Duckweed and Vermiculture Projects

 

Duckweed Project in Sanghol

 

Of late, the village ponds in Punjab, that hitherto used to be the centre of a thriving rural life, have degenerated into virtual cesspools owing to a host of factors such as dumping of cow dung, overflow of septic tanks and flow of sullage water. The duckweed project primarily aims at meeting this challenge of deteriorating water quality in village ponds.

The project is essentially a duckweed based waste water treatment system which in conjunction with pisciculture provides decent economic returns and generates reasonable employment as well. Duckweed is a fast growing aquatic plant which has the ability to bio-accumulate nutrients dissolved solids and even toxic elements present in the waste water. At the same time, it serves as a complete feed for fish since it is a rich source of proteins, fiber vitamins A&C. Moreover, native varieties of duckweed are common in nearby ponds and ditches.

To exploit these multiple characteristics of the duckweed, a pilot duckweed was conceived by the Government, of Punjab on 2001 and the archelogically famous village Sanghol of the district was selected as one of the sites. For this purpose, technical help was sought from State council for Science and Technology.
The project covers and area of about 2.5 acres of an erstwhile pond . The layout consists of a duckweed pond, a fish pond and a reserve pond. The sullage water flows into the duckweed pond where it is decontaminated by the duckweed and then chanelled into the fish pond. Fish seedlings are added to this pond for the cultivation of the fish. The reserve pond is meant for storing excess of water.For the first couple of years the operation and maintenance was done by the Sulabh international but now this project is operated and maintained by the panchayat itself. On the whole the duck weed project has proved to be a win- win proposal both in terms of its environmental and economic spin-offs The Duckweed project at Sanghol is thriving very well.

 

 

FAQS - Duckweed Technology

 

What is duckweed ?

  
 

The duckweed is a fast growing aquatic plant which has the ability to bio accumulate nutrients, dissolved solids and reduces Biochemical Oxygen Demand (BOD), Chemical Oxygen Demand (COD), suspended solids, bacterial pathogens of waste water to a level quite safe for disposal.

From where one can get duckweed?

 
 

Native varieties of duckweed may be collected from nearby ponds or ditches and released directly in the duckweed pond.

How Duckweed looks like?

 
 

Duckweed species are small floating aquatic plants consisting of flat, ovoid frond having hair like rootlets.
How fast does duckweed grow?  
 

The duckweed grows very fast and biomass doubles in about 2-3 days (under ideal conditions of nutrient availability, sunlight and temperature).

What is the mechanism involved in duckweed treatment?  
 

The duckweed has the ability to bio-accumulate nutrients, dissolved solids and even toxic elements present in the waste water. These are removed from the waste water as plants are harvested.

How much duckweed should be harvested?  
 

The prolific growth of duckweed averaging approximately 100 g per m ² per day should be harvested daily from the duckweed pond to achieve healthy production of duckweed.

What makes duckweed a complete feed for the fish?

 
 

Duckweed is highly nutritious due to high content of protein (30-40%), fiber content (5-15%) and vitamins A & C which makes it a complete feed for fish.
Does the duckweed based treatment site stink?  
 

A duckweed based treatment unit usually does not stink. However, one must ensure that duckweed pond is not loaded beyond its designed capacity and harvesting of duckweed is done regularly.

What is the temperature requirement for growth of duckweed?  
 

Duckweed grows very well in the temperature range of 10-40°C. Duckweed, however, shows hardly any growth during winter when temperature falls below 10°C.

How the wastewater treatment takes place in the absence of duckweed growth during winters?

 
 

The treatment takes place through biological oxidation, as the duckweed pond acts as a stabilization pond.

What should be fed to the fish when there is no duckweed?

 
 

Interestingly, the duckweed species grow faster in warm weather when fish need more feed and more slowly in cold weather when the fish do not require much feed. However, to meet the feed requirement of the fish, conventional feed like rice bran and oil cake may be fed to the fish.

Does duckweed allow mosquito breeding in the pond?  
 

Even though the duckweed does not allow mosquito breeding in the pond, yet fish (Gumbusia), which feed on mosquito larvae can be stocked in the ponds to prevent mosquito breeding.

What are the salient points for operation & maintenance of the duckweed?

 
 

Organic loading in the duckweed pond should correspond to its designed capacity. Regular harvesting of duckweed. Dressing of earthen bunds, removal of floating debris from the screen, desludging of sedimentation tank. Keeping ponds cleared of all algal growth. Maintaining bamboo grid as per given instructions

How much duckweed should be fed to the fish?

 
 

Duckweed be fed to fish from morning till evening as would be consumed by it. However, it should be ensured that duckweed fed to the fish is finished up in the fish feeding station before the sunset.
What are the salient points for maintenance of a fish pond?  
 

Pond should be dewatered, desilted and limed to make it clear from any surviving carnivorous fish in muddy water. Maintain water level of 5’ in the pond. Maintain dissolved oxygen level of more than 4ppm, pH between 6-8. Any floating scum on the water surface should be removed. Fish should be regularly fed with duckweed. Periodical netting should be carried out to check the growth of fish. Regular harvesting of fish should be carried to sell out over/under sized fish. Strict vigil should be kept to avoid any theft of fish.

 
 
 
 
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