Efficiency of coconut coir-pith as an alternative substrate in the treatment of submerged macrophyte wetland systems in tropical conditions.

Abstract

The effects of coconut coir-pith as an alternative substrate material in submerged macrophyte wetland systems were investigated in three similar pilot-scale wetlands (WL1, WL2 and WL3) planted with Hydrilla verticillata. The substrate layers of WL1 and WL3 were river sand and coconut coir-pith, respectively, whereas that of WL2 was a mixture of river sand and coir-pith (ratio 1 : 1). The influent and effluent water-quality parameters were examined weekly to identify the effects of coir-pith on the treatment process. The results showed that the total nitrogen removal efficiency was higher in WL2 (52.3%) andWL3 (62.1%) than in WL1 (29.1%). The most efficient removals of biodegradable organic compounds (54.4%) and total dissolved solids (40.5%) were encountered in WL2, whereas the maximum total suspended solids (66.4%) and conductivity (38.5%) reductions were found in WL3. However, the PO3−4 –P removal efficiency was only slightly improved in WL2 (74.2%) and WL3 (74.4%) overWL1 (68.7%). Microbiological investigations revealed that WL2 and WL3 were more efficient in removing Escherichia coli than WL1. Statistical analyses by ANOVA showed that the water treatment efficiencies of WL2 and WL3 were substantially better than WL1 (p < 0.05).