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The co-contamination of aquatic systems with antimony (Sb) and humic acid (HA) is a global concern due to their potential risks to human health and environment. In this research, three-level-three-variable Box–Behnken design (BBD) was investigated for simultaneous Sb(III) and total organic carbon (TOC) removal responses from groundwater by use of ferric chloride (FC) as a coagulant. This study focuses on three operating variables, including initial Sb(III) concentration (100, 550, and 1000 μg/L), HA concentration (2, 6, and 10 mgC/L) and FC dosages (20, 60, and 100 mg/L). The proposed quadratic model presented good correlation with experimental values having R2 and adjusted R2 values of response variables (Sb(III): 0.9981 and 0.9956) and (TOC: 0.9935 and 0.9851), respectively. The most pronounced influence of FC dosage was observed in the removal responses of TOC and Sb(III). Interestingly, the model revealed that a high level of FC dosage had the same TOC removal potential regardless of increasing HA concentration. The statistical model for both Sb(III) and TOC responses was used to optimize the experimental conditions. Moreover, the experimental results were successfully validated with predicted values having high accuracy. The sludge volume produced for studied variables followed the decreasing order as FC dosage > HA concentration > Sb(III) concentration. Under optimum conditions, 0.45 mL/L sludge volume was produced in the treatment of ground water in Nawabshah. In general, the results of the current study may provide some insights into the predictability of simultaneous removal performance of Sb species and organic substances from groundwater.

In this study, an attempt has been made to reduce the sludge using novel homogenizer coupled solar photo Fenton (HPF) process. At an optimum pH of 3 and Fe2+ to H2O2 dosage of 1:6, PF process yielded 63.7% solids reduction at a time interval of 45 min. Coupling of homogenizers with photo Fenton (PF) process effectively enhanced treatment efficiency. When homogenizer (specific energy - 1150.694 kJ/kg TS) was coupled with PF, a sharp increase in solid reduction 73.5% and decrease in reaction time (20 min) were observed. Cost benefit analysis revealed the efficiency of HPF process and achieved a net cost of 15.59 USD whereas PF achieved a negative net cost of −82.69 USD. Based on the above study it can be concluded that coupling of homogenizers with PF not only increased its efficiency but also make it field applicable.

This study reports the result of sodium citrate induced exopolymer extraction on the photocatalytic thin film (TiO2) pretreatment efficiency of waste activated sludge (WAS). TiO2 is immobilized through DC spluttering method followed by annealing process. The exopolymer removal of 94.2% by sodium citrate (0.05 g/g SS) promotes better disintegration. This TiO2 thin film efficiently extricate the intracellular components of exopolymer extracted sludge at 50 min increasing the solubilization to 19.33%. As a result, the exopolymer extracted sludge shows high methane generation (0.24 gCOD/gCOD) than the other (pretreated sludge without exopolymer removal – 0.12 gCOD/gCOD and raw sludge without treatment – 0.075 gCOD/gCOD). The methane generated in sodium citrate induced TiO2 thin film pretreated sludge is 398.99 kWh. In cost analysis, it gives net cost of −57.46 USD/ton of sludge. In addition, the proposed method also accounts 51.3% of solid reduction.

Coprecipitation-adsorption plays a significant role during coagulation-flocculation-sedimentation (C/F/S) of antimony (Sb) in water. This work uses a Box&ndash, Behnken statistical experiment design (BBD) and response surface methodology (RSM) to investigate the effects of major operating variables such as initial Sb(III, V) concentration (100&ndash, 1000 &micro, g/L), ferric chloride (FC) dose (5&ndash, 50 mg/L), and pH (4&ndash, 10) on redox Sb species. Experimental data of Sb(III, V) removal were used to determine response function coefficients. The model response value (Sb removal) showed good agreement with the experimental results. FC showed promising coagulation behavior of both Sb species under optimum pH (6.5&ndash, 7.5) due to its high affinity towards Sb species and low residual Fe concentration. However, a high dose of 50 mg/L of FC is required for the maximum (88&ndash, 93%) removal of Sb(V), but also for the highest (92&ndash, 98%) removal of low initial concentrations of Sb(III). Furthermore, BBD and RSM were found to be reliable and feasible for determining the optimum conditions for Sb removal from environmental water samples by a C/F/S process. This work may contribute to a better understanding and prediction of the C/F/S behavior of Sb(III, V) species in aqueous environments, to reduce potential risks to humans.

A mixed culture utilizing 1,4-dioxane as a sole carbon and energy source was obtained from the activated sludge at a textile wastewater treatment plant. The biodegradation of 1,4-dioxane was characterized by a model based on the Monod equation. The effects of the presence of easily degradable carbon sources other than 1,4-dioxane were investigated using dextrose. Structural analogs commonly found in 1,4-dioxane-containing wastewater such as tetrahydrofuran (THF), 2-methyl-1,3-dioxolane, and 1,4-dioxene were also evaluated for their potential effects on 1,4-dioxane biodegradation. The presence of dextrose did not show any synergetic or antagonistic effects on 1,4-dioxane biodegradation, while the structural analogs showed significant competitive inhibition effects. The inhibitory effects were relatively strong with heptagonal cyclic ethers such as THF and 2-methyl-1,3-dioxolane, and mild with hexagonal cyclic ethers such as 1,4-dioxene. It was also shown that the treatment of 1,4-dioxane in the raw textile wastewater required 170% more time to remove 1,4-dioxane due to the co-presence of 2-methyl-1,3-dioxolane, and the extent of delay depended on the initial concentration of 1,3-doxolane.

In this study, a novel attempt has been made to generate energy-efficient biomethane from marine macroalgae (Chaetomorpha antennina) by coupling thermochemical liquefaction with a disperser (thermo-chemo disperser (TCD) liquefaction). A temperature of (80 °C), pH 11 and disperser g-force of 1613 g were considered optimal parameters for effective solubilization and energy-efficient methane generation. This combinative liquefaction considerably reduced the treatment time and specific energy from 60 to 15 min and 6294 to 800 kJ/kg TS. The highest volatile fatty acids (VFA) accumulation of 890 mg/L was recorded in TCD compared to a thermo disperser (TD) (750 mg/L) and disperser (D) (322 mg/L) during anaerobic fermentation. TCD enhances the methane production potential of macroalgal biomass and a higher methane production of 215 mL/g VS was achieved for TCD compared to TD (149 mL/g VS) and D samples (100 mL/g VS), respectively. Cost analysis confirmed the field applicability of TCD liquefaction with a net profit of 90 USD/ton of marine macroalgae. A high energy ratio of 1.5 was achieved with the proposed mode of pretreatment (TCD) compared to TD (0.95) and D (0.28) pretreatment. Therefore, C. antennina is considered a suitable feedstock for methane generation.

The present study highlights the options to enhance the methane potential of partially digested anaerobic sludge using disperser-induced bacterial disintegration. Floc dispersion with no biomass disintegration was achieved at a disperser-specific energy input of 9.5 kJ/kg TS. The outcomes of both sole bacterial disintegration (S-BD) and disperser-induced bacterial disintegration (D-BD) were assessed in terms of changes in lysate, biopolymer release and increase in biodegradability and methane generation. A higher lysate solubilization of about 22.4% was achieved in D-BD compared to S-BD (11.3%), indicating the efficiency of floc dispersion prior to bacterial disintegration. The biochemical methane result implies that D-BD shows higher methane potential of 0. 279 gCOD/gCOD. Considering the overall outcome achieved in this study, disperser-induced bacterial disintegration is proved to be an effective disintegration process for enhanced biodegradation and higher methane production.

An artificial neural network (ANN) was first developed to predict the transmembrane pressure in an anoxic-aerobic membrane bioreactor (AO-MBR) treating domestic wastewater. A few studies about prediction of membrane fouling in MBRs using ANNs have been published so far, even though our recent work indicates that ANNs show a great potential for this application. In this study, 10 parameters linked to wastewater treatment and measured in the different parts of the AO-MBR system were used as the input variables of the ANN. The goal was to select the most relevant input parameters to predict the evolution of the transmembrane pressure based on the performances of the ANN. An ANN model was selected for its satisfying performances (R2 = 0.850). In conclusion, ANNs could be a valid method to predict membrane fouling in AO-MBR systems treating domestic wastewater.

In this study, recalcitrant rich retting-pond wastewater was treated primarily by anaerobic treatment and subsequently treated with a solar photofenton process to remove phenol and organics. The anaerobic treatment was carried out in a granulated laboratory scale hybrid upflow anaerobic sludge blanket reactor (HUASBR) with a working volume of 5.9 L. It was operated at different hydraulic retention times (HRT) from 40 to 20 h over a period of 140 days. The optimum HRT of the anaerobic reactor was found to be 30 h, with corresponding chemical oxygen demand (COD) and phenol removal of 60% and 47%, respectively. Primary anaerobically treated wastewater was subjected to secondary solar photofenton treatment which was carried out at pH 3.5. Response surface methodology (RSM) was used to design and optimize the performance of the solar photofenton process. Regression quadratic model describing COD removal efficiency of the solar photofenton process was developed and confirmed by analysis of variance (ANOVA). Optimum parameters of the solar photofenton process were found to be: 4 g/L of fenton as catalysts, 25 mL of hydrogen peroxide, and 30 min of reaction time. After the primary anaerobic treatment, solar photofenton oxidation process removed 94% and 96.58% of COD and phenol, respectively. Integration of anaerobic and solar photofenton treatment resulted in 97.5% and 98.4% removal of COD and phenol, respectively, from retting-pond wastewater.

In the present study, a new and novel attempt was made to investigate the effect of liquefaction (20–60%) on energy efficient gaseous biofuel recovery and cost during chemo thermo disperser liquefaction of food waste (CTDL). The outcome of the study revealed that rpm (10,000), specific energy input (174 kJ/kg TS), disintegration time (5 min) and energy efficiency of about 11.1 kg SCOD/KWh were considered as optimum in terms of energy and cost. The cost incurred to achieve 20–40% liquefaction was estimated to be 0.0132–0.0168 USD and found to be comparatively very low than the cost incurred (0.0367–0.0547) to achieve 50–60% liquefaction. The biodegradability results showed that a significant increment in biodegradability was achieved (from 0.26 gCOD/gCOD to 0.8 gCOD/gCOD) when the liquefaction was increased from 30 to 40% and an insignificant increment in biodegradability (from 0.8 gCOD/gCOD to 0.84 gCOD/gCOD) was achieved when the liquefaction was increased from 40 to 60%, respectively. The impact of liquefaction on energy balance and cost at tonnage level revealed that 40% liquefaction was considered to be profitable with energy ratio and net profit of about 1.12 and 93 USD/Ton, respectively.

This study aimed to improve the biomethane potential of dairy waste activated sludge (WAS) by H2O2-acidic pH induced microwave disintegration (HAMW-D) pretreatment approach. The results of HAMW-D compared with the microwave disintegration (MW-D) alone for energy and economic factors. In the two phase disintegration process, the H2O2 concentration of about 0.5mg/g SS under acid pH of 5 was found to be optimum for effective dissociation of Extracellular Polymeric Substances (EPS) matrix. A higher liquefaction of about 46.6% was achieved in HAMW-D when compared to that of MW-D (30%). It subsequently improved the methane yield of about 250mL/g VS in HAMW-D, which was 9.6% higher than MW-D. A net profit of about 49€/ton was achieved for HAMW-D, therefore it is highly recommended for WAS pretreatment.

Recently, there has been an emergent interest in developing novel and less energy consuming disintegration process to combat excess sludge generation and enhance energy recovery during anaerobic digestion. In the present study, a novel attempt was made to recover energy (methane) in an efficient way by floc disruption through low temperature thermochemical (LTTC) treatment followed by antibiotic secreting bacterial disintegration (ABD). Growth optimization studies were performed using response surface methodology (RSM). Results revealed that the optimal pH, temperature, and growth time were 6.5, 40 °C, and 24 h, respectively. LTTC followed by ABD was found to be more efficient than the ABD process alone in terms of degree of cell lysis (17% vs. 10.5%) and methane production potential (0.24 gCOD/gCOD vs.0.15 gCOD/gCOD). The efficiency of LTTC pre-treatment with the ABD process was also proven kinetically through linear and non-linear regression analysis. Energetic investigation and cost analysis of the present study showed that the LTTC+ABD could be used as a less energy consuming and economic process with a net profit of about 2.58 USD/Ton of sludge.

In this study, an attempt was made to disintegrate waste activated sludge (WAS) in a cost-effective way. During the first phase of this study, effective break down of extracellular polymeric substance (EPS) was performed by deflocculating WAS with 0.1 g/g SS of MgSO4. Deflocculation rate was 92% with discharge rate of extractable EPS at 185 mg/L. In the second phase, effective bacterial cell disintegration was obtained at 36 h post treatment. Maximum solubilization of deflocculated sludge was approximately 21%, which was higher than that of flocculated sludge (14.2%) or the control (4.5%). Biodegradability studies were assessed through kinetic analysis by non-linear regression modeling. Results revealed that the deflocculated sludge had higher methane generation (at about 235.8 mL/gVs) compared to flocculated sludge (at 146.1 mL/gVs) or the control (at 34.8 mL/gVs). Cost assessment of the present work revealed that the net yield for each ton of the deflocculated sludge was about 32.99 USD.

Physiochemical disintegration of waste activated biosolids (WAB) through thermochemical (TC) pretreatment requires high energy and cost for efficient energy generation. Therefore in the present study, an attempt has been made to enhance the biodegrdability and to minimize the operational cost of TC pretreatment by combining it with ozonation. A higher solubilization of about 30.4% was achieved at lesser energy input of about 141.02 kJ/kg TS and a ozone dosage of about 0.0012 mg O 3 /mg SS through this combined thermo chemo ozone (TCO 3 ) pretreatment. The methane production potential (0.32 g COD/g COD) of TCO 3 pretreatment was comparatively higher than the (0.19 g COD/g COD) TC pretreatment. The energetic analysis and economic assessment of the proposed method of pretreatment can possibly reduces the energy requirement of TC pretreatment with a positive net profit of about 35.49 $/ton of biosolids.

A platform chemical is a molecule with a number of functional groups which can thus produce a broad range of many other molecules. Platform chemicals are considered as building blocks from which different kinds of secondary chemicals, intermediates, and products can be produced. Bio-based platform chemicals such as lactic acid, fatty acid, succinic acid, citric acid, tartaric acid production, 1,3-propanediol, 3-hydroxypropionic acid, and 2,3-butanediol have the ability to replace petrochemicals. Food waste is considered to be the best feedstock for the production of these platform chemicals because these wastes contain fermentable carbohydrates, proteins, and lipids. The food waste-based biorefinery is considered as an ideal concept which has received significant attention in recent years. This possibility of converting valueless food waste into platform chemicals has gained worldwide interest. A number of research studies have been carried out to produce such chemicals from food wastes, some of which are discussed in this chapter.

Engineered nanomaterials (ENMs), such as copper oxide nanoparticles (CuO NPs), are emerging as pollutants extensively used in many commercial and industrial applications, thus raising environmental concerns due to their release into water bodies. It is, therefore, essential to remove these pollutants from water bodies in order to minimize the potential threat to the aquatic environment and human health. The objective of this study was to investigate the removal of CuO NPs from waters by the coagulation process. This study also explored the efficiency of coagulation to remove hydrophobic/hydrophilic dissolved organic matter (DOM) and turbidity with varying polyaluminum chloride (PACl) doses. According to the results, a high concentration of DOM affects both the CuO NPs zeta potential and hydrodynamic diameter, thereby decreasing the agglomeration behavior. At effective coagulation zone (ECR), high removal of CuO NPs (&gt, 95%) was observed for all studied waters (hydrophobic and hydrophilic waters), above ECR excess charge induced by coagulant restabilized particles in solution. Furthermore, waters containing hydrophobic DOM and those with high UV254nm values needed more coagulant dose than hydrophilic waters to obtain similar CuO NP removals. The primary mechanism involved in CuO NPs removal might be charge neutralization. These findings suggest that PACl is an effective coagulant in the removal of CuO NPs, however, water characteristics are an influencing factor on the removal performance of ENMs during the coagulation process.

The widespread use of copper oxide nanoparticles (CuO NPs) and surfactants in various consumer products makes it likely that they coexist in aqueous environments, making it important to study the effects of surfactants on the fate and transport behavior of CuO NPs. The present study aims to investigate the influence of anionic sodium lauryl sulfate (SLS) and nonionic nonylphenol ethoxylate (NPEO, Tergitol NP-9), on CuO NPs adsorption, aggregation, and removal from water by the coagulation process. The result of the sorption study indicates that both surfactants could be adsorbed on the surface of CuO NPs, and that SLS remarkably decreases the &zeta, potential as well as the hydrodynamic diameter (HDD) of CuO as compared to NP-9. The kinetic aggregation study showed that both SLS and NP-9 reduced the HDD of CuO NPs and retarded the settling rates at surfactant concentrations above 0.015% (w:v) over a 24 h-period. Moreover, enhanced aggregation of CuO NPs was observed in two environmental waters as compared to pure water, which could be related to their high ionic strength. The addition of surfactants in natural waters has been shown to reduce the aggregation and sedimentation of CuO, however, the reductive effect of SLS was more pronounced than that of NP-9. Finally, the coagulation results showed that the removal efficiencies of CuO, Cu2+, and the surfactant in all tested waters at optimum ferric chloride dosage reached around 98, 95, and 85%, respectively. Furthermore, the coagulation mechanism revealed that the combination of charge neutralization and adsorptive micellar flocculation (AMF) might be involved in the removal of both pollutants. The results of the present study provide new insight into the environmental behavior of coexisting NPs and surfactants in wastewater treatment processes.

The co-occurrence of arsenic (As) and organic ligands in water bodies has raised environmental concerns due to their toxicity and adverse effects on human health. The present study aims to elucidate the influences of hydrophobic/hydrophilic organic ligands, such as humic acid (HA) and salicylic acid (SA), on the interactive behavior of As species in water. Moreover, the competitive removal behaviors of As(III, V) species and total organic carbon (TOC) were systematically investigated by coagulation-flocculation-sedimentation (C/F/S) under various aqueous matrices. The results showed the stronger binding affinity of As(V) than As(III) species, with a higher complexation ability of hydrophobic ligands than hydrophilic. The media containing hydrophilic ligands require smaller ferric chloride (FC) doses to achieve the higher As(III, V) removal, while the optimum FC dose required for As(III) removal was found to be higher than that for As(V). Moreover, hydrophobic ligands showed higher TOC removal than hydrophilic ligands. The pronounced adverse effect of a higher concentration of hydrophobic ligands on the removal efficiencies of As(V) and TOC was observed. The adsorption of As(V) on Fe precipitates was better fitted with the Langmuir model but the Freundlich isotherm was more suitable for As(III) in the presence of hydrophilic SA. Moreover, TOC removal was substantially decreased in the As(V) system as compared to the As(III) system due to the dissolution of Fe precipitates at higher As(V) concentrations. The results of FC composite flocs demonstrated that the combined effect of oxidation, charge neutralization and adsorption played an important role in the removal of both toxicants during the C/F/S process. In summary, the findings of the present study provide insights into the fate, mobility and competitive removal behavior of As(III, V) species and organic ligands in the water treatment process.

The presence of natural organic matter (NOM) in drinking water sources can stabilize toxic antimony (Sb) species, thus enhancing their mobility and causing adverse effects on human health. Therefore, the present study aims to quantitatively explore the complexation of hydrophobic/hydrophilic NOM, i.e., humic acid (HA), salicylic acid (SA), and L-cysteine (L-cys), with Sb in water. In addition, the removal of Sb(III, V) species and total organic carbon (TOC) was evaluated with ferric chloride (FC) as a coagulant. The results showed a stronger binding affinity of hydrophobic HA as compared to hydrophilic NOM. The optimum FC dose required for Sb(V) removal was found to be higher than that for Sb(III), due to the higher complexation ability of hydrophobic NOM with antimonate than antimonite. TOC removal was found to be higher in hydrophobic ligands than hydrophilic ligands. The high concentration of hydrophobic molecules significantly suppresses the Sb adsorption onto Fe precipitates. An isotherm study suggested a stronger adsorption capacity for the hydrophobic ligand than the hydrophilic ligand. The binding of Sb to NOM in the presence of active Fe sites was significantly reduced, likely due to the adsorption of contaminants onto precipitated Fe. The results of flocs characteristics revealed that mechanisms such as oxidation, complexation, charge neutralization, and adsorption may be involved in the removal of Sb species from water. This study may provide new insights into the complexation behavior of Sb in NOM-laden water as well as the optimization of the coagulant dose during the water treatment process.

Antimony (Sb) is a regulated pollutant that is frequently present at elevated concentrations in natural bodies of water due to natural sources and human activities. Therefore, its purification from fresh water streams is of ultimate importance. This study focused on the iron hydroxide (FHO) formation and removal of Sb ions from water via ferric chloride (FC) coagulation. The effects of pH, contact time, concentration, temperature, and ionic strength (IS) were studied to explore the mechanistic insights into the removal behavior of both Sb ions during potable water purification. Results indicated that the solubility of FHO decrease by increasing the pH, thus repulsing the oxyanions at alkaline pH, decreasing in turn the adsorption capacity of Sb(V) species. The influence of contact time and equilibrium Sb concentration on FHO formation was found to be insignificant. The adsorption of Sb on FHO was well fitted with Pseudo-first order and Langmuir-Freundlich (L–F) models. Physical adsorption of Sb ions onto FHO was identified to be the major mechanism using the Dubinin-Radushkevich (D–R) isotherm model. Thermodynamic parameters (ΔG, ΔH, and ΔS) suggested that the Sb adsorption process was spontaneously exothermic with increased randomness. A more pronounced effect of IS on high Sb feed was observed with increasing sorption affinities upon enhancing electrolyte concentration. The mechanism was further supported by X-ray diffraction spectroscopy, which revealed the likelihood of inner-sphere complexation and physisorption of Sb onto FHO. Moreover, an involvement of coprecipitation phenomena during growing FHO was observed as key phenomena for greater Sb(III) removal. In general, the results of current research may provide detailed insights into the adsorption ability of FHO and the potential mechanisms responsible for the removal of Sb ions during potable water treatment.

The objective of this study was to determine the impact of solubilization during thermo-chemo-sonic pretreatment of waste activated sludge (WAS) on anaerobic biodegradability and cost for biogas production. The results revealed that it was possible to achieve 40-50% of solubilization of WAS when ultrasonic energy input was doubled (11,520-27,000kJ/kgTS). The cost to achieve 30-35% of solubilization of WAS was calculated to be 0.22-0.24USD/L, which was relatively lower than the cost of 0.53-0.8USD/L when 40-50% of solubilisation of WAS was achieved. There was no significant difference in biodegradability (0.60-0.64gCOD/gCOD) for samples with solubilization efficiency of 35-50%. Comparing energetic balance and economic assessment of samples with different solubilization percentages, the results showed that samples with 30-35% of solubilization had lower net cost (7.98-2.33USD/Ton of sludge) and negative energy balance compared to samples with other percentages of solubilization.

The aim of this study was to increase the sludge disintegration and reduce the cost of microwave (MW) pretreatment. Thermodynamic analysis of MW hydrolysis revealed the best fit with a first-order kinetic model at a specific energy of 18,600 kJ/kg total solids (TS). Combining H2O2 with MW resulted in a significant increment in solubilization from 30 to 50 % at 18,600 kJ/kg TS. The pH of H2O2-assisted MW-pretreated sludge (MW + H2O2) was in the alkaline range (pH 9-10), and it made the sludge unfavorable for subsequent anaerobic digestion and inhibits methane production. In order to nullify the alkaline effect caused by the MW + H2O2 combination, the addition of acid was considered for pH adjustment. H2O2-assisted MW-pretreated sludge in acidic conditions (MW + H2O2 + acid) showed a maximum methane production of 323 mL/g volatile solids (VS) than others during anaerobic biodegradability. A cost analysis of this study reveals that MW + H2O2 + acid was the most economical method with a net profit of 59.90 €/t of sludge.

A novel perchlorate-reducing bacterium (PCRB), PMJ, was isolated from the mixed liquor suspended solids in the aerobic tank of a wastewater treatment plant. The 16S ribosomal RNA (rRNA), perchlorate reductase, and chlorite dismutase gene sequences revealed that PMJ belonged to the genus Azospira. PMJ was removed high-strength (700 mg/L) perchlorate and also removed low-strength (≤50 mg/L) perchlorate below the detection limit (2 μg/L) when acetate was used as a sole and carbon source. The maximum specific perchlorate utilization rate, q max, was 0.96 mg ClO4 (-)/mg dry cell weight day, and the half-saturation constant, K S , was lower than 0.002 mg ClO4 (-)/L. PMJ also utilized inorganic electron donors [(H2, S(0), and Fe(II)] with perchlorate as an electron acceptor. Perchlorate reduction by PMJ was completely inhibited by oxygen and chlorate but was not inhibited by nitrate. In the presence of similar concentrations (100∼140 mg/L) of nitrate and perchlorate, PMJ simultaneously removed both electron acceptors. Therefore, it was concluded that the strains PMJ might possess separate pathways for perchlorate and nitrate reduction. These results indicated that Azospira sp. PMJ could be efficiently used for treating perchlorate-contaminated groundwater and wastewater because many of these water bodies are known to contain both perchlorate and nitrate. In addition, low K S value and autotrophic perchlorate reduction of PMJ might be useful to design the biological treatment systems.

The zinc oxide nanoparticles (ZnO NPs) and surfactants that are widely used in commercial and industrial products lead to the likelihood of their co-occurrence in natural water, making it essential to investigate the effect of surfactants on the fate and mobility of ZnO NPs. The present study seeks to elucidate the effect of an anionic sodium dodecyl sulfate (SDS) and a nonionic nonylphenol ethoxylate (NPEO), on ZnO NPs adsorption, aggregation, dissolution, and removal by the coagulation process. The results indicate that the presence of SDS in ZnO NPs suspension significantly reduced the &zeta, potential and hydrodynamic diameter (HDD), while the effect of NPEO was found not to be significant. The sorption of SDS and NPEO by ZnO NPs were fitted with Langmuir model, but the Freundlich isotherm was more suitable for SDS at pH 9.0. Moreover, the adsorption was strongly pH-dependent due to the formation of mono-bilayer patches onto the NPs. The SDS remarkably affect the dissolution and aggregation phenomena of ZnO NPs in natural waters as compared to NPEO. Finally, the coagulation results showed that the removal efficiency of ZnO, Zn2+ and the surfactant in synthetic and wastewaters at optimum ferric chloride (FC) dosage reached around 85&ndash, 98% and 20&ndash, 50%, respectively. Coagulation mechanism investigation demonstrated that the cooperation of charge neutralization and adsorptive micellar flocculation (AMF) might play an important role. In summary, this study may provide new insight into the environmental behavior of coexisting ZnO NPs and surfactants in water treatment processes, and it may facilitate their sustainable use in commercial products and processes.

In most countries, arsenic (As) and antimony (Sb) are regulated pollutants, due to their significant impacts on the environment and human health. Iron-based (Fe) coagulants play a fundamental role in the removal of both elements from aqueous media. This study aims to investigate the competitive removal of As and Sb in relation to Fe solubility. Coagulation experiments were conducted in synthetic water under various pH and contaminant loading, using ferric chloride (FC) as a coagulant. In the single system, the pentavalent species significantly reduced the Fe solubility and thereby enhanced the mobility of As and Sb under these environmental conditions. The coexistence of pentavalent and trivalent species in the binary system considerably decreases the Fe solubility at acidic conditions while enhancing the dissolution under alkaline conditions, thus affecting the overall removal of both species. The presence of four redox species in the quaternary system decreases the Fe solubility remarkably over a wide pH range, with better Sb removal, as compared to As under similar conditions. The adsorption study of the single system showed a decrease in As(V) adsorption capacity at higher concentration, while in the binary system, the Sb(III) showed strong adsorption potential, compared to other species. In the quaternary system, the presence of all four redox species has a synergistic effect on total Sb adsorption, in comparison to the total As. Furthermore, the results of Fourier transform infrared (FT-IR) analysis of FC composite contaminant flocs confirm that the combined effect of charge neutralization and inner sphere complexation might be a possible removal mechanism. These findings may facilitate the fate, transport and comparative removal of redox species in the heterogeneous aquatic environment.

The large-scale production and usage of zinc oxide nanoparticles (ZnO NPs) may lead to their post-release into the aquatic environment. In this study, the effect of hydrophobic/hydrophilic organic ligands on sorption and sedimentation of ZnO NPs has been systematically investigated. In addition, the coagulation efficiency of ZnO NPs, Zn2+, dissolved organic carbon (DOC), and UV254 with varying ferric chloride (FC) dosages in synthetic waters were also evaluated. The results showed that the higher concentration of organic ligands, i.e., humic acid (HA), salicylic acid (SA), and L-cysteine (L-cys) reduced the &zeta, potential and hydrodynamic diameter (HDD) of particles, which enhanced the NPs stability. The adsorption of organic ligands onto ZnO NPs was fitted with the Langmuir model, with maximum adsorption capacities of 143, 40.47, and 66.05 mg/g for HA, SA and L-cys respectively. Removal of up to 95% of ZnO NPs and Zn2+ was achieved in studied waters at the effective coagulation zone (ECR), above which excess charge induced by coagulant restabilized the NPs in suspension. Moreover, the removal rate of DOC and UV254 were found to be higher in hydrophobic waters than hydrophilic waters. The width of ECR strongly depends on the characteristics of source water. The waters with hydrophobic ligand and higher UV254 values require more coagulant than hydrophilic waters to achieve the similar ZnO NPs and Zn2+ removal. The results of Fourier transform infrared (FT-IR) analysis of ZnO NPs composite contaminant flocs indicated that the combined effect of enmeshment and charge neutralization might be a possible removal mechanism. These findings may facilitate the prediction of fate, transport, and removal of ZnO NPs in the natural waters, and might contribute to risk assessment, as well as decision making about engineered nanoparticles (ENPs) in aquatic systems.

The extensive use of engineered nanoparticles (ENPs) such as zinc oxide nanoparticles (ZnO NPs) in various commercial fields has spurred significant concern about its possible toxicological effects of ZnO NPs on human health and eco-system. Therefore, it is substantial to understand the aggregation phenomena which could attenuate this effect. This data article provides information on aggregation of ZnO NPs under the influence of various parameters of water chemistry. Moreover, Taguchi orthogonal array L27(313) design matrix was used to evaluate the effect of multiple parameters in aqueous solution. The data were obtained from single beam UV-Vis spectrophotometer (Optizen 2120 UV, Mecasys, Korea) using Optizenview 4.2.5 PC interference software, Fourier transform infrared spectrometer (FT/IR-4700, spectroscopy, JASCO Analytical Instruments, Easton, USA) and particle electrophoresis (NanoZS, Zetasizer, Malvern Instruments Ltd, Worcestershire, UK). The dataset draws attention on dominant parameters influencing aggregation of ZnO NPs in water. The analysis of variance (ANOVA) data revealed that electrolyte concentration, type and natural organic matter (NOM) concentration were the most significant parameters. Furthermore, FT-IR data presents a possible mechanism of ZnO NPs stabilization in the presence of different NOM. This data will be helpful for the development of environmental risk assessment strategies and prediction of fate and mobility of other ENPs in the aquatic environment.

Zinc oxide nanoparticles (ZnO NPs) are among the most widely used engineered nanoparticles (ENPs) in various commercial sectors to achieve both social and economic benefits. The post-use release of these NPs to the environment is inevitable, and may pose threat to the human and eco-system. In the present study, we investigated the influence of single and multiple environmental factors on sedimentation behavior of ZnO NPs. The fractional-factorial method based on Taguchi orthogonal array (OA) L27(313) design matrix was used for systematic investigation on the contribution and significance of multiple factors and their interactions. The result of single-factor showed that the ZnO NPs were unstable at or near pHzpc, with high electrolyte concentration; however, the adsorption of natural organic matter (NOM) i.e., humic acid, salicylic acid, and citric acid reverses the surface charge and enhanced NP stability. The Fourier transform infrared (FT-IR) analysis confirms the organic capping ligands on the NP surface. Moreover, the matrix result of analysis of variance (ANOVA) showed that electrolyte concentration and type, and NOM concentration were the most significant factors (p < 0.001) in promoting and influencing aggregation, while the interaction between the factors was also found insignificant. In addition, the result of aggregation kinetics and environmental water samples indicated that the mobility of ENPs may vary substantially in an environment with complex and heterogeneous matrices. This study may contribute to better understanding and prediction of the sedimentation behavior and fate of ZnO NPs in aqueous environments, to facilitate their sustainable use in products and process.

Coagulation and precipitation appear to be the most efficient and economical methods for the removal of antimony from aqueous solution. In this study, antimony removal from synthetic water and Fe solubility with ferric chloride (FC) coagulation has been investigated. The effects of pH, FC dosage, initial antimony loading and mixed Sb(III), Sb(V) proportions on Fe solubility and antimony removal were studied. The results showed that the Sb(III) removal efficiency increased with the increase of solution pH particularly due to an increase in Fe precipitation. The Sb(V) removal was influenced by the solution pH due to a change in Fe solubility. However, the Fe solubility was only impaired by the Sb(III) species at optimum pH 7. The removal efficiencies of both Sb species were enhanced with an increase in FC dose. The quantitative analysis of the isotherm study revealed the strong adsorption potential of Sb(III) on Fe precipitates as compared to Sb(V). Furthermore, the removal behavior of antimony was inhibited in mixed proportion with high Sb(V) fraction. In conclusion, this study contributes to better understanding the fate of Sb species, their mobilities, and comparative removal behavior, with implications for Fe solubility using ferric chloride in different aqueous environments.

In the present paper, the study focuses on the effects of sodium dodecyl sulfate (SDS) surfactant on the release of extracellular polymeric substance (EPS) followed by pretreatment with a thermophilic protease-secreting bacterial strain on WAS (waste activated sludge). This in turn enhanced the subsequent anaerobic biodegradability. The extracellular polymeric substances were released using SDS (0.03 g/g SS of dosage) to stimulate the bacterial pretreatment. The thermophilic bacterial pretreatment results indicated that deflocculated (EPS released with SDS and pretreated with bacteria) sludge showed higher Suspended Solids (SS) reduction of about 27% and Chemical Oxygen Demand (COD) solubilization of about 24%, whereas flocculated (pretreated with bacteria alone) showed SS reduction of about 18% and COD solubilization of about 16%. The biogas production potential of deflocculated, flocculated, and raw (untreated) samples was found to be 2.5211 L/(gVS), 1.7677 L/(gVS), and 0.6140 L/(gVS), respectively. As a result, the EPS release followed by disintegration of sludge by bacteria enhanced the biogas production.

An investigation was performed to study the influence of ultrasonic aided bacterial disintegration on the aerobic degradability of sludge. In first phase of the study, effective floc disruption was achieved at an ultrasonic specific energy input of 2.45kJ/kg TS with 44.5mg/L of Extracellular Polymeric Substance (EPS) release including 0.035U/mL and 0.025U/mL protease and amylase activity respectively. In second phase, experimental outcomes revealed bacterial disintegration of floc disrupted-sludge showing a maximum solubilization of about 23% and was observed to be superior to bacterially disintegrated (11%) and control (6%), respectively. The result of aerobic biodegradability of ultrasonic aided bacterially pretreated sludge showed volatile solids (VS) degradation of about 40.2%. The kinetic study of aerobic biodegradability through non linear regression modelling reveals that floc disrupted sludge showed better biodegradability with decay constant of about 0.19d(-1) relatively higher than the control (0.14d(-1)) and bacterially disintegrated (0.17d(-1)) sludges.

The present study investigates the influence of phase separated disintegration on waste activated sludge (WAS) biodegradability in a profitable manner. An effort has been taken in this study to disintegrate WAS in an economical way by deflocculating the WAS with 0.04 g/g SS of MgCl 2 . The bacterial cell disruption was proficient at 42 h, where floc disrupted-bacterially pretreated sludge showed prominent solubilization of about 21.4% than the bacterially pretreated sludge (10.5%). The kinetic analysis of disintegration (suspended solids (SS) reduction and particulate chemical oxygen demand (PCOD) reduction) for control, bacterially disintegrated, floc disrupted-bacterially disintegrated sludges was observed to be first order with rate constants 0.001, 0.003, 0.005 and 0.001, 0.002, 0.005 (h −1 ), respectively. The proposed method articulates the effectiveness of sludge disintegration in terms of VFA production of about 640 mg/L in anaerobic fermentation experiment. The model (exponential rise to maximum) explaining the Biochemical methane potential (BMP) assay was implemented in Matlab. 12v. The parameter estimation analysis affords an estimate of parameter uncertainty and correlation, and is obviously explains that floc disrupted-bacterially pretreated sludge showed higher biodegradability of about 0.22 (g COD/g COD) than the others. Cost estimation of the present study revealed net profit of about 27.3 USD in floc disrupted-bacterially pretreated sludge.

The effect of combined surfactant-dispersion pretreatment on dairy waste activated sludge (WAS) reduction in anaerobic digesters was investigated. The experiments were performed with surfactant, Sodium dodecyl sulfate (SDS) in the range of 0.01 to 0.1 g/g suspended solids (SS) and disperser with rpm of 5000-25,000. The COD (chemical oxygen demand) solubilization, suspended solids reduction, and biogas generation increased for an energy input of 7377 kJ/kg total solids (TS) (12,000 rpm, 0.04 g/g SS, and 30 min) and were found to be 38, 32, and 75 %, higher than that of control. The pretreated sludge improved the performance of semicontinuous anaerobic digesters of 4 L working volume operated at four different SRTs (sludge retention time). SRT of 15 days was found to be appropriate showing 49 and 51 % reduction in SS and volatile solids (VS), respectively. The methane yield of the pretreated sample was observed to be 50 mL/g VS removed which was observed to be comparatively higher than the control (12 mL/g VS removed) at optimal SRT of 15 days. To the best of the authors' knowledge, this study is the first to be reported and not yet been documented in literature.

In the present study, the influence of NaCl mediated bacterial disintegration of waste activated sludge (WAS) was evaluated in terms of disintegration and biodegradability of WAS. Floc disruption was efficient at 0.03 g/g SS of NaCl, promoting the shifts of extracellular proteins and carbohydrates from inner layers to extractable – soluble layers (90 mg/L), respectively. Outcomes of sludge disintegration reveal that the maximum solubilization achieved was found to be 23%, respectively. The model elucidating the parameter evaluation, explicates that floc disrupted – bacterially disintegrated sludge (S3) showed superior biodegradability of about 0.23 (gCOD/gCOD) than the bacterially disintegrated (S2) and control (S3) sludges of about 0.13 (gCOD/gCOD) and 0.05 (gCOD/gCOD), respectively. Cost evaluation of the present study affords net profits of approximately 2.5 USD and −21.5 USD in S3 and S2 sludge.

In this study, ultrasonication was used for sludge deflocculation, followed by cell disintegration using ozone. The effect of this phase separated sono-ozone pretreatment is evaluated based on extra polymeric substances release, deoxyribonucleic acid (DNA) in the medium, solubilization of intra cellular components and suspended solids (SS) reduction. Ultrasonically induced deflocculation was optimized at an energy dosage of 76.4 (log 1.88) kJ/kg TS. During cell disintegration (ozone dosage 0.0011 mg O3/mg SS), chemical oxygen demand solubilization (COD) and SS reduction of sonic mediated ozone pretreated sludge were 25.4% and 17.8% comparatively higher than ozone pretreated sludge, respectively. Further, biogas production potential of control (raw), flocculated (ozone pretreated), and deflocculated (sonic mediated ozone pretreated) sludges were observed to be 0.202, 0.535 and 0.637 L/(g VS), respectively. Thus, the phase separated pretreatment at lower ultrasonic specific energy and low dose ozone proved to enhance the anaerobic biodegradability efficiently.

Four bench-scale solar photocatalytic reactors were fabricated viz. solar photocatalytic single-baffle reactor (SPSBR), solar photocatalytic multiple-baffles reactor (SPMBR), solar photocatalytic cascade reactor (SPCR) and solar photocatalytic pond reactor (SPPR) of 5-L capacity. Evaluation of the reactors performance was carried out by varying the volume of wastewaters in the range of 1–5 L and the recycle flow rates in the range of 250–750 mL/min for the degradation of phenolic wastewaters. The single-baffle reactor gives the maximum phenol removal efficiency irrespective of all volume of wastewater. The phenol removal efficiency increases when the recycle flow rate is increased from 250 to 500 mL/min and then decreased for the recycle flow rate of 750 mL/min. The single-baffle reactor showed the maximum phenol removal efficiency with recycle flow rate of 500 mL/min. For untreated pulp and paper mill wastewater of 200 mg/L phenol concentration, the BOD5/COD ratio is 0.02, while solar photocataly...

Recalcitrant compounds like phenol found in coconut husk retting effluent cause the deterioration of water quality when discharged from retting ponds into other water sources. Continuous upflow microbial fuel cell (MFC) was evaluated for treating retting wastewater at different loading rates to determine power generation, chemical oxygen demand (COD) consumption rate and phenol removal for a period of 270 days. A maximum power density of 254 mW/m2 was achieved during the treatment of retting wastewater (external resistance — 350Ω). COD removal of 70% was accomplished at a loading rate of 0.45 g COD/L reactor/day and phenol removal of 95% was obtained at a loading rate of 0.28 g phenol/L reactor/day. The power density exhibited an increasing pattern as the loading rate of MFC was increased from 0.45 to 2.69 g COD/L reactor/day. This study describes the treatment of retting wastewater employing continuous upflow MFC with 95% phenol removal. Therefore, MFC can be considered as an alternative for the efficient removal of phenol and current generation in retting wastewater.

This study investigated the practical application of combined advanced oxidation processes (AOPs), such as homogeneous TiO2 photocatalysis and heterogeneous photo-Fenton, for the treatment of tannery wastewaters. An optimization study was conducted on the photocatalytic degradation of tannery wastewaters, in order to understand the effects of different operating parameters on the degradation kinetics. The chemical oxygen demand of tannery wastewater decreased from an initial level of 3,400 mg/L in raw wastewater to 140 mg/L (96% removal) in wastewater treated by the combined advanced oxidation process at optimum pH 7, TiO2 dosage of 0.2 g/L, Fe2+ dosage of 0.5 g/L, H2O2 dosage of 1.8 g/L and a treatment time of 4 hours. The biodegradability of wastewater increased from an initial level of 0.4 to 0.7 after treatment under optimum experimental conditions at a treatment time of 60 min. An annual treatment cost of US$21.34/m3 of treated water was obtained. The combined advanced oxidation process proved to be an efficient and appropriate technique for the effective removal of complex organic compounds in industrial wastewater.

This study focuses on improving the efficiency of the microwave (MW) pretreatment of waste activated sludge (WAS) through deflocculation mediated by sodium tripolyphosphate (STPP), a cationic binding agent. Deflocculated sludge was subjected to MW pretreatment to assess its impact on biomass disintegration. At the optimised energy for MW pretreatment (14,000 kJ/kg TS), the chemical oxygen demand (COD) solubilisation was 28% and 21% and the reduction in suspended solids (SS) was 38% and 26%, respectively, for deflocculated (treated with a cationic binding agent followed by microwaves) and flocculated (treated by microwaves alone) sludge samples. The formation of volatile fatty acids in the deflocculated sludge medium (840 mg/L) was comparatively higher than that in the flocculated sludge (420 mg/L) and the control (62 mg/L). This study indicates that deflocculated sludge is more amenable to hydrolysis. The results of a test of biochemical methane potential also confirmed the greater amenability of deflocculated sludge for anaerobic degradation.

The present study details about the biodegradation of 1,4-dioxane by Rhodanobacter AYS5 isolated from bacterial consortia enriched from industrial sludge. Rhodanobacter AYS5 potently degraded 95 % of 1,4-dioxane (1000 ppm) in 10 days as sole carbon source. To accelerate the growth of Rhodanobacter AYS5 and to reduce the time taken for degradation, additional carbon source (glucose, yeast extract and tetrahydrofuran) were added and analysed. The study revealed that, yeast extract and tetrahydrofuran (THF) accelerated the degradation of 1,4-dioxane by reducing the time taken for degradation. Growth on glucose reduced the degradation potential of the bacterial strain. Study on carbondioxide evolution and metabolites formation confirmed complete mineralisation of 1,4-dioxane by Rhodanobacter AYS5. Further study on different concentration of 1,4-dioxane with and without additional substrate (THF and yeast extract) revealed that, Rhodanobacter AYS5 is a promising bacterial strain for 1,4-dioxane degradation. In lab scale reactor study with industrial wastewater, Rhodanobacter AYS5 showed 91 % chemical oxygen demand (COD) removal, and complete degradation of 1,4-dioxane and THF in 5 days. The 1,4-dioxane degrading bacterial strain was identified as Rhodanobacter AYS5 (JQ419753) using molecular and biochemical techniques.

In this investigation, the application of citric acid was explored for the removal of extracellular polymeric substance (EPS) from waste activated sludge (WAS), followed by ultrasonic pretreatment, which enhanced the subsequent anaerobic biodegradability. EPS was removed with 0.05 g/g SS of citric acid. The chemical oxygen demand (COD) solubilization and suspended solids (SS) reduction that occurred for specific energy input of 171.9 kJ/kg TS, in deflocculated (EPS removed and ultrasonically pretreated) sludges were found to be 22.70% and 20.28% and was comparatively higher, than the flocculated (with EPS and ultrasonically pretreated). The biogas yield potential of flocculated and deflocculated sludges (specific energy input – 171.9 kJ/kg TS) was found to be 0.212 L/(g VS) and 0.435 L/(g VS), respectively. Accordingly, the deflocculation and ultrasonic pretreatment improved the anaerobic biodegradability efficiently. Thus, this chemo mediated sonic pretreatment is an effective method for enhancing biodegradability and improving clean energy generation from WAS.