Hello Eva,
I know that in Brazil, the Brazilian Agricultural Research Corporation (Embrapa9), in the early 2000, developed some studies on re-use of the reject water from small reverse osmosis systems implemented in rural areas. They were re-using the reject water to raise fish (Tilapia) and irrigate a plant called erva-sal (salt grass), which has good forage properties for consumption by goats and sheep. I think that the local farmers are still using it. If you want I can put you in contact with someone from Embrapa.