The design of the HUD water treatment plant utilizes advanced treatment technologies to provide for the purification of drinking water. These processes include dissolved air flotation, membrane filtration, granular activated carbon contactors, UV disinfection, and onsite generation of sodium hypochlorite.
These dissolved air flotation units allow for loading rates of 12 gpm/ft2, which is much greater than that of a traditional settling basin. The units promote the removal of organics by floating the sludge, which is removed by a scraper mechanism. This process requires approximately 30% less coagulant and provide for effective removal of organic material, such as algae, that create problems for membrane filters.
A Pall membrane system will be used for the filtration. The membranes provide for the removal of all material greater than 1 micron. This provides for a 3-log removal credit for cryptosporidium, and a constant effluent water quality.
After filtration, water will enter the granular activated carbon contactors. These contactors provide for the adsorption of dissolved organic precursors and humic acids that react with chlorine to form disinfection by-products. This process also eliminates taste and odor problems that are common with surface water.
To eliminate the concerns of storing gas chlorine the facility will generate a 0.8% bleach solution from salt. The process uses salt and electricity to generate a low concentration bleach solution to obtain free chlorine residual in the finished water.
This project is scheduled for completion in August 2014.