Title: Aquatic plant systems for sustainable wastewater treatment: Indian case studies

Biography:

Goutam Banerjee is specialized in environmental engineering and sanitation with civil engineering background. He has been engaged in research and field evaluation on low-cost wastewater treatment systems for about last two decades. His research is primarily focused on tertiary treatment of conventionally treated wastewater of municipal origin for appropriate reuses in Indian context. For doing so, he has been actively engaged in biological as well as non-biological treatment of wastewaters for rendering them fit for different applications such as irrigation, industrial, groundwater recharging, and domestic consumption in sustainable ways.

Abstract

There is a growing concern world-wide now for not allowing waste discharges into natural water bodies as it might lead to ecological imbalance and may affect adversely aquatic lives, and thus it has become imperative that discharging wastes into such natural water bodies must now meet regulatory requirements and is mostly being discouraged. This aspect has given rise the need to construct artificial ecosystems as a functional part of waste water treatment. Such artificial systems mimic natural systems but without the constraint associated with natural water bodies.

Duckweeds belong to the family Lemnaceae (3 species) and are floating aquatic flowering plants found throughout the world and as stated above, flourish in a variety of climates. Reduction of BOD, COD, TSS, nitrogen, phosphorus, arsenic, and Coliforms and heavy metals are reported to be remarkable in duckweed ponds.

Furthermore, the growth of duckweed is so rapid that harvesting would result in revenue earning by generating biogas or selling as fish, animal or poultry feed. The density of plant species in the respective ponds was found, when fully grown, to be in the range of 0.8 – 1.1 Kg/m² for duckweeds and 1.8 – 2.3 Kg/m² for salvinia species. The harvestable fraction of both the species are about 10% of the total biomass in the pond, which amounts to about 0.08 – 0.11 Kg/m²/day for duckweeds and 0.20 – 0.23 Kg/m²/day in case of salvinia species.

The combined average removals of BOD₅, COD, TSS, NH₄⁺-N, Phosphorus (as PO₄^--P), Arsenic and Faecal coliforms (FC) in Salvinia and Duckweed ponds with a total detention time of 12 days (5.3 days in Salvinia pond followed by 6.7 days in Duckweed pond, when the ponds are in series, excepting 6 days of overall detention time for arsenic removals,) were found to be 73.15%, 62.9%, 88.0%, 84.5%, 58.2%, 63.6% (6-d detention), and above 99.99%, respectively.