AWWA WQTC55187

This study evaluated three promising alternatives for pretreating Colorado River water (from the Central Arizona Project canal) prior to nanofiltration/reverse osmosis (NF/RO) treatment. Microfiltration was found to be the most appropriate pretreatment technology for the surface water that was evaluated. Slow sand filtration also appeared to produce water of desirable quality for NF/RO treatment. Membrane autopsy results indicated that catalytic conditioning was effective in controlling scaling from calcium-based salts but was ineffective in preventing sulfate scale formed from non-calcium co-ions such as barium and strontium. Chemical conditioning appeared to be effective in controlling both carbonate and sulfate scales. Since sulfate scale is more difficult to clean than carbonate scale and because of the high precipitation potential for barium sulfate in Colorado River water, chemical conditioning with acid and anti-scalant addition is recommended for this water. Includes tables, figures.