Use of Sewage Water for Irrigation

Introduction

Considering the fact that in a water-scarce State like Gujarat where surface water sources are scattered and ground water is inadequate, use of sewage for irrigation is a lucrative choice. However, the impacts of such an activity on the soil, crops and human health is a matter of concern and thus it has been identified as an area of study. GEMI is monitoring the quality of wastewater, soil and crops and based on the outcomes, it will suggest the preventive and mitigation measures in the form of a management plan.

The study of sewage which is used for irrigation possess great significance due to its adverse effects on the farmers, consumers eating the crops grown using sewage and its effects on the land where irrigation is done using such waters.

GEMI’s aim is to collect and analyse the quality of untreated sewage disposed in rivers and also the sewage from Sewage Treatment Plants and compare its quality with the water supplied in irrigation canals. Based on the results, it will be assessed as to whether the sewage is fit for irrigation and if not, an effective and feasible treatment scheme for the same is suggested. The analysis of sewage samples has been started by GEMI.

The present study is taken up in four phases for Ahmedabad cluster.

        

In Phase I monitoring of sewage water at the source wherein the quality of major wastewater (primarily sewage) outfalls from various treatment plants of the city was monitored over a period of one year. Phase II, III & IV are about monitoring the sewage, soil as well as crop quality respectively at the point of their use in irrigation i.e. at the agricultural areas of villages in the vicinity of the sewage receiving streams. The last three phases can be carried out collectively.

Objectives

  • To study the quality of sewage from wastewater outfalls and that received at the agricultural fields by analyzing various physico-chemical and biological constituents.
  • To analyse the concentration of toxic constituents in sewage, soil and crops and trace its source.
  • To assess the short and long term impacts of sewage irrigation on soil, crop and human health.
  • To know the farmer’s perspective of using sewage for irrigation and to assess the actual changes in crop yield, irrigation pattern, pesticides/fertilizer use with sewage farming compared to farming with potable water.
  • To suggest and recommend appropriate treatment and wastewater management techniques for safe usage of sewage in irrigation
  • To frame a Comprehensive Management Plan for using sewage water in irrigation.

Project Benefits

The project will have the following benefits:

  • Farmers as they can directly use the sewage for irrigation, if the quality of sewage is found under the desired norms.
  • Local Authority could be made aware about the actual performance of the city’s STP’s   

Deliverables

  • The wastewater which would have been disposed in natural streams can be diverted for reuse in irrigation purposes, thus reducing the pollution load on the environment.
  • Sewage is a good source for irrigation in water scare conditions. In regions where groundwater is drawn for watering agricultural fields, the water table decreases quickly. In such conditions, sewage farming can be the best alternative.
  • It has been reported that crop yield and productivity increases with the use of sewage for irrigation.
  • Cost of purchasing chemical fertilizers to increase crop productivity can be reduced as the sewage is rich in nutrients to some extent.
  • Commercial crops can be easily grown on sewage farms.