Investigation of concentrate discharge methods in desalination systems used for greenhouses

Greenhouse cultivation has a special position in agricultural development and increase of production in this sector in Iran. It's important because of sustainability and continues production during the year and out of agricultural season. As important issues in greenhouses production systems, availability of the inputs such as fertilizers, pesticides and etc., and depletion of irrigation water quality by increasing salinity (especially in groundwater) could be mentioned. Under this situation, the greenhouse owners have to use water desalination systems (WDS) to better production and benefit. Using WDS is along with a more salty concentrated discharge (CD) in comparison with inflow water where improper disposal may cause serious environmental issues. In this research to study the disposal CD issues, several greenhouses were investigated in Qazvin, Alborz and Tehran provinces. The water samples from well water, desalinated water and CD were collected and laboratory analyzed. Also, a questioner was designed to collect supplementary information's. The results showed that in most of such greenhouses, the main option is dispose of CD into the environment without any considerations. Only in one of the greenhouse, they were using the CD in production of industrial ice. The salinity of well water pumped to WDS was between 0.67 to 3.59 dS/m and the salinity of concentrated discharge was ranged from 1.12 to 5.72 dS/m. The SAR amounts for CDs varied between 0.51 to 6.52. The training level of operators to use WDS was low and it was mostly about the general concepts. According to the results, development of WDS application in greenhouses without considering environmental aspects, especially in relation with CD, causes serious environmental issues such as contamination of groundwater, soil degradation and salts accumulation in soils.