| Popis: |
Water demand in the semiarid southwestern United States is approachingsustainable limits. Treated wastewater is frequently the last major untapped waterresource. Secondary effluent contains traces of hormones and other endocrine disruptingcontaminants. In Tucson, the vast majority of treated wastewater is either discharged tothe Santa Cruz River (which would otherwise be dry for 10-11 months of the year, orinfiltrated for groundwater recharge at the Sweetwater Recharge Facility (SRF). Soilaquifertreatment at the SRF is relied upon to polish effluent prior to its recoveryand reuse for landscape irrigation.There were three primary venues for the study described here: (i) the Roger RoadWastewater Treatment Plant (RRWTP), (ii) the SRF, and (iii) the Santa Cruz River.Secondary treatment at the RRWTP lowered the estrogenic activity of wastewater(influent to effluent) by 35-60 percent. Residual estrogenic activity in RRWTP effluentdecreased to near zero over a 24-hr detention period in the SRF infiltration basins, whileanti-estrogenic activity increased over the same period. Water collected from theunderlying unconfined aquifer, however, was again estrogenic, probably due to theselective removal of anti-estrogens during percolation.In the effluent-dependent Santa Cruz River, estrogenic activity decreasedcontinuously from the plant outfalls to a point about 25 miles downstream whereestrogenic activity reached the limit of detection. A corresponding increase in antiestrogenicactivity was evident. Monitoring wells along the stream produced levels of24estrogenic activity that were related to the fraction of wastewater effluent in respectivesamples (determined by the boron isotope ratio).The yeast estrogen screen (YES) procedure was modified by lysing the yeast afterreporter gene expression to establish the dependence of bioassay response on dyetransport kinetics. It was determined that β-galactosidase remains primarily inside thecell throughout the normal YES procedure. Furthermore, the rate of color developmentwas sensitive to trans-membrane transport of the dye substrate as well as the estrogencontent of the waters tested. The modified (LYES) procedure was capable of detectingboth estrogenic and anti-estrogenic activity in samples from effluent dependent streams. |
