Transformation Of Steroid Estrogens During Anaerobic Process

Steroid estrogens, as a typical endocrine-disrupting compound, arecharacterized by highly toxic with low doses, mainly derived from sewagetreatment plant effluent and livestock waste, especially dairy cattle manure. Inrecent years, with the development of the dairy industry, estrogen pollutionhas become more and more seriously in the environment surrounding dairyfarms. To resolve the problem on removal of steroid estrogens in dairy cattlemanure, in this study, the anaerobic transport and transformationcharacteristics of steroid estrogens were investigated by static adsorptiveexperiment and batch-type anaerobic digestion experiments.17β-estradiol(E2) and estrone(E2) adsorption to inactivated anaerobicsludge was studied by static test. The results followed that the adsorptionprocess of17β-estradiol (E2) and estrone (E2) could be described well bypseudo-second-order kinetic equation and Freundlich equation. And theadsorption rate of E1and E2was very large in the first60min and the first20min respectively, and the adsorption equilibrium time was just90min and60min respectively. The adsorptions were spontaneous and exothermic physicaladsorption processes on the basis of thermodynamic analysis, which wasaffected by pH and ferric-ion to some extent. The adsorbance of E1and E2were the largest in neutral solution. And the adsorption of E2was promoted byferric-ion, the adsorption of E1was promoted by ferric chloride while wasinhibited by FeOOH.The effect of ferric-ion and calcium ion on the degradation of estrogen indairy cattle manure was investigated by batch-type anaerobic digestionexperiments. The results indicated that the production of volatile fatty acidsand methane was affected by spiked E1, E2and E3. Acetate and valerate wasproducted mainly in five different conditions during the anaerobic digestionprocess, that organic acid was cumulated at later stage of the experiments.Methane-producing rate could be followed the first order kinetic model wellamong the5th-15th day, and the maximum production of methane was largestin the digestion experiments spiked with E3while was smallest in the digestion experiments spiked with E1. The inhibitory effect of calcium ion onmethane production was found in the digestion experiments spiked with E1,E2and E3. The long-term experiment results showed that the The degradationeffect of E1, E2and E3was poor. However, the concentration of E1, E2andE3decreased rapidly at the first two days, which due to the interaction ofadsorption and degradation. During the process of the long-termexperiment(2-120days), the concentration of E1increased with thetransformation of E2and then decreased slightly. And the concentration of E2decreased slowly and was to stabilize at last. And he concentration of E3increased after30days, decreased after the42days and was to stabilize afterthe100day.The effect of ferric-ion and calcium ion on the degradation of mixed estrogens(E1, E2, E3and EE2) in dairy cattle manure was investigated by batch-typeanaerobic digestion experiments. The results showed that the volatile fattyacids was main acetate and then propionate. And methane was produced laterand the producton was lower in the experiment spiked with ferric chloride thanother experiments. Methane-producing rate followed first order kinetic modelwell among the the7~54day in five different conditions during the anaerobicdigestion process. The final concentration of E1, E2, E3and EE2was0.64-0.92mg/l,0.02-0.07mg/l,0.84-1.16mg/l and0.18-0.32mg/l in five different conditions.However, the total transformation rate was very low. And the totalconcentration of steroidal estrogens decreased rapidly at the first3days andthen varied little. It was taken place that E2transformed into E1and E3,which leaded to the concentration of E1and E3increasing, but thetransformation of EE2was not obvious. Compared with the results of theexperiments spiked with one estrogen, mixed estrogens boosted the formationof propionate but inhibited the formation of valerate, and the facilitation ofcalcium ion to produce methane was found in the experiments both spikedwith one estrogen and mixed estrogens, ferric-ion boosted the production ofmethane in the experiments spiked with one estrogen but inhibited in theexperiments spiked mixed estrogens. The concentration of E1increased largerafter the20th day but lower when tended to stabilize in the experiments spikedE1than spiked mixed estrogens. The concentration of E3varied very littleamong the9th-30th day, and increased larger among the31th-100th day in the experiments spiked E1, but it was the same tended to stabilize as in theexperiments spiked mixed estrogens.