Trihalomethanes (THMs) are formed when excess chlorine during chlorination of water reacts with organic material in water. They have mutagenic and carcinogenic properties. Moringa oleifera (MO) has found wide acceptance by many people in Nigeria who have used it for food for both humans and fauna, for health purposes, and as a coagulant for water treatment. However, the seed husks are currently discarded as waste and they have not been used as adsorbent to remove THMs from water. The physicochemical properties of both the treated and raw surface water were determined using standard methods, and the concentration of THMs was determined from the water treatment plant at different stages of treatment using gas chromatography with flame ionization detector (GC-FID). Recovery experiments were carried out to validate the procedure. The efficiencies of activated carbon of Moringa oleifera seed husk (MOSH) adsorbent for the removal of THMs in the water and as a coagulant for water treatment were also assessed. Batch adsorption experiments were carried out, and different parameters such as pH (5, 7, and 9), adsorbent dosage (0.2, 0.4, and 0.8 g), contact time (30, 60, and 90 minutes), and initial concentration (0.2, 0.4, and 0.6 mg/l) were optimized for the removal of trichloromethane and tribromomethane using the MOSH activated carbon. Experimental adsorption data from different initial concentrations of trichloromethane and tribromomethane were used to test conformity with Langmuir and Freundlich adsorption isotherms. The percentage recovery from our procedures ranged from 96.0 ± 1.41 to 100.0 ± 0.00 for trichloromethane while for tribromomethane the range was 60 ± 2.82 to 100.0 ± 0.00. The mean percentage adsorption efficiencies for the simulation experiment ranged from 34.365 ± 1.41 to 93.135 ± 0.57 and from 41.870 ± 0.27 to 94.655 ± 0.41 for trichloromethane and tribromomethane, respectively. The optimum conditions for both trichloromethane and tribromomethane were pH 9, 0.8 g adsorbent dosage, 60-minute contact time, and 0.6 mg/l initial concentration. The optimum values of these parameters used for the adsorption of the two THMs in the surface water serving the treatment plant gave an efficiency of 100.00 ± 0.00%. The turbidity values for the coagulation experiment reduced from 9.76 ± 0.03 NTU in the raw water before coagulation to 5.92 ± 0.13 NTU after coagulation while all other physicochemical parameters of the surface water decreased in value except conductivity and total dissolved solid which increased from 104.5 ± 3.54 to 108.0 ± 2.83 μS/cm and 63.00 ± 11.31 to 83.0 ± 8.49 mg/l, respectively. The experimental data best fit into Langmuir than Freundlich adsorption isotherm. The study concluded that MOSH activated carbon could serve as an adsorbent for the removal of THMs, calcium, and sulphur from water samples.

Heavy metal contamination in drinking water remains a pervasive global challenge with significant consequences for environmental quality and human health. This review synthesizes findings from recent studies examining heavy metal concentrations in different sources of drinking water, including municipal tap water, groundwater, surface water, and bottled/sachet water across various geographical regions. The study used a systematic review of studies published from 2015 to 2024. The result showed a variation in the concentrations of heavy metals from all the sources, with tap water generally exhibiting lower heavy metal levels. Pb, Fe, Mn, and other metals persist in different sources and from many regions with levels above the permissible limits recommended by the World Health Organization (WHO) in some instances, which were sometimes linked to aging distribution systems and other pollution sources. Bottled and sachet water, commonly regarded as safer alternatives, also showed some levels of heavy metals such as Pb, Cd, and Cr, reflecting inconsistent packaging or production oversight. Surface waters display variability with heavy metals pollution, driven by industrial discharge, mining activities, agricultural runoff, and urban wastewater inputs. Groundwater sources, although naturally shielded, frequently contained elevated concentrations of As, Hg, and Ni due to both geological and anthropogenic factors. Pb concentrations were below detection limit in some of the published papers; however, the values reported in this study ranged from ND to 260.0 µg/L (tap water), ND to 0.259 mg/L (surface water), ND to 0.791 mg/L (groundwater), and ND to 123.15 µg/L (bottled water). Arsenic (As) concentrations ranged from ND to 692 µg/L from different sources, with the highest concentration from groundwater. Collectively, these patterns underscore the need for strengthened monitoring frameworks, improved water treatment technologies, and integrated pollution-prevention strategies. Addressing heavy metal contamination in drinking water requires coordinated policy approach and continuous monitoring to reduce human exposure and safeguard global public health.

Trichloroacetic acid (TCA), a chlorination-derived disinfection by-product, can persist in treated water and requires effective removal approaches. This study evaluated the performance of polyethylene terephthalate-derived activated carbon (PAC), periwinkle shell powder (PSP), and PAC–PSP composites for TCA removal, with emphasis on process optimisation, characterisation, equilibrium behaviour, reusability, and application to field water. PAC was produced from waste PET using cocoa pod husk-derived alkaline activation and carbonisation, while composites were prepared at PAC:PSP ratios of 70:30 (STC) and 40:60 (FSC). Adsorbents were characterised by Fourier-transform infrared spectroscopy and scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy. Batch experiments examined pH, adsorbent dosage, contact time, and initial TCA concentration. PAC achieved 99.33% removal at pH 9, 0.06 g dosage, and 4 min contact time, while maximum removals for STC, PSP, and FSC were 95.52%, 89.81%, and 88.86%, respectively. Under optimised conditions, field water TCA removal ranged from 86.51% to 98.04%, with STC achieving 94.28% removal in raw water and 98.04% in conventionally treated water. All adsorbents retained more than 75% removal efficiency through five regeneration cycles, although performance declined with repeated use. The Freundlich model provided a better empirical fit than the Langmuir model based on comparative coefficients of determination (R2). Overall, PAC, PSP and PAC–PSP composites demonstrated promising potential for TCA removal while supporting waste valorisation and circular water treatment strategies. PAC showed a 16.43% carbon yield and 1.97% ash content, while characterisation indicated distinct carbonaceous and mineral-rich surface features. The findings support practical waste-to-resource applications for sustainable domestic water treatment under the investigated operating conditions.

This preprint has been withdrawn at the request of the authors due to major errors in the data analysis and interpretation that significantly affect the validity of the reported findings and conclusions.

Pharmaceutical contaminants, particularly ciprofloxacin, persist in aquatic environments due to their chemical stability and low biodegradability, posing ecological and public health risks. This study reports the synthesis of graphene oxide from coconut shell biochar (CS-GO) as a sustainable and cost-effective adsorbent for ciprofloxacin removal from pharmaceutical wastewater. CS-GO was prepared via a modified Hummers’ method and characterised using Fourier Transform Infrared Spectroscopy (FT-IR), Scanning Electron Microscopy with energy-dispersive X-ray analysis (SEM-EDX), and X-ray Diffraction (XRD), revealing a heterogeneous, porous-looking surface morphology, abundant oxygen-containing functional groups, and crystalline features favourable for adsorption. Batch adsorption experiments were designed and optimised using Response Surface Methodology–Central Composite Design (RSM-CCD) to evaluate the effects of adsorbent dosage, contact time, temperature, pH, and initial ciprofloxacin concentration. Under optimised conditions (0.926 g CS-GO, 28.5 min, 28 °C, pH 7.4, 59.652 mg/L ciprofloxacin), a maximum removal efficiency of 95.4% was achieved. Adsorption followed the Langmuir isotherm (R² = 0.9475), indicating monolayer coverage on a homogeneous surface, with a maximum adsorption capacity of 1.5555 mg g⁻¹. Desorption and reusability studies demonstrated that CS-GO retained over 90% of its adsorption capacity after five cycles, confirming its structural stability and regeneration potential. Post-treatment physicochemical analysis revealed substantial reductions in ciprofloxacin concentration and other pollutants, with water quality approaching regulatory standards. These findings highlight the potential of CS-GO as a low-cost, eco-friendly, and effective adsorbent for pharmaceutical wastewater remediation, contributing to circular economy practices through the valorisation of agricultural waste.