Elimination of steroidal sex hormones by conventional water treatment and membrane processes

According to date from the literature, steroidal sex hormones are present in water environments in very low concentrations, about 1 ng/l (yet for organisms they are physiologically active). Estradiol and ethinylestradiol were also found in drinking water samples at concentrations of up to 2.1 ng/l and 0.5 ng/l, respectively. Consequently, producing drinking water from hormone-contaminated surface water calls for processes that completely remove these compounds. Therefore, there is a need to develop a method for hormone removal to reduce risk to both humans and the environment. Nanofiltration (NF) is a promising membrane technique with a large number of applications in the field of process water, drinking water or wastewater treatment. NF membranes can separate small organic micropollutants and multivalent ions from liquid streams. Previously the rejection properties of NF membranes for THMs, PAHs and phthalates were examined, and it was found that higher desalting membranes can effectively reject many hazardous organic pollutants. This paper discusses elimination of natural and synthetic steroidal sex hormones by conventional water treatment and membrane techniques from the aqueous phase. The efficiency of coagulation and adsorption on a granulated activated carbon process were not good enough to remove these compounds completely from water. As a second stage of water treatment, NF and coagulation–NF integrated systems were proposed. The application of NF in the second step of water treatment made it possible to remove the estrogens to a high degree: (1) >63%, NF and (2) >81.5% coagulation–NF.

The processes in question removed estrogens from the water flux in the following increasing order of efficiency: CFe < CAl < NF < CAl+NF < SGAC < SPAC. The lowest efficiency was observed during coagulation while sorption on activated carbon produced the best effects. The results found for NF suggest that it also may be applied to the treatment of water and wastewater; however, the need for further investigation into NF with respect to the elimination of estrogens from water flux should be emphasized. The question whether more advanced techniques such as UV radiation or ozonation should be employed becomes important. The literature suggests [13] that they are more efficient in estrogen elimination but not very common due to the costs. The main problem, however, lies in the lack of research on the toxicity of their byproducts. Estrogens lose their biological activity, but that does not mean they become harmless in drinking water.