Browsing by Author "Liberatus J. Mpaka"

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Adsorption kinetics of picloram on chitosan‑modified Strychnos pungens fruit shell activated carbon
(Springer, 2025-09) Liberatus J. Mpaka; Alinanuswe J. Mwakalesi
Activated carbon (AC) fabricated using Strychnos pungens fruit shells (biowaste) and encapsulated in a chitosan biopolymer (CHO) was applied for the removal of picloram from aqueous solutions. The synthesized activated carbon-chitosan beads (ACCHO) were characterized using Scanning Electron Microscopy (SEM), X-ray diffraction (XRD), Infrared spectroscopy (IR) and Emmett Teller (BET) surface area analysis. The findings demonstrated the successful encapsulation of AC to produce ACCHO with both crystalline and amorphous properties. The application of ACCHO for picloram removal was affected by solution pH, adsorbent dosage, and initial picloram concentration. The efficiency increased with adsorbent dosage, reaching an optimum at 40 g/L. Similarly, efficiency increased as pH increased from 2 to 6, but declined at pH 8. Optimal conditions of pH 6, 40 g/L ACCHO dosage and 50 mg/L picloram produced 88% removal efficiency. The picloram adsorption kinet- ics best fitted the pseudo-first order (PFO) model. Langmuir and Freundlich adsorp- tion isotherms provide a good description of the picloram adsorption process. The adsorption mechanism on ACCHO was postulated to involve multiple interactions caused by electrostatic and weak forces of attraction. The results of the current study suggest that ACCHO can be used as a potential adsorbent for removing picloram and similar chemicals from contaminated water.
Unexpected heroes: invasive macrophytes boost performance of faltering waste stabilization ponds
(Water Practice & Technology, 2026) Liberatus J. Mpaka; Alinanuswe J. Mwakalesi; Douglas Mushi
Waste stabilization ponds (WSPs) are a widely used technology for removing organic matter and pathogens from wastewater. However, their effectiveness is often hindered by hydraulic overload, sludge accumulation, and the proliferation of invasive macrophytes–the impacts of these challenges are not fully understood. In this study, standard methods were used to assess WSPs under these operational challenges for the removal efﬁciency of physical, nutrient, and organic pollutants, as well as faecal indicator bacteria (FIB); the extent of macrophyte occupancy; and the level of FIB colonizing invasive macrophyte − 3− roots. Results indicated high removal efﬁciencies (73.38–99.67%) for turbidity, total nitrogen, NO− 3 , NO2 , NH3, PO4 , BOD5, total coliforms, Escherichia coli, enterococci, and Clostridium perfringens, whereas total dissolved solids, electrical conductivity, and total phosphorus showed considerably lower removal (33.5–45.2%). Signiﬁcant correlations (r = 0.47–0.96, P < 0.05) were found between the removal efﬁciencies of physical, nutrient, and organic pollutants, as well as FIB, and macrophyte occupancy. Furthermore, high densities of FIB colonizing the macrophyte roots suggest that these roots may have positively contributed to the performance of the WSPs. The ﬁnal efﬂuent complied with East African standards for all pollutants except turbidity, BOD5, and FIB. This study reveals that ignoring WSP maintenance signiﬁcantly compromises treatment performance, with potential implications for public health, and underscores the role of macrophytes in enhancing the performance of faltering WSPs.