Efficacy of Cassava Peel Extracts for the Removal of Heavy Metals from Hospital Sewage Sludge in Nigeria

Abstract

Background. The use of strain-specific microbial fermentation in the production of organic acids for the removal of heavy metals from sludge has been extensively studied. However, there is scarce information on the use of microflora for fermentation. Objectives. To assess the efficacy of cassava peel extracts for the removal of heavy metals from hospital sewage sludge in Nigeria. Methods. A composite sewage sludge sample was collected from the University College Hospital sewage treatment plant in Ibadan, Nigeria and analyzed for heavy metals using standard methods. Aspergillus niger fermentation and crude fermentation extract were obtained from the cassava peels strain of Aspergillus niger and indigenous microflora, respectively. The experiment was carried out by adding 10 ml of the treatment to 3 g of each sludge sample (extracts and controls) at varied temperatures (room and elevated) and pH (3–5). The mixture was centrifuged after a contact time of 1–12 days at 1000 rpm for 1 hour. The filtrate was analyzed for heavy metals concentrations and compared with the standards. Data were analyzed using descriptive statistics and adsorption models. Results. Mean heavy metal concentrations in the sludge were estimated for copper (2.22±0.2 mg/kg), zinc (52.3±0.1 mg/kg), chromium (1.46±0.1 mg/kg), nickel (5.6±0.01 mg/kg), and lead (1.9±0.1 mg/kg) and were below permissible limits. Optimum heavy metal removal for Aspergillus niger fermentation extract at room temperature was achieved on day 12 at pH 3.5 for zinc (74.5%), while optimum heavy metal removal at elevated temperature was achieved on day 9 at pH 3.0 for lead (79.3%). The optimum pH for crude fermentation extract lies between pH 3.0–4.5 for nickel (76.2%) at room temperature and chromium (76.6%) at elevated temperature. Conclusions. Crude fermentation extract of cassava peel was found to be effective in removing heavy metals from sewage sludge. Therefore, its use could be adopted and promoted for removing heavy metals from sewage sludge to achieve safe disposal. Competing Interests. The authors declare no competing financial interests.

Direct and Indirect Neurotoxic Potential of Metal/Metalloids in Plants and Fungi Used for Food, Dietary Supplements, and Herbal Medicine

“…For example, cassava tubers supply ~70% of the daily calorie input for >50 million people in Nigeria, the world’s largest cassava producer (49 million metric tons/year). Fresh cassava root contains >30% carbohydrate, >2% protein, 0.1% fat, and >75% moisture content [ 82 , 83 ]. However, M. esculenta also synthesizes cyanogenic glucosides (linamarin and its methylated relative lotaustralin; 97:3), the concentration of which must be substantially reduced before the tuber is used for human consumption.…”

Residuals, sludge, and biosolids: Advancements in the field

“…After centrifugation at 1,000 rpm for 1 hour, the heavy metal concentrations of treated samples were analyzed and compared to control samples. It was found that the Aspergillus niger treatment resulted in concentrations of zinc, copper, chromium, nickel, and lead that were all below permissible limits, indicating that cassava peel extract may be used as an alternative method to remove heavy metals from wastewater sludge (Adeolu & Adewoye, 2019). Bogusz and Oleszczuk (2020) concluded that Cd and Cu were more mobile in control soil when compared to wastewater sludge-treated and biochar-treated soil.…”

“…Adeolu and Adewoye (2019) conducted a study to assess the use of microflora to remove heavy metals from wastewater sludge generated by a Nigeria hospital. Cassava peels were used to obtain Aspergillus niger fermentation extract, and 10ml of the extract was added to 3g of wastewater sludge sample.…”

Literature Review: Fabrication Method, Characterization, Performance, and Application of Cassava Peel as Bio-Coagulant for Wastewater Treatment

“…In addition, cassava starch granules consist of amylose (20%) and amylopectin (80%) [14]. Therefore, the sludge produced from the coagulation process by vegetable coagulants, including cassava, is cost-effective, highly biodegradable, non-toxic, non-corrosive and unlikely to produce air with extreme pH [15]. In addition, natural coagulants are relatively inexpensive to obtain and are available locally.…”

“…Another way to view a co-word map or keyword map on research developments in a specific field of science is through density visualization [15]. Figure 3 depicts a high-level overview of keyword density in cassava peel research.…”