The paper presents the antibacterial and antioxidant activities of silver nanoparticles (AgNPs) when conjugated with two antibiotics levofloxacin and ciprofloxacin as well as biologically synthesized nanoparticles from Moringa oleifera and Curcuma longa. Leaves of Moringa and powder of Curcuma were used in the green synthesis of silver nanoparticles. Ultraviolet-visible spectroscopy (UV), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) were used for the characterization of the synthesized silver nanoparticles. Comparison of levofloxacin and ciprofloxacin and their conjugated AgNPs was also studied for antibacterial and antioxidant activity. The synthesis of Moringa-AgNPs, turmeric-AgNPs, levofloxacin-AgNPs, and ciprofloxacin-AgNPs was confirmed by UV spectroscopy. An absorption peak value of 400-450 nm was observed, and light to dark brown color indicated the synthesis of AgNPs. Moringa-AgNPs revealed high antioxidant activity (80.3 ± 3.14) among all of the synthesized AgNPs. Lev-AgNPs displayed the highest zone of inhibition for Staphylococcus aureus, while in Escherichia coli, Cip-AgNPs showed high antibacterial activity. Furthermore, AgNPs synthesized using green methods exhibit high and efficient antimicrobial activities against two food-borne pathogens. Biologically synthesized nanoparticles exhibited antibacterial activity against E. coli (13.73 ± 0.46 with Tur-AgNPs and 13.53 ± 0.32 with Mor-AgNPs) and S. aureus (14.16 ± 0.24 with Tur-AgNPs and 13.36 ± 0.77 with Mor-AgNPs) by using a well diffusion method with significant shrinkage and damage of the bacterial cell wall, whereas antibiotic-conjugated nanoparticles showed high antibacterial activity compared to biologically synthesized nanoparticles with 14.4 ± 0.37 for Cip-AgNPs and 13.93 ± 0.2 for Lev-AgNPs for E. coli and 13.3 ± 0.43 for Cip-AgNPs and 14.33 ± 0.12 for Lev-AgNPs for S. aureus. The enhanced efficiency of conjugated silver nanoparticles is attributed to their increased surface area compared to larger particles. Conjugation of different functional groups contributes to improved reactivity, creating active sites for catalytic reactions. Additionally, the precise control over the size and shape of green-synthesized nanoparticles further augments their catalytic and antibiotic activities.

Farmers near towns and cities are using a wide range of highly polluted wastewaters for crop irrigation in Pakistan due to severe freshwater shortage. The present study aimed to promote indigenous bacterial strains isolated from domestic, hospital, textile, pharmaceutical and mixed wastewaters to remove contaminants and colour and render these wastewaters safer for irrigation. Thirty seven bacterial strains were isolated from five wastewater samples collected from different sites in Lahore, Pakistan. Under optimal growth conditions, three isolates (D6, D7 and P1) showed >93% decolourisation potential in the treatment of hospital wastewater. 16S rDNA sequencing identified two of these isolates (D6 and D7) as showing 100% and 99.86% homology to Bacillus paramycoides spp. – novel strains from B. cereus group. Isolate P1 showed 97.47% homology to Alcaligenes faecalis. GCMS analysis of the untreated hospital wastewater revealed the presence of pharmaceutic pollutants, i.e. Phenol (876 µg/L), Salicylic acid (48 µg/L), Caffeine (7 µg/L), Naproxen (23 µg/L), Octadecene (185 µg/L) and Diazepam (14 µg/L). The analysis of treated hospital wastewaters showed percentage degradation of pharmaceutic pollutants (100%–43%) and significant reduction in the BOD₅ (91%–68%), COD (89%–52%) and heavy metals concentrations. These strains therefore can represent a low-cost and low-tech alternative to bioremediate complex matrices of hospital wastewater prior to crop irrigation to support the achievement of clean re-usable water in developing countries like Pakistan. GRAPHICAL ABSTRACT

Farmers near towns and cities are using wide range of untreated wastewaters for crop irrigation in Pakistan due to severe freshwater shortage. The present study aimed to treat different types of wastewater including domestic, hospital, textile, pharmaceutical and mixed wastewaters using indigenous bacterial isolates to remove contaminants and render these wastewaters safer for irrigation. 37 bacterial strains were isolated from the 5 wastewater samples collected from different sites in Lahore, Pakistan. Under optimum growth conditions, the isolates D6, D7 and P1 showed maximum decolourisation potential of 96, 96, 93 %, respectively against hospital wastewater. GCMS analysis of the untreated hospital wastewater confirmed the presence of pharmaceutic pollutants i.e. Phenol, Salicylic acid, Caffeine, Naproxen, Octadecene and Diazepam. These organic compounds were biodegraded into derivate Ticlopidine in the case of isolate D6, derivatives Tetradecene and Griseofulvin in the case of isolate D7, and derivatives Lidocaine and Butalbital in the case of isolate P1. 16S rDNA sequencing was used to identify these isolates. Isolates D6 and D7 showed 100 and 99.86 % homology to Bacillus paramycoides , a novel strain from Bacillus cereus group (Liu et al., 2017). Isolate P1 showed 97.47 % homology to Alcaligenes faecalis . These strains therefore could represent a low-cost and low-tech alternative to bioremediate complex wastewaters prior to irrigation to support the achievement of the Sustainable Development Goal 6 - clean water and sanitation in Pakistan.

The presence of antibiotics in the wastewater is a growing concern, as they tend to bioaccumulate and are increasing the resistance of bacteria. This study investigates the microbial degradation of ciprofloxacin (CIP) in water using Escherichia coli (E. coli) and Enterococcus faecium (E. faecium). This research aims to degrade the ciprofloxacin antibiotic, which is creating multiple problems in the environment and wastewater. Bacterial strains were isolated from wastewater and sludge samples, and their identities were confirmed through 16S rRNA sequencing. The degradation potential was assessed using a shake flask method under varying conditions, including different antibiotic concentrations, temperatures, pH levels, and inoculum densities. E. coli effectively degraded CIP, achieving 90% degradation at 50 mg/L in 18 days, in optimal conditions like a temperature of 37 °C, a pH of 6.5, and an inoculum concentration of 10⁻⁸ CFU/mL. However, at higher concentrations (150 mg/L), degradation decreased. Similarly, E. faecium showed a maximum degradation rate of 100% at 50 mg/L of CIP in 18 days, with optimal degradation occurring at 40 °C, a pH of 6.5, and an inoculum density of 10⁻⁸ CFU/mL. This study underscores the effectiveness of selected microbial strains in bioremediation processes, highlighting their potential application in mitigating antibiotic pollution in aquatic environments. This is the preliminary study to explore the potential of isolated bacteria to degrade CIP, and their degradation ability can be utilized to develop a CIP-contaminated wastewater treatment plant.

The increasing human population continues to exert pressure on the freshwater scarcity. The availability of freshwater for crop irrigation has become challenging. The present study aimed to use domestic wastewater (DWW) for the irrigation of two rice cultivars (CVs) after treatment with the bacterial strain Alcaligenes faecalis MT477813 under a hydroponic culture system. The first part of this study focused on the bioremediation and analysis of the physicochemical parameters of DWW to compare pollutants before and after treatment. The biotreatment of DWW with the bacterial isolate showed more than 90% decolourisation, along with a reduction in contaminants. The next part of the study evaluated the impacts of treated and untreated DWW on the growth of two rice cultivars, i.e., PK 386 and Basmati 515, under a hydroponic culture system which provided nutrients and water to plants with equal and higher yields compared to soil. Growth parameters such as the shoot and root length and the wet and dry weights of the rice plants grown in the treated DWW were considerably higher than those for the plants grown in untreated DWW. Therefore, enhanced growth of both rice cultivars grown in biotreated DWW was observed. These results demonstrate the bioremediation efficiency of the bacterial isolate and the utility of the DWW for rice crop irrigation subsequent to biotreatment.

Raw hospital wastewater is a source of excessive heavy metals and pharmaceutical pollutants. In water-stressed countries such as Pakistan, the practice of unsafe reuse by local farmers for crop irrigation is of major concern. In our previous work, we developed a low-cost bacterial consortium wastewater treatment method. Here, in a two-part study, we first aimed to find what physico-chemical parameters were the most important for differentiating consortium-treated and untreated wastewater for its safe reuse. This was achieved using a Kruskal–Wallis test on a suite of physico-chemical measurements to find those parameters which were differentially abundant between consortium-treated and untreated wastewater. The differentially abundant parameters were then input to a Random Forest classifier. The classifier showed that ‘turbidity’ was the most influential parameter for predicting biotreatment. In the second part of our study, we wanted to know if the consortium-treated wastewater was safe for crop irrigation. We therefore carried out a plant growth experiment using a range of popular crop plants in Pakistan (Radish, Cauliflower, Hot pepper, Rice and Wheat), which were grown using irrigation from consortium-treated and untreated hospital wastewater at a range of dilutions (turbidity levels) and performed a phytotoxicity assessment. Our results showed an increasing trend in germination indices and a decreasing one in phytotoxicity indices in plants after irrigation with consortium-treated hospital wastewater (at each dilution/turbidity measure). The comparative study of growth between plants showed the following trend: Cauliflower > Radish > Wheat > Rice > Hot pepper. Cauliflower was the most adaptive plant (PI: −0.28, −0.13, −0.16, −0.06) for the treated hospital wastewater, while hot pepper was susceptible for reuse; hence, we conclude that bacterial consortium-treated hospital wastewater is safe for reuse for the irrigation of cauliflower, radish, wheat and rice. We further conclude that turbidity is the most influential parameter for predicting bio-treatment efficiency prior to water reuse. This method, therefore, could represent a low-cost, low-tech and safe means for farmers to grow crops in water stressed areas.