reductase (NR) activity slightly increased at 5 and 15 mg/L Al₂O₃ NPs and declined at 30 and 50 mg/L Al₂O₃ NPs. The microbial reactive oxygen species (ROS) production and lactate dehydrogenase (LDH) release merely raised 14.80% and 20.72% at 50 mg/L Al₂O₃ NPs by contrast with 0 mg/L Al₂O₃ NPs, respectively. Al₂O₃ NPs enhanced the production, protein content and polysaccharide content of extracellular polymeric substances owing to preventing the microbes from Al₂O₃ NPs biotoxicity. The existence of Al₂O₃ NPs led to the variations of microbial richness and diversity in the SBR due to their biotoxicity.

Comparison of Novel and Established Nitrification Inhibitors Relevant to Agriculture on Soil Ammonia- and Nitrite-Oxidizing Isolates

Nitrification inhibitors (NIs) applied to soil reduce nitrogen fertilizer losses from agro-ecosystems. NIs that are currently registered for use in agriculture appear to selectively inhibit ammonia-oxidizing bacteria (AOB), while their impact on other nitrifiers is limited or unknown. Ethoxyquin (EQ), a fruit preservative shown to inhibit ammonia-oxidizers (AO) in soil, is rapidly transformed to 2,6-dihydro-2,2,4-trimethyl-6-quinone imine (QI), and 2,4-dimethyl-6-ethoxy-quinoline (EQNL). We compared the inhibitory potential of EQ and its derivatives with that of dicyandiamide (DCD), nitrapyrin (NP), and 3,4-dimethylpyrazole-phosphate (DMPP), NIs that have been used in agricultural settings. The effect of each compound on the growth of AOB (Nitrosomonas europaea, Nitrosospira multiformis), ammonia-oxidizing archaea (AOA; "Candidatus Nitrosocosmicus franklandus," "Candidatus Nitrosotalea sinensis"), and a nitrite-oxidizing bacterium (NOB; Nitrobacter sp. NHB1), all being soil isolates, were determined in liquid culture over a range of concentrations by measuring nitrite production or consumption and qPCR of amoA and nxrB genes, respectively. The degradation of NIs in the liquid cultures was also determined. In all cultures, EQ was transformed to the short-lived QI (major derivative) and the persistent EQNL (minor derivative). They all showed significantly higher inhibition activity of AOA compared to AOB and NOB isolates. QI was the most potent AOA inhibitor (EC50 = 0.3-0.7 μM) compared to EQ (EC50 = 1-1.4 μM) and EQNL (EC50 = 26.6-129.5 μM). The formation and concentration of QI in EQ-amended cultures correlated with the inhibition patterns for all isolates suggesting that it was primarily responsible for inhibition after application of EQ. DCD and DMPP showed greater inhibition of AOB compared to AOA or NOB, with DMPP being more potent (EC50 = 221.9-248.7 μM vs EC50 = 0.6-2.1 μM). NP was the only NI to which both AOA and AOB were equally sensitive with EC50s of 0.8-2.1 and 1.0-6.7 μM, respectively. Overall, EQ, QI, and NP were the most potent NIs against AOA, NP, and DMPP were the most effective against AOB, while NP, EQ and its derivatives showed the highest activity against the NOB isolate. Our findings benchmark the activity range of known and novel NIs with practical implications for their use in agriculture and the development of NIs with broad or complementary activity against all AO.

Screening and mutagenesis of high-efficient degrading bacteria of linear alkylbenzene sulfonates

As a widely used detergent, anionic surfactant linear alkylbenzene sulfonates (LAS) is a common toxic pollutant in wastewater. In this study, Pseudomonas sp. strain H6 was isolated from activated sludge and municipal wastewater, which had good degradation effect on LAS. The results showed that strain H6 could grow with LAS as the sole carbon source. When the concentration of LAS was less than 100 mg/L, strain H6 could degrade more than 80% of the LAS within 24 h. Meanwhile, the growth of strain H6 increased with the increase of LAS concentration, reaching the maximum growth at the presence of 100 mg/L LAS. When the concentration of LAS was over 100 mg/L, strain H6's cell growth and degradation of LAS showed a downward trend due to the strong toxicity of LAS, and the degradation rate of LAS almost tended to zero with 500 mg/L LAS. Further mutagenesis analysis of strain H6 showed that positive mutation occurred under ultraviolet and nitrite mutagenesis with using ampicillin to increase the screening pressure, and the degradation rate of LAS was 44.91% higher than that of original strain.

Insights into long-term effects of amino-functionalized multi-walled carbon nanotubes (MWCNTs-NH2) on the performance, enzymatic activity and microbial community of sequencing batch reactor

Carbon nanotubes (CNTs) inevitably enter domestic sewage and industrial wastewater with the continuous increase of their production and application field. The potential effect of CNTs on biological wastewater treatment processes has raised wide concerns due to their biotoxicity. In the present study, the performance, microbial community and enzymatic activity of sequencing batch reactors (SBRs) were evaluated under 148-day exposure of amino-functionalized multi-walled CNTs (MWCNTs-NH₂) at 10 and 30 mg/L. The COD removal efficiency at 10 and 30 mg/L MWCNTs-NH₂ gradually reduced from 91.03% and 90.43% on day to 89.11% and 86.70% on day 148, respectively. The NH₄⁺-N removal efficiency at 10 and 30 mg/L MWCNTs-NH₂ gradually reduced from 98.98% and 98.46% on day 1 to 96.65% and 63.39% on day 148, respectively. Compared to 0 mg/L MWCNTs-NH₂, the oxygen-utilizing rate, ammonia-oxidizing rate, nitrite-oxidizing rate, nitrite-reducing rate and nitrate-reducing rate at 30 mg/L MWCNTs-NH₂ were decreased by 52.35%, 60.58%, 55.12%, 56.56% and 57.42% on day 148, respectively. The microbial reactive oxygen species and lactate dehydrogenase release on day 148 was increased by 59.71% and 55.28% at 30 mg/L MWCNTs-NH₂, respectively. The key microbial enzymatic activity related to nitrogen removal decreased with the increase of operation time under MWCNTs-NH₂ stress. The relative abundances of Nitrosomonas, Nitrosospira, Nitrospira and some denitrifying bacteria at 10 mg/L MWCNTs-NH₂ gradually reduced with an increment in operation time. The changes of nitrogen removal rate, microbial community and enzymatic activity of SBR were related to the time-cumulative nonlinear inhibition effect under long-term exposure.

Microbial community assembly in detergent wastewater treatment bioreactors: Influent rather than inoculum source plays a more important role

In this study, three sequencing batch reactors Ra, Rb, Rc with different inoculum sources (activated sludge; activated sludge plus detergent degrading consortium; detergent degrading consortium) were used to treat detergent wastewater [consisting of sodium dodecyl sulfate, polyoxyethylene lauryl ether and tetrasodium ethylenediamine tetraacetate (Na₄EDTA)]. Fast start-up and highest performance in phase I and II (organic loading rate were 0.28, 0.39 kgCOD/kgMLSS/d, respectively) were observed in Rc. In contrast, Rb showed highest impact resistance to the increase of EDTA concentration in phase III. High-throughput sequencing analysis showed that inoculum sources led to significant differences on microbial community in phase I. However, regardless of the influent variation in phases II and III, the differences on microbial community among three SBRs were diminished along long-term operation. Pseudomonas, Sphingopyxis, Luteimonas, Pseudoxanthomonas and SM1A02 were found to be the core taxa, they might contribute to the excellent performance of detergent wastewater treatment.

Effects of detergents on natural ecosystems and wastewater treatment processes: a review

Among the different contaminants, detergent as an important pollutant has serious risks to natural ecosystems. Furthermore, detergents can pass into the wastewater treatment plants and have bad effect on their performance. They are part of human life and consumed for different aims especially hygienic purposes. Therefore, detergent components can enter to soil and water bodies from different sources. Detergents affect fauna and flora, and they have direct and indirect effects on ecosystems. Eutrophication, foaming, and altering parameters such as temperature, salinity, turbidity, and pH are more important, and their effects need to be managed and controlled. Researchers confirmed that aerobic processes are able to degrade the most of detergents but anaerobic degradation is not possible because of restricted metabolic pathways and toxicity of them. Therefore, production of environment-friendly detergent is an important issue around the world. Graphical abstract.

A review on the application of chemical surfactant and surfactant foam for remediation of petroleum oil contaminated soil

Soil, exposed to petroleum oil contaminants (in the form of petrol, diesel, gasoline, crude oil, used motor oil), may cause potential damage to the environment, animal and human health. In this review article, mechanisms of the petroleum oil contaminant removal from soil by chemical surfactant systems such as surfactant solution, surfactant foam and nanoparticle stabilized surfactant foams are explained. Laboratory based research works, reported within the last decade on the application of similar systems towards the removal of petroleum oil contaminant from the soil, have been discussed. It is an important fact that the commercial implementation of the chemical surfactant based technology depends on the environmental properties (biodegradability and toxicity) of the surfactants. In recent times, surfactant foam and nanoparticle stabilized surfactant foam are becoming more popular and considered advantageous over the use of surfactant solution alone. However, more research works have to be conducted on nanoparticle stabilized foam. The impact of physicochemical properties of the nanoparticles on soil remediation has to be explored in depth.

Effect of magnesium oxide nanoparticles on microbial diversity and removal performance of sequencing batch reactor

The performance, microbial enzymatic activity and microbial community of a sequencing batch reactor (SBR) have been explored under magnesium oxide nanoparticles (MgO NPs) stress. The NH₄⁺-N removal efficiency kept relatively stable during the whole operational process. The MgO NPs at 30-60 mg/L slightly restrained the removal of chemical oxygen demand (COD), and the presence of MgO NPs also affected the denitrification and phosphorus removal. The specific oxygen uptake rate, nitrifying and denitrifying rates, phosphorus removal rate, and microbial enzymatic activities distinctly varied with the increase of MgO NPs concentration. The appearance of MgO NPs promoted more reactive oxygen species generation and lactate dehydrogenase leakage from activated sludge, suggesting that MgO NPs had obvious toxicity to activated sludge in the SBR. The protein and polysaccharide contents of extracellular polymeric substances from activated sludge increased with the increase of MgO NPs concentration. The microbial richness and diversity at different MgO NPs concentrations obviously varied at the phylum, class and genus levels due to the biological toxicity of MgO NPs.

Graft-modified cellulose nanocrystals as CO2-switchable Pickering emulsifiers

Cellulose nanocrystals (CNC) grafted with <25 wt% PDEAEMA or PDMAPMAm were used as CO₂-switchable Pickering emulsifiers for the reversible emulsification/demulsification of oil and water.

Solvent-Induced Molecular Folding and Self-Assembled Nanostructures of Tyrosine and Tryptophan Analogues in Aqueous Solution: Fascinating Morphology of High Order

Hydrophobic derivatives of tyrosine and tryptophan, viz. octyl and dodecyl esters of tyrosine and octyl ester of tryptophan, are synthesized, and the interfacial and bulk properties in aqueous media are investigated as models for the membrane proteins. Molecular modeling by the density functional theory method is carried out to understand the molecular conformation and geometry for the purpose of determining the packing parameters. Water-induced molecular folding of the esters of both tyrosine and tryptophan, as observed using rotating frame nuclear Overhauser effect spectroscopy, indicates that the segregation of the hydrophobic and hydrophilic blocks in water is the key to the development of fascinating interfacial property displayed by the aromatic amino acid esters. The unusually high-order morphology of the aggregates, as observed using high-resolution transmission electron microscopy, is highly uncommon for single-chain amphiphiles and points to the fact that the self-assembly behavior of the present systems resembles that of block copolymers. The study of the growth of mesosized hollow aggregates with internal bilayer structures from tyrosine and tryptophan-based model systems would add to the understanding of biochemistry and biotechnology relevant to the cell membrane. The potential of biocompatible nanostructured motifs as the drug carriers is discussed. The highly functional role played by the aromatic amino acids at the membrane-water interface will be considered with the present amphiphilic models for future perspective.

Changes in fluorescent dissolved organic matter upon interaction with anionic surfactant as revealed by EEM-PARAFAC and two dimensional correlation spectroscopy

Surfactants are present in significant amounts in both domestic and industrial wastewater, which may interact with dissolved organic matter (DOM). The present study investigated the interactions of sodium dodecyl sulfate (SDS) with three different DOM solutions, including bovine serum albumin (BSA), humic acid (HA), and the mixture of the two (BSA-HA), based on two advanced spectroscopic tools: excitation emission matrix (EEM) combined with parallel factor analysis (EEM-PARAFAC) and two dimensional correlation spectroscopy (2D-COS). The responses of two protein-like components to the addition of SDS differed depending the presence and the absence of HA. A decreasing and an increasing trend was observed for tryptophan-like (C1) and tyrosine-like (C2) components, respectively, in the BSA solution, while the BSA-HA mixture exhibited increasing fluorescence trends for both protein-like components. The conflicting results suggest that HA plays a secondary role in the protein-SDS interactions. No interaction between the SDS and humic-like component was found. 2D-COS combined with fluorescence spectra demonstrated that the protein-SDS interaction occurred on the order of C2 > C1 for the BSA solution but C1 > C2 for the BSA-HA mixture. Analyses of Scatchard plots confirmed the sequential order interpreted from 2D-COS, showing consistent trends in the binding constants. However, the presence of HA affected the protein-SDS interactions in different manners for C1 and C2, enhancing and reducing the binding constants, respectively. Circular dichroism spectra confirmed the occurrence of conformational changes in BSA with SDS. EEM-PARAFAC and 2D-COS successfully explained different interactions of surfactant with protein-like components in the presence of HA.

Effects of short-term exposure to linear anionic surfactants (SDBS, SLS and SDS) on anammox biomass activity

This work demonstrates the feasibility of nitrogen removal from wastewater containing linear anionic surfactants, including sodium dodecyl benzene sulfonate, sodium lauryl sulfate and sodium dodecyl sulfonate, by using the anammox process.

Use of surfactants for the remediation of contaminated soils: a review

Due to the great harm caused by soil contamination, there is an increasing interest to apply surfactants to the remediation of a variety of contaminated soils worldwide. This review article summarizes the findings of recent literatures regarding remediation of contaminated soils/sites using surfactants as an enhancing agent. For the surfactant-based remedial technologies, the adsorption behaviors of surfactants onto soil, the solubilizing capability of surfactants, and the toxicity and biocompatibility of surfactants are important considerations. Surfactants can enhance desorption of pollutants from soil, and promote bioremediation of organics by increasing bioavailability of pollutants. The removal of heavy metals and radionuclides from soils involves the mechanisms of dissolution, surfactant-associated complexation, and ionic exchange. In addition to the conventional ionic and nonionic surfactants, gemini surfactants and biosurfactants are also applied to soil remediation due to their benign features like lower critical micelle concentration (CMC) values and better biocompatibility. Mixed surfactant systems and combined use of surfactants with other additives are often adopted to improve the overall performance of soil washing solution for decontamination. Worldwide the field studies and full-scale remediation using surfactant-based technologies are yet limited, however, the already known cases reveal the good prospect of applying surfactant-based technologies to soil remediation.

Suppression of intestinal microbiota-dependent production of pro-atherogenic trimethylamine N-oxide by shifting L-carnitine microbial degradation

AIMS

Trimethylamine-N-oxide (TMAO) is produced in host liver from trimethylamine (TMA). TMAO and TMA share common dietary quaternary amine precursors, carnitine and choline, which are metabolized by the intestinal microbiota. TMAO recently has been linked to the pathogenesis of atherosclerosis and severity of cardiovascular diseases. We examined the effects of anti-atherosclerotic compound meldonium, an aza-analogue of carnitine bioprecursor gamma-butyrobetaine (GBB), on the availability of TMA and TMAO.

MAIN METHODS

Wistar rats received L-carnitine, GBB or choline alone or in combination with meldonium. Plasma, urine and rat small intestine perfusate samples were assayed for L-carnitine, GBB, choline and TMAO using UPLC-MS/MS. Meldonium effects on TMA production by intestinal bacteria from L-carnitine and choline were tested.

KEY FINDINGS

Treatment with meldonium significantly decreased intestinal microbiota-dependent production of TMA/TMAO from L-carnitine, but not from choline. 24hours after the administration of meldonium, the urinary excretion of TMAO was 3.6 times lower in the combination group than in the L-carnitine-alone group. In addition, the administration of meldonium together with L-carnitine significantly increased GBB concentration in blood plasma and in isolated rat small intestine perfusate. Meldonium did not influence bacterial growth and bacterial uptake of L-carnitine, but TMA production by the intestinal microbiota bacteria K. pneumoniae was significantly decreased.

SIGNIFICANCE

We have shown for the first time that TMA/TMAO production from quaternary amines could be decreased by targeting bacterial TMA-production. In addition, the production of pro-atherogenic TMAO can be suppressed by shifting the microbial degradation pattern of supplemental/dietary quaternary amines.

Biodegradation of nonylphenols using nitrifying sludge, 4-chlorophenol-adapted consortia and activated sludge in liquid and solid phases

The biodegradation of a technical mixture of nonylphenols (tNP) with three different biomasses (nitrifying sludge, 4-chlorophenol-adapted consortia and activated sludge) was evaluated in batch tests. The tNP degradation was determined in solid and liquid phases. The three biomasses studied were able to biodegrade the technical mixture of nonylphenols. It was found that 33% to 44% of the initial tNP was adsorbed on to the sludge after 250 h. Nitrifying sludge presented the highest biodegradation percentage (43.1% +/- 2.3%) and degradation rate (3.10 x 10(-3) micromol/d). Acclimated 4-chlorophenol and activated sludge degraded 34.3% +/- 1.2% and 18.2% +/- 0.5% of the initial tNP, respectively. Actual half-life times of 10.9, 12.0 and 22.8 days were obtained for the biodegradation of tNP by nitrifying, acclimated 4-chlorophenol and activated sludge, respectively. It was concluded that, although nitrifiying biomass posses a high initial adsorption rate, this biomass can also biodegrade the tNP faster than the other tested biomasses.

A sensitive crude oil bioassay indicates that oil spills potentially induce a change of major nitrifying prokaryotes from the archaea to the bacteria

The sensitivity of nitrifiers to crude oil released by the BP Deepwater Horizon oil spill in Gulf of Mexico was examined using characterized ammonia-oxidizing bacteria and archaea to develop a bioassay and to gain further insight into the ecological response of these two groups of microorganisms to marine oil spills. Inhibition of nitrite production was observed among all the tested ammonia-oxidizing organisms at 100 ppb crude oil. Nitrosopumilus maritimus, a cultured representative of the abundant Marine Group I Archaea, showed 20% inhibition at 1 ppb, a much greater degree of sensitivity to petroleum than the tested ammonia-oxidizing and heterotrophic bacteria. The differing susceptibility may have ecological significance since a shift to bacterial dominance in response to an oil spill could potentially persist and alter trophic interactions influenced by availability of different nitrogen species.

Nitrification of an industrial wastewater in a moving-bed biofilm reactor: effect of salt concentration

Nitrification of wastewaters from chemical industries can pose some challenges due to the presence of inhibitory compounds. Some wastewaters, besides their organic complexity present variable levels of salt concentration. In order to investigate the effect of salt (NaCl) content on the nitrification of a conventional biologically treated industrial wastewater, a bench scale moving-bed biofilm reactor was operated on a sequencing batch mode. The wastewater presenting a chloride content of 0.05 g l(-1) was supplemented with NaCl up to 12 g Cl(-) l(-1). The reactor operation cycle was: filling (5 min), aeration (12 or 24h), settling (5 min) and drawing (5 min). Each experimental run was conducted for 3 to 6 months to address problems related to the inherent wastewater variability and process stabilization. A PLC system assured automatic operation and control of the pertinent process variables. Data obtained from selected batch experiments were adjusted by a kinetic model, which considered ammonia, nitrite and nitrate variations. The average performance results indicated that nitrification efficiency was not influenced by chloride content in the range of 0.05 to 6 g Cl(-) l(-1) and remained around 90%. When the chloride content was 12 g Cl(-) l(-1), a significant drop in the nitrification efficiency was observed, even operating with a reaction period of 24 h. Also, a negative effect of the wastewater organic matter content on nitrification efficiency was observed, which was probably caused by growth of heterotrophs in detriment of autotrophs and nitrification inhibition by residual chemicals.

Rapid and sensitive Nitrosomonas europaea biosensor assay for quantification of bioavailable ammonium sensu strictu in soil

Knowledge on bioavailable ammonium sensu strictu (i.e., immediately available for cellular uptake) in soil is required to understand nutrient uptake processes in microorganisms and thus of vital importance for plant production. We here present a novel ammonium biosensor approach based on the lithoautotrophic ammonia-oxidizing bacterium Nitrosomonas europaea transformed with a luxAB sensor plasmid. Bioluminescence-based ammonium detection was achieved within 10 min with a quantification limit in liquid samples of ∼20 μM and a linear response range up to 400 μM. Biosensor and conventional chemical quantification of ammonium in soil solutions agreed well across a range of sample and assay conditions. The biosensor was subsequently applied for a solid phase-contact assay allowing for direct interaction of biosensor cells with soil particle-associated (i.e., exchangeable plus fixed) ammonium. The assay successfully quantified bioavailable ammonium even in unfertilized soil and demonstrated markedly higher ratios of bioavailable ammonium to water- or 2 M KCl-exchangeable ammonium in anoxic soil than in corresponding oxic soil. Particle-associated ammonium contributed by at least 74% and 93% of the total bioavailable pool in oxic and anoxic soil, respectively. The N. europaea biosensor should have broad relevance for environmental monitoring of bioavailable ammonium and processes depending on ammonium bioavailability.

Evaluation of bacterial surfactant toxicity towards petroleum degrading microorganisms

The acute toxicity of bacterial surfactants LBBMA111A, LBBMA155, LBBMA168, LBBMA191 and LBBMA201 and the synthetic surfactant sodium dodecyl sulfate (SDS) on the bioluminescent bacterium Vibrio fischeri was evaluated by measuring the reduction of light emission (EC(20)) by this microorganism when exposed to different surfactant concentrations. Moreover, the toxic effects of different concentrations of biological and synthetic surfactants on the growth of pure cultures of isolates Acinetobacter baumannii LBBMA04, Acinetobacter junni LBBMA36, Pseudomonas sp. LBBMA101B and Acinetobacter baumanni LBBMAES11 were evaluated in mineral medium supplemented with glucose. The EC(20) values obtained confirmed that the biosurfactants have a significantly lower toxicity to V. fischeri than the SDS. After 30 min of exposure, bacterial luminescence was almost completely inhibited by SDS at a concentration of 4710 mg L(-1). Growth reduction of pure bacterial cultures caused by the addition of biosurfactants to the growth medium was lower than that caused by SDS.

Effects of selected pharmaceutically active compounds on the ammonia oxidizing bacterium Nitrosomonas europaea

Pharmaceutically active compounds (PhACs) are commonly found in wastewater influent. However, little research has focused on determining their impact on fundamental processes in wastewater treatment such as nitrogen removal. In this study, focus was placed on 4 commonly occurring PhACs (ketoprofen, naproxen, carbamazepine and gemfibrozil). Their effect was ascertained in the ammonia oxidizing bacterium (AOB), Nitrosomonas europaea in terms of membrane integrity and nitrite production. These PhACs were shown to inhibit nitrite production at concentrations of 1 and 10 μM while no effect was observed at 0.1 μM. The maximum observed nitrification inhibition was 25%, 29%, 22% and 26% for ketoprofen, naproxen, carbamazepine and gemfibrozil, respectively. A decrease in the live/dead ratio ranging from 10% to 16% suggests that these PhACs affect membrane integrity in N.europaea. The difference in nitrite production between PhACs treated cells and non PhAC treated controls was still significant following washing suggesting that inhibition is irreversible. Finally, nitrite production when adjusted to the live fraction of cells was also found to decrease suggesting that PhACs inhibited the activity of surviving cells. These results suggest that the presence of PhACs may affect AOB activity and may impact nitrogen removal, a key function in wastewater treatment. Follow up studies with additional AOB and in mixed culture are needed to further confirm these results.