Photochemical transformation of pharmaceuticals plays an important role in their natural attenuation, especially in lagoon-based wastewater treatment plants and surface waters receiving substantial sunlight. In this study, the photodegradation of five important pharmaceuticals was studied in samples obtained from a wastewater treatment plant and surface water sources. Batch photodegradation studies for a mixture of pharmaceuticals (diclofenac, sulfamethoxazole, acetaminophen, carbamazepine and gemfibrozil) were carried out in a photochemical reactor. Multiple aliquots of samples removed from the reactor during the experiment were analyzed through high-performance liquid chromatography (HPLC) coupled to a photodiode array (PDA) detector. Intermediate products formed due to photodegradation were identified by ultra-high-performance liquid chromatography coupled with a time-of-flight mass spectrometry (UHPLC-MS/MS). Diclofenac and sulfamethoxazole were found to undergo direct photodegradation due to strong light absorption, whereas the indirect route of photosensitized degradation in the presence of dissolved organic matter (DOM) and model humic acid was significant for acetaminophen, carbamazepine, and gemfibrozil. The reactive radicals such as hydroxyl (OH•), singlet oxygen (1O2) and excited states of DOM (*DOM) were predominantly responsible for the indirect photodegradation of acetaminophen, gemfibrozil and carbamazepine, respectively. Computational analysis revealed that chlorine and carbon atoms belonging to the benzene ring of diclofenac were more reactive to radical attack. Sulfamethoxazole photodegradation occurred through oxidation of the NH2 group. Acetaminophen was more susceptible to electrophilic radical attack at the O-11, and N-7 positions and carbon atoms ortho to the phenolic oxygen and the amine group. The double bonds between C-7, C-8 and C-13 were the most reactive sites for carbamazepine that participated in the phototransformation pathway. Organic matter plays a critical role in the photodegradation of emerging contaminants. The coupling of DFT calculations with UHPLC-MS/MS analysis provided insights on key functional groups participating in the phototransformation pathway. Thus, both parent pharmaceuticals and the photodegradation intermediates should be considered during wastewater treatment. ... Read more

Dissolved organic matter (DOM) is the primary precursor that reacts with chlorine to form potentially carcinogenic/mutagenic disinfection byproducts (DBPs). The prime objective of this study was to compare the nature of DOM in samples collected from drinking water and wastewater treatment plants in western India and to relate their nature and concentration to trihalomethane (THM) formation. The effects of chlorine dose, bromide ion, contact time, and pH on THM formation were also studied. The surrogate parameters, such as UV absorbance at 254 nm and dissolved organic carbon (DOC) were monitored for each experiment to understand their correlation with THM formation in the selected water and wastewater systems. Fluorescence spectroscopy revealed that DOM in wastewater was dominated by protein-like components, while DOM in water samples consisted mostly of humic-like components, which exhibited greater THM formation potential. Fractionation of DOM into various fractions followed by reaction with chlorine revealed that the hydrophobic acid and neutral fractions of DOM were primarily responsible for THM formation. Thus, methods that target removing these fractions before chlorination would have maximum impact on reducing THM formation. ... Read more

In the present study, wastewater samples acquired from five wastewater treatment plants (WWTPs), located in western India were characterized using fluorescence spectroscopy, and resin-based fractionation was conducted to fractionate DOM into hydrophobic and hydrophilic base, acid, and neutral fractions. Among several fractions, the hydrophilic acid (HIA) and hydrophilic neutral (HIN) fractions were present in higher abundance (more than 50% of DOC) compared to the hydrophilic base (HIB) fraction in both influent and effluent wastewater stream obtained from WWTPs. Tryptophan-like and tyrosine-like substances were also abundant in the influent and effluent stream of WWTPs. Further, LC-MS/MS analysis could identify 235 and 288 DOM proteins in the influent and effluent stream of WWTP-1, respectively. These proteins revealed varying percentage of tryptophan and tyrosine residues. The tryptophan residues primarily contributed to protein-like fluorescence in wastewater. The proteins were further classified based on their role in biological processes, location in the cell, and molecular function. Among several proteins, Alzheimer's and Huntington disease biomarkers were identified at WWTP-1. Their presence in the surface water can serve as an early warning system for wastewater-based epidemiology. ... Read more

Pharmaceutical compounds are categorized as contaminants of emerging concern owing to their widespread consumption, persistence in the aquatic environment, development of antibiotic resistance in microorganisms, and growing evidence of chronic and endocrine disruption effects. Therefore, pharmaceuticals have been reported to exist in numerous environmental compartments, including surface water, groundwater, and drinking water throughout the world. The principal pathway of entry of these compounds into water bodies is via treated and untreated sewage. In aquatic environments, natural attenuation of pharmaceuticals takes place through various physical, chemical, and biological processes, including dispersion and dilution, volatilization, sorption onto sediments, biotransformation, and phototransformation. Among the listed attenuation processes, both direct and indirect phototransformation play an important role in deciding the fate of pharmaceuticals. In addition to cations and anions present in the aquatic environment, dissolved organic matter (DOM) can have multiple impacts during photolytic degradation, such as photosensitization, light screening, scavenging, and oxidative inhibition. The absorption of UV rays by DOM results in the formation of a variety of photochemically produced reactive radicals, such as triplet excited states of DOM (3DOM), hydroxyl radical (HO•), and singlet oxygen (1O2). This work presents a thorough assessment of various attenuation processes, with specific attention to aqueous photochemistry of pharmaceuticals evaluated using laboratory-scale and on-site observations. This review will highlight the general extent of natural attenuation for specific classes of pharmaceuticals and focus on the governing mechanisms—underlying such attenuation processes based on studies conducted worldwide. ... Read more

The manufacture and use of pharmaceuticals for human and veterinary use is on the rise in Southeast Asian countries. Thus, the discharge from wastewater treatment plants may contain pharmaceuticals across a wide range of drug classes. Various regions in Southeast Asia are characterized by species richness, presence of threatened species and diversity of endemic species. The rapidly growing economy, aquaculture and livestock industries, increased incidence of infectious diseases, and change in lifestyle may adversely affect these biodiversity hotspots due to increased release of pharmaceuticals. This review focuses on use and occurrence of five commonly used pharmaceutics, i.e., atenolol, carbamazepine, diclofenac, sulfamethoxazole, and 17 α-ethinylestradiol in the influent and effluent of wastewater treatment plants and in various aquatic environments, i.e., surface water, groundwater, marine environment and sediments. Threats posed by these pharmaceuticals are evident from a discussion on their adverse effects on various freshwater species. Species sensitivity distribution (SSD) constructed for each of the pharmaceuticals using reproductive toxicity data for universal biomarker species reported in the literature, reveal the community level toxic effects of these pharmaceuticals in the aquatic ecosystem. Based on SSD and occurrence data, 17 α-ethinylestradiol poses the highest risk, while atenolol and carbamazepine poses negligible risk on reproductive toxicity/reproductive failure at the concentrations currently prevailing in the aquatic environment. The high risk posed by 17 α-ethinylestradiol is due to its ability to cause reproductive failure and/or vitellogenin induction at concentrations of the order of ng/L. ... Read more

Currently, there is increasing awareness regarding the effect of antibiotics on various organisms in the ecosystem even though they may occur at relatively low concentration. Thus, their concentration needs to be quantified precisely in various matrices including ground water, surface water, and municipal wastewater. The use of liquid chromatography together with high-resolution mass spectrometry (HR-LC-MS/MS) has enhanced the reliability, accessibility, and accuracy with which antibiotics can be detected. In the present study, a HR-LC-MS/MS-based method was developed for four antibiotics (ciprofloxacin, norfloxacin, azithromycin, and sulfamethoxazole). Initially, various mobile phases and LC columns were evaluated. The effect of solution pH, drying time of cartridge, and solvent used in the concentration step on recovery of antibiotics during solid-phase extraction (SPE) was also evaluated. Subsequently, the recovery of antibiotics from influent and effluent wastewater samples, obtained from a wastewater treatment plant (WWTP) in India, was determined based on the matrix spike method. The results revealed that for these wastewater samples even the use of structurally similar, isotopically labelled (deuterated) standards could not adequately improve the recovery of target antibiotics. ... Read more

The objective of this study was to study the occurrence, fate, and seasonal variations of pharmaceuticals at two urban wastewater treatment plants (WWTPs) in India and compare the results with a similar study conducted in the United States. This is the first study of its kind in comparing occurrence and fate of pharmaceuticals in wastewater of two different countries with the same methodology and analytical techniques. Twelve most relevant pharmaceuticals were selected for seasonal monitoring at two Indian WWTPs based on the comprehensive survey and through literature review. The yearly average influent concentrations of total pharmaceuticals were found to be 537 ± 5 μg/L at WWTP-1 and 353 ± 9 μg/L at WWTP-2. WWTP-2 exhibited comparatively higher removal efficiency of total pharmaceuticals (85% versus 59%, excluding monsoon season), possibly due to the cyclic activated sludge technology followed by chlorination employed at WWTP-2. Comparison with a similar study conducted in the United States revealed that concentration of most of the pharmaceuticals detected in the U.S. WWTPs were, on an average, more than 50% lower. U.S. WWTPs also exhibited 10–30% higher removal efficiencies for total pharmaceuticals. Our study results show that preliminary treatment and biological treatment alone are not adequate for complete removal of pharmaceuticals and polishing step and tertiary treatment is a necessity if higher removal of pharmaceuticals is desired in Indian WWTPs. Information obtained from this study will not only aid the local utilities but will also benefit understanding of global trends in usage of pharmaceuticals and their distribution in the environment. ... Read more