The minimal availability of fresh water during the dry season seems to be a classic problem that occurs in Pamekasan Regency. Based on data from the Regional Disaster Management Agency (BPBD) of the Pamekasan Regency Government, it shows that the drought that occurred in Pamekasan in 2019 was 325 hamlets in 82 well-known villages in 11 sub-districts. This data shows that most of the coastal areas in Pamekasan Regency are still experiencing a fresh water crisis. Therefore, alternative water treatment is needed to help provide fresh water in this area. Desalination is an important technology for coastal areas far from fresh water sources. The main objective of this study is to create a mini design for reverse osmosis desalination (RO) production in coastal areas to supply fresh water at the hamlet scale. The RO design for fresh water production of 5 m3/day is compact with brackish water well as raw material which has a TDS ranging from 5,000-10,000 ppm. In addition, this study also analyzes the economics of small-scale desalination based on the Revenue Cost Ratio (RC Ratio) with an RC Ratio value of 5.03, a Payback Period value of 0.17 years (2 months), and a production Break Event Point (BEP). Amounting to 149,007 liters (7843 gallons) and a BEP price of IDR 79.47/liter, the small-scale desalination business is declared profitable and feasible to be realized.

The most widely used salt production technique is the process of evaporating seawater into salt by utilizing sunlight. This study conducted to measure the weather parameter and salt production during the salt season in 2019. The method used to measure the rate of evaporation was with a impermeable pan to prevent leakage of water samples. The results show that the evaporation rate of freshwater (0°Be) is greater than saltwater (20°Be) and the evaporation in July (0.62 cm/day) is smaller than October (1 cm/day). The correlation coefficient during July until October 2019 for air temperature (r) = 0.964, humidity (r) = -0.985, wind speed (r) = 0.622, and sunshine duration (r) = 0.987. The total salt production was from July until October 2019 reached 37395 kg on a demonstration plot area of 0.43 hectares. It is estimated the total of production per hectare will reach 87 tons /season. And for 2020 based on in-situ data it is estimated that production will decrease which is salt production will begin in July 2020, unlike 2019 which began in June, this is due to the influence of changes from the West wind (Asian monsoon) to East wind (Australian monsoon).