Watervap’s Patented Zero Liquid Discharge Technology

Description

Brine (and other dissolved mineral solutions) concentrator systems are frequently faced with the unique challenge of handling a fluid containing inverse solubility scaling constituents, such as silica and calcium sulfate.  These troublesome fluids will always create severe scaling, fouling and plugging problems within conventional heat exchangers. The development of the Fluidized Bed Heat Exchanger (FBHX) Technology in Europe in the mid 1970’s led to a highly successful seawater desalination plant installation in the late 1970’s.  This facility demonstrated the FBHX Technology’s capability of handling chemically untreated seawater at temperatures approaching 250°ƒ.  The success of this “breakthrough technology” demonstration led to multiple installations involving troublesome waters with high scaling and fouling tendencies.

The FBHX Technology was then found to provide the ideal solution for handling geothermal brines in Iceland.  The high concentration of dissolved solids, with both sodium and silica present in the geothermal brines (1200 ppm TDS – parts per million total dissolved solids), will cause severe fouling in conventional heat exchangers.  The scouring action of high density metallic particles within the FBHX provide continuous cleaning of the heat exchanger tubes removing all deposits as they form.

Although FBHX technology was originally applied to seawater and brine applications, the demands of industrial clients (Exxon, DuPont, Phillips, BP Chemical, Royal Dutch Shell, Hoechst-Celanese, Bayer, BASF, and others) have applied it to a diversity of applications.

As illustrated here, the initial stage is membrane distillation.  If the input is dilute, membrane distillation will desalinate the bulk (50% to 80%) of the water very efficiently, thereby reducing the overall energy cost of achieving a dry salt output.  If the input is too concentrated, the membrane distillation stage will be skipped and the flow directed to Stage 1 of Watervap’s Brine Disposal System (BDS). This is the case in seawater reverse osmosis plants where100 gallons of sea water produces about 50 gallons of potable water and 50 gallons of highly concentrated effluent, which becomes a direct input to Watervap’s BDS.

The BDS Stage 1 further reduces the input effluent to potable water and a now super concentrated outflow is directed to the second stage.  The second stage is a Fluidized Bed Spray Dryer capable of reducing the FBHX outflow to dry minerals and a small amount of steam.  It is this final stage that enables Watervap’s technology to claim “Zero Liquid Discharge” to satisfy federal and local regulations.

Although multiple stages increase the initial capital cost, this is more than offset by reduced operational costs over the life of the installation.  A spray dryer can handle virtually any fluid that can be sprayed, but it is not particularly energy efficient.  Preceding the spray dryer with the FBHX, which is much energy efficient, reduces the volume to be processed by the less efficient the spray dryer.  Similarly, in those instances here the input effluent is sufficiently dilute, membrane distillation is placed in front of the FBHX because it is a still more energy-efficient technology.

The first Watervap unit. It demonstrated Watervap’s technology in a variety of industries from Wisconsin to Florida and Texas.	Dry salt created incident to a demonstration of Watervap technology treating landfill.
Landfill leachate and the purified water created from it by Watervap technology.	Watervap BDS 2500 GPD unit at the manufacturing plant.