Nanomembranes - Nanotechnologies for Water Environment Applications - page 378

human observations, it has been suggested that these compounds may affect human
reproductive system via food and drinking water. These adverse effects include the
development of hormone-dependent cancers, disorder of reproductive tract, decreased
levels of sperm production and compromised reproductive fitness (Zhang and Zhou,
2005).

Estrogenicity in wastewater effluents and surface water, where feminization of
male fish was observed, has been reported in many countries, such as USA, Australia,
and Germany. For example, Kolpin et al. (2002) reported 17-estradiol, 17-
ethynylestradiol, and testosterone to be present at averages of 9, 73 and 116 ng/L,
respectively, in surface water. Ethynylestradiol and 17-estradiol were also previously
reported at concentrations ranging from 0.2 to 2.6 ng/L (Snyder et al., 1999). Amongst
the estrogenic pollutants, the impacts of steroid estrogens such as estrone, estradiol and
ethinylestradiol are prominent as they have the highest endocrine disrupting potency
than other synthetic EDCs, despite of their low concentrations.

Four commercial NF/RO membranes were studied (Jin, 2007) for the removal of
EDCs (e.g., estrone) using a lab-scale cross-flow membrane cell system (Figure 12.6). It
appeared that estrone rejection was initially higher than 90% and decreased continually
until it reached a plateau value when adsorption equilibrium between estrone and
membrane was achieved. The continual decrease in the observed estrone rejection was
not surprising due to the continual decrease in the feed concentration of estrone and the
corresponding increase in the permeate concentration of estrone.

Concentrate

Permeate

Bypass

Test Cell

Pump

Water
Circulator

Feed Tank

Figure 12.6 Schematic diagram of the cross-flow filtration unit.