UMPP Seawater Reverse Osmosis Plant, India

A seawater desalination plant is under construction at India's first ultra mega power project (UMPP) at Mundra coast, in the Kutch district of the state of Gujarat. It is one of the country's first major desalination plants in recent years.

The main boiler and utilities of the UMPP will use treated seawater from the desalination plant for cooling and various end-user applications.

The desalination facility at the power plant will use seawater reverse osmosis (SWRO) technology and will have a seawater treatment capacity of 25,200m³ a day (4,622gpm / 25.2mld).

Construction of the desalination plant began in March 2009 and the entire SWRO project is scheduled for completion by mid-2010.

Project purpose

The coal-fired 4,000MW UMPP is India's first private sector power project to use super-critical technology. The Rs17bn ($4.2bn) project will be one of the most energy-efficient and environment-friendly power plants in the country. It is expected to be commissioned by the end of 2012.

The seawater required for the power plant is drawn from the Mundra coast in Gujarat. Total dissolved solids (TDS) in the feed water vary from 42,000mg per litre to 46,000mg per litre with a maximum temperature of 95°F (35°C).

The main challenge in the design of the desalination plant is that it should be able to recover 40% TDS from the difficult feed water through permeates.

UMPP plant design

The RO desalination plant consists of a 514gpm (2 x 1,400m³ per hour) pre-treatment plant with lamella clarifiers, two-stage pressure filters with dual media and pressure sand filters, an SWRO system consisting of four streams of SWRO banks and two banks of brackish water reverse osmosis (BWRO).

Two open channels measuring approximately 6.5km and 4.9km in length will be constructed at the plant for seawater intake and the discharge of condenser cooling seawater, respectively.

Water pre-treatment

Sodium hypochlorite is added to the feed seawater and pre-treatment is done in the lamella clarifiers where coagulant and polymers are added. The clean water will then be fed to the primary filters followed by polishing filters.

The filtered water can be sent to a filtered water tank and filtration can be repeated by pumping the water through backwash pumps.

Water treatment process

Prefiltration antiscalants are added to the filtered water before passing it through cartridge filters. The water will be then added with sodium bisulphite and pumped into seawater RO units using SWRO booster pumps. The desalinated water is transferred to a suckback tank and finally stored in a permeate tank. The treated water is supplied to the power plant from the permeate tank.

A part of the desalinated water in the permeate tank will be further treated in the BWRO system to produce permeates of 3,600m³ per day (660gpm). The pure water will be passed to the upstream mixed beds demineralisation plant for boiler feed applications.

The technology by Aquatech at SWRO outlet will produce treated water quality with TDS levels of less than 450mg per litre for a feedwater TDS of 42,000ppm. The TDS levels at the BWRO outlet will be less than 5mg per litre. The concentrate disposal generated from the plant is discharged back to the sea with a line connected to the cooling tower.

Key players

The Mundra UMPP is entirely owned by Coastal Gujarat Power (CGPL), a special purpose vehicle formed for the project by Tata Power. Tata Power is the largest private sector power utility in India with a power generation capacity of 2,300MW and is also involved in trading, transmission and distribution of power.

In October 2008, CGPL awarded the engineering procurement and construction contract for the SWRO desalination plant to Aquatech Systems Asia. The value of the contract is approximately Rs710m ($15.47m). Aquatech will also provide operation and maintenance services for the desalination plant for three years after the project's commissioning.