Hormones and pharmaceutical residues reduction by the NBS

NBS as a buffer to maintaining river life – An Italian-Israeli

Treated water of varying quality is fed into rivers all over the world. In Israel, all water sources are used for drinking water, so treated water is the only water source for rivers. In many cases, the quality of treatment is not sufficient. We present a case where even the “Shafdan”, an activated sludge facility in Israel, considered state of the art, meeting Israeli (and European) regulations, fails to cope with hormones and pharmaceutical residues.

Long-run chemical and biological monitoring of the river has shown:

  1. An activated sludge facility is sensitive to fluctuations and cannot guarantee consistent
  2. Though it sometimes complies with BOD and TSS regulations, other parameters make the water unsuitable for maintaining river life.
  3. Throughout its course, the river is getting non-point and illegal wastewater fed into it, dramatically affecting quality.
  4. Adding treated water of this quality to the river and the effect of the non-point sources brings disastrous results: from total extinction of species to sex changes in fish.

The “Shafdan” project, established in 2004-2005 and run for five years, was financed by the Italian government, designed and executed by Eli Cohen/Ayala, and was checking the ability of NBS to bring the secondary water to a level that ensures safety for all living creatures, and serves as a buffer in cases of “Catastrophes” and severe fluctuation of water quality. Special attention is given to parameters not addressed by regulators (E.g., hormones) that affect rivers and other water aquifers.

For this purpose, we had been asked by the project research team to design and construct an NBS system that will allow demonstrate the abilities of the natural base solution in different conditions and hydrology regimes and parallel to other conventional technologies. The designed system contains 21 ponds in 7 parallel systems, three units in each system acting as a complete independent treatment system. The systems received secondary effluent from the activated sludge facility; the last pond in each row simulates the river. This project was designed to run for five years.

This project demonstrated the ability of NBS to treat pharmaceutical residues, E.g., Hormones, out of secondary and tertiary conventionally treated sewage water, contaminates which were proven to affect life in water and to reach drinking water sources further. On a larger scale, the NBS can be a part of the river and its riverbank bio-sphere, serving as a powerful treatment and buffer zones as well as a tourist and educational attraction while maintaining the balance that enhances life in that section of the river.

This project was designed to give the regulators and authorities a tool to maintain living rivers where the natural fauna and flora can flourish and human beings can find peace and beauty with no hazards to their health.

The research outcome, attached to the article’s chapter, has shown a remarkable ability of the NBS to reduce 96% of Hormones carried in treated water!


Dana Milsteina, Avital Gasitha and Dror Avisarb

aFaculty of Life sciences, Department of Zoology, Tel Aviv University, Israel

bGeography and Human Environment, Hydrochemistry Laboratory, Tel Aviv University, Israel

One of the key environmental problems facing humanity emanates from the widespread and diverse contamination of freshwater (Schwarzenbach et al., 2006). New contaminants are continuously being identified and become the focus of new investigations. Recently, micro-pollutants were recognized as a threat to the integrity of aquatic environments (Schwarzenbach et al., 2006). These pollutants are compounds that are present in the environment in minute concentrations (micro and nanograms per liter) and thus are hard to detect. Known micro-pollutants include chemicals for human use such as pesticides, pharmaceuticals and cosmetic products. Such contaminants reach aquatic systems and soils together with the effluents and sludge that are discharged into the environment (Shore et al., 1993; Ingerslev and Halling-Sørensen, 2003). The presence of estrogens in primary and secondary effluents reveals that they are not completely removed by conventional wastewater treatments (Kreuzinger et al., 2004; Pawlowski et al., 2004; Kolodziej et al., 2003). Developing and implementing cost-effective wastewater treatment technologies to remove micro-pollutants is therefore a major challenge (Schwarzenbach et al., 2006). Here we review the current knowledge on the removal efficiency of estrogens from municipal wastewater effluent by environmentally friendly, wetland technology. Findings of our recently completed research are included (Milstein et al., in preparation).

Discussion and conclusions

Only a few studies on the removal of estrogens or estrogenicity from municipal effluent by wetland systems have been reported, all from 2000 on (7 on SF and 4 on SSF). The estrogens examined are mostly the natural ones E2 and E1 and a synthetic one EE2. These estrogens were commonly found in domestic sewage effluent and are considered the most potent ones among the endocrine disruptors (e.g. Khanal et al., 2006).

In most cases direct evidence for the pathway of estrogen removal is lacking. Measurable attenuation as well as failure of significant removal of estrogens was reported in SF wetlands. The attenuation of estrogens in SF is attributed mostly to adsorption and biotransformation. It is suggested that increasing vegetation density will improve estrogen removal by providing greater surface area for biofilm development, enhancing adsorption and biotransformation processes (Brix, 1997; Gray and Sedlak, 2005). Decreasing wetland depth so that more water flows through the roots and sediments as well as increasing hydraulic retention time were also recommended (Gray and Sedlak, 2005). However, achieving high removal of estrogens by the latter will require an HRT of months (Metamoros and Bayona, 2008), making most SF CW impractical. Additional improvement of estrogen removal in SF wetlands can be attained by enhancing oxygenation of the system to support a higher rate of biodegradation (Laboratory experiments, Milstein et al., in preparation; Lee and Liu, 2002; Andersen et al., 2004). We found no evidence for removal of estrogens in SF CW by photo-degradation. In an experiment in which E2 was dissolved in secondary effluent and exposed to sunlight for 24hrs in open glass beakers, only 10% was photo-degraded, compared to none in the dark (Mansell et al., 2004). Little or no photo-degradation may be expected in turbid or shaded SF systems (Gray and Sedlak, 2005; White et al., 2006). Existing evidence suggests that in sub-surface flow wetlands estrogens are mostly attenuated under aerobic conditions by biotransformation and degradation (Song et al., 2009; Milstein et al., in preparation). This conclusion is supported by findings that in conventional wastewater treatment plants too, estrogenic compounds are mostly degraded under aerobic, nitrifying conditions (e.g., Liu et al., 2009).

Indeed, high estrogen removal within a short HRT (hours) was found in vertical flow wetlands, which are characterized by aerobic conditions. Lower removal rate may be expected in horizontal systems which are characterized by a network of aerobic, hypoxic and anoxic zones (Vymazal, 2003). Indeed, no attenuation of estrogens was recorded in both the HSSF and SF systems, where hypoxic conditions prevailed (Peterson and Lanning, 2009; Milstein et al., in preparation). This conclusion is also supported by the observation that estrogen attenuation was reduced in vertical saturated wetlands, compared to that measured in unsaturated conditions (Song et al., 2009). High (>90%) removal of estrogen in HSSF CW reported by Masi et al. (2004) contradicts the above conclusion. However, Masi et al. (2004) examined estrogen removal from primary effluent in which estrogen concentration as well as the concentration of suspended solids was extremely high. It is highly probable that the estrogens were adsorbed to suspended solids and removed by TSS filtration and sedimentation. It should be noted that the detection limit of estrogens in Masi et al.‘s study was 15ng/l; hence the presence of high residual concentration of estrogens in the HSSF effluent is possible.

Although high and rapid attenuation of estrogens in wetlands is attributed mainly to biotic processes, adsorption cannot be ruled out as an important mechanism under certain conditions. For example, in wetlands with a high surface area and rich in organic substrate (Ingerslev and Halling-Sørensen, 2003; White et al., 2006).

The role played by the vegetation in estrogen removal is unclear. Higher estrogen removal in SF wetlands is attributed to vegetation (Gray and Sedlak, 2005; Peterson and Lanning, 2009). Song et al., (2009) suggest that the vegetation enhances removal efficiency in VSSF by providing a dense root system with a large surface area for biofilm development and pollutant adsorption. Moreover, they argue that the vegetation increases oxygen concentration in the rhizosphere, releases exudates that are exploited by estrogen degrading microorganisms, and takes up and assimilates estrogens in plant tissue. In contrast, we have demonstrated a similar efficiency of estrogen removal in plant-free and densely vegetated VSSF cells (Milstein et al., in preparation). We therefore suggest that the biofilm coating the wetland gravel in VSSF systems can account for most estrogen transformation and degradation activity.

More studies are needed to examine estrogen removal efficiency, particularly in full-scale wetlands. Furthermore, studies are needed to elucidate the removal mechanisms and their significance in different wetlands types, and under different operation variables and climate conditions. Particular attention should be given to quantifying the contribution of the vegetation.