No abstract

Removal and formation of mutagenic activity during advanced wastewater treatment were investigated by using the Salmonella typhimurium strain TA100. The activity of direct acting mutagens appeared to increase at the recarbonation stage, where 6-10 mg/L of chlorine was added. Subsequent activated carbon treatment removed activity effectively but was apparently ineffective in removing precursors. Final chlorination typically with 25 mg/L of chlorine led to the reoccurrence of mutagenicity. Organic concentrates obtained by XAD-8 adsorption were separated by liquid-solid chromatography on silica gel. Mutagenicity was consistently found in the methanol fractions, which were further examined by GC/mass spectrometry. These fractions contained primarily carboxylic acids including brominated and nonbrominated alkylphenol polyethoxy carboxylic acids (BrAPECs and APECs). APECs were brominated during chlorination. Correlation between the occurrence of mutagenicity in the methanol fraction and the formation of BrAPECs suggested potential mutagenicity of these brominated compounds. However, preliminary experiments failed to confirm this hypothesis.

A full-scale (8-cfs [ 0.22-m3/s]) reverse osmosis (RO) water treatment plant equipped with conventional cellulose acetate membranes, and two pilot RO plants, equipped with polyamide membranes, were tested for their ability to remove total organic carbon and a broad range of trace organics, including volatiles, purgeables, neutrals, bases, phenols, and acids from lime-clarified secondary municipal wastewater. The full-scale RO system removed total organic carbon (TOC) by 89 percent to 0.95 mg/L at 84-percent water recovery, and the pilot RO systems removed TOC by 99 percent to 0.1 mg/L at water recoveries of 52 and 67 percent, respectively. The two membranes tested showed significant differences in their ability to reject trace organics. All membranes rejected branched, complex molecules but varied in their rejection characteristics for smaller molecules, such as chlorinated solvents. The latter group was rejected to a varying degree by polyamide membranes but passed through cellulose acetate membranes. The use of RO for trace organics removal is evaluated by comparing cumulative removals of different treatment schemes with and without RO treatment. Percent 84 52 67 *SF--Spread factor APRIL 1986 MARTIN REINHARD ET AL 163