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Section 2. Environmental protection / treatment technology REMOVAL OF 17β-ESTRADIOL (E2) AND PHOSPHORUS IN
ALTERNATING ATTACHED GROWTH FILTERS
Sutthipong Lapanunt1,2, Qing Tian3, Say Kee Ong4, and Tawan Limpiyakorn5 1 International Postgraduate Programs in Environmental Management, Graduate School, Chulalongkorn University, Bangkok 10330 Thailand 2 National Center of Excellence for Environmental and Hazardous Waste Management, Chulalongkorn University, Bangkok 10330 Thailand 3 Department of Environmental Science and Engineering, DongHua University, Shanghai 200051 China 4 Department of Civil, Construction, and Environmental Engineering, Iowa State University, Iowa 50011 USA 5 Department of Environmental Engineering, Faculty of Engineering, Chulalongkorn University, Bangkok 10330 Thailand 1. Introduction
E2 are known to be mainly removed through adsorption on floc/biofilm followed by
subsequent degradation by microbes within the floc/biofilm1. Significant removal of E2 has
been found in the presence of nitrifiers which have been shown to have estrogen removing
capability2. Long solids retention time (SRT) also tend to give better removal of E2 due to
longer exposure which is favorable for the effective adsorption and degradation3. In addition,
the high mixed liquor suspended solids (MLSS) will also contribute toward the adsorption of
E24. It is possible that attached growth filters with their long SRT and nitrification may be
able to remove E2 from wastewater. Biofilters can also retain high phosphorus-accumulating
biomass which may have several advantages in phosphorus removal over conventional
suspended growth systems5. Even though alternating filters are being developed to remove
phosphorus, there is a possibility that estrogenic compounds may not be removed in one of
the cycles of anaerobic and aerobic conditions.
2. Experimental Approach
A schematic of the attached growth filters system is presented in Fig. 1. Two identical filters made of PVC pipe with a diameter of 75 mm and approximately 1.70 m. Gravel with an average diameter of 5-10 mm as the packed media. Five equally spaced sampling ports were installed along the depth of each biofilter. The alternating filters were seeded using activated sludge from the aeration tank of a municipal wastewater treatment plant. The two biofilters were exposed to alternating anaerobic/aerobic conditions in cycles. The flow direction was reversed at the end of each cycle and the influent was always introduced into the anaerobic filter. Both biofilters were operated in an upflow Anaerobic
direction and the aeration rate was maintained at 3.0 L/min. Raw synthetic wastewater containing COD of 350 mg/L, 8 Fig. 1. Schematic of biofilters.
International Symposium on Environmental Management : Hazardous-Environmental Management Toward Sustainability 22-23 September 2008 Royal Hill Resort & Spa Nakorn Nayok, Thailand Section 2. Environmental protection / treatment technology
3. Results and Discussion
In this part, the effect of HRT at cycle duration of 12 ANAEROBIC
hr on phosphorus removal is shown in Fig. 2. Net phosphorus removal reached a maximum measured value of approximately 82% for an HRT of 4 hours. Removal rate dropped significantly at HRT 3 hours to as low as 5%. Low removal rate may be due to the lack of time allowed for phosphorus removal. The data suggested that the HRT has significant impact on biological removal of phosphorus in biofilters. Influent 1
10 Effluent
Sampling Ports
Fig. 2. Effect of HRT on phosphorus
Ammonia oxidation was not observed in the release and uptake with media depth
anaerobic column but in the aerobic column as shown in Fig. 3. The results show that nitrifiers quickly regained ANAEROBIC
their activity when it was re-aerated. HRT of 3 and 2 hours nitrifiers seem to be affected since nitrification /L
were decreased. Correspondingly, some denitrification -N 15
was observed under anaerobic condition (see Figure 4) while the increase in nitrate under aerobic conditions Influent 1
10 Effluent
Sampling Ports
Ongoing experiments on the removal of E2 under Fig. 3. Effect of HRT on the
aerobic and anaerobic are being conducted. E2 in the transformation of ammonia
liquid samples are extracted using solid phase extraction ANAEROBIC
and analyzed using GC-MS. Results of E2 removal under anaerobic and aerobic conditions will be presented at the 4. Conclusions
Phosphorus removal by using alternating anaerobic and aerobic conditions provided good phosphorus as high as 82% removal rate. Accordingly, the results suggested Influent 1
10 Effluent
Sampling Ports
that cycle duration and HRT had significant impact on the Fig. 4. Effect of HRT on the
biological activity. The overall impact of cycle duration transformation of nitrate
was to create environmental conditions which enhanced or inhibited phosphorus release and uptake. Acknowledgements
The research is partially supported by U.S. Environmental Protection Agency, contract no. References
1.
S.K. Khanal, et al., Environ. Sci. Technol., 40, 6537-6546 (2006).
J.S. Vader, et al., Chemosphere, 41, 1239-1243 (2000).
T.A. Ternes, et al., Sci. Total Environ. 225, 81-90 (1999).
Y.X. Ren, et al., Water Res. 41, 2341-2348 (2007).
D. Pak and W. Chang, Water Sci. Technol. 41, 487–492 (2000).
International Symposium on Environmental Management : Hazardous-Environmental Management Toward Sustainability 22-23 September 2008 Royal Hill Resort & Spa Nakorn Nayok, Thailand

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