A Sea of Opportunities: Desalination to help achieve water supply stability

Desalination to help achieve water supply stability

The rate of population growth and levels of urbanisation in India have been as rapid as the pace of economic development. This has resulted in dwindling water resources and excessive exploitation of groundwater reserves across the country. Therefore, urban local bodies (ULBs) today face the daunting task of delivering an adequate quantity of freshwater to every household. A paucity of fresh water supply has not only caused inconvenience to citizens but also imposed a negative externality on the environment by way of depleting groundwater resources.

Today, the surge in demand for assured water supply is forcing most municipal agencies and industrial entities to look beyond conventional sources of fresh water. Accordingly, desalination has been identified as a key technology to address the ever-rising water demand and to ease the escalating dearth of water, both in terms of quantity and quality. Some coastal states have already deployed desalination plants to reduce the reliance on freshwater sources. In Gujarat and Tamil Nadu, a number of industrial players have set up desalination plants to meet their process water requirements. States like Maharashtra, Puducherry and Karnataka have also set up small-scale desalination facilities to provide potable water to industrial units. On the municipal front, Chennai has installed two desalination plants with a capacity of 100 million litres per day (mld) each. Also, there are plans to set up small-scale desalination plants to meet the growing drinking water requirements in the Visakhapatnam and Gopalpur coastal areas.

However, barring Tamil Nadu, most of the states have set up very small capacity desalination plants with limited coverage and significant scope for expansion.

Given the low penetration rate of desalination at present, the country offers huge potential, especially for industrial users such as thermal power plants, steel plants, nuclear power stations and oil refineries.

Market size and growth

India, with a vast coastline of over 7,515 km, is a buoyant market for desalination projects and currently ranks among the top 10 desalination markets in the world. Industry estimates suggest that the Indian desalination market (industrial and municipal) has been growing at a compound annual growth rate ranging between 15 and 18 per cent. In terms of value, the total estimated market size of the desalination industry stands at about $1 billion (2016). Going forward, the market value is expected to increase to over $2.83 billion by 2021.

The demand for desalinated water comes from both industrial and domestic consumers. Within the industrial space, desalination pro-

jects have been executed primarily to meet water requirements for thermal power plants as they are one of the biggest consumers of water, accounting for over 60 per cent of the total industrial water consumption. This is followed by oil refineries and cement industries. Within the municipal space, desalination projects have largely been executed to meet drinking water requirements of the growing urban population. Among states, Maharashtra, Karnataka, Rajasthan, Lakshadweep, Puducherry, and the Andaman and Nicobar Islands are attractive markets for the desalination industry.

Technology options

The two basic technologies used in desalination plants are membrane based and thermal based. Membrane-based technologies include reverse osmosis (RO) and electrodialysis, while thermal-based technologies include multi-stage flash evaporation, multieffect distillation (MED), multistage flash distillation (MFD) and multistage vapour compression.

Of all the feasible solutions, RO is the most commonly used technology in the country. In this method, drinking water is produced by forcing seawater through a semi-permeable membrane, producing pure water on one side and concentrated brine on the other. The total dissolved solids (TDS) count of water produced is normally around 300 parts per million (ppm). As per World Health Organization standards, the recommended TDS count for drinking water is fixed at between 300 and 500 ppm.

While the RO technology dominates the desalination market, MED technology is also being used extensively by the industrial segment for the simultaneous production of desalinated water and energy. As per industry estimates, MED technology consumes about 50 per cent less electricity as compared to RO.

Current deployment

Currently, the desalination market in India is dominated by small-scale plants that employ RO to treat seawater. Region-wise, the adoption of desalination processes is largely concentrated in the western and southern parts of the country. Tamil Nadu, which is the most active desalination market, has set up medium- to large-scale plants to meet its drinking water requirements. While Gujarat has also experienced a tremendous increase in desalination demand due to industrial growth, its market is largely characterised by small-scale plants that provide potable or industrial-grade water to industries.

In other coastal areas too, rapid urbanisation and population growth and the surge in demand for assured water supply is leading to the overutilisation of surface water and groundwater resources. All these factors are forcing industrial entities, and in some cases, municipal agencies to look beyond conventional methods, one of these being desalination.

Over the years, acceptability of desalination has gained ground and the industrial uptake has been fairly encouraging. Industries with large water footprints find desalination a feasible option to meet their water requirements efficiently and at a lower cost as compared to other water treatment modes. Thermal power plants and oil refineries are driving growth in the desalination market.

On the municipal front, currently, Chennai is the only city that has set up desalination plants to meet its drinking water requirements. Others like Visakhapatnam and Jamnagar are in the process of developing desalination plants to plug their water shortages, and these plants are currently in the preliminary planning stage.

Cost economics

Typically, the desalination process involves both high capex and opex costs owing to the high cost of energy in the country. In terms of cost per unit, there is no significant variation when using RO or MSF technology for desalination. A point to note is that MSF plants are more cost-intensive, but usually have higher production capacities. However, this technology is rarely used for brackish water. On the other hand, RO is a cheaper and more flexible technology, and can be applied to both brackish water and seawater. At present, the cost of establishing a desalination plant with a capacity of 1 mld (excluding the water intake system) is estimated to be in the range of Rs 50 million-Rs 60 million for plants using thermal technologies and Rs 40 million-Rs 50 million for plants using membrane technologies.

Over the years, desalination treatment costs have dropped steadily, making it a more competitive water supply augmentation and treatment option. However, high energy costs, opposition from NGOs, and the cost-competitiveness of other water treatment processes, still act as major deterrents to wider use of the technology. Besides, factors such as feedwater quality (brackish or seawater), type of technology, energy availability, geographic location and plant capacity also influence the cost of setting up a desalination plant.

The way forward

The potential of desalination of seawater and brackish water to meet growing municipal and industrial requirements is beginning to be realised slowly. Coastal areas like Chennai, Visakhapatnam, Dahej and Jamnagar are augmenting their existing desalination capacities and installing new units to meet future water demand.

The Indian desalination market is currently on a high growth trajectory. It is gaining prevalence as industries such as power, refineries and chemicals continue to adopt efficient and sustainable desalination technologies for the regular supply of fresh water.

Going forward, with the development of new and more advanced technologies such as the ultrafiltration membrane technology, electrochemical desalination module technology and solar desalination, the cost of desalination is expected to decline. However, RO will continue to be the preferred technology for executing projects in municipal areas and small-scale industrial units, at least in the short run.

That said, desalination can have an adverse impact on the environment through brine discharge. Moreover, it requires a large quantity of power. These factors have to be weighed against the benefits of using desalination to provide treated water.