Besides the salinity and alkalinity hazard of water, some industrial effluents and sewage water are also problem waters that can be reused by proper treatment. The complex growth of industries and urbanization (Urban development) leads to massive increase in wastewater in the form of sewage and effluent.
Waste water supplies not only nutrients but also some toxic elements such as total solids of chloride, carbonate, bicarbonate, sulphate, sodium, chromium, calcium, magnesium, etc., in high concentration. Besides this, the effluent or wastewater creates BOD (Biological Oxygen Demand). These wastewaters when used for irrigation lead to surface and sub surface source of pollution due to horizontal and vertical seepage.
Points to be considered
• Application of greater amounts of organic matter such as FYM, compost etc., to the soil to improve permeability and structure.
• Increasing the proportion of calcium, through addition of gypsum (CaSO4) to the irrigation water in the channel, by keeping pebbles mixed gypsum bundles in the irrigation tank.
• Mixing of good quality water with poor water in proper proportions so that both the sources of water are effectively used to maximum advantage.
• Periodical application of organic matter and raising as well as incorporation of green manure crops in the soil.
• Irrigation the land with small quantities of water at frequent intervals instead of large quantity at a time.
• Application of fertilizer may be increased slightly more than the normally required and preferably ammonium sulphate for nitrogen, super phosphate and Di Ammonium Phosphate (DAP) for phosphorus application.
• Drainage facilities must be improved.
• Raising of salt tolerant crops such as cotton, ragi, sugar beet, rice, groundnut, sorghum, corn, sunflower, chillies, tobacco, onion, tomato, garden beans, amaranthus and lucerne.
Projected waste-water utilization –
It is estimated that 2,87,000 million m3 of waste water can be reusable. Hence, these waste waters can be properly treated as follows:
• Dilute with good quality water in the ratio of 50:50 or 75:25.
• Alternate irrigation with waste water and good quality water.
• Treat the effluent water through fill and draw tanks, lime tank, equalization tank, settling tank, sludge removal tank, aerobic and anaerobic treatment tanks etc.
Read More-
- Basics of Irrigation Water Management
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- Agro-Climatic Zones of India
- Basics of Vegetable Crops
