Agricultural Waste Water Management
Suhas Dixit, CMD, Pyrocrat Systems LLP, Navi Mumbai.
Agriculture Waste Water ď‚—
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Controlling the pollution from surface runoff from farms that may be contaminated by chemicals in fertilizer, pesticides, animal slurry, crop residues or irrigation water is called as Agricultural Waste Water Treatment. Agricultural Waste Water can be classified into Point Source and Non-Point Source.
Non-point source pollution
Sediment Runoff: Soil washed off fields is the largest source of agricultural pollution. Excess sediment results in high levels of turbidity in water bodies This can result in inhibition of growth of aquatic plants, clogging of fish gills and smothering of animal larvae.
Reducing Sediment Runoff Non-point source pollution can be controlled by activities like. Contour ploughing crop mulching crop rotation planting perennial crops installing riparian buffers
Nutrient Runoff ď‚— ď‚—
Nitrogen and phosphorus from fertilizers and manure are key pollutants found in runoff. Can be avoided by proper mapping of fields, obtaining realistic estimitation of crop yields, conducting soil tests, analyzing fertilizers and manure.
Pesticides ď‚— ď‚— ď‚—
Pesticides are often used for increasing productivity by controlling pests. The pesticides are hence found even in the surface water. Integrated Pest management can be done to promote usage of biological pesticides over chemical ones.
Point Source Pollution
It is an issue largely associated with farms with livestock and poultry. The waste water is composed of animal waste slurry. Animal Waste Slurry can be treated by containment in lagoons before being sprayed on grasslands.
Silage liquor ď‚—
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Fresh grass or other green crops can be made into a semifermented product using sulphuric or formic acid called silage which can be stored and used as winter forage for cattle. The process of silage making frequently produces a yellow-brown strongly smelling liquid which is one of the most polluting organic substances known. Silage liquor that is produced can be used as part of the food for pigs.
Dairy Farming Waste
Milk causes rapid rapid de-oxygenation of water. Dairy farming wastes also consists of wash-down water, some animal waste and disinfection chemicals. Milking parlour wastes are often treated in admixture with human sewage in a local sewage treatment plant. This ensures that disinfectants and cleaning agents are sufficiently diluted and amenable to treatment.
Firewater ď‚—
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Fire is a rare event in farms but Stores of pesticides, herbicides, fuel oil for farm machinery and fertilizers can all help promote fire and can all be present in environmentally lethal quantities in firewater from fire fighting at farms. Containment of substantial quantities of firewater shall be preplanned along with its subsequent recovery and disposal by specialist disposal companies as the concentration of contaminants in firewater makes them unsuitable for the wastewater to be used for any other application.
Agricultural Waste Water Treatment
Screening : At this stage, large objects like diapers, sanitary items, bottle caps, plastics, broken bottles, etc. are separated from the waste. Primary Treatment : This part of the process is used to remove organic material from the water. The waste is then placed in large settlement tanks for the sludge to sink to the bottom. Secondary Treatment – Once the sludge has been removed, the water is placed in rectangular tanks called aeration lanes. Final Treatment – The water is moved into settlement tanks. More sludge is formed at the bottom of the tanks due to the bacteria breakdown. It is scraped and collected for treatment. Water is then released into the river.
Physical Treatment ď‚—
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Sedimentation, flotation, adsorption, barriers such as bar racks, screens, deep bed filters, and membranes are used in physical agricultural wastewater treatment. The use of this method removes waste by using naturally occurring forces including gravity, electrical attraction and van der Waal forces in addition to physical barriers.
Chemical Treatment Chemicals are used to accelerate disinfection using various techniques like. Chemical Coagulation – Most common method for removing dissolved metals from wastewater solution containing toxic metals. Chemical Precipitation – Involves destabilizing wastewater particles so that they aggregate during chemical flocculation. Chemical Oxidation – An oxidizing agent is added during chemical oxidation. Electrons move from the oxidant to the pollutants in wastewater.
Chemical Treatment (contd.)
Advanced Oxidation – Helps remove any organic compounds that are created as a result of chemical oxidation. Ion Exchange – Ion exchange is a process that can be used to soften water. Positive sodium ions in the form of sodium chloride, salt or brine are added to the water. Chemical Neutralization and Stabilization – Similar to chemical oxidation, sludge is treated with a large amount of oxidant. This slows down the rate of biological growth in the sludge. This also works as a deodorizing agent.
Biological Treatment ď‚—
Biological wastewater treatment uses organisms like bacteria, nematodes, and other small organisms to break down organic substances in wastewater.
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