AWWA ACE68912

Growing demand, concerns over droughts, over-allocation of surface waterresources, and depletion of freshwater aquifers have all made desalination of brackishgroundwater an increasingly important option for inland communities. However, thesecommunities must find a means to dispose of the concentrated saline residual wastestream in an environmentally sound manner. Evaporation ponds are one of the primaryoptions, but this technology has a large land requirement, which makes it costly. Aconcern for large facilities is that this technology is one of the few treatment methods thatoffers decreasing returns to scale due to increasing boundary layer resistance for largerponds.This study evaluated a number of innovative options for improving the performanceof evaporation ponds. Viable methods identified from the literature include the following: fabricevaporators; wetted boundary layer breakers; salt-tolerant plants; and, dropletspraying. Two cost models are developed, one for boundary layer breakers and one fordroplet spraying. Incremental costs and incremental evaporation enhancements arecompared with site-specific cost information for a wastewater treatment facility inCalifornia's Central Valley. Results indicate that both boundary layer breakers and spraytechnologies are cost-effective compared to a simple expansion of the pond area.Boundary layer breakers appear to be more cost-effective per gallon incremental capacitybut have a lower evaporation enhancement capacity compared to droplet spraying (24%enhancement vs. 35% enhancement). For a new facility, an example calculation withpreliminary cost information indicates that spray evaporation is more cost-effectivebecause of avoided pond excavation and lining costs. Boundary layer breakers arepreferred as a retrofit to an existing facility, if they provide sufficient additional capacityto avoid the need for an expansion of the pond. Includes 16 references, appendices.

Product Details

Edition:

Vol. - No.

Published:

11/01/2008

Number of Pages:

13

File Size:

1 file , 650 KB