Management of BWRO systems using long-term monitoring of feed water quality to avoid future membrane process failure

Abstract

A B S T R A C TPumping of wells from aquifers that are used to supply brackish-water reverse osmosis (BWRO) treatment systems commonly causes increases of water salinity in time. Some key aspects of assuring operational security are the magnitude of the water quality changes to assure that treatment can continue without failure of the process, reduction in installed capacity, or the necessity to modify the process by increasing the operational pressure and changing the membranes. An example of a BWRO system that uses a leaky aquifer system as a source of feed water located in Florida shows that careful monitoring of the well water quality and individual well pumping rates over a 10-year operating period can be used to assess the projected long-term changes in water quality with regard to the treatment facility design. The total dissolved solids concentration of the wellfield began with an average TDS of 2,461 mg/L which changed over 10 years to an average of 2,855 mg/L. The variation in time is linear and the projected average change for the next 20 years shows that the average TDS for the current pumping rate will increase to 3,611 mg/L which is well below the design maximum TDS treatment ability of 8,129 mg/L.

Impacts of Feedwater Quality Change on the Oldest Continuously Operated Brackish-Water Reverse Osmosis Desalination Plant in the United States

“…The changes in water quality at the City of Cape Coral South Wellfield are similar to those found at Bonita Springs Utilities, Florida [20], the Island Water Association (Sanibel Island, Florida) [43], the Town of Jupiter, Florida [44], and the City of Clewiston, Florida [45]. The impact of a fault shows some enhanced upward movement of higher salinity water in some wells, which is similar to that found in the North Cape Coral Plant, Florida [42], and the City of Fort Myers, Florida Plant [46].…”

“…Many other BWRO facilities have been designed and operated without using groundwater solute transport modeling during the design process, such as the Bonita Springs [20] and City of Clewiston [45] facilities in southern Florida. The Bonita Springs facility was conservatively designed, and the changes in feedwater quality did not change significantly, thereby allowing normal operations for the full life expectancy of the plant.…”

Sustainable Groundwater Exploitation Aiming at the Reduction of Water Vulnerability in the Brazilian Semi-Arid Region

“…Regarding the desalination process, weighted concerns comprise the possibility of increasing the salinity of the wells that supply water to BWRO systems [88], which, in case the correct disposal of the effluent (concentrate) does not happen, will be rendered unproductive. In this context, another point to be highlighted, this time foreseen in the PAD design, is the use of effluents in a productive system contemplating fish farming and farming.…”

Pumping-Induced Feed Water Quality Variation and Its Impacts on the Sustainable Operation of a Brackish Water Reverse Osmosis Desalination Plant, City of Hialeah, Florida, USA

“…The groundwater model developed to evaluate the site-specific conditions needs to match the life expectancy of the BWRO facility, with a common range of 20 to 30 years based on the facility design criteria and the conceptual model of the feedwater source aquifer [13]. The most common conceptual solute transport model used in southern Florida shows that the changes in water quality are caused by the upward movement of higher salinity water during pumping, which is controlled to a large extent by the pumpinginduced drawdown in the source aquifer and the leakance of the lower confining unit [18] (Figure 1). ing a hydraulic analysis that assesses the water level (pressure) drawdown in the proposed wellfield, which is used for optimizing well spacing and yields, and the solute transport aspect, which predicts the changes in water quality (TDS or dissolved chloride) with time [4].…”