Removal of 17B-estradiol(E2) and phosphorus using alternating attached growth filters

Abstract

The widespread presence of endocrine-disrupting chemicals (EDCs) in municipal and livestock wastewaters, especially E2, and the problem of excess phosphorus discharge have raised extensive concerns. Enhanced biological phosphorus removal (EBPR) is an effective method for the removal of phosphorus. An innovative approach is to use continuous flow alternating biological filter operated with two biofilters in series. The condition of each biofilter was alternated between anaerobic and aerobic conditions and vice versa. The highest phosphorus removal was 87.5±0.2 % for a cycle duration (CD) of 24 hours and HRT of 6 hours. Maximum nitrogen removal was 72.1±0.6 % for a CD of 3 hours and HRT of 3 hours. The results of the experiments indicate that CD and HRT had a significant impact on the biological activity. The overall impact of the CD was to create the environmental conditions for enhanced or inhibited phosphorus release and uptake. For short CD, a shorter HRT would favor higher phosphorus percent removal and vice versa. The experimental results show that a CD:HRT ratio of less than 4:1 should be used. In addition, for a given CD, the lower the HRT the worse off is the COD and TP removal (increasing ratios of CD:HRT). Increasing the COD:N and COD:P of the influent wastewater negatively affected phosphorus uptake as opposed to an increase of air:water ratio which was found to positively affect phosphorus removal. Experiment conducted at a low TP influent concentrations of 8 mgP/L indicated that percent removal was similar to that for an influent concentration of 16 mgP/L. The alternating biofilters were found to be effective in the removal of E2 with an overall removal of 96.5 %. For E2 removal, the efficiency declined for a decrease in the HRT of the system and air:water ratio. For the anaerobic biofilter, the percent removal of E2 was found to decrease with shorter HRTs. In the case of aerobic biofilter, an HRT of 3 hours gave similar percent removal as for higher HRTs. E2 removal was found to increase with a decrease in COD:N. In all studies, the metabolite, E1, was found which subsequently degrade within the column. For batch sorption experiments, the sorption coefficient, KF, of the Freundlich model 8.43 (μg1-1/n.L1/n.g-1) while the 1/n value was 0.664. Using mass balance, about 60 % of E2 was found to biodegrade and 14 % was adsorbed indicating that biodegradation may be the dominant removal mechanism.