A Techno-Economic Assessment of Distributed Membrane-Based Water Treatment Systems

Driven by an increased use of nitrogen-based fertilizers and nitrogen-fixing crops, groundwater nitrate contamination and water salinity have reached severe levels in many remote disadvantaged communities (DACs) adjacent to agricultural sites. These communities lack a centralized potable water supply and are dependent on groundwater for their drinking water. The Salinas Valley Distributed Water Treatment (SVDWT) Project was proposed as a reliable and affordable option for supplying safe drinking water to DACs where alternative measures were infeasible. In this approach, multiple wellhead water treatment systems in multiple DACs are virtually networked and operated remotely to provide economies of scale, leading to affordable operating costs. Reverse osmosis (RO) membrane systems with septic tank concentrate handling has proved to be a technically feasible means of treating groundwater in remote communities. Such systems are operationally simplistic and can remove a variety of contaminants over a wide range of nitrate and salinity levels, while meeting community water demand and regulatory water requirements. Here, we conduct a techno-economic assessment of a remotely operated wellhead water treatment system using actual expenditures and process data from a pilot plant operating in the Salinas Valley. Capital expenditures (CapEx) of the treatment system and site infrastructure (e.g. water tanks, septic tank) were calculated using recorded costs of constructing the pilot site. Operational expenditures (OpEx) were modeled using pilot plant process data. To further contextualize the cost of water treatment via a remotely monitored membrane-based system, it is compared to the modeled cost of treatment via ion exchange technology. It is demonstrated that remotely operated, distributed membrane-based water treatment systems are an economically viable solution to DACs suffering from groundwater nitrate contamination.