Wastewater: a useful resource for agriculture

With increasing population, the gap between supply and demand for water has widened. 

The unavailability of water is affecting human existence in many parts of the world. Scientists all over the world are focusing on new ways of conserving water. Therefore, it is an acute time to reuse wastewater for irrigation and other purposes. This could release clean water for use in other sectors that need fresh water and provide water to sectors that can utilize wastewater e.g., for irrigation and other ecosystem services.  

To provide exposure and experience about the impacts of wastewater use in agriculture, students of final year (2k15-PDBatch) of Department of Soil Science, Sindh Agriculture University Tandojam visited wastewater irrigated fields at Nasarpur, Tando Allahyar Pakistan on past 17th March. The students were accompanied by Dr Saleem Maseeh Bhatti (Associate Professor Department of Soil Science) and YPARD Pakistan member Zohaib Ur Rehman Bughio. 

During the visit, students surveyed the fields where untreated wastewater was frequently applied as a source of irrigation. During the discussion with farmers, they were told that they have been using wastewater from the last twenty-two years. 

The main purpose of using untreated wastewater is to fulfil the water requirement of crops during the unavailability of fresh water. The farmers said that they found this water good for crops as its application has resulted in higher yields. The farmer community has not yet noticed any health problem related to the use of untreated wastewater. The crops which are mainly cultivated on wastewater includes fodder maize and wheat. 

To provide a detailed report about the farmer’s field, students also collected soil, wastewater and plant samples from the farm. These samples will be analyzed by the students and the report will be presented to the farmers along with some recommendation. 

What is wastewater? 

Wastewater is basically thrown away water we produce form homes, schools, offices, hospitals and public places. Wastewater generally contains liquid wastes generated from household and other commercial activities. Wastewater disposal is the biggest problem faced by large cities with limited area for land disposal. On the other hand, wastewater is a resource which can be used for productively since it contains nutrients required for agriculture and aquaculture. 

The actual composition of wastewater varies from place to place depending upon the places which are involved in the production of wastewater. But in general, waste contains: 

• Organic Matter
• Nutrients (N, P, K)
• Dissolved minerals
• Toxic chemicals
• Pathogens

Application of wastewater

In both developed and developing countries it is a common practice of applying wastewater (treated or untreated) to land.  In developed countries where environmental standards are enforced, there wastewater is treated and used for irrigating fodder, seed crops and orchards. 

Wastewater is also used for landscaping, construction dust control and groundwater recharge. In many countries including Pakistan, China, India and Mexico untreated wastewater is used for agriculture and aquaculture. Wastewater can be a source of nutrients for crops but it may also contain some toxic chemicals which can pose serious problems if untreated wastewater is used.  

Governments should take necessary steps for establishing wastewater treatment facilities so that this water can be used on a large scale with no health hazards. Environmental valuation techniques and other related tools should be employed to guide decision-making. 

Moreover, the economic effects of wastewater irrigation need to be evaluated not only from the social, economic, and ecological standpoint but also from the sustainable development perspective.

 

Photo credit: Zohaib Bughio