Lahat BWRO plant: technical and economic evaluation of energy recovery alternatives

摘要

The Lahat BWRO plant was constructed as part of the southern Israel coastal aquifer rehabilitation project. Two RO trains, with a capacity of 10,000m(3)/d each, were commissioned in August 2010. In both trains a turbocharger (TC) energy recovery device was installed, wherein the turbine side utilizes the energy of the second stage brine to boost the second stage feed. Lahat plant expansion with two additional 11,300m(3)/d BWRO trains is currently under construction. As part of the pre-design phase, a techno-economic analysis was conducted with the purpose of finding the most cost-effective energy recovery configuration. Comparing existing design of TC added with a booster pump with alternative isobaric energy recovery with ERI PX devices, it was shown that implementation of isobaric PX results in a life cycle saving of 1,091,882$, about 1.5 times more than the TC alternative. Accordingly, in the design of the two additional RO units, isobaric energy recovery device was implemented. Apart from the cost benefit, this configuration has several advantages versus the TC, mainly the control of the second stage booster pressure with increased accuracy and flexibility. This enables a better balance of the first and second stage flux in comparison with TC option. The current paper includes an introduction about the southern Israel coastal aquifer rehabilitation project, and the construction plan of the Gat, Granot, and Lahat brackish water RO BWRO desalination plants. In addition, it presents the complexity of the marine brine disposal pipeline of these inland plants, and the rational that led to the innovative idea of energy recovery in the Lahat BWRO plant. Finally, the technical and economic considerations of energy recovery alternatives in BWRO plants are discussed and summarized.