Biosorption of tetradecyl benzyl dimethyl ammonium chloride on activated sludge: kinetic, thermodynamic and reaction mechanisms

Recovery of organic matters by activated sludge from municipal wastewater: Performance and characterization

Municipal wastewater treatment processes consume a significant amount of energy and generate substantial carbon emissions. However, organic matters existing in municipal wastewater hold the potential as a valuable carbon source. Activated sludge has the potential to capture and recover the organic matters, thereby enriching carbon sources and facilitating subsequent sludge anaerobic digestion as well as in line with the concept of sustainable development. Based on above, this study investigated the enrichment and recovery characteristics and mechanisms of activated sludge adsorption on carbon sources in municipal wastewater, while optimizing the recovery conditions. The results indicated that insoluble organic matters, as well as a fraction of dissolved organic matters, can be effective recovered within approximately 40 min. Specifically, 74.1% of insoluble organic matters and 25.8% of soluble organic matters were successfully captured by the activated sludge, resulting in a 5.0% increase in sludge organic matter content. Moreover, activated sludge demonstrated remarkable recovery of particulate organic matters across various particle sizes, particularly larger particles (>5 μm) with high protein content. Notably, the dissolved biodegradable organics such as tryptophan and tyrosine protein-like substances according to 3D-EEM and lipids, proteins/amino sugars, and carbohydrates according to FT-ICR MS can be effectively recovered. Finally, the study revealed that the recovery of organic matters from the wastewater by activated sludge followed the pseudo-second-order kinetics model, with surface binding, hydrogen bonding and interparticle diffusion in sludge flocs as the primary adsorption mechanisms. This approach had abroad application prospects for improving the profitability of wastewater treatment plants.

Emerging contaminants and their potential impacts on estuarine ecosystems: Are we aware of it?

Emerging contaminants (ECs) are becoming more prevalent in estuaries and constitute a danger to both human health and ecosystems. These pollutants can infiltrate the ecosystem and spread throughout the food chain. Because of the diversified sources and extensive human activities, estuaries are particularly susceptible to increased pollution levels. A thorough review on recent ECs (platinum group elements, pharmaceuticals and personal care products, pesticides, siloxanes, liquid crystal monomers, cationic surfactant, antibiotic resistance genes, and microplastics) in estuaries, including their incidence, detection levels, and toxic effects, was performed. The inclusion of studies from different regions highlights the global nature of this issue, with each location having its unique set of contaminants. The diverse range of contaminants detected in estuary samples worldwide underscores the intricacy of ECs. A significant drawback is the scarcity of research on the toxic mechanisms of ECs on estuarine organisms, the prospect of unidentified ECs, warrant research scopes.

Quaternary Ammonium Compounds (QACs) in Wastewater Influent and Effluent Throughout the COVID-19 Pandemic

Quaternary ammonium compounds (QACs) are used in consumer and industrial products, including disinfectants. Due to the COVID-19 pandemic, disinfectant use has increased, purportedly increasing loads to wastewater treatment plants and the environment. To understand how the increased usage has affected QAC loadings to treatment plants and to determine how effectively plants remove QACs from liquid effluent that is discharged to surface and groundwaters, influent and effluent wastewater samples were collected from four treatment plants (treatment capacities < 5 MGD to > 100 MGD) for 21 months beginning in May 2020. Influent QAC concentrations were hundreds of μg/L and effluent QAC concentrations were < 1 μg/L, corresponding to an average removal of 98% from all four plants. The most prevalent QACs in influent were those used most commonly in disinfectants, specifically benzylalkyldimethylammonium compounds (BACs) and short-chain dialkyldimethylammonium compounds (DADMACs), and influent levels of these compounds were correlated with QAC sales. Prior to this study, ethylbenzylalkyldimethylammonium compounds (EtBACs) had not been studied, and they comprised 13 ± 6% of QACs in influent. While removal was high at all plants, low μg/L concentrations were still continuously discharged into the environment. For QACs with equivalent alkyl chain lengths, those with aromatic substituents (BACs and EtBACs) appear to be removed more effectively than those with only alkyl chains (DADMACs).

Metagenomic insights into the effects of benzyl dodecyl dimethyl ammonium bromide (BDAB) shock on bacteria-driven nitrogen removal in a moving-bed biofilm reactor (MBBR)

The use of disinfectants made from quaternary ammonium compounds (QACs) has greatly increased since the outbreak of SARS-CoV-2. However, the effect of QACs on wastewater treatment performance is still unclear. In this study, a commonly used QAC, i.e., benzyl dodecyl dimethyl ammonium bromide (BDAB), was added to a moving-bed biofilm reactor (MBBR) to investigate BDAB's effect on nutrient removal. When the BDAB concentration was increased to 50 mg L^-1, the ammonia removal efficiency (ARE) greatly decreased, as did the nitrate production rate constants (NPR). This inhibition was partly recovered by decreasing the BDAB concentration to 30 mg L^-1. Metagenomic sequencing revealed the functional genera present during different stages of the control (Rc) and BDAB-added reactors (Re). The enriched genera (Rudaea, Nitrosospira, Sphingomonas, and Rhodanobacter) in Rc mainly related to the nitrogen metabolism, while the enriched genera in Re was BDAB-concentration dependent. Functional genes analysis suggested that a lack of ammonia oxidase-encoding genes (amoABC) may have caused a decrease in ARE in Re, while the efflux pump-encoding genes emrE, mdfA, and oprM and a gene encoding BAC oxygenase (oxyBAC) were responsible for BDAB resistance. The increase in the total abundance of antibiotic resistance genes (ARGs) in Re revealed a potential risk arising from BDAB. Overall, this study revealed the potential effect and ecological risks of BDAB introduction in WWTPs.

Stochastic Dynamic Mass Spectrometric Quantitative and Structural Analyses of Pharmaceutics and Biocides in Biota and Sewage Sludge

Mass spectrometric innovations in analytical instrumentation tend to be accompanied by the development of a data-processing methodology, expecting to gain molecular-level insights into real-life objects. Qualitative and semi-quantitative methods have been replaced routinely by precise, accurate, selective, and sensitive quantitative ones. Currently, mass spectrometric 3D molecular structural methods are attractive. As an attempt to establish a reliable link between quantitative and 3D structural analyses, there has been developed an innovative formula [DSD″,tot=∑inDSD″,i=∑in2.6388.10−17×Ii2¯−Ii¯2] capable of the exact determination of the analyte amount and its 3D structure. It processed, herein, ultra-high resolution mass spectrometric variables of paracetamol, atenolol, propranolol, and benzalkonium chlorides in biota, using mussel tissue and sewage sludge. Quantum chemistry and chemometrics were also used. Results: Data on mixtures of antibiotics and surfactants in biota and the linear dynamic range of concentrations 2–80 ng.(mL)−1 and collision energy CE = 5–60 V are provided. Quantitative analysis of surfactants in biota via calibration equation ln[D″SD] = f(conc.) yields the exact parameter |r| = 0.99991, examining the peaks of BAC-C12 at m/z 212.209 ± 0.1 and 211.75 ± 0.15 for tautomers of fragmentation ions. Exact parameter |r| = 1 has been obtained, correlating the theory and experiments in determining the 3D molecular structures of ions of paracetamol at m/z 152, 158, 174, 301, and 325 in biota.

Biosorption of LMW PAHs on activated sludge aerobic granules under varying BOD loading rate conditions

Polycyclic aromatic hydrocarbons belong to the main priority substances for the aquatic environment. One of the emission sources of these compounds to environment is wastewater discharged from conventional wastewater treatment systems, which are not designed to cope with this type of pollution. Thus, due to the widely discussed properties of aerobic granular activated sludge in the literature - a conducted study has proven its ability to remove LMW PAHs (naphthalene (Nap), acenaphthylene (Acy), acenaphthene (Ace), fluorene (Flu), phenanthrene (Phe) and anthracene (Ant)) from wastewater by biosorption process at varying loadings of organic compounds expressed as BOD (kg/kg·d) on the activated sludge mass. The maximum biosorption of Nap was 605 µg/kg_d.m., Acy equals to 134 µg/kg_d.m., Ace equals to 355 µg/kg_d.m. Flu equals to 104 µg/kg_d.m. Phe equal to 204 µg/kg_d.m. and Ant equal to 173 µg/kg_d.m. The study showed that the BOD loading rate is one of the factors affecting the biosorption process of LMW PAHs. However, as the amount of adsorbed LMW PAHs increased, the condition of aerobic granular activated sludge deteriorated, which was evidenced by gradual increase in the values of technological parameters of activated sludge (SVI, HRT, SRT) and a smaller increase in activated sludge dry mass.

Magnetite-Functionalized Horse Dung Humic Acid (HDHA) for the Uptake of Toxic Lead(II) from Artificial Wastewater

Magnetite-functionalized horse dung humic acid (HDHA) has been successfully prepared by the coprecipitation method, and the as-prepared adsorbent (MHDHA) has been applied as an easy-handling adsorbent for toxic Pb(II) in artificial wastewater. The MHDHA was characterized by Fourier transform-infrared spectroscopy (FT-IR), X-ray powder diffraction (XRD), transmission electron microscopy (TEM), energy dispersive X-ray (EDX), and vibrating sample magnetometer (VSM). The FT-IR study showed that the MHDHA had the characteristics peaks of HA and Fe-O stretching. The XRD analysis revealed that the MHDHA had the $2\theta$ characteristic for magnetite. The TEM image and EDX analysis exhibited that the MHDHA with an average size of ∼14 nm was partially aggregated and contained ( $w/w$ ) 9.89% carbon, 2.89% nitrogen, and 32.74% oxygen based on functional groups of HDHA. The stability improvement of MHDHA was showed by decreasing HDHA dissolved from 95% to less than 30% at pH 12 after magnetite functionalization. The post-adsorption handling improvement was evidenced by easy and quick retraction by an external magnet with a 62.95 emu/g magnetic strength value. The adsorption capacities were influenced by the pH and ionic strength, whilst the adsorption rates were well simulated by the Ho pseudo-second-order model. The removal uptake of Pb(II) ions increased when the initial concentration was increased and fitted well with the Langmuir isotherm model when the monolayer adsorption capacity was $2.78\times {10}^{-4}\text{mol}/\text{g}$ (equal to 57.64 mg/g). The value of Dubinin-Radushkevich adsorption energy ( $E_{D-R}$ ) found in this study was 14.78 kJ/mol, which implied that ion exchange is the main mechanism involved in the adsorption process. The regeneration studies of MHDHA show that there was no significant change in composition, morphology, crystallinity, and functional group after five consecutive cycles of the adsorption-desorption process.

A Review on the Fate of Legacy and Alternative Antimicrobials and Their Metabolites during Wastewater and Sludge Treatment

Antimicrobial compounds are used in a broad range of personal care, consumer and healthcare products and are frequently encountered in modern life. The use of these compounds is being reexamined as their safety, effectiveness and necessity are increasingly being questioned by regulators and consumers alike. Wastewater often contains significant amounts of these chemicals, much of which ends up being released into the environment as existing wastewater and sludge treatment processes are simply not designed to treat many of these contaminants. Furthermore, many biotic and abiotic processes during wastewater treatment can generate significant quantities of potentially toxic and persistent antimicrobial metabolites and byproducts, many of which may be even more concerning than their parent antimicrobials. This review article explores the occurrence and fate of two of the most common legacy antimicrobials, triclosan and triclocarban, their metabolites/byproducts during wastewater and sludge treatment and their potential impacts on the environment. This article also explores the fate and transformation of emerging alternative antimicrobials and addresses some of the growing concerns regarding these compounds. This is becoming increasingly important as consumers and regulators alike shift away from legacy antimicrobials to alternative chemicals which may have similar environmental and human health concerns.

Comprehensive screening of quaternary ammonium surfactants and ionic liquids in wastewater effluents and lake sediments

Quaternary ammonium compounds (QACs) are widely applied as surfactants and biocides in cleaning and personal-care products. Because of incomplete removal during wastewater treatment, QACs are present in wastewater effluents, with which they are discharged into natural waters, where they accumulate in sediments. To assess the levels of QACs in aquatic environments, a liquid chromatography high-resolution mass spectrometry method using both target and suspect screening was developed. The water and sediment sample preparation, measurement, and data analysis workflow were optimized for 22 target compounds with a wide range of hydrophobicity, including ionic liquids that have potential use as solvents and QACs common in personal-care and sanitizing products. In wastewater effluents, average concentrations of all target and suspect QACs combined ranged from 0.4 μg L-1 to 6.6 μg L-1. Various homologs of benzylalkyldimethylammonium (BAC) and dialkyldimethylammonium (DADMAC) as well as the ionic liquid butylpyridinium and 15 suspect QACs were detected in at least one wastewater effluent sample. A spatial profile of sediment samples in a lake demonstrated potential inputs from both municipal wastewater effluent and agricultural sources for BACs. In sediment cores, two distinct trends of temporal QAC accumulation were observed. In lakes with large watersheds and mixed domestic and industrial wastewater sources (Lake Pepin and Duluth Harbor), peak concentrations of QACs were found at depths corresponding to deposition in the 1980s and decreases after this time are attributed to improved wastewater treatment and source control. In a smaller lake with predominantly domestic wastewater inputs (Lake Winona), concentrations of QACs increased slowly over time until today.

Existence, removal and transformation of parent and nitrated polycyclic aromatic hydrocarbons in two biological wastewater treatment processes

Polycyclic aromatic hydrocarbons (PAHs) and nitrated polycyclic aromatic hydrocarbons (NPAHs) are pollutants commonly present in the environment. Some NPAHs are considered to have more severe toxic effects than their parent PAHs. The existence of 16 PAHs (678.5-3817.8 ng/L in wastewater, 499.9 ng/g-1239.6 ng/g in sludge) and 5 NPAHs (175.8-1392.4 ng/L in wastewater, 483.5 ng/g-2763.1 ng/g in sludge) was determined in a biological wastewater treatment plant (WWTP) in Qingdao, China. Anthracene and naphthalene were the predominant PAHs, and 2-nitrofluorene and 9-nitroanthracene were the predominant NPAHs. Petroleum, liquid fossil fuel combustion and exhaust emissions were the main sources of PAHs and NPAHs in this study. In both the sequencing batch reactor/moving-bed biofilm (SBR/MBBR) and the anaerobic-anoxic-aerobic (A²O) process, low-molecular-weight PAHs were mainly removed through volatilization and biodegradation/biotransformation. Meanwhile, the removal of high-molecular-weight PAHs and NPAHs depended on adsorption and sedimentation. The transformation from PAHs to NPAHs mainly occurred in the aqueous-phase, especially in summer and that was confirmed by mass flow and ratios variation. Overall, the removal capacity of the A²O process for PAHs and NPAHs was better than that of the SBR/MBBR process. Tertiary treatment processes had little effect or even a negative effect on the removal of PAHs and NPAHs.

Accumulation of quaternary ammonium compounds as emerging contaminants in sediments collected from the Pearl River Estuary, China and Tokyo Bay, Japan

In this work, the distribution of quaternary ammonium compounds (QACs) in two dated sediment cores, collected from the Pearl River Estuary (PRE) and Tokyo Bay (TB), were investigated to understand the historical input of QACs and their diagenetic behavior in urban estuarine environments. The vertical variation profiles of QAC concentrations showed that benzylalkyldimethyl ammonium compounds (BACs) and dialkyldimethyl ammonium compounds (DADMACs) were widely used during 1970s and 1980s both in China and Japan. The declining environmental concentrations of QACs suggested a compositional change of commodities and the effectiveness of emission control strategies. For the individual QAC homologues, BAC homologues decreased significantly over time, while DADMAC compositions remained relatively stable. The differences in concentration and composition profiles of BACs and DADMACs in the sediment cores provided useful information on the patterns of use of QACs in China and Japan, as well as their diagenetic behaviors in the sediments.

Removal characteristic of surfactants in typical industrial and domestic wastewater treatment plants in Northeast China

Surfactants are widely used in household and industrial products for cleaning and/or solubilization in our daily life. Therefore, they are finally discharged into wastewater treatment plants (WWTPs), which may be the major point pollution source for environment if they were not completely removed during wastewater treatment. In this study, two typical industrial and domestic WWTPs with different wastewater treatment technologies were considered for the topic. Totally, two types of surfactants were analyzed in 24 h influent and each processing unit effluent. Four linear alkylbenzene sulfonates (LASs) with the alkyl chain from C10 to C13, and two benzalkonium chlorides (BACs) with the alkyl chain of C12 and C14 were selected as target compounds. The total concentrations of LASs in influent varied from 19.2 to 1889 μg/L and LAS-C11 and LAS-C12 were the predominant compounds with the concentration from 6.01 to 641 μg/L and 8.02-674 μg/L, respectively. The total concentrations of BACs were much lower than those of LASs, with the concentration ranging from 0.00935 to 1.85 μg/L. Significant positive correlations were observed between concentrations of LASs and BACs in influent, indicating their same and/or similar sources. Compared with the concentration of influent, the concentration of effluent was much lower, indicating the high removal efficiency by the two wastewater treatment processes. Biological treatment unit and cyclic activated sludge system were the main treatment units for the removing of surfactants, which suggested that these two types of surfactants can be easily degraded under aerobic condition. Seasonal variation indicated that the removal efficiencies of surfactants in autumn were a little higher than those in winter. The results of this study provided new insights into the environmental fate of surfactants in wastewater treatment system.

Quaternary ammonium compounds (QACs): a review on occurrence, fate and toxicity in the environment

Quaternary ammonium compounds (QACs) are widely applied in household and industrial products. Most uses of QACs can be expected to lead to their release to wastewater treatment plants (WWTPs) and then dispersed into various environmental compartments through sewage effluent and sludge land application. Although QACs are considered to be aerobically biodegradable, the degradation is affected by its chemical structures, dissolved oxygen concentration, complexing with anionic surfactants, etc. High abundance of QACs has been detected in sediment and sludge samples due to its strong sorption and resistance to biodegradation under anoxic/anaerobic conditions. QACs are toxic to a lot of aquatic organisms including fish, daphnids, algae, rotifer and microorganisms employed in wastewater treatment systems. And antibiotic resistance has emerged in microorganisms due to excessive use of QACs in household and industrial applications. The occurrence of QACs in the environment is correlated with anthropogenic activities, such as wastewater discharge from WWTPs or single source polluters, and sludge land application. This article also reviews the analytical methods for determination of QACs in environmental compartments including surface water, wastewater, sewage sludge and sediments.

The biodegradation of monomeric and dimeric alkylammonium surfactants

Quaternary ammonium compounds (QACs) are salts known for having antiseptic and disinfectant properties. These compounds are toxic to aquatic organisms and should thus be removed from wastewater before its discharge into surface waters. The biodegradation of QACs takes place in the presence of microorganisms under aerobic conditions. The susceptibility of these compounds to degradation depends on numerous parameters. A number of them, such as the structure-adsorption on solids, and concentration of the QACs, as well as the presence of additional substances, have been reviewed in this article. Moreover, the biodegradability of new dimeric alkylammonium salts, i.e., cationic gemini surfactants, has been discussed and compared with that of anionic and nonionic geminis. The biodegradation study of monomeric and dimeric alkylammonium surfactants show that they are not easily degraded. The degradation process is very complex and strongly depends on the structure of the compound, adsorption-desorption processes on sludge, type of microorganism consortia and the presence of anions. Alkylammonium surfactants with biological motifs, like amide, peptides or carbohydrates, are much better degraded.

Occurrence, behavior and removal of typical substituted and parent polycyclic aromatic hydrocarbons in a biological wastewater treatment plant

Wastewater treatment plant (WWTP) effluent is the major source for substituted polycyclic aromatic hydrocarbons (SPAHs) to the receiving rivers, as well as the parent PAHs. Some of the SPAHs showed higher toxicities and levels than their parent PAHs. The occurrence and behavior of typical SPAHs were investigated in a representative biological WWTP in Beijing, China. Methyl PAHs (MPAHs) (149-221 ng/L in the influent; 29.6-56.3 ng/L in the effluent; 202-375 ng/g in the activated sludge), oxygenated PAHs (OPAHs) (139-155 ng/L; 69.9-109 ng/L; 695-1533 ng/g) and PAHs (372-749 ng/L; 182-241 ng/L; 2402-3321 ng/g) existed, but nitrated PAHs (NPAHs) were not detected. 2-Methylnaphthalene, anthraquinone, 9-fluorenone and 2-methylanthraquinone were the predominant SPAHs. OPAHs were deduced to be formed from PAHs especially during summer, based on the ratios variation and removal efficiencies of the two seasons, and the surplus mass in the outflows. Low molecular weight compounds (2-3 rings) might be mainly removed by mineralization/transformation and adsorption in the anaerobic unit, and by volatilization in the aerobic unit. High molecular weight compounds (4-6 rings) might be mainly removed by adsorption in the anaerobic unit. The total outflows of SPAHs and PAHs were 66 g/d in summer and 148 g/d in winter from the WWTP to the receiving river. The percentage of OPAHs was higher in summer than in winter.

N-[3-(Benzyldimethylazaniumyl)propyl]-N′,N′,N′′,N′′-tetramethylguanidinium bis(tetraphenylborate)

In the crystal structure of the title salt, C₁₇H₃₂N₄²⁺·2C₂₄H₂₀B⁻, the C—N bond lengths in the CN₃ unit of the guanidinium ion are 1.323 (4), 1.336 (5) and 1.337 (5) Å, indicating partial double-bond character in each. The C atom of this unit is bonded to the three N atoms in a nearly ideal trigonal–planar geometry [N—C—N angles = 117.7 (4), 120.9 (3) and 121.4 (3)°] and the positive charge is delocalized in the CN₃ plane. The bonds between the N atoms and the terminal C-methyl groups of the guanidinium moiety all have values close to a typical single bond [1.452 (5)–1.484 (6) Å]. In the crystal, C—H⋯π inter­actions are present between guanidinium H atoms and the phenyl rings of both tetra­phenyl­borate ions. This leads to the formation of a two-dimensional supramolecular pattern along the ab plane.

Modeling the fate and effect of benzalkonium chlorides in a continuous-flow biological nitrogen removal system treating poultry processing wastewater

The fate and effect of the antimicrobial compounds benzalkonium chlorides (BACs) on the biological nitrogen removal (BNR) processes for a continuous-flow, three-stage laboratory-scale BNR system were modeled. Three kinetic sub-models, corresponding to each reactor, were developed and then combined in a comprehensive ASM1-based model. Kinetic parameters for the three sub-models were evaluated using experimental data obtained from independent batch assays. The biodegradation of BACs was modeled with a mixed-substrate Monod equation. The inhibitory effect of BACs on the utilization of degradable COD and denitrification was modeled as competitive inhibition, whereas non-competitive inhibition was used to model the effect of BACs on nitrification and inhibition coefficients were evaluated. The model simulated well the long-term performance of the BNR system treating a poultry processing wastewater with and without BACs. Enhanced BAC degradation by heterotrophs and increased resistance of nitrifiers to BACs, reflecting acclimation/enrichment over time, is a salient feature of the model.

Influence of solution chemistry on Cr(VI) reduction and complexation onto date-pits/tea-waste biomaterials

Tea waste (TW) and Date pits (DP) were investigated for their potential to remove toxic Cr(VI) ions from aqueous solution. Investigations showed that the majority of the bound Cr(VI) ions were reduced to Cr(III) after biosorption at acidic conditions. The electrons for the reduction of Cr(VI) may have been donated from the TW and DP biomasses. The experimental data obtained for Cr(VI)-TW and Cr(VI)-DP at different solution temperatures indicate a multilayer type biosorption, which explains why the Sips isotherm accurately represents the experimental data obtained in this study. The Sips maximum biosorption capacities of Cr(VI) onto TW and DP were 5.768 and 3.199 mmol/g at 333 K, respectively, which is comparatively superior to most other low-cost biomaterials. Fourier transform infrared spectroscopic analysis of the metal loaded biosorbents confirmed the participation of -COOH, -NH(2) and O-CH(3) groups in the reduction and complexation of chromium. Thermodynamic parameters demonstrated that the biosorption of Cr(VI) onto TW and DP biomass was endothermic, spontaneous and feasible at 303-333 K. The results evidently indicated that tea waste and date pits would be suitable biosorbents for Cr(VI) in wastewater under specific conditions.

Influence of the presence of three typical surfactants on the adsorption of nickel (II) to aerobic activated sludge

The effects of different surfactants (SDBS, C(14)BDMA, Tween20) on the sorption of nickel(II) onto aerobic activated sludge were studied. Results showed that the influence of surfactants on the adsorption of nickel(II) strongly depended on the type of the surfactants. The presence of SDBS enhanced nickel(II) sorption, in contrast, the presence of C(14)BDMA and Tween20 both caused a nickel(II) sorption reduction, but Tween20 had a slighter effect. With the presence of individual surfactant, the sorption kinetics and isotherms were good agreement with pseudo-second-order kinetic model and Langmuir isotherm, respectively. The surfactant impelled the nickel(II) adsorption process onto aerobic activated sludge to transform from chemisorption to physisorption, and the existence of SDBS in solution even changed the exothermic nature. From FT-IR measurements and zeta potential measurements, there was competitive relationship between C(14)BDMA and nickel(II) at the adsorption onto sludge.

Fate and effect of benzalkonium chlorides in a continuous-flow biological nitrogen removal system treating poultry processing wastewater

Quaternary ammonium compounds (QACs) are used for sanitation in many poultry processing facilities. This work investigated the fate and effect of a mixture of benzalkonium chlorides (BACs), a class of QACs widely used in commercial antimicrobial formulations, on the biological nitrogen removal (BNR) processes. A laboratory-scale BNR system was operated continuously for 670 days, fed with poultry processing wastewater amended with a mixture of BACs. Initially, the nitrogen removal efficiency deteriorated at a BAC feed concentration of 5 mg/L due to the complete inhibition of nitrification. However, after 27 days of operation, the system recovered and achieved 100% ammonia removal. High nitrogen removal efficiency was achieved even after the feed BAC concentration was stepwise increased up to 120 mg/L. Batch nitrification assays performed before, during, and after BAC exposure, showed that rapid microbial acclimation and BAC biodegradation contributed to the recovery of nitrification achieving efficient and stable long-term BNR system operation.

Analysis of quaternary ammonium compounds in urban stormwater samples

A method for benzalkonium analysis has been developed to measure benzalkonium concentration in dissolved and particulate fractions from urban runoff samples. The analysis was performed by liquid chromatography coupled with mass spectrometry (LC-MS/MS). The dissolved matrix was extracted by Solid Phase Extraction (SPE), with cationic exchange and the particles by microwave extraction with acidified methanol. Recovery percentages were closed to 100% for benzalkonium C12 and C14. The protocol was applied to roof runoff samples collected after a roof demossing treatment, and to separative stormwater samples from a 200 ha catchment. The results illustrate an important contamination of the roof runoff, with a maximum concentration close to 27 mg/L during the first rain. The benzalkonium concentration (sum of C12 and C14) stayed high (up to 1 mg/L) even 5 months after the treatment. Benzalkonium concentration measured in stormwaters was low (0.2 μg/L) but with contaminated suspended solids (up to 80 μg/g).