https://ir.cut.ac.zw/xmlui/handle/123456789/407 Department of Environmental Engineering Research Articles Thu, 16 Jul 2026 22:28:36 GMT 2026-07-16T22:28:36Z https://ir.cut.ac.zw/xmlui/handle/123456789/585 Regeneration, recycling, and disposal of spent biochars Mpeta, Miranda; Wenga, Terrence; Marondedze, Kudzanayi Andrew; Sadondo, Phenias Among the technologies that are employed to immobilize and degrade both organic and inorganic contaminants in vari ous polluted environmental compartments, biomass-based biochar has been demonstrated to be an effective and environmentally friendly strategy (Crini et al., 2019; Liao et al., 2022; Nguyen et al., 2023; Rasheed et al., 2020; Wang et al., 2020). In addition, biochar has several other advantages, for instance, high-cost efficiency due to the abundance of low-cost feedstock, as well as simplicity of preparation methods (Barquilha & Braga, 2021). To further improve the biochar pollutant removal efficiency and capture capacity, increasing efforts are currently being carried out to design and develop biochar with improved properties for the immobilization of both organic and inorganic pollutants (Dutt et al., 2020; Liao et al., 2022). However, the main drawback is the management of the spent biochar loaded and concentrated with various pollutants (Hossain et al., 2020). Several technologies are available for the recovery of spent biochar, including filtration, sedimentation, centrifugation, and magnetic separation (Kar et al., 2022). The spent biochar is then either regenerated for reuse or safe disposal via landfilling or incineration (Kozyatnyk et al., 2020), as illustrated in Fig. 20.1. Regeneration of spent biochar for several other decontamination cycles further lowers the running and operational cost of remediating the contaminated environmental media. In essence, biochar’s high recycling and reuse capabilities are fundamental for the economic management of polluted environments (Herath et al., 2021 Wed, 01 Jan 2025 00:00:00 GMT https://ir.cut.ac.zw/xmlui/handle/123456789/585 2025-01-01T00:00:00Z https://ir.cut.ac.zw/xmlui/handle/123456789/412 ThePotential of Elephantorrhiza goetzei Seed Extract as a Coagulant for Household Drinking Water Treatment Diver, Denzil; Nhapi, Innocent; Ruziwa, Walter; Wang, Hongtao; Li, Fengting Pooraccess toadequate, clean, andsafewaterisoneofthegreatestworldproblemspeopleencounter.Therehasbeenconsiderable attention in recenttimestowardtheuseofnaturalcoagulantsforwatertreatment.Thisstudyseekstopromotethisbyinvestigating the potential of Elephantorrhiza goetzei (E. goetzei) seed extract as natural coagulants for water treatment. This included the determinationofkeyingredientsresponsibleforthecoagulationprocessandoptimaldosagesfortheremovalofturbidity,fluoride, manganese, and iron. The residual content of organic matter in the treated water and the quality of sludge produced were also investigated. The methodology consisted of a proximate analysis procedure to investigate the active ingredient(s) responsible for coagulation and standard jar tests. Standard methods were used for the analyses. Coagulant dosages ranging from 0 to 300 mg/L at a rapid mixing speed of 120 rpm for 1 min, a slow mixing speed of 30 rpm for 15 min, and a settling time of 15 min were used for the jar test. The analysis of variance (ANOVA) using IBM SPSS Version 20 was conducted, and regression models were developed to determine the effect of coagulant dosage on turbidity, pH, total dissolved solids, fluoride, iron, manganese, chemical oxygen demand (COD), nitrogen, and phosphorus. The results obtained from the proximate analysis of E. goetzei seed extract show that values of 5.25%, 21.40%, 8.23%, 32.99%, 2.20%, and 29.93% were obtained for moisture, crude protein, crude fiber, fat, ash, and carbohydrate content, respectively. Moreover, seed extract of E. goetzei achieved removal efficiencies up to 94.8%, 50.1%, 90.0%, and53.9%forturbidity, fluoride, iron, and manganese in water, respectively. The coagulant has the potential to achieve the desired World Health Organization (WHO) drinking water standards for turbidity, fluoride, iron, and manganese. The COD increased from 55.3 to 419.3 mg/L as the coagulant dosage increased from 0 to 100 mg/L. This could cause an unwanted rise in microbial activities, affecting the microbiological quality of the treated water. The total nitrogen and phosphorus concentrations obtained in the sludge at 100 mg/L were 0.343 and 0.194 µg/kg, respectively, and this compromises its attractiveness for agricultural reuse purposes. Fri, 26 Jul 2024 00:00:00 GMT https://ir.cut.ac.zw/xmlui/handle/123456789/412 2024-07-26T00:00:00Z https://ir.cut.ac.zw/xmlui/handle/123456789/411 The potential and constraints of replacing conventional chemical coagulants with natural plant extracts in water and wastewater treatment Diver, Denzil; Nhapi, Innocent; Ruziwa, Walter Rutendo Coagulation is a vital stage in treating contaminated water using coagulants that can be either synthetic or natural. Currently, water is being treated by water treatment plants that use aluminum- or iron-based salts and synthetic polymers for coagulation. However, these synthetic coagulants have flaws, including the production of large amounts of chemical sludge, considerable effects on the pH of the purified water, relatively expensive to use, and potentially toxic effects on the environment. The potential and constraints of replacing chemical co agulants with natural plant extracts for water treatment are reviewed in this paper. Various natural coagulants previously investigated for the removal of heavy metals, turbidity, pathogens, and other contaminants from surface and synthetic water were analyzed based on dosage rates, active ingredients responsible for coagulation, and extraction methods among other criteria. A comparative analysis was performed in studies in which both conventional chemical coagulants and natural plant extracts were used for water treatment. Various studies have shown that it is possible to replace chemical coagulants with plant-based extracts. It has been demonstrated that it is possible to replace chemical coagulants with natural plant-based extracts because seed extracts such as those of fenugreek can achieve turbidity removal efficiencies as high as 98% as compared to 85% for alum. The use of natural coagulants may be beneficial for water treatment plants because they may produce less sludge than chemical coagulants; this increases environmental sustainability while decreasing the cost of handling sludge. They are less toxic than chemical coagulants and do not pose any adverse threats to the environment; therefore, they are a safer alternative. However, studies are needed on how these plant-based coagulants can be commercialized in the same way that chemical coagulants are readily available. Fri, 15 Sep 2023 00:00:00 GMT https://ir.cut.ac.zw/xmlui/handle/123456789/411 2023-09-15T00:00:00Z