Constructed wetlands as a cost effective cleaning option

Hyderabad, which is India's fourth largest city, has a population of almost 7 million. The Musi river, originating from the Anantagiri hills, divides the city into north and south. The River flows through the city and joins the Krishna in Nalgonda.

The paper titled "Stakeholder views, financing and policy implications for reuse of wastewater for irrigation: A case from Hyderabad, India" published in the journal Water, informs that Hyderabad has been facing issues related to the management of wastewater as its treatment lags behind when compared to the pace of urban growth.

The poisoned waters of the Musi

Water use continues to grow in the city, thereby increasing the generation of wastewater. Partially treated as well as untreated wastewater is picked up by the Musi river from the entire Municipal Corporation as well as the surrounding areas. As high as 76% of this water is used downstream for agriculture, 20% for domestic purposes and 4% for industry. The use of polluted river water for irrigation not only increases the health risks for farmers and consumers of food crops, but also for the environment.

Constructed wetlands as solutions to treat the Musi waters

As a solution, treating the river water using natural treatment systems such as constructed wetlands is being contemplated before its use for irrigation.

Constructed wetlands are artificially created or restored existing wetlands that are very useful for treatment of wastewater, stormwater runoff or treatment of sewage. Wetlands act as a biofilters and remove sediments and pollutants such as heavy metals from the water. Vegetation in a wetland provides a substrate such as roots, stems, and leaves upon which microorganisms grow and break down organic materials and help in treatment of waste [1].

Study on the perceptions of stakeholders

This paper presents the findings of a study that investigated the:

• risks involved in the use of untreated wastewater from the river for irrigation,
• interests and perceptions of government stakeholders and farmers on treating river water for irrigation,
• farmer and consumer willingness to pay for vegetables irrigated with treated river water, and
• views on policy instruments that could help in the implementation of a treatment system.

Findings of the study:

Risks involved in the use of untreated wastewater

• The water from the river was contaminated with fecal coliforms post monsoons increasing the risk of infection to humans, as the E coli infected water used for irrigation can enter the food chain via leafy vegetables.
• The fluoride concentration in some groundwater samples was above the World Health Organisation (WHO) and Indian guideline values for both drinking water and irrigation.
• Sodium and salinity hazards were found to be high, which could affect all types of vegetables and paddy grown in this area.
• The concentrations of total dissolved solids (TDS) in one well was rated as high risk for drinking water.
• Nitrogen and phosphorus concentrations in several samples were above recommended guideline values for human (nitrate) and environmental endpoints.
• Water samples were found to be positive for pesticides such as DDT, HCH, atrazine, malathion, and parathion.

Perceptions of government stakeholders

Discussions with high level decision makers, government stakeholders and researchers  to validate the above findings showed that the concerned government institutions were aware of the health problems for farmers and consumers of vegetables, caused by using untreated river water for the irrigation. They wanted to end this unlawful practice and approved of the idea to treat the river water prior to irrigation.

Perceptions of consumers

Among consumers, most respondents considered that treatment of irrigation water was in their interest. A high percentage considered government support for setting up necessary infrastructure as suitable, while many thought of fining farmers for using untreated river water.

Perceptions of the farmers

Farmers were aware of the health risks of using untreated river water, but they considered this as an acceptable payoff for the nutrient content of wastewater. Majority of them said that they used river water for irrigation and considered it to be of good quality. A large number of farmers, however, were ready to pay for the treated water, even though their lease terms entitled them to water supply. 

However, very few were willing to contribute to the construction costs of a water treatment system, and a majority thought that the government or local agencies were responsible for providing infrastructure for cleaner irrigation water.

The paper ends by arguing that:

• If water has to be treated, the use of treated water should be prescribed by the law, which should be effectively implemented.
• Farmers and consumers should be made aware of the risks of using untreated river water.
• Continuous quality monitoring of treated water should be done.
• The government should support farmers in setting up treatment facilities such as constructed wetlands, but farmers (and consumers, indirectly,  through higher vegetable prices) should take responsibility for payment for the operation and maintenance of the wetlands.

References

1. Wikipedia (2015) Constructed wetland. Downloaded on the 6th March 2015.

Please download a copy of the paper below.