Attached growth processes for wastewater treatment have significantly been improved during recent years. Their application can be extended to sustainable municipal wastewater treatment in remote locations and in developing countries for the purpose of organic matter (biochemical oxygen demand, BOD) removal and pathogenic decontamination. The aim of this study is to assess selected packing media for biological trickling filters (BTFs) and to develop a simplified model for describing the capacity of BOD removal in BTFs. In this work, BTFs with four different media viz., rubber, polystyrene, plastic and stone have been investigated at two temperature ranges of 5–15°C and 25–35°C. The average removal of both chemical oxygen demand and BOD was higher than 80 and 90% at temperature ranges of 5–15 and 25–35°C, respectively. The geometric mean of faecal coliforms in BTF using polystyrene, plastic, rubber and stone as filter media was reduced by 4.3, 4.0, 5.8 and 5.4 log₁₀, respectively, at a low temperature range of 5–15°C. At a higher temperature range of 25–35°C, the faecal coliform count was reduced by 3.97, 5.34, 5.36 and 4.37 log₁₀ from polystyrene, plastic, rubber and stone media BTF, respectively. Simplified model was developed and used to estimate the optimal BOD loading rates (B_vd) for designing robust BTF systems, with appropriate filter media. It has been concluded that highly efficient BTFs can be designed using various filter media, which may be capable of treating organic loading rates of more than 3 kg BOD/m³ day. These types of BTFs can be applied for the BOD and microbial contaminants removal of wastewater for potential reuse in developing countries.

At present time, every nation is absolutely concern about increasing agricultural production and bioremediation of petroleum-contaminated soil. Hence, with this intention in the current study potent natural surfactants characterized as lipopeptides were evaluated for low-cost production by Bacillus subtilis SNW3, previously isolated from the Fimkessar oil field, Chakwal Pakistan. The significant results were obtained by using substrates in combination (white beans powder (6% w/v) + waste frying oil (1.5% w/v) and (0.1% w/v) urea) with lipopeptides yield of about 1.17 g/L contributing 99% reduction in cost required for medium preparation. To the best of our knowledge, no single report is presently describing lipopeptide production by Bacillus subtilis using white beans powder as a culture medium. Additionally, produced lipopeptides display great physicochemical properties of surface tension reduction value (SFT = 28.8 mN/m), significant oil displacement activity (ODA = 4.9 cm), excessive emulsification ability (E24 = 69.8%), and attains critical micelle concentration (CMC) value at 0.58 mg/mL. Furthermore, biosurfactants produced exhibit excellent stability over an extensive range of pH (1–11), salinity (1–8%), temperature (20–121°C), and even after autoclaving. Subsequently, produced lipopeptides are proved suitable for bioremediation of crude oil (86%) and as potent plant growth-promoting agent that significantly (P < 0.05) increase seed germination and plant growth promotion of chili pepper, lettuce, tomato, and pea maximum at a concentration of (0.7 g/100 mL), showed as a potential agent for agriculture and bioremediation processes by lowering economic and environmental stress. Graphical Abstract

Synergistic combinations of various antimicrobial agents are considered ideal strategies in combating clinical and multidrug resistant (MDR) infections. In this study, antibacterial potential of Jatropha curcas crude seed extracts, seed oil, commercially available antibiotics, and their combinations were investigated for their synergistic effect against clinical, MDR and ATCC bacterial strains by agar well diffusion assay. Methanolic extracts remained more active against Staphylococcus aureus (ATCC), with zone of inhibition (ZOI) of 21 mm, than clinical and methicillin-resistant S. aureus (MRSA) strains (ZOI range ~ 15.0–17.0 mm). Molecular docking demonstrated that beta-monolaurin from methanolic extract exhibited greater affinity conformation for UDP-N-acetylmuramoyl-tripeptide–d-alanyl-d-alanine (MurF) ligase’s active pocket with binding energy of -7.3 kcal/mol. Moxifloxacin exhibited greater activity against Escherichia coli (ATCC) (ZOI ~ 50.0 mm), followed by ofloxacin against Pseudomonas chlororaphis (47.3 mm), moxifloxacin against P. monteilii (47 mm), P. aeruginosa (46.3 mm) and MRSA2 (46 mm) and ofloxacin against S. aureus (ATCC) strains (45.7 mm). Methanolic extract in combination with rifampicin showed the highest synergism against MRSA strains, A. baumannii, E. coli, E. faecalis, S. aureus, and P. aeruginosa, A. baumannii (MDR strain), P. chlororaphis, E. coli ATCC25922 and S. aureus ATCC25923. In combinations, moxifloxacin exhibited the highest antagonism. The methanolic, n-hexane, aqueous extracts and seed oil in various combinations with antibiotics showed 44.71, 32.94, 9.41 and 25.88% synergism, respectively. The current study showed that potency of antibiotics was improved when screened in combination with J. curcas seed’s components, supporting the drug combination strategy to combat antibacterial resistance.