Discarding of rising volumes of waste-water, because of quickly growing urban agglomerations and mounting industrialization become hot issue which developing countries are currently harassed to deal.
The technology for treating waste water is often painstaking as unreasonable luxuries suitable only to prosperous countries. On the other hand, the insufficiency of water for irrigation is a constantly rising problem, due to which utilization of waste water in agricultural production has become a regular practice in three fourth of the cities in Asia, America, and Africa.
Use of waste water for farmland application is the most suitable channel as it offers a chance to reuse the beneficial plant nutrients restricted in this waste-water for crop production. Thus the secure and sustainable use of waste-water in agriculture give out as a low cost substitute of treatment and helps in avoid unrestrained discarding of waste water into lakes and streams.
In the urban and peri-urban areas this waste-water is used for enhancement of nutrients. Benefits of these nutrients depend on the quantities of waste-water applied, application time, nutrient concentration in sewage-water, intrinsic productiveness of soil and nature of crop grown.
The nutrient providing capacity is believe to be the major driver for sewage irrigation but negative effects by excessive use through encouragement of over watering, lodging and the consequential loss of crop yields. Because the fertilization is inseparable from irrigation with sewage-water; the farmers are using this water with liberty respect to free cost.
Irrigation rate depends on crop water needs and not the nutrient requirements. Continuous use of such waste-water results in contamination of water and soil.
Among these contaminants toxic metal contamination is really debatable issue. Different toxic metals are being used as backbone in agglomerating industries. Toxic metals elevated uptake effect both animals and plants. The most widespread visual symptoms of toxicity of metals in plants includes turgor loss, stunted growth, chlorosis, necrosis, fewer germination and reduced photosynthetic activity which even responsible for plant death.
While in human beings excessive uptake of toxic metals causes disease including skeletal, endocrine, kidney dysfunction, skin cancer, hypertension, proliferative lesions, lung cancer, reproductive, nervous, enzymatic, circulatory and immune system failure.
By knowing the deleterious effects because of toxic metals in our ecosystem their phyto-availability should be reduced. To achieve these aim different types of physical, chemical and biological techniques are used. Physically soil upper contaminated surface removed and may be replaced, high voltage to make volatile metals, deep horizon mixing. Chemical technique includes amendments (organic and organic) that bound metals and lower uptake by plants.
Biological method is in situ, non-deteriorating and natural remediation including use of hyper-extractor plant species and low accumulating species. Vegetable on or near contaminated sites have tendency to accumulate metals from surrounding environment, which leave humans on a great risk. Low accumulating species can be successfully grown to avoid metals uptake by crop plants. It has already been well documented from research that metals accumulation in edible plant parts and straw differ greatly among genetically different cultivar even in the same environment.
Waste water contains metals which pose deleterious effects on plant as well on human health. Government should pay special attention to make policies and take action strictly against industrialists and bound them to run water treatment units. Farmers should be educated on this issue so that they may use remediation technology. Cultivars with low metals accumulating should be preferred.
This article is collectively authored by Arslan Rauf1*, Muhammad Zia-ur-Rehman1, Muhammad Zeeshan1 and Zahoor Ahmad2 -1Institue of Soil and Environmental Sciences, University of Agriculture Faisalabad 2Cholistan Institute of Desert Studies, The Islamia University of Bahawalpur.