Phycoremediation integrated approach for the removal of pharmaceuticals and personal care products from wastewater - A review

An evaluation of conventional and nature-based technologies for controlling antibiotic-resistant bacteria and antibiotic-resistant genes in wastewater treatment plants

Antibiotic resistance is a globally recognized health concern which leads to longer hospital stays, increased morbidity, increased mortality, and higher medical costs. Understanding how antibiotic resistance persists and exchanges in environmental systems like soil, water, and wastewater are critically important for understanding the emergence of pathogens with new resistance profiles and the subsequent exposure of people who indirectly/directly come in contact with these pathogens. There are concerns about the widespread application of prophylactic antibiotics in the clinical and agriculture sectors, as well as chemicals/detergents used in food and manufacturing industries, especially the quaternary ammonium compounds which have been found responsible for the generation of resistant genes in water and soil. The rates of horizontal gene transfer increase where there is a lack of proper water/wastewater infrastructure, high antibiotic manufacturing industries, or endpoint users - such as hospitals and intensive agriculture. Conventional wastewater treatment technologies are often inefficient in the reduction of ARB/ARGs and provide the perfect combination of conditions for the development of antibiotic resistance. The wastewater discharged from municipal facilities may therefore be enriched with bacterial communities/pathogens and provide a suitable environment (due to the presence of nutrients and other pollutants) to enhance the transfer of antibiotic resistance. However, facilities with tertiary treatment (either traditional/emerging technologies) provide higher rates of reduction. This review provides a synthesis of the current understanding of wastewater treatment and antibiotic resistance, examining the drivers that may accelerate their possible transmission to a different environment, and highlighting the need for tertiary technologies used in treatment plants for the reduction of resistant bacteria/genes.

Utilization of microalgal-bacterial energy nexus improves CO2 sequestration and remediation of wastewater pollutants for beneficial environmental services

Carbon dioxide (CO2) emissions from the combustion of fossil fuels and coal are primary contributors of greenhouse gases leading to global climate change and warming. The toxicity of heavy metals and metalloids in the environment threatens ecological functionality, diversity and global human life. The ability of microalgae to thrive in harsh environments such as industrial wastewater, polluted lakes, and contaminated seawaters presents new, environmentally friendly, and less expensive CO2 remediation solutions. Numerous microalgal species grown in wastewater for industrial purposes may absorb and convert nitrogen, phosphorus, and organic matter into proteins, oil, and carbohydrates. In any multi-faceted micro-ecological system, the role of bacteria and their interactions with microalgae can be harnessed appropriately to enhance microalgae performance in either wastewater treatment or algal production systems. This algal-bacterial energy nexus review focuses on examining the processes used in the capture, storage, and biological fixation of CO2 by various microalgal species, as well as the optimized production of microalgae in open and closed cultivation systems. Microalgal production depends on different biotic and abiotic variables to ultimately deliver a high yield of microalgal biomass.

A pilot-scale study on the removal of binary mixture (ciprofloxacin and norfloxacin) by Scenedesmus obliquus: Optimization, biotransformation, and biofuel profile

Ciprofloxacin (CIP) and norfloxacin (NOR) belong to the organic contaminants of emerging concern (OCECs) that are frequently detected in wastewater matrices at ng/L to mg/L concentrations. This study investigates the potential of Scenedesmus obliquus in the treatment of CIP and NOR as a binary mixture from raw wastewater. Optimization of inoculum was done to find the required cell density concentration that has less inhibition and high removal. The optimum inoculum (cell density: 200 × 105 cells/mL and OD680: 1.0) has shown 75% removal with no inhibition of growth. A pilot scale study was conducted in controlled environment using high-rate algal pond to investigate the contribution of abiotic and biotic removal. Abiotic removal is negligible in comparison with the biotic contribution of removal. The order of removal efficiency is observed as COD (88%) > NOR (84.8%) > CIP (84.6%) > NH4+ (71.7%) with biodegradation as the major removal mechanism. Biotransformed products of CIP + NOR were identified inside the Scenedesmus obliquus. During the pilot-scale study, Biomass (3.70 ± 0.07 g/L) was harvested with carbohydrates (17.85 ± 0.1%), lipids (38.36 ± 0.13%), and proteins (28.18 ± 1.63%). Lipid productivity in binary mixture was 2.6 times higher than the lipid production in control condition. Transesterification of these lipids yielded good biofuel composition of 32.72% of saturated fatty acids and 21.7% of unsaturated fatty acids.

An investigation on removal of ciprofloxacin and norfloxacin by phycoremediation with an emphasis on acute toxicity and biochemical composition

Ciprofloxacin (CIP) and norfloxacin (NOR) belong to the class of emerging contaminants that are frequently detected in the aquatic environment as a binary mixture, responsible for the development of antibiotic-resistant genes and antibiotic-resistant bacteria. This study aims to investigate five different algal species Chlorella vulgaris (Cv), Chlorella pyrenoidosa (Cp), Scenedesmus obliquus (So), Tetradesmus sp (T) and Monoraphidium sp (M) for their tolerance and removal of binary mixture. The effects on biochemical composition in the algal species concerning the binary mixture and its removal efficiency are first reported in this study. The acute toxicity (96 h EC50) values are in the order of So > Cp > T > M > Cv, Chlorella vulgaris is the most sensitive algal species with 17.73 ± 0.24 mg/L and Scenedesmus obliquus is the least sensitive algal species with 39.19 ± 0.79 mg/L. The removal efficiency of the binary mixture was found to be in the order of So > Cp > T > M > Cv, Scenedesmus obliquus removed CIP (52.4%) and NOR (87.5%) with biodegradation as the major contributing removal mechanism. Furthermore, less toxic biotransformed products were detected in Scenedesmus obliquus and the biochemical characterization revealed that the growth-stimulating effect is higher with lipid (35%), carbohydrate (18%), and protein (33%) providing an advantage in the production of valuable biomass.

Recent advances in the biological treatment of wastewater rich in emerging pollutants produced by pharmaceutical industrial discharges

Pharmaceuticals and personal care products present potential risks to human health and the environment. In particular, wastewater treatment plants often detect emerging pollutants that disrupt biological treatment. The activated sludge process is a traditional biological method with a lower capital cost and limited operating requirements than more advanced treatment methods. In addition, the membrane bioreactor combines a membrane module and a bioreactor, widely used as an advanced method for treating pharmaceutical wastewater with good pollution performance. Indeed, the fouling of the membrane remains a major problem in this process. In addition, anaerobic membrane bioreactors can treat complex pharmaceutical waste while recovering energy and producing nutrient-rich wastewater for irrigation. Wastewater characterizations have shown that wastewater's high organic matter content facilitates the selection of low-cost, low-nutrient, low-surface-area, and effective anaerobic methods for drug degradation and reduces pollution. However, to improve the biological treatment, researchers have turned to hybrid processes in which all physical, chemical, and biological treatment methods are integrated to remove various emerging contaminants effectively. Hybrid systems can generate bioenergy, which helps reduce the operating costs of the pharmaceutical waste treatment system. To find the most effective treatment technique for our research, this work lists the different biological treatment techniques cited in the literature, such as activated sludge, membrane bioreactor, anaerobic treatment, and hybrid treatment, combining physicochemical and biological techniques.

Catalytic Activation of Hydrogen Peroxide Using Highly Porous Hydrothermally Modified Manganese Catalysts for Removal of Azithromycin Antibiotic from Aqueous Solution

Hydrogen peroxide catalytic activation holds great promise in the treatment of persistent pollutants. In this study, the novel Mn-Acacair/Al, Mn-Acacarg/Al and Mn-BTCarg/Al catalysts, supported on Al2O3, were applied for rapid hydrogen peroxide activation and azithromycin antibiotic removal. The catalysts were prepared by the calcination-hydrothermal method under air or argon atmosphere. The characterization confirmed that the modification of manganese with acetylacetonate and benzene-1,3,5-tricarboxylic acid (H3BTC) O-donor ligands highly improves the catalyst porosity, amorphousity, and abundance of coordinately unsaturated sites, which facilitate the generation of reactive oxygen species. The hydrogen peroxide activation and azithromycin removal reached 98.4% and 99.3% after 40 min using the Mn-BTCarg/Al catalyst with incredible stability and reusability. Only a 5.2% decrease in activity and less than 2% manganese releasing in solutions were detected after five regeneration cycles under the optimum operating conditions. The removal intermediates were identified by LC-MS/MS analysis, and the pathways were proposed. The hydroxylation and decarboxylation reactions play a key role in the degradation reaction.

Recent advances on microalgae cultivation for simultaneous biomass production and removal of wastewater pollutants to achieve circular economy

Microalgae are known for containing high value compounds and its significant role in sequestering carbon dioxide. This review mainly focuses on the emerging microalgae cultivation technologies such as nanomaterials technology that can improve light distribution during microalgae cultivation, attached cultivation and co-cultivation approaches that can improve growth and proliferation of algal cells, biomass yield and lipid accumulation in microalgal. This review includes a comprehensive discussion on the use of microbubbles technology to enhance aerated bubble capacity in photobioreactor to improve microalgal growth. This is followed by discussion on the role of microalgae as phycoremediation agent in removal of contaminants from wastewater, leading to better water quality and high productivity of shellfish. The review also includes techno-economic assessment of microalgae biorefinery technology, which is useful for scaling up the microalgal biofuel production system or integrated microalgae-shellfish cultivation system to support circular economy.

Effect of Applied Electrical Stimuli to Interdigitated Electrode Sensors While Detecting 17α-Ethinylestradiol in Water Samples

The effect of impedance measurements of applied voltage on the detection of 17α-ethinylestradiol (EE2) in water samples using interdigitated electrodes (IDE) coated or not with thin films, is described. Firstly, the effect of immersion in EE2 aqueous solutions of layer-by-layer films prepared with poly(allylamine hydrochloride) (PAH), graphene oxide (GO), poly(1-(4-(3-carboxy-4-hydroxyphenylazo) benzene sulfonamido) 1,2 ethanediyl, sodium salt) (PAZO), polyethylenimine (PEI) and poly(sodium 4-styrenesulfonate) (PSS) was analyzed. These results demonstrated that PAH/GO films desorb during the immersion on EE2 solutions, while EE2 adsorbs on PAH/PAZO and PEI/PSS films with characteristic time values of 16.7 and 7.1 min, respectively, demonstrating that both films are adequate for the development of EE2 sensors. However, as the adsorption characteristic time is shorter, and the EE2 adsorbed amount is smaller, the PEI/PSS films are more suitable for the development of sensors. The effect of the applied voltage was analyzed using both IDEs covered with PEI/PSS films as well as those uncoated. The capacitance spectra are best fitted to analyze this effect, and the loss tangent spectra are advantageous to analyze the aqueous media. Furthermore, it was concluded that lower voltage values are best suited to perform measurements of this nature, given that higher voltages lead to less reliable results and cause irreparable damage to the sensors.