Green wall system coupled with slow sand filtration for efficient greywater management at households

Abstract

Green walls are gaining attention for greywater management in the imminent terrestrial space and land constraint scenario. They have been tested primarily with greywater from a single source such as showers, hand or wash basins, laundry, and kitchen or a mix of a couple of these sources but barely with mixed greywater from all these household activities. Here, a green wall system coupled with a slow sand filter (SSF) was tested for managing household greywater. It consisted of a set of five serial hydraulic flow-connected reactors and an SSF unit. Each reactor housed an Epipremnum aureum sapling embedded in the support bed matrix, consisting of cocopeat and granular activated charcoal. The system operated at 150 cm d(-1) hydraulic loading rate (HLR) achieved 90 +/- 0.7%, 85 +/- 4.5%, 72.9 +/- 4.4%, and 60.6 +/- 5.1% removal efficiencies for turbidity, chemical oxygen demand (COD), total nitrogen (TN), and total phosphorous (TP), respectively. The system maintained similar treatment performance with varying greywater strength when COD and TN were below similar to 400 and similar to 15 mg L-1, respectively. The polished effluent produced by SSF operated at 187 cm d(-1) HLR, with characteristics <5 mg L-1 COD, <2 NTU turbidity, <1 mg L-1 TN, similar to 0.5 mg L-1 TP, similar to 7.8 pH, and <100 MPN per 100 ml fecal coliforms, qualifies the standards for non-potable reuse applications. Along with reclaimed water reuse, green walls provide environmental benefits by fixing CO2 in plant biomass. Overall, the low-cost system offers efficient greywater management in an eco-friendly way with minimized resource consumption and areal footprint.