Performance and Life Cycle/Life Cycle Cost Assessment of Low-Cost Adsorbents’ Application in Drinking Water/Wastewater Treatment

Abstract

The impact of water pollution has led to the search for cost-effective and environmentally friendly treatment processes to alleviate the associated environmental hazards.  Adsorption is identified as an advanced treatment technology that offers simplicity and cheap alternatives to water treatment technologies when low-cost adsorbents such as industrial byproducts, waste, agricultural waste, etc are utilized. Nanomaterials and other advanced materials like MOFs were reported to be less environmentally friendly. It is therefore, paramount to employ low-cost and green materials for adsorption to be sustainable.  This thesis, investigated the applicability of low-cost natural earth materials for tannery wastewater decontamination and achieved removal efficiency of (63.59%, qe: 65.5 mg/g) lime rock > pristine gravel (48.88% and 50.4 mg/g)> pristine sea shell (39.03%, qe: 40.2 mg/g)> pristine zeolite (38.5%, qe: 39.7 mg/g) > pristine clay (33.55%, qe: 34.5 mg/g) for Cr (VI) from tannery wastewater. In order to improve the removal efficiency of these sorbents, different modification techniques such as thermal activation, sodium activation, metal doping, were employed on clay, date palm waste biomass and biochar.  This modification proved to increase the removal efficiency of biochar doped with Fe3O4 for removal of MB from textile wastewater by 29% and Na2CO3 activated, hydrothermally carbonized clay by 51.6% for removal of Cd (II) from electroplating wastewater as well as maintaining an effective removal of Fe, Pb, Cu, Cr, and Zn. The materials were further used to develop a point-of-use drinking water treatment system (modified biosand filter) containing earth materials -gravel and sand, with biochar achieving the removal of Cu (99.23%), Zn (100%), Mn (89.99%), Fe (78.94%), NH4+ (30.62%), PO43- (99.53%), NO3- (8.18%), K (16.41%), Total coliform (92.89%), Turbidity (100%) from groundwater which meets to WHO drinking water requirement. When integrated with sequence batch reactor it improved the effluent concentration of treated domestic wastewater for reuse irrigation of edible crops. Finally, a Lifecycle assessment was conducted to evaluate the sustainability and impact of the developed biosand filter and modification routes employed in this research. Results revealed that while our modified biosand filter was more environmentally friendly in comparison to others in literature the environmental impact of the modification routes was in the order -Activation > Polymerization> Metal doping > Hybridization. This thesis recommends the adoption of low-cost material with low impact modification techniques for sustainable water treatment.