Affiliation:
1. Department of Environmental Engineering, School of Engineering Sciences and Technology Chinhoyi University of Technology Chinhoyi Zimbabwe
2. Centre for Urban Resilience Water and Climate Change Chinhoyi Zimbabwe
3. Department of Fuels and Energy, School of Engineering Sciences and Technology Chinhoyi University of Technology Chinhoyi Zimbabwe
4. UN Environment‐Tongji Institute of Environment for Sustainable Development, College of Environmental Sciences and Engineering, State Key Laboratory of Pollution Control and Resource Reuse Tongji University Shanghai People's Republic of China
Abstract
ABSTRACTPoor access to adequate, clean, and safe water is one of the greatest world problems people encounter. There has been considerable attention in recent times toward the use of natural coagulants for water treatment. This study seeks to promote this by investigating the potential of Elephantorrhiza goetzei (E. goetzei) seed extract as natural coagulants for water treatment. This included the determination of key ingredients responsible for the coagulation process and optimal dosages for the removal of turbidity, 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%, and 53.9% for turbidity, 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.