Assessment of Mpanda groundwater contamination and the effectiveness of the baobab seeds-derived biochar for iron removal from groundwater

Abstract

Groundwater in Mpanda District, Tanzania, faces excessive iron content, causing a reddish brown colouration due to oxidized iron species. The present study evaluated Mpanda groundwater contamination and the effectiveness of baobab seeds-derived biochar for iron removal from groundwater. First, the physicochemical quality of groundwater was investigated. Nineteen boreholes were randomly selected for assessment, with samples collected in rainy and dry seasons. The study revealed significant variations in groundwater quality both between seasons and among boreholes. Temperature, total dissolved solids, electrical conductivity, lead, iron and manganese exceeding World Health Organization and Tanzania Bureau of Standards limits in some boreholes; necessitating water treatment for human use. Second, the effectiveness of baobab seeds-derived biochar for iron removal from groundwater was assessed. Baobab seeds, were sun-dried, oven dried at 105 ºC, carbonized at 700 ºC, and ground into fine powder. The influence of pH, time, temperature and dose of biochar on the iron removal from groundwater was assessed. Six 1000 mL beakers were filled with groundwater and adsorbent doses of 0.6 g/L, 1.2 g/L, 1.8 g/L, 2.4 g/L, and 3.0 g/L were added into five beakers with the sixth serving as a control. The highest removal efficiency of iron was observed within 5.0-8.0 pH range. Over time, the removal efficiency increased to 87% at 120 minutes and 3.0 g dose, with an initial iron concentration of 5.88 mg/L and residual concentration of 0.76 mg/L. Baobab seeds-derived biochar showed promising efficiency in removing iron ions and is recommended for sustainable iron removal from groundwater.