ABSTRACT
A laboratory scale study on Fe and Mn removal in upflow anaerobic bioreactor of a working volume of 20 L with coir fibre as the filter medium was investigated for a period of 312 days. The maximum Fe and Mn levels considered were 10 and 5 mg/L respectively, which are the typical average values of textile effluents subsequent to the primary and secondary treatments. Ten sub-experimental runs were conducted with varying HRTs (5 days to 1 day), ratios of COD:SO42- (20 to 3.5), Fe levels (0.005 to 10 mg/L) and Mn levels (0 to 5 mg/L). COD:SO2 of 3.5 was identified as the optimum point at which sulphate reducing bacteria (SRBs) out competed methane producing bacteria (MPBs) and further reduction of this ratio caused total and/or significant inhibition of MPBs, thus building sulphate reducing conditions. The effluent contained Fe and Mn below the permissible levels (1.6 and 1.1 mg/L for Fe and Mn, respectively) stipulated by US National Pollution Discharge Elimination System (NPDES) for inland surface waters at HRTs higher than 3 days. Results of the mass balance showed more Fe accumulation (60%) in sediments whereas 27% in the filter media. An opposite observation was noticed for Mn.
Subject(s)
Cellulose , Iron/isolation & purification , Lignin/analogs & derivatives , Manganese/isolation & purification , Waste Disposal, Fluid/methods , Water Pollutants, Chemical/isolation & purification , Bacteria, Anaerobic/metabolism , Bioreactors , Cocos , Industrial Waste , Iron/metabolism , Manganese/metabolism , Sulfates/metabolism , Textile Industry , Water Pollutants, Chemical/metabolismABSTRACT
This paper elucidates the phytoremediation potential of water hyacinth (Eichhornia crassipes [Mart.] Solms) for TN and TP rich industrial wastewaters determined for 15 weeks under different set-ups of 2-fold (56 TN mg/l and 15.4 TP mg/l), 1-fold, 1/2-fold, 1/4-fold and 1/8-fold and a control with no nutrients in duplicate. A mass balance was conducted to evaluate the phytoremediation efficiencies and to identify the key mechanisms of nutrient removal from the wastewaters. Our results manifested that water hyacinth is a promising candidate for a batch removal of TN and TP from wastewaters. 100% removal of both TN and TP was observed at the end of the 9th week in all the set-ups mainly due to assimilation and the period between 6-9weeks became the optimum period after which complete harvesting is recommended. Plants having an age of 6 weeks are ideal to commence the free-floating wetland and 21 days hydraulic retention time (HRT) is recommended for optimum removal of TN and TP. Assimilation and denitrification were the key mechanisms of TN removal while assimilation and sorption became the prominent mechanisms in the removal of TP from wastewaters.
