Constructed wetlands are nature’s ingenious solution for wastewater treatment in India

These ecosystems can significantly contribute to sustainable industrial progress and preservation of water resources

By Diksha Pandey
Published: Tuesday 07 May 2024
Kolkata East Wetlands in West Bengal, designated as a Ramsar site, feature a vast network of natural and constructed wetlands. Photo: iStock

Rapid development in India has brought about significant environmental challenges, particularly concerning the management of industrial wastewater. The discharge of untreated or inadequately treated industrial effluents into waterbodies poses serious threats to ecosystems, public health and water security. 

With industries spanning diverse sectors such as manufacturing, textiles, chemicals and mining, the scale of pollution is considerable. Traditional treatment methods often prove insufficient in tackling the array of pollutants present in industrial wastewater, necessitating a shift towards more comprehensive and nature-based solutions. 

Constructed wetlands emerge as a promising approach, offering not only effective treatment but also environmental and economic benefits. These remarkable ecosystems marry the elegance of natural processes with human innovation, providing an eco-friendly alternative to conventional treatment methods. 

What are constructed wetlands?

Constructed wetlands, at their essence, are engineered structures designed to replicate the functions of natural wetlands. They are comprised of meticulously chosen vegetation, soil and water, orchestrated to facilitate a seamless process of purification.

Unlike conventional concrete tanks, these wetlands foster biodiversity, welcoming a diverse array of life forms — ranging from microorganisms to aquatic plants and even birds — to engage in the purification process.

Constructed wetlands are typically divided into two categories: subsurface flow (SSF) and surface flow (SF). SSF wetlands direct wastewater through gravel beds or porous media, promoting microbial activity that degrades organic matter. In contrast, SF wetlands demonstrate their aesthetic appeal above the water’s surface, with gently flowing streams and lush vegetation. 

While each design exhibits distinct advantages, both variants share a unified objective: to convert pollutants into benign compounds through natural processes.

The selection of plants holds paramount importance. These botanical superheroes — consider cattails, bulrushes and sedges — serve as vital nutrient absorbers, particularly for nitrogen and phosphorus, functioning as living filters. Their roots offer hospitable habitats for bacteria, facilitating the breakdown of complex molecules into simpler compounds. 

However, beyond their functional roles, aesthetics also play a crucial role. Picture a wetland bedecked with vibrant irises and elegant water lilies — an enchanting spectacle captivating both humans and dragonflies alike.

Underneath the water’s surface, a mesmerising microbial ballet takes place. Bacteria, archaea and fungi harmonise, engaging in intricate chemical manoeuvres. Toxic ammonia is transformed into benign nitrate, while phosphorus molecules form stable compounds, preventing downstream havoc. 

This symphony of life unfolds without a conductor, guided only by the innate rhythm of existence.

Our verdant allies serve diverse functions. Their roots oxygenate the soil, fostering an environment conducive to aerobic bacteria. 

As water meanders through their intricate root systems, nutrients are absorbed while contaminants are ensnared. However, this relationship isn't unidirectional; plants also benefit. They flourish on the organic feast provided by the microbes.

Nature’s filtration system

Constructed wetlands replicate the functionalities of natural wetlands but are purposefully designed to efficiently treat wastewater. They comprise shallow basins adorned with wetland vegetation such as reeds, rushes and sedges. 

As wastewater traverses through these basins, a series of physical, chemical and biological processes unfold, effectively eliminating contaminants and enhancing water quality. Constructed wetlands present numerous benefits:

Cost-Effectiveness: In contrast to traditional treatment facilities, constructed wetlands frequently offer a more economical option for construction and upkeep. Their construction and maintenance entail minimal energy consumption and lower operational expenses, rendering them especially appropriate for settings with limited resources.

Versatility: Constructed wetlands can be customised to address diverse forms of industrial wastewater, effectively managing a broad spectrum of pollutants and contaminants. These wetlands can be configured as either free-water surface or subsurface flow systems, chosen based on the particular needs of the location and the characteristics of the pollutants present.

Environmental benefits: In addition to their primary role in wastewater treatment, constructed wetlands offer supplementary environmental advantages. They function as habitats for a wide array of plant and animal species, promoting biodiversity conservation. Moreover, they contribute to ecosystem services such as flood control and carbon sequestration, further enhancing their ecological significance.

Scalability and bdaptability: Constructed wetlands are flexible in their scalability, able to be adjusted to fit various industrial operations and spatial limitations. They are versatile, accommodating both centralised and decentralised wastewater treatment methods, thereby providing adaptability in their deployment.

India boasts several remarkable locations where constructed wetlands are utilised for wastewater treatment. 

One such example is the Asola Bhatti Wildlife Sanctuary in Delhi, situated on the city’s outskirts. Here, a constructed wetland system aids in purifying sewage from nearby settlements while also providing a sanctuary for diverse flora and fauna, thus contributing to regional biodiversity conservation.

In Chennai, Tamil Nadu, Perungudi and Kodungaiyur regions have implemented constructed wetlands as part of their decentralised wastewater treatment strategy. These wetlands effectively treat sewage from local communities, alleviating the burden on centralised treatment facilities and significantly reducing pollutant levels.

The Kolkata East Wetlands in West Bengal, designated as a Ramsar site, feature a vast network of natural and constructed wetlands. These wetlands play a vital role in treating wastewater from Kolkata and its environs while also offering livelihood opportunities for local communities engaged in fishing and agriculture.

In Haryana, Palla village located along Yamuna river hosts a constructed wetland system that treats wastewater from Delhi before its discharge into the river. This initiative helps enhance water quality in the Yamuna and mitigates pollution levels downstream, benefiting both human populations and aquatic ecosystems.

Auroville, an international township in Tamil Nadu, has implemented decentralised wastewater treatment systems, including constructed wetlands, to manage sewage generated within its premises. These systems align with Auroville’s principles of sustainability and ecological stewardship, highlighting the potential for community-driven approaches to wastewater management.

In Rajasthan, the Sariska Tiger Reserve has embarked on an innovative initiative, utilising constructed wetlands for treating wastewater from nearby villages. This approach not only addresses the sanitation needs of local communities but also aids in maintaining the ecological integrity of the reserve, supporting the conservation of wildlife habitats.

Opportunities and challenges in Indian context

In India, the potential for utilising constructed wetlands in industrial wastewater treatment is immense. With its rich biodiversity and abundance of wetland ecosystems, the country presents favourable conditions for their widespread adoption. 

Additionally, the decentralised nature of many industries in India makes constructed wetlands an appealing option for on-site or cluster-level wastewater treatment. 

However, several challenges must be dealt with to fully harness the benefits of constructed wetlands in India. Clear policies and regulatory frameworks are essential to encourage the adoption of constructed wetlands in industrial wastewater treatment. Providing incentives and subsidies can incentivize industries to invest in sustainable wastewater management practices.

Raising awareness and enhancing technical expertise among stakeholders, including industry professionals, regulators and local communities, is also vital for the successful implementation and operation of constructed wetlands.

Continuous monitoring and research efforts are necessary to evaluate the performance of constructed wetlands in diverse industrial settings. This includes optimising design parameters and addressing emerging challenges such as new contaminants and the impacts of climate change.

Engaging local communities in the planning, design and management of constructed wetlands fosters a sense of ownership and ensures the long-term sustainability of these systems. Active participation from community members is essential for the success of constructed wetland projects.

Constructed wetlands present a hopeful remedy for combating industrial wastewater pollution in India. By leveraging the innate filtration capabilities of wetland ecosystems, these systems adeptly treat wastewater while also yielding supplementary environmental advantages. 

Through the implementation of appropriate policies, capacity-building initiatives and community involvement, constructed wetlands have the potential to significantly contribute to the attainment of sustainable industrial progress and the preservation of water resources for forthcoming generations.

Diksha Pandey is Scientist ‘B’, Haryana State Pollution Control Board

Views expressed are the author’s own and don’t necessarily reflect those of Down To Earth

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