Origin The potential of duckweed was first realized in 1950 in Asia.

In India first installation of later type has been designed in 1995 in

Pondicherry near Madras, funded by World Bank/UNDP.

Some duckweed ponds also exist in Bangladesh since 1990 using

natural pond as duckweed pond as well as fish pond

In Punjab, a pilot duckweed project for bio- remediation of village

pond was initiated in 2001 by the State Government in

collaboration with Punjab State Council for Science and

Technology (PSCST) in villages Sanghol and Chanarthal kalan in

District Fatehgarh Sahib.

Duckweed Botany Duckweeds are small, fragile and free floating aquatic plants belong to

four genera;

Spirodela, Lemna Wolfia Wolffiella

Distribution

The Lemnacae family is world wide, but most diverse species appear in the

subtropical or tropical areas.

Temperature Condition: Duckweeds grow at water temperatures between 6

and 33° C.

Water, pH: Duckweed survives at pHs between 5 and 9 but grows best over

the range of 6.5-7.5.

Lemnaceae wastewater Treatment System

It basically consists of two parts:

Primary Treatment

Post Primary Treatment

Two basic principles for pond design and operation are used

for duckweed treatment:

Plug-flow Batch system

Harvesting of Duckweed

Manual Harvesting Mechanical Harvesting

Biological Processing In Duckweed Pond System

Pollutant Removal Mechanism

TSS Removal:

TSS are to a major extend removed by sedimentation. A minor fraction is adsorbed on the roots of the fronds, where microorganisms degrade a part, and a part of the degraded products is assimilated in the plants.

Organic Matter and BOD Removal :

BOD is aerobically digested by microorganisms attached to the duckweed fronds.Anaerobic processes are responsible for BOD removal in the sediment

Nitrogen Removal:

Besides plant uptake, denitrification and volatilisation of ammonia are quantitatively relevant processes for nitrogen removal in duckweed systems.

Phosphorus Removal:

Plant uptake and sedimentation are quantitatively relevant for phosphorous removal in duckweed systems

Pathogen removal takes place through natural die-off (long detention times).

Toxins that are lipophilic (= hydrophobic) get greatly accumulated in the lipids of the cell membrane from where they are excreted to the inner side of a Lemnaceae cell.

Duckweed Project in Fatehgarh Sahib

Duckweed Technology at Sanghol

The project covers land area of about 2.5 acres of an erstwhile pond. Panchayats earn revenue up to the tune of Rs 1.5 lakh to Rs 2 lakh per

year

Duckweed Pond At Chanarthal Kalan

Treatment efficiency By Duckweed Wastewater Treatment Plant:

Average flow of 125 m³/day of hospital, school, and residential

wastewater

Produced by a population of between 2,000 and 3,000 persons

Treatment

Phase

BOD5

(mg/l)

NH3

(mg/l)

P

(mg/l)

Turbidity

(FTU

Raw

Influent

120 39.40 1.90 113

Primary 60 32.20 2.00 85

Duckweed 1 0.03 0.03 10

US

Standards

10 2 1.00 20

Advantages These technologies are traditional, rudimentary, and easy to

implement, ideal for rural areas.

Wetland systems are easy to build, simple to operate, and require little

or no maintenance.

Most small-scale wetland treatment systems require relatively small

land areas.

Wetland technologies reduce nutrient contamination of natural

systems.

Heavy metals absorbed by the plants in wetland treatment systems are

not returned to the water.

Duckweed-based ponds and other wetland systems produce plant

biomass that can be used as a fertilizer, animal feed supplement, or

source of methane

Duckweed produces more protein per square meter than soybeans.

Duckweed is easier to harvest than algae or other aquatic plants.

Thank You