Sustainable treatment scheme for in-situ remediation of contaminated drains using engineered natural systems.

Ensuring water security in resource-constrained, densely populated regions is a significant challenge globally. Due to insufficient treatment infrastructure, untreated sewage discharge into drainage channels is prevalent, especially in developing countries. This leads to the pollution of already dwindling water bodies and threatens future water availability. In this context, in-situ treatment within drains using nature-based systems is an attractive option. This study evaluates microbial bioremediation and phytoremediation as engineered natural solutions for in-stream treatment of municipal wastewater. A three-stage treatment system consisting of anoxic biofilm, aerobic biofilm, and hydroponic floating wetlands was adopted. Each stage was optimized for operational parameters through batch and continuous flow studies. The anoxic biofilm system using autoclaved aerated concrete (AAC) as the attachment media, at an optimized hydraulic retention time (HRT) of 2 h, showed the best performance with respect to COD removal. Comparable COD removal was observed in both externally aerated and non-aerated aerobic biofilm systems with coir fibre at 6 h HRT. However, aerated system outperformed non-aerated system at low HRTs. The hydroponic system with Canna indica effectively removed residual ammonia-N with an HRT of 2 h. The sequential continuous flow studies employing the optimized conditions showed significant removals of COD (86%) and ammonia-N (97.6%). The results highlight that locally available materials having a high specific surface area can be used as biofilm supports for COD removal, and floating wetlands employing indigenous macrophytes can be an ideal choice for in-situ nutrient removal. The Life Cycle Assessment (LCA) showed that the developed system did not have direct significant impacts on freshwater eco-toxicity and eutrophication. The proposed hybrid treatment system can be implemented as modular units without major drainage modifications or energy-intensive operations. The study, therefore, finds potential application in densely populated settlements in low-income countries where systematic sewage treatment options remain inadequate.

Recent Advances in High-Rate Solar-Driven Interfacial Evaporation.

Recent advances in solar-driven interfacial evaporation (SDIE) have led to high evaporation rates that open promising avenues for practical utilization in freshwater production and industrial application for pollutant and nutrient concentration, and resource recovery. Breakthroughs in overcoming the theoretical limitation of 2D interfacial evaporation have allowed for developing systems with high evaporation rates. This study presents a comprehensive review of various evaporator designs that have achieved pure evaporation rates beyond 4 kg m-2 h-1, including structural and material designs allowing for rapid evaporation, passive 3D designs, and systems coupled with alternative energy sources of wind and joule heating. The operational mechanisms for each design are outlined together with discussion on the current benefits and areas for improvement. The overarching challenges encountered by SDIE concerning the feasibility of direct integration into contemporary practical settings are assessed, and issues relating to sustaining elevated evaporation rates under diverse environmental conditions are addressed.

Feasibility of a Planar Coil-Based Inductive-Capacitive Water Level Sensor with a Quality-Detection Feature: An Experimental Study.

This paper presents a new water-level-sensing mechanism based on planar coils fabricated on a printed circuit board (PCB). In addition to level, the sensor detects any relative increase in conductivity compared to that of clean water, which is an indicator of its quality. The sensing mechanism utilizes the eddy current induced in the water column, the corresponding change in the coil inductance, and the change in the turn-to-turn capacitance of the coil in the presence of water. Although several level sensors are available, there is none that gives the level and quality information using a single sensing element. Since both water quantity and quality measurements are fundamental in realizing efficient water and wastewater management, obtaining these two parameters from the same sensor is very beneficial. A scalable, planar coil-based sensor that helps achieve this goal is designed, fabricated, and tested in a laboratory setting. The results illustrate that the reactance of the sensor coil measured at a frequency (1 kHz for the prototype) much lower than the self-resonance of the coil gives reliable information about the level of water, while the measurement made at resonance, using an inductance-to-digital converter, is a clear indicator of its conductivity and, hence, quality.

Fate of carbamazepine and its effect on physiological characteristics of wetland plant species in the hydroponic system.

Plants play a cardinal role in removing various pollutants through the synergistic interaction with filling materials and microbes of constructed wetlands (CWs). However, the information regarding the selection of plant species to remove pharmaceutically active compounds (PhACs) is not adequate. The present study attempted to select an appropriate plant species for CWs, considering their characteristics and physiological response to PhACs. In this regard, batch hydroponics studies were carried out to assess the removal, fate, and antioxidative response of carbamazepine (CBZ) in four wetland plant species (Canna indica, Colocasia esculenta, Phragmites australis, and Chrysopogon zizanioides). The specific uptake potential of CBZ (in terms of plant dry biomass) was found to be in the order: C. indica (14.48 mg/g) >P. australis (11.71 mg/g) >C. esculenta (8.67 mg/g) >C. zizanioides (6.04 mg/g). The results showed that exposure to CBZ (0-30 days) caused an accumulation of reactive oxygen species (ROS) in the plant tissues, causing a decline in chlorophyll content, root activity, and increased oxidative stress. However, the selected plants could recover from the oxidative damages to a certain extent in the recuperation phase (31-60 days). C. indica exhibited relatively lesser ROS accumulation and oxidative damage during the experimental phase than other selected plants. The study also showed that plant biomass, transpiration rate, chlorophyll content, root exudates, and root activity influenced the removal of CBZ by various plants (r - 0.76 to 0.98, P < 0.05). The mass balance analysis indicated that a significant proportion of CBZ (49.2 to 72.7 %) underwent metabolism in the plant tissues. Apart from higher removal, lesser accumulation, and lower oxidation stress, multi-criteria decision analysis showed that C. indica is a potential plant species for the removal of CBZ.

Mechanistic insights into carbo-catalyzed persulfate treatment for simultaneous degradation of cationic and anionic dye in multicomponent mixture using plastic waste-derived carbon.

Upcycling waste into value-added products for utilization in wastewater abatements has been explored in a number of treatment technologies. One such waste, single-use plastic, which poses significant adverse environmental and economic impact, has been chosen and converted into graphitic carbon to reduce the waste burden sustainably and economically. The sorptive and catalytic performance of synthesized plastic waste-derived carbon (PWC) was evaluated using brilliant green (BG) and eosin yellow (EY) as target pollutants. The adsorption capacity of PWC was very low for BG (7.41 mg/g) and EY (4.93 mg/g). The coupling of PWC with peroxymonosulfate (PMS) promoted dye degradation. Complete degradation of the dye, with ~61% reduction in TOC and ~95% reduction in toxicity, was achieved by oxidative treatment (initial concentration: 10 mg/L). The functionalities of PWC facilitated better electron transfer to PMS for its effective activation, which led to the production of SO4•- and OH•. The quenching study confirmed that the degradation of dyes was primarily due to SO4•-. Additionally, the pathways of dye degradation were proposed based on the intermediates identified. Thus, this study established the high potential of PWC as a metal-free catalyst in PMS activation for the abatement of organic pollutants.

Enhanced degradation of complex organic compounds in wastewater using different novel continuous flow non - Thermal pulsed corona plasma discharge reactors.

The presence of pharmaceutically active compounds (PhAcs) in water bodies is a major concern due to their persistence, biological activity, and detrimental environmental effects. The present study focuses on the application of pulsed corona plasma technology to degrade such compounds. Three different plasma reactors, namely, sequential flow plasma reactor (SFR), continuous flow top discharge plasma reactor (TDPR) and continuous flow side discharge plasma reactor (SDPR), are designed and fabricated for their performance evaluation with respect to PhAC degradation. In all the reactors, wastewater was discharged as fine droplets for better interaction between the reactive oxidizing species (ROS) generated in the system and the pollutants. Enhanced degradation of the selected pharmaceutical compounds, i.e., diclofenac (DCF) and verapamil hydrochloride (VPL), is achieved with decreased treatment time and lower energy consumption. In SFR reactor water was recycled, whereas in continuous flow reactors hydraulic retention times (HRTs) were varied. The degradation efficiency of DCF (1 mg/L) and VPL (1 mg/L) was 99 % in SDPR, at HRTs of 9 and 12 min, respectively. Deposited energies (SFR- 71 W, TDPR - 92 W, SDPR- 51 W) varied due to the difference in reactor geometries. In the SDPR reactor, 99 % degradation of mixed pollutants with an initial concentration of 10 mg/L was achieved, at a HRT of 21 min. With an input power of 51 W, good energy efficiency (EEO) of 3.8 kWh/m3 and high yield (G) of 256.2 mg/kWh were obtained. . Nitrate formation was reduced by 73.2 % in TDPR and 85.0% in SDPR (32.1-8.6 mg/L) as compared to SFR (32.1 mg/L). The operating cost estimated was 0.71 $/m3, 0.80 $/m3 and 0.67 $/m3 for SFR, TDPR and SDPR, respectively. The results clearly indicate that the continuous flow reactor with side discharge is a viable alternative to traditional plasma reactors.

Spatio-temporal distribution of pharmaceutically active compounds in the River Cauvery and its tributaries, South India.

Pharmaceutically active compounds (PhACs) present in the environment are a great threat to human well-being and the ecosystem. Eventhough recognized as the pharmacy of the world", studies addressing the distribution of PhACs in the Indian environment are scarce. Hence, in the current study, selected PhACs, heavy metals (HMs), and physicochemical parameters (PCPs) were measured from the surface waters of the River Cauvery during the pre- and post-monsoon. PhACs such as caffeine, carbamazepine, and diclofenac were detected in most samples, whereas topiramate, ibuprofen, and verapamil were found only in few stations. In contrast, the distribution of ciprofloxacin, atenolol, and isoprenaline was strongly influenced by the seasonal pattern (p < 0.05). PhACs such as loperamide, glafenine, erythromycin, and gemfibrozil were not detected during the study. Distribution of PhACs based on average concentration (ng/L) are, CBZ (205.62) > CAF (114.09) > DCF (28.51) > CIP (25.23) > ATL (18.86) > IPL (13.91) > PPL (11.26) > TCS (10.39) > IBF (7.34) > TPT (3.09) > VPL (1.16). Bivariate and multivariate statistical analyses have revealed a positive correlation expressed by the majority of the PhACs with PCPs (COD, TOC), nutrients (TN, TP), and HMs (Pb, Mn, Ni) in the range from 0.540** to 0.961**(p < 0.01). Whereas, DO revealed negative correlation with most of the parameters in the range from -0.559** to -0.831** (p < 0.01). A high average concentration of PhACs was recorded in the upstream (52.08 ng/L) and wastewater discharge points (55.60 ng/L). Further, the environmental risk assessment study has identified the higher risk exhibited by TCS (RQ: 3.29) and CAF (RQ: 38.82) on algae and Daphnia respectively. The study portrays the distribution of emerging contaminants in the River Cauvery and its tributaries and also delivers preliminary data about the distribution of isoprenaline, topiramate, verapamil, and perindopril in the Indian freshwater system.

Continuous flow pulsed power plasma reactor for the treatment of aqueous solution containing volatile organic compounds and real pharmaceutical wastewater.

The degradation of four recalcitrant and toxic VOCs (volatile organic compounds) present in pharmaceutical wastewater was studied using a continuous flow plasma reactor, along with evaluating its potential for real effluent treatment. The wastewater was sprayed into the plasma zone of the reactor, and it was re-circulated for better performance. The effect of different HRTs (hydraulic retention time) and initial concentrations of VOCs on the degradation efficiency were evaluated. In continuous reactor, complete removal of 200 mg/L of chloroform, chlorobenzene, and toluene was achieved at a HRT of 33.3 min, with an energy consumption of 22.4 kWh/m3. The study on the effect of different inlet loading rates of VOCs on elimination capacity showed that, the removal was limited initially by diffusion of reactive species and at higher loads, it was limited by insufficient amount of reactive species produced. During degradation of VOC mixture, more than 90% removal of chloroform, chlorobenzene and toluene was achieved at HRT of 33.3 min, and the TOC removal was 78.3%. The degradation efficiency of VOC mixture reduced slightly compared to that of individual compounds, due to insufficient amount of reactive species produced. The COD and BOD removal achieved after 140 min of direct plasma treatment of real pharmaceutical wastewater in batch reactor was 92.7% and 95.2%, respectively. Coagulation pre-treatment did not have a significant effect on the plasma treatment of real wastewater. When pharmaceutical effluent treatment was carried out in continuous flow reactor, 91.8% COD removal, 90.9% BOD removal and more than 90% degradation of all VOCs were achieved at a HRT of 150 min. Plasma treatment alone was capable of effectively treating the real pharmaceutical wastewater without any pre-treatment.

Comparative study of degradation of toluene and methyl isobutyl ketone (MIBK) in aqueous solution by pulsed corona discharge plasma.

Effectiveness of pulsed power plasma for the degradation of two toxic volatile organic compounds (VOCs), toluene and methyl isobutyl ketone (MIBK), in aqueous solution was evaluated. The plasma degradation of MIBK has been studied for the first time. The influence of initial concentration of target compound, solution pH and scavengers on percentage degradation was evaluated. 100% removal of 200 mg/L of toluene and MIBK was achieved both in liquid and gaseous phases after 12 and 16 min of plasma treatment, respectively. The first order rate constant of toluene and MIBK degradation (for 200 mg/L each) was 0.421 and 0.319 min-1 respectively when they were treated individually, and these values decreased slightly during degradation of their mixture. MIBK degradation was slower than toluene and it might be due to semi volatile and hydrophilic nature of MIBK. The effect of initial concentration of toluene and MIBK showed different degradation patterns. Highest degradation of both the compounds was obtained in neutral pH and in absence of scavengers. •OH radical was the major reactive species involved in their degradation. Their degradation in real environmental matrices showed that removal reduced significantly in secondary effluent due to scavenging of reactive species by various ions and organic matter. The total number of degradation intermediates identified in case of toluene and MIBK was 11 and 14 respectively and formate was the one recalcitrant byproduct generated. The degradation pathway of toluene and MIBK involving reactions of reactive oxygen and nitrogen species and reductive species is proposed.

Thermal modeling, characterization, and enviro-economic investigations on inclined felt sheet solar distiller for seawater desalination.

Sustainable desalination can be achieved by adopting renewable energy-based low-cost and low-impact desalting techniques. In this investigation, capability of inclined felt sheet solar distiller in desalting seawater is assessed by evaluating its performance, distillate water quality, economics, and environmental impacts. The distiller with 1.18-m2 aperture area produced around 4.60 L/day of distillate for a cumulative incident solar radiation intensity of about 20.52 MJ/m2 day. Its pollutant removal efficiency is very much superior to other available solar stills reported in literatures. Thermal model developed for estimating distiller's performance is able to predict its productivity with reasonable accuracy (only 8.0% deviation from experimental values) and was used for estimating distiller's performance in various seashore locations in India with varying clear days (191 to 246). Yearly mean distillate production and thermal and exergy efficiencies of the proposed distiller range between 3.60 to 4.50 L/day, 36.45 to 42.39%, and 2.85 to 3.65%, respectively, in east seashore locations of India. Moreover, 18.46 tons of CO2, 132.72 kg of SO2, and 54.20 kg of NO emission can be mitigated by adopting the distiller for potable water production. Distillate production cost of inclined felt sheet solar distiller is in the range of 1.15 to 2.29 INR/L and highly depends on the interest rate at which the distiller is financed. Generation of reasonable quantity of high-quality potable water at low cost with huge environmental benefits makes proposed inclined felt sheet solar distiller a suitable option for quenching thirst in coastal and remote locations.

Smartphone-based Fluoride-specific Sensor for Rapid and Affordable Colorimetric Detection and Precise Quantification at Sub-ppm Levels for Field Applications.

Higher levels of fluoride (F-) in groundwater constitute a severe problem that affects more than 200 million people spread over 25 countries. It is essential not only to detect but also to accurately quantify aqueous F- to ensure safety. The need of the hour is to develop smart water quality testing systems that would be effective in location-based real-time water quality data collection, devoid of professional expertise for handling. We report a cheap, handheld, portable mobile device for colorimetric detection and rapid estimation of F- in water by the application of the synthesized core-shell nanoparticles (near-cubic ceria@zirconia nanocages) and a chemoresponsive dye (xylenol orange). The nanomaterial has been characterized thoroughly, and the mechanism of sensing has been studied in detail. The sensor system is highly selective toward F- and shows unprecedented sensitivity in the range of 0.1-5 ppm of F-, in field water samples, which is the transition regime, where remedial measures may be needed. It addresses multiple issues expressed by indicator-based metal complexes used to determine F- previously. Consistency in the performance of the sensing material has been tested with synthetic F- standards, water samples from F- affected regions, and dental care products like toothpastes and mouthwash using a smartphone attachment and by the naked eye. The sensor performs better than what was reported by prior works on aqueous F- sensing.

Electrochemical process employing scrap metal waste as electrodes for dye removal.

In the present study, efficiency of electro-coagulation-flotation (EC-F) process using waste metal scrap of Al and Fe collected from construction and demolition waste of Indian Institute of Technology Madras (IIT M) campus for the removal of double azo bond dye Acid Red 66 (AR66) was studied. The key operating parameters such as current density and electrical conductivity were optimized individually with an initial dye concentration of 50 mg/L, at pH 7. Different electrode combinations and connection modes (parallel MP-P, series (MP-S, BP-S)) were tested, at pre-optimized conditions, in order to achieve better removal of AR66 dye with minimum energy consumption. Series connection in bipolar electrode mode (BP-S) showed better COD reduction from 164 mg/L to 26.2 mg/L with complete decolourization (BDL). Hybrid electrode system of Fe-Al-Fe-Al-Fe-Al showed maximum reduction of COD from 164 mg/L to 11.3 mg/L along with 86.3% TSS reduction and complete decolourization. LC-MS analysis showed the formation of intermediates with m/z 195, m/z 210.6 and m/z 159.3 due to the destruction of AR66 dye during electrolysis. Highest current efficiency (CE φ = 107%) was observed in case of hybrid electrode system compared to Al (φ = 30.1%) and Fe (φ = 98.3%) electrode system at similar operating conditions. Compared to the same electrode material as anode and cathode, use of appropriate hybrid electrode combination can improve the removal efficiency and reduce the energy consumption (ENC). The influence of aeration on the performance of the system was also studied. Aeration significantly improved the COD removal efficiency (98.3%) along with complete decolourization (100%). The use of waste metal scrap as electrodes reduced the overall cost of the treatment process from 1.6 $/m3 to 0.06 $/m3. Using waste metal scrap as electrodes not only reduces the metal accumulation in the environment but also reduces the cost of EC-F process.

Characterization of segregated greywater from Indian households-part B: emerging contaminants.

Emerging contaminants (ECs) have become an increasing area of concern due to the likely impacts of these compounds on human health and the environment. Generally, products which are used for households and personal care activities contribute to major percentage of ECs in household greywater. Not much information on the presence of xenobiotic organic compounds in greywater is currently available. Therefore, the present study focused on the qualitative and quantitative analyses of emerging contaminants from different classifications of Indian households. The qualitative screening of emerging pollutants by solid-phase extraction-gas chromatography and mass spectroscopy (SPE-GC-MS) showed the presence of 78 different emerging contaminants from three different sources, which are categorized into ten different groups based on their chemical properties. The quantitative analysis of few selected target pollutants such as phthalic esters, namely diethyl hexyl phthalate, diethyl phthalate, dibutyl phthalate, dioctyl phthalate, triclosan, bisphenol A, caffeine, acetaminophen, 3-methyl salicylic acid, 4-octylphenol, and 4-nonylphenol were found to be 0.38 ± 0.39 µg/L, 1.57 ± 1.54 µg/L, 4.77 ± 2.57 µg/L, 0.712 ± 0.17 µg/L, 5.82 ± 1.85 µg/L, 11.08 ± 2.64 µg/L, 2.30 ± 1.19 µg/L 13.18 ± 4.48 µg/L, 3.75 ± 1.90 µg/L, 4.95 ± 2.21 µg/L, and 5.96 µg/L, respectively. Risk assessment indicated that 63 compounds identified in the greywater can be considered priority pollutants. Based on the results obtained in the present study, effective zero-discharge liquid system can be designed for different sources of greywater and it can be recycled and reused without much risk. Graphical abstract .

Characterization of segregated greywater from Indian households: part A-physico-chemical and microbial parameters.

Greywater has attracted global attention as a feasible alternative water source over the last few decades. Reuse and recycling of greywater is an economically viable and attractive option for meeting the future water demand. However, its treatment and reliable reuse continue to be based on conventional parameters such as BOD, COD, turbidity, suspended solids and pathogen level. The current investigative study focused on the characterization of segregated grey wastewater (greywater from bathroom, laundry and kitchen) from different economic classes of Indian households which included physical and chemical parameters, organics, nutrients, pathogens, heavy metals, oil and grease and surfactants. Apart from this, the data related to water consumption, frequency and products used for their daily activities were gathered using a questionnaire survey. The average water consumption among different household was found to be 108 L per capita per day. The maximum concentrations of organics such as BOD (678.6 ± 179 mg/L), COD (1507 ± 508 mg/L) and TOC (176.4 ± 131 mg/L) were found in kitchen wastewater. However, maximum concentrations of surfactants (14.02 ± 3.74 mg/L) were obtained in laundry wastewater. Faecal coliform concentration was more in the households which had inhabitants of children below 4 years. Statistical analysis revealed that the parameters monitored differ significantly between different economic classes. The present study showed that the characteristics of greywater highly depend on the wastewater source, household behaviour and activities. This study will be helpful to design a sustainable cost-effective treatment system, enabling greywater generated from different sources to be safely recycled and reused by households. Graphical abstract.

Assessment of novel rotating bipolar multiple disc electrode electrocoagulation-flotation and pulsed plasma corona discharge for the treatment of textile dyes.

The current study evaluates the performance of the designed novel electrolytic reactor with rotating bipolar multiple disc electrode (RBDE) in the electrocoagulation-flotation (EC-F) process and a pulsed plasma reactor for the removal of toxic textile dyes. Two different classes of dyes, Methyl Orange (MO), an azo group of dye, and Reactive Blue 19 (RB19), a reactive group of dye, were selected. Efficient removal of both the dyes at a faster rate was obtained with the designed RBDE reactor compared to the EC-F process with static electrodes. RB19 and MO were completely decolourized (100%) within 2 min of electrolysis time with rotating and 6 min with static (non-rotating) electrodes, respectively. Similarly, the maximum chemical oxygen demand removal of 86.4% and 93.2% was obtained for RB19 and MO, respectively, with the rotating electrode EC-F process. On the other hand, complete decolourization was obtained in 10 min and 12 min of pulsed corona discharge for MO (50 mg/L) and RB19 (50 mg/L), respectively. The comparison studies of RBDE and pulsed power plasma reactor (PPT) showed that MO removal was faster than RB19 removal in both RBDE EC-F and PPT processes. Relatively long treatment time was needed for RB19 compared to MO due to its complexity of structure and high solubility. RB19 and MO were completely degraded through pulsed corona discharge without any sludge production. The results show that the designed RBDE reactor performed much better than existing conventional electrocoagulation reactors. The RBDE reactor can be used as a pre-treatment unit for industrial wastewater, which can improve the treatment efficiency and reduces the energy consumption. Plasma technology showed complete degradation of pollutant without sludge production. The formation of a wide variety of reactive oxygen species during corona discharge helps in degrading the pollutants. Plasma technology can be used as a secondary treatment system along with the RBDE as pre-treatment process for complex industrial wastewaters. This will improve the quality of treated effluent and reduce the overall cost of treatment.

Fate and impact of pharmaceuticals and personal care products during septage co-composting using an in-vessel composter.

The present study aimed at understanding the impact of pharmaceutical and personal care product (PPCP) load on compost dynamics and fate of PPCPs during the composting. In addition, the compost dynamics during single PPCP degradation and multiple PPCPs degradation were investigated. Results revealed that co-composting could degrade the pharmaceutical, carbamazepine (CBZ) up to 83% during single pollutant degradation while it was 66% during multiple pollutant system, at an initial concentration (IC) of 5 mg/kg dw. In case of personal care product, namely triclosan (TCS), single pollutant degradation resulted in 86% removal whereas the removal efficiency was 83% in multiple pollutant system. Relatively high concentration of CBZ showed a negative impact on compost dynamics compared to that of TCS. Higher IC resulted in lower temperature development and relatively lower pollutant removal. The study on pollutant transfer in compost solid surface and in leachate revealed that TCS was not leached out while the leaching of CBZ was significant during composting process. The various transformation products formed during composting were identified and tentative pathways for CBZ and TCS degradation were proposed.

Application and performance evaluation of a cost-effective vis- LED based fluidized bed reactor for the treatment of emerging contaminants.

Visible light induced photocatalysis is considered as one of the most potential technologies which can achieve new levels of sustainability in water treatment. The current study explores the performance of immobilized visible light active catalyst on inert media for light driven catalysis of pharmaceuticals. These coated media is used in a continuous flow fluidized column reactor equipped with spirally arranged visible Light Emitting Diodes (LEDs) as irradiation source. The treatment efficiency of the system is evaluated for the removal of pharmaceutical drugs such as carbamazepine, diclofenac and ibuprofen. For the present study, system parameters such as light intensity and flow rate are optimized for maximum removal rate. The system shows complete elimination of the pharmaceuticals under the given experimental conditions. Complete mineralization of the target compounds are confirmed by TOC analysis. Recyclability is an important attribute for full scale commercialization of a treatment technology. An investigation on the reusability study of the photocatalyst displayed no significant reduction in the removal efficiency for a run of six cycles, hence rendering the photocatalyst reusable. The results acquired indicate an immense potential for scaling up the photoreactor as a sustainable tertiary treatment technology in water treatment plants.

Validation of 'lock-and-key' mechanism of a metal-organic framework in selective sensing of triethylamine.

To develop the metal-organic framework (MOF)-based sensing of triethylamine (TEA) in an aqueous phase, Al-MIL-101-NH2 (MIL: Material Institute Lavoisier) with a tripod-like cavity was utilized based on a lock-and-key model. Al-MIL-101-NH2 (Al-MOF) was found to be an excellent fluorescent sensor for the TEA molecules in the range of 0.05-0.99 mM. The limit of detection (LOD) and linear calibration range of this probe towards TEA were found to be 3 µM and 0.05-0.40 mM, respectively. The mechanism of the sensing process indicates the dominant role of physical processes (e.g., non-covalent bond interactions). In addition, the exact fit of the TEA molecule (6.5 Å) in the tripod-like cavity (6.78 Å) supported the strong interaction between three ethyl groups (TEA) and aromatic rings (MOF). This kind of specific suitability between size/shape of the TEA and tripod-like cavity of MOF (ΔG: -46.7 kJ mol-1) was not found in other molecules such as ethylamine (ΔG: -2.20 kJ mol-1 and size: 3.7 Å), formaldehyde (ΔG: +1.50 kJ mol-1 and size: 2.8 Å), and ammonia (ΔG: +0.71 kJ mol-1 and size: 1.6 Å). As such, Al-MOF was found to be a selective and stable sensor for TEA.

Variation in cell surface characteristics and extracellular polymeric substances during the biodegradation of monocyclic and heterocyclic aromatic hydrocarbons in single and multi-substrate systems.

The variation in surface characteristics and the composition of extracellular polymeric substances (EPS) of bacterial cells during biodegradation of single and multi-aromatic hydrocarbons was investigated in the present study. The maximum cell surface hydrophobicity (CSH) of 80.1% was observed during the degradation of toluene. Bacterial cells acquired more negative surface charge with an increase in CSH and vice versa. Proteins constituted the major fraction of EPS during biodegradation of benzene and toluene with protein/carbohydrate ratio varying between 2.19 and 3.1. Carbohydrates constituted the major fraction of EPS in the presence of pyridine. A significant variation in cell surface characteristics was observed in multi-substrate systems involving heterocyclic and monocyclic aromatic hydrocarbons. An increase in EPS production (62.89 mg/g) did not facilitate enhanced degradation of hydrophobic substrates in multi-substrate system involving benzothiophene, benzofuran, benzene and toluene. Under toxic conditions, especially at higher concentration of target pollutants, a significant increase in concentration of polysaccharides was observed compared to proteins.

Technical, hygiene, economic, and life cycle assessment of full-scale moving bed biofilm reactors for wastewater treatment in India.

Moving bed biofilm reactor (MBBR) is a highly effective biological treatment process applied to treat both urban and industrial wastewaters in developing countries. The present study investigated the technical performance of ten full-scale MBBR systems located across India. The biochemical oxygen demand, chemical oxygen demand, total suspended solid, pathogens, and nutrient removal efficiencies were low as compared to the values claimed in literature. Plant 1 was considered for evaluation of environmental impacts using life cycle assessment approach. CML 2 baseline 2000 methodology was adopted, in which 11 impact categories were considered. The life cycle impact assessment results revealed that the main environmental hot spot of this system was energy consumption. Additionally, two scenarios were compared: scenario 1 (direct discharge of treated effluent, i.e., no reuse) and scenario 2 (effluent reuse and tap water replacement). The results showed that scenario 2 significantly reduce the environmental impact in all the categories ultimately decreasing the environmental burden. Moreover, significant economic and environmental benefits can be obtained in scenario 2 by replacing the freshwater demand for non-potable uses. To enhance the performance of wastewater treatment plant (WWTP), there is a need to optimize energy consumption and increase wastewater collection efficiency to maximize the operating capacity of plant and minimize overall environmental footprint. It was concluded that MBBR can be a good alternative for upgrading and optimizing existing municipal wastewater treatment plants with appropriate tertiary treatment. Graphical abstract ᅟ.