VPE 511: Environment and Environmental Hygiene (2+1)

RECYCLING OF FARM SURPLUS/WASTES

• The farm waste may be solid, semisolid or liquid. Some waste may be treated primarily as sewage and the residues emanating from the digestion tank serve as manure. The sludge from the primary sedimentation tank could be disposed by land bury or by composting while the liquid effluent after the separation of activated sludge in the secondary sedimentation tank is disposed to courses. Besides, the sludge may also be disposed in the sea as done in Mumbai, spread over the land or used as manure.
• The effluent from secondary settling tank, ie disposed into water courses such as rivers and streams should be diluted at least 8:1 (water: effluent) in manner that it should not contain > 10 ppm of suspended solids and 10ppm of BOD. Since people may use as source waters, the effluents needs essentially to be rendered pathogen free by chlorination. If chemicals are not removed from the water it could prove toxic to man, fish, agriculture and limits its use for other purpose.

Oxidation pond

• It is a cheap method of sewage treatment. It is an open shallow pool 1 to 1.5m deep with an inlet and outlet. It functions in the presence of algae, certain types of bacteria and sunlight. The organic matter is oxidized by bacteria to CO₂ , ammonia and water.
• The algae with the help of sunlight utilizes CO₂ , water and inorganic minerals for their growth and liberates oxygen which together with atmospheric oxygen induces the process of oxidation in the pond. It can become profitable of sewage purification for a small community. Twenty two acres of land is required to develop an oxidation pond.

Oxidation ditches

• With the use of mechanical rotors for extended aeration, the aerated lagoons can also be used for purification of sewage and wastes generated by townships with 5000 to 20000 population. Only one acre of land is required for an oxidation ditch and 2.5 acres for aerated lagoon.

Collection of wastes

• Dung, feed wastes, soiled bedding , etc. forming solid wastes and waste water constituting liquid manure can be collected separately or flushed out together with plenty of water through hose pipes. The former group of wastes are lifted into wheel barrows or trolleys and drawn out by bullock carts.
• Solid manure is to be collected and removed from the shed at least twice daily and should be stored in manure pit with impervious walls which is located at a minimum distance of 10m from a well, river, tank or boundary of an adjoining land property to safeguard against the menace of foul odours and flies.