Agriculture Sector and its Challenges in water treatment

The agricultural sector in Peru is the largest user of water, accounting for 89% of the country’s water consumption. However, only 22% of agricultural land is irrigated, making it challenging for farmers to grow crops effectively. This inefficiency in water use is due to the poor condition of existing infrastructure, which adds to the difficulties of managing water resources.

Climate change is also a significant factor affecting the availability of water in Peru. The country is facing severe water scarcity because of climate change, which has led to the disappearance of glaciers and the drying up of lagoons that used to be crystalline water reservoirs for agriculture.

Reverse Osmosis and its unviability

Reverse osmosis (RO) is a technology used to purify water by pushing it under pressure through a semi-permeable membrane. The membrane will allow some atoms or molecules to pass but not the contaminants in the water such as suspended solids, salts, organics, and microorganisms. Reverse osmosis is a powerful technology to remove contaminants from water and is even used to desalinate sea water to produce drinking water. However, the technology comes with some limitations and disadvantages that limit its application at scale for reliable and low-cost decontamination of river water for household use and agricultural purposes.

One of the main limitations of RO is that it is a wasteful process, in the sense that for every liter of purified water, a reject stream of ‘contaminated’ water is produced with an increased concentration of the contaminants originally present in the water. Industrial RO systems typically run anywhere from 50% to 85% recovery depending on the feed water characteristics, which implies that for every m3 of clean water, 0.3-1 m3 of wastewater is produced. The wastewater flow itself may present a problem, depending on how it is disposed of, but the loss of 30-50% of the initial amount of available water is often not desirable.

In addition, RO has a relatively high cost in terms of the investment required for the installation itself, the cost of maintenance, and the (energy) cost of operating the plant. Since the principle of RO is based upon pushing water under pressure through a membrane, the pumps operating the RO plant require a constant source of energy. The total energy consumption depends on the quality of the incoming water (the more contaminated the water, the more energy is needed to push it through the RO membrane), but the process will require an order of magnitude of 2.5 kWh/m3 of energy. Estimates of the total cost of RO for decontaminating water are between 0.50 and 1 USD per cubic meter of purified water.