RO

We are trying to get a water purification system for our college. I have been looking at the quotations and specifications. What worries me is the use of RO systems. Our plant may have a capacity of 500-1000 litres/hour. The ground water is quite hard....about 300-400 ppm CaCO3. The reject water will be really concentrated...say 12-1500 ppm. That water would probably not be suitable for plants or the lawn. So about 30 or 40 % of the water is wasted. On a large scale, RO is really wasteful.