Growing demand, concerns over droughts, over-allocation of surface water
resources, and depletion of freshwater aquifers have all made desalination of brackish
groundwater an increasingly important option for inland communities. However, these
communities must find a means to dispose of the concentrated saline residual waste
stream in an environmentally sound manner. Evaporation ponds are one of the primary
options, but this technology has a large land requirement, which makes it costly. A
concern for large facilities is that this technology is one of the few treatment methods that
offers decreasing returns to scale due to increasing boundary layer resistance for larger
ponds.
This study evaluated a number of innovative options for improving the performance
of evaporation ponds. Viable methods identified from the literature include the following: fabric
evaporators; wetted boundary layer breakers; salt-tolerant plants; and, droplet
spraying. Two cost models are developed, one for boundary layer breakers and one for
droplet spraying. Incremental costs and incremental evaporation enhancements are
compared with site-specific cost information for a wastewater treatment facility in
California's Central Valley. Results indicate that both boundary layer breakers and spray
technologies are cost-effective compared to a simple expansion of the pond area.
Boundary layer breakers appear to be more cost-effective per gallon incremental capacity
but have a lower evaporation enhancement capacity compared to droplet spraying (24%
enhancement vs. 35% enhancement). For a new facility, an example calculation with
preliminary cost information indicates that spray evaporation is more cost-effective
because of avoided pond excavation and lining costs. Boundary layer breakers are
preferred as a retrofit to an existing facility, if they provide sufficient additional capacity
to avoid the need for an expansion of the pond. Includes 16 references, appendices.
| Edition : | Vol. - No. |
| File Size : | 1
file
, 650 KB |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 13 |
| Published : | 11/01/2008 |
