"Tata Chemicals is challenging Unilever’s India unit for the world lowest cost home water purifier, based on a rice husk ash filter. With a starting retail price of $16 for the unit, it costs less than half of Hindustan Unilever‘s breakthrough PureIt unit which has been a runaway success in India with $40 million in sales and three million units delivered already. The replacable filter for the Tata unit costs $6." (Quoted from article)