In Pakistan, domestic and industrial waste water is either discharged directly to a sewer system, a nearby field, an internal septic tank, a natural drain or water body. Mostly, this wastewater is not treated and none of the cities have any biological treatment process except Islamabad and Karachi, and even these cities treat only a small proportion (<8%) of their wastewater before disposal.
As far as wastewater production is concerned total discharge of wastewater for 14 major cities of Pakistan, is about 1.83 × 107m3 h−1 (FAO, 2002). Latest investigation shows that total quantity of wastewater produced in Pakistan is 962,335 million gallons (4.369 x 109m3/yr) including 674,009 million gallons from municipal and 288,326 million gallons from industrial use. International Water Management Institute (IWMI), Lahore, Pakistan made a nationwide survey, which indicates 32,500 hectares area in Pakistan is directly irrigated with wastewater i.e. 26 percent of vegetables are being produced from wastewater.
Increasing scarcity of fresh water resources in many arid and semi-arid regions and wastewater volumes, driven by rapid urbanization, a poorly performing irrigation distribution system, made it a low-cost alternative to conventional irrigation water. Cost benefit analysis shows that on an average Rs. 5.56 is returned as a net benefit from crop production per rupee invested for wastewater irrigation as compared to Rs. 2.20 for fresh water irrigation. But average days of illness were 11.44 days per person per annum in wastewater area as compared to 8.04 days in fresh water area.
Now PFA has decided to introduce food safety regulation in fruit and vegetable supply chain (Agricultural produces).Punjab food authority banned waste water use for edible crops. But ban is not sufficient without proper planning to execute it. This planning includes use of waste water for non edible crops.
The use of plants and associated microorganisms to remediate the contaminated soil, sediment, water is referred as Phytoremidiation. This technique is efficient for removal of metals and contaminates. Selection of suitable plants according to contaminates is crucial step for phytoremidiation because all plants do not show same potential for different compounds due to different genetic back ground, physiology, morphology. Irrespective of the fate of chemicals, the first step is use of chemicals or metals through its root system. Considering this step, grasses are suitable option with fibrous root system, highest root surface area per m3 as compared to other plants, with high microbial colonization (microbes are used to degrade different chemicals), adequate space for interaction with contaminates. Moreover grasses cover the contaminated area quickly as they are fast growing, which in turn prevent the leaching of contaminates. Grasses are also source of biomass as these are bioenergy crops. There is a possibility that depletion of global fossil fuels will occur in next 40 to 50 years due to high dependence on fossil fuels and rapid increase in consumption rate of these non-renewable resources. Therefore alternative source is biofuel by using bioenergy crops.
Considered the advantages of grasses, it is suitable alternative to edible crops for waste water. Lolium multiflorum (rye grass), Madicago sative (lucern), Phalaris arundinacea (canary grass), few grasses from sedge family are suitable for this purpose.
This article is collectively authored by Maria Batool, Dr. M. Umar Chattah, Dr. Imran khan, Umair Hassan.