Evaluation of laterite as filter media to remove arsenic from groundwater

Arsenic (As) in drinking water has a chronic effect on humans and thus is a global health issue. Mostly people of Pakistan use groundwater for drinking, consequently prone to As toxicity. The objective of this study was to evaluate laterite as an adsorbent media for As removal, and subsequent preparation of a low-cost As filter. Laterite was tested for As adsorption capacity through batch sorption experiment and fitting Langmuir model. Two identical filters were prepared using a variable particle size of laterite and substrate material ratios (sand, activated carbon, and brick chips). Arsenic contaminated water was poured daily and collected at the bottom for analysis. The water samples were analyzed for As using an atomic absorption spectrophotometer coupled with hydride generation assembly. Other water quality parameters viz., electrical conductivity (EC), pH, chloride (Cl), total suspended solids (TSS), total dissolved salts (TDS), nitrate (NO-3), calcium (Ca), magnesium (Mg), sodium (Na), potassium (K), carbonate (CO-3), bicarbonate (HCO-3), and sulfate (SO-4) were also tested. Filter1 had an As removal efficiency of about 83 to 93 % while Filter 2 had about 67 to 85 %. Most of the water quality parameters remained under the WHO recommended limits indicating no harmful addition to the filtered water by substrates. It appears that laterite may serve as an economical option for As removal from contaminated groundwater.

Sorption of Selected Heavy Metals with Different Relative Concentrations in Industrial Effluent on Biochar from Human Faecal Products and Pine-Bark

The removal of heavy metals from effluents at source could reduce contamination of soil and water bodies. A batch sorption experiment was performed to determine the effects of feedstock of biochars pyrolysed at increasing temperature on sorption capacities of Cu, Cr and Zn from industrial effluent and aqueous solutions. Sewage sludge, latrine faecal waste and pine-bark biochars were used. The sorption data were fitted to the Langmuir isotherm. Maximum sorption capacities of latrine waste, sewage sludge and pine-bark biochar (350 °C) were, respectively, 313, 400 and 233 mg kg−1 for Zn, 102, 98.0 and 33.3 mg kg−1 for Cu, and 18.9, 13.8 and 67.1 mg kg−1 for Cr from industrial effluent. Conversely, sorption capacities from single metal solutions were 278, 227 and 104 mg Zn kg−1, 97.1, 137 and 21.3 mg Cu kg−1, 122, 106 and 147 mg Cr kg−1 on latrine waste, sewage sludge and pine-bark biochar, respectively. Step-wise regression analysis showed that the combined effects of ash, fixed C, pH influenced Zn sorption, ash and fixed C affected Cu sorption, and Cr sorption by ash and specific surface area of the biochar. The findings of the study imply that biochar from human faecal waste, particularly sewage sludge, has the potential to be utilized as sorbents of heavy metals from multiple metal effluent and that the sorption is affected by relative concentrations.