Removal Of Steroid Estrogens Research Articles

Nature based solutions for removal of steroid estrogens in wastewater.

Estrogens are a growing problem in wastewater discharges because they are continuously entering the environment and are biologically active at extremely low concentrations. Their effects on wildlife were first identified several decades before, but the environmental limits and the remedial measures are still not completely elucidated. Most conventional treatment processes were not designed with sufficiently long retention times to effectively remove estrogens. Nature-based wastewater treatment technologies such as treatment wetlands (TW) and high-rate algal ponds (HRAP) are economically feasible alternatives for decentralized wastewater treatment and have promise for removing steroid hormones including estrogens. For small communities with populations below 50,000, the overall cost of TWs and HRAPs is considerably lower than that of advanced decentralized treatment technologies such as activated sludge systems (AS) and sequencing batch reactors (SBR). This results from the simplicity of design, use of less materials in construction, lower energy use, operation and maintenance costs, and operation by non-skilled personnel. The nature-based technologies show high removal (>80%) for both natural and synthetic estrogens. Estrogen removal in TWs can be enhanced using alternative media such as palm mulch, biochar, and construction wastes such as bricks, instead of traditional substrates such as sand and gravel. While TWs are effective in estrogen removal, they have the disadvantage of requiring a relatively large footprint, but this can be reduced by using intensified multilayer wetland filters (IMWF). Using filamentous algae in HRAP (high-rate filamentous algal pond; HRFAP) is an emerging technology for wastewater treatment. The algae supply oxygen via photosynthesis and assimilate nutrients into readily harvestable filamentous algal biomass. Diurnal fluctuations in oxygen supply and pH in these systems provide conditions conducive to the breakdown of estrogens and a wide range of other emerging contaminants. The performance of these nature-based systems varies with seasonal changes in environmental conditions (particularly temperature and solar irradiation), however a greater understanding of operating conditions such as loading rate, hydraulic retention time (HRT), pond/bed depth, dissolved oxygen (DO) concentration and pH, which influence the removal mechanisms (biodegradation, sorption and photodegradation) enable TWs and HRAPs to be successfully used for removing estrogens.

Removal of Steroid Estrogens and Total Nitrogen by Denitrification Biofilter with UV/Peracetic Acid Pretreatment: Performance, Microbial Characteristics, and Mechanism

Total nitrogen (TN) and steroid estrogens (SEs) in secondary effluent challenge widely used denitrification biofilter (DNBF) in achieving the regulated limit value in water reuse, as well as toxicity reduction. Herein, we first use UV/peracetic acid (PAA) as a pretreatment of DNBF for advanced wastewater treatment, followed by an evaluation of its effectiveness in removing TN and SEs from low C/N wastewater. The results showed that UV/PAA-biofilter significantly improved the removal of TN and SEs compared to conventional DNBF. Under the conditions of [PAA]0 = 15 mg/L, UV = 1250 μW/cm2, photoreaction time of 30 min, and biofilter hydraulic retention time (HRT) = 3 h, the SE removal rates could reach more than 95% and the effluent TN maintained less than 10 mg/L. Furthermore, UV/PAA-biofilter improved the reduction of estrogenic activity but not of acute toxicity. Increased extracellular polymeric substance (EPS) content and relative abundance of napA gene were observed in DNBF pretreated with UV/PAA, and Azospira was identified as the core microorganism for denitrogenation. Our investigations confirmed the feasibility of the UV/PAA-biofilter to remove SEs and TN simultaneously, highlighting the great potential of its application in the advanced purification of secondary effluent for safe wastewater reuse.

A novel in-situ enhancement strategy of denitrification biofilter for simultaneous removal of steroid estrogens and total nitrogen from low C/N wastewater

Widely-used denitrification biofilter (DNBF) is facing the challenge towards the simultaneous removal of steroid estrogens (SEs) and total nitrogen (TN) from secondary effluent. Herein, slow-release calcium peroxide (SR-nCP) was firstly introduced into DNBF to construct SR-nCP/biofilter to in-situ enhance the removal of SEs and TN from low carbon to nitrogen (C/N) ratio wastewater. Results showed that the SEs removal rate could reach >95 % and the effluent TN maintained <15 mg/L. Under hydraulic retention time (HRT) = 3 h, 17α-ethinyl estradiol (EE2) removal increased by 22.0 %–27.0 %, and the denitrification load increased by 123.5 % to reach (60.8 ± 4.8) g·N (m3·d)−1. Moreover, SR-nCP/biofilter improved the reduction of both endocrine disrupting and acute toxicity, and the enhancement effect was more prominent under the low HRT condition. Furthermore, Sediminibacterium and Steroidobacter were identified as core aerobic bacterium that acted on SEs degradation and anaerobic bacterium that was responsible for simultaneous removal of SEs and TN, respectively. The presented strategy exhibited a synergistic effect of oxygen and organic carbon from SR-nCP and confirmed the feasibility of the SR-nCP/biofilter for the removal of SEs and TN from low C/N wastewater, highlighting a promising in-situ enhancement method for upgrading the function of current DNBF in advanced wastewater purification.

The occurrence and removal of steroid estrogens in a full-scale anaerobic/anoxic/aerobic-membrane bioreactor process and the implication of the bacterial community dynamics

The occurrence and removal of estrone (E1), 17β-estradiol (E2), and 17α-ethinylestradiol (EE2) as typical steroid estrogens (SEs) and the bacterial community structure in a full-scale anaerobic/anoxic/aerobic-membrane bioreactor (A2O-MBR) process were investigated. Residual E1 and EE2 were detected in the effluent, while the excess sludge remained all types of SEs. The biodegradation of SEs occurred primarily in the aerobic tank and the sorption capacity of SEs on activated sludge decreased along the flow course. The internal recirculation ratio applied in the A2O-MBR process failed to form distinct redox conditions. Water temperature was the predominant factor affecting bacterial community composition and SEs biodegradation. Genera not previously reported as SE biodegraders might be responsible for SEs biodegradation in full-scale processes exposed to environmentally relevant SEs concentrations. Heterotrophic cometabolism was inferred as the primary SEs biodegradation mechanism. The present study revealed the correlations between operational factors and SEs biodegradation and the significance of enriching bacterial populations responsible for SEs biodegradation to improve the potential of A2O-MBR process as a SEs barrier.

Degradation of steroid estrogens by UV/peracetic acid: Influencing factors, free radical contribution and toxicity analysis

Steroid estrogens (SEs) are a group of refractory organic micropollutants detected in secondary effluent frequently. The advanced oxidation processes (AOPs) are usually used to deep remove the SEs from the secondary effluent. Herein, we first investigated the UV/peracetic acid (PAA), a PAA-based AOP, to degrade SEs. Using estrone (E1), 17β-estradiol (E2), estriol (E3), and 17α-ethinyl estradiol (EE2) as representatives, the results showed that UV can effectively activate PAA to enhance the degradation of the four SEs, which degradation followed the pseudo-first-order kinetics (R2 > 0.99), and the rate constant (kobs) of degradation increased with increasing the PAA dosage in the range investigated. Little pH dependence was also observed in the degradation of SEs by UV/PAA. Furthermore, the degradation of SEs was improved in the presence of coexisting substrates (Cl−, HCO- 3, NO- 3, and HA) in relatively low concentrations. Quenching experiments revealed that the carbon-centered radicals (R–C•) produced from the UV/PAA process were recognized as the predominant contributors to the degradation of the four SEs. Also, we found that the estrogenic activity decreased by more than 94%, but the acute toxicity inhibition increased to 37% in the solution after 30 min UV/PAA treatment. In addition, the 130% additional total organic carbon (TOC) was generated after UV/PAA process. These findings obtained in this work will facilitate the development of the UV/PAA process as a promising strategy for the deep removal of SEs in secondary effluent.

Carbon-mediated visible-light clay-Fe2O3–graphene oxide catalytic nanocomposites for the removal of steroid estrogens from water

This study reports the development of efficient photosensitive nanocomposites made from clay, Fe2O3, and graphene oxide (GO). These nanocomposites were used for the removal of steroid estrogens (E1, E2, E3 and EE2) from water under visible-light. The use of these photocatalytic nanocomposites led to oxidation of the steroid estrogens at >80 % even under simultaneous presence of all estrogens in water. Mineralization was obtained for these estrogens within the range of 58–73 %. The presence of Fe-oxide in the nanocomposites increased the photocatalytic efficiency but addition of GO further improved the photocatalytic efficiency. This improved efficiency was further doubled when the nanocomposites were prepared with a carbon source (Carica papaya seeds). The presence of carbon in the nanocomposite matrix was confirmed using X-ray photoelectron spectroscopy and Elemental analysis. The main contributors to photocatalytic efficiency of these nanocomposites are superoxide radicals (· O2-) and holes (h+). Under competitive conditions, the photocatalysts are still active although the extent of estrogen oxidation is somewhat lower. Changes in the ionic strength did not significantly influence the efficiency of the photocatalyst. This signifies that adsorption only plays a minor role in estrogen removal from water. Toxicity tests show that the treated water is safe for human consumption and the most efficient nanocomposite can be recycled three times without any significant loss of performance. Overall, the nanocomposite show high potential for the effective removal of a cocktail of estrogens in raw wastewater, tap and rain water, attaining contamination levels that are within WHO safe limits.

Tuning ZnO/GO p-n heterostructure with carbon interlayer supported on clay for visible-light catalysis: Removal of steroid estrogens from water

• Synthesis of new ZnO/GO p-n heterostructured visible-light catalyst on kaolinite. • Catalyst photodegradation efficiency of the estrogens, >90%. • New photocatalyst efficient for the treatment of real wastewater. • Mild toxicity from treated water which is below the acute level of estrogens. • Efficiency of photocatalyst stable over three cycles. This study demonstrates the efficiency of a new visible-light p-n ZnO/GO heterostructured composite catalyst supported on clay with carbon interlayer. This photocatalyst was prepared via microwave assisted technique for the removal of four steroid estrogens in water: Estrone (E1), 17-β-estradiol (E2), Estriol (E3) and the synthetic estrogen 17-α ethinylestradiol (EE2). The prepared catalyst was characterized by different techniques: FE-SEM, EDX, RAMAN, ATR-FTIR, XPS, BET, UV–VIS, and PL. Studies confirmed that the presence of carbon interlayer (from carica papaya seeds) and graphene oxide (GO) were important for the visible-light efficiency of the photocatalyst. In single solute systems, estrogen removal was >89% and as high as 98% and this was not significantly different in a competitive system. In real wastewater samples, efficiency was 63–78% estrogen removal. A reuse study suggested that the photocatalyst efficiency was slightly >80% after 3 reuse cycles. The presence of humic acid reduced the efficiency to ≥70% for all estrogens while the addition of 1% H 2 O 2 raised photodegradation of estrogens to 100% in 10 min. However, using the chemical oxidation demand test, the actual oxidation level of steroid estrogens after photodegradation was 51–77% for the various steroid estrogens. Important reactive oxygen species responsible for photodegradation was hydroxyl radical (HO ) via superoxide radical ( O 2 – ) and hole (h + ) formation from the photocatalytic composite. Test with ceriodaphnia silvestrii suggests very mild toxicity from treated water which is below the acute level of these estrogens (LC 50 = ca. 0.89 mg/L).

Effect of Heavy Metal Ions on Steroid Estrogen Removal and Transport in SAT Using DLLME as a Detection Method of Steroid Estrogen

Environmental endocrine-disrupting chemicals have become a global environmental problem, and the distribution, transport, and fate of estrogens in soil and water environments closely relate to human and ecological health as well as to the remediation scheme design. A new micro-extraction technique termed dispersive liquid–liquid micro-extraction (DLLME) combined with high-performance liquid chromatography with fluorescence detector (HPLC-FLD) was developed for the determination of the concentration of steroid estrogens in water samples. The detection limits of HPLC-FLD and DLLME-HPLC/FLD were 0.68–1.73 μg L−1 and 7.16–69.22 ng L−1, respectively. Based on this method, the isothermal adsorption of 17β-E2 on sand and a breakthrough experiment of 17β-E2 and Cu2+ in a soil aquifer treatment (SAT) system were studied. The 17β-E2 adsorption capacity of sand in 17β-E2 solution was detected to be larger than that in a mixed solution of 17β-E2 and Cu(NO3)2 solution, and the breakthrough curves of 17β-E2 and Cu2+ in the mixed solution shifted forward in sand column experiments. Both suggested that the competitive adsorption of 17β-E2 and Cu2+ in the mixed solution might occur on the surface of the sand. In the process of the removal of 17β-E2 in wastewater by SAT, the existence of Cu2+ slightly inhibited the adsorption of 17β-E2 and accelerated the breakthrough of 17β-E2. These results ought to be a warning for SAT application for 17β-E2 removal in water where heavy metals coexist.

Removal Characteristics of Steroid Estrogen in the Mixed System through an Ozone-Based Advanced Oxidation Process

In this work, the removal of estrone (E1), 17β-estradiol (E2), and 17α-ethinylestradiol (EE2) in their coexisting micro-polluted solution through an ozone-based oxidation process was studied in depth. The results showed that all of the estrogens in the mixed solution could be completely degraded and their degradation processes fitted the pseudo-first-order kinetic model well. As the initial concentration of the mixed solution increased from 50 to 300 μg L−1, the removal rate constants of E1, E2, and EE2 decreased by 65.9%, 66.5%, and 67.0%, respectively. However, when the initial solution pH increased from 2.0 to 7.0, the removal rate constant of E1, E2, and EE2 increased by 271.4%, 149.7%, and 152.4%, respectively. When the H2O2 or UV was introduced into the ozonation system, the removal efficiency of steroid estrogens in the mixed solution was substantially enhanced. Moreover, main intermediates of E1, E2, and EE2 were proposed. The synthetic estrogen EE2 was chosen as the representative compound to evaluate the estrogenic activities during O3, O3/H2O2, and O3/UV processes. In the O3/H2O2 and O3/UV processes, the degradation products still possessed certain estrogenic activities, which led to a hysteresis of the decrease of estrogenic activity compared with that of the estrogen concentration. These findings provided some reliable research data, alternative oxidants, and oxidation manners for the removal of steroid estrogens from the aquatic environment.

Response of bloom-forming cyanobacterium Microcystis aeruginosa to 17β-estradiol at different nitrogen levels

Co-existence of cyanobacterial harmful algal blooms (CyanoHABs) and steroid estrogens (SEs) has been an increasing concern in eutrophic waters. The cellular responses and biodegradation of 17β-estradiol (E2) in cyanobacterium Microcystis aeruginosa were investigated at different nitrogen levels. During the 10-d experiment, the growth of M. aeruginosa was stimulated by 10–100 μg L−1 of E2 at the lowest nitrogen level of 0.5 mg L−1, whereas the presence of E2 inhibited the cyanobacterial growth at 5 mg L−1 of nitrogen. With nitrogen concentration increased to 50 mg L−1, the impact of E2 on levels of growth rate and chlorophyll a (Chla) alleviated. Exposure to E2 also promoted the superoxide dismutase activity of M. aeruginosa, coupled with cellular oxidative damage as indicated by the increasing malondialdehyde content. A sufficient nitrogen supply mitigated the oxidative stress of E2 through enhancing the synthesis of detoxification-related enzymes. Simultaneously, the secretion of tryptophan-like substances in loosely- and tightly-bound extracellular polymeric substances was triggered for adapting to an E2 addition in the short term. Moreover, significant biodegradation of E2 was observed, and the process followed a first-order kinetic reaction. The obtained half-lives decreased with nitrogen levels and ranged from 2.47 to 2.81 and 3.39–5.04 d, respectively, at 10 and 100 μg L−1 of E2. These results provide a better understanding of the potential effects of SEs on CyanoHABs formation, as well as the important role of CyanoHABs on SEs removal in aquatic ecosystems, which should be fully considered in the control of combined pollution.

Quantification of selected steroid hormones (17β-Estradiol and 17α-Ethynylestradiol) in wastewater treatment plants in Klang Valley (Malaysia)

Steroid estrogens, such as 17β-estradiol (E2) and 17α-ethynylestradiol (EE2) are potent and were categorized as “Watch List” in Directive 2013/39/EU because of their potential risks to aquatic environment. Commercialized enzyme-linked immunosorbent assay (ELISA) kits have been used to quantify steroid estrogens in wastewater samples due to their simplicity, rapid, cost-effectiveness, and validated assays. Hence, this study aims to determine the occurrence and removal of steroid hormones in Malaysian wastewater treatment plants (WWTPs) by ELISA, to identify the association of removal efficiency (E2 and EE2) with respect to WWTPs operating conditions, and to assess the potential risks of steroid estrogens to aquatic environment and human. Results showed E2 concentration ranged from 88.2 ± 7.0 ng/L to 93.9 ± 6.9 ng/L in influent and 35.1 ± 17.3 ng/L to 85.2 ± 7.6 ng/L in effluent, with removal of 6.4%–63.0%. The EE2 concentration ranged from 0.2 ± 0.2 ng/L to 4.9 ± 6.3 ng/L in influent and 0.02 ± 0.03 ng/L to 1.0 ± 0.8 ng/L in effluent, with removal of 28.3–99.3%. There is a correlation between EE2 removal with total suspended solid (TSS) and oxidation reduction potential (ORP), and was statistically significant. Despite the calculated estrogenic activity for E2 and EE2 was relatively high, dilution effects could lower estrogenic response to aquatic environment. Besides, these six selected WWTPs have cumulative RQ values below the allowable limit, except WWTP 1. Relatively high precipitation (129–218 mm) could further dilute estrogens concentration in the receiving river. These outputs can be used as quantitative information for evaluating the occurrence and removal of steroid estrogens in Malaysian WWTPs.

N-propyl functionalized spherical mesoporous silica as a rapid and efficient adsorbent for steroid estrogen removal: Adsorption behaviour and effects of water chemistry

To achieve an enhanced and selective adsorption of steroid estrogens, the n-propyl functionalization was applied to the mesoporous silica material (MCM-41) according to the physico-chemical property analysis of steroid estrogens. Adsorption behaviour and water chemistry effects were evaluated with the most concerned steroid estrogens: estrone (E1), 17β-estradiol (E2) and 17α-ethinyl estradiol (EE2) based on the materials characterization. The results showed the uptakes of E1, E2, and EE2 onto the modified MCM-41 were enhanced and accelerated by the n-propyl functionalization, which was positively correlated with the hydrophobicity of the synthesized materials. Kinetic data fitted the pseudo-second-order model well. Based on the Langmuir model, the maximum adsorption capacities of the n-propyl modified MCM-41 were up to 119.87, 88.38, and 86.91 mg g−1 for EE2, E1, and E2, respectively. Importantly, both acid and neutral solutions were beneficial to estrogen removal, but ionic strength and humic acid did not affect the estrogen adsorption. The above results suggested that the n-propyl functionalized MCM-41 would be a promising adsorbent for the rapid and efficient removal of estrogens with the selectivity from natural organic matter like humic acid. Mechanism analysis showed the key role of hydrophobic interaction, and it also confirmed the contribution of the carbonylic lone pair electrons of E1, which helped the formation of stronger hydrogen bonds with silicon hydroxyls and enhanced the dipole-dipole interaction between E1 and the synthesized materials.

Co-metabolic degradation of steroid estrogens by heterotrophic bacteria and nitrifying bacteria in MBRs

ABSTRACTThree membrane bioreactors (MBRs) with different carbon/nitrogen ratios were operated in parallel to investigate the effects of heterotrophic bacteria and nitrifying bacteria on the co-metabolic degradation of the steroid estrogens (SEs) estrone (E1) and 17α-ethinylestradiol (EE2). The functional community structures of the MBRs were analyzed using fluorescence in situ hybridization, and correlations between the functional community structures and SE removal efficiencies were established. The results showed that α-Proteobacteria, β-Proteobacteria, and γ-proteobacteria were responsible for the removal of E1, whereas ammonia-oxidizing bacteria, Nitrosomonas sp., Nitrosospira sp., Nitrospira sp., and Nitrobacter sp. were responsible for EE2 removal. Nitrifying activated sludge degraded E1 and EE2 alone, with degradation efficiencies of 71.04 and 65.51%, respectively. Moreover, biodegradation of E1 and EE2 was reduced significantly (by 30.30 and 34.03%, respectively) when nitrification was inhibited. Heterotrophic and nitrifying bacteria were responsible for E1 and EE2 degradation, but nitrification was considered to be the key process in the enhancement of SE degradation. Organic co-metabolism by heterotrophic bacteria had a significant effect on E1 removal, and nitrification co-metabolism by nitrifying bacteria had a significant effect on EE2 removal. These results improve our understanding of the co-metabolic degradation of SEs, which is useful for improving SE removal and guaranteeing the health of aqueous environments.

Sources, mechanisms, and fate of steroid estrogens in wastewater treatment plants: a mini review

Steroid estrogens, such as estrone (E1), 17β-estradiol (E2), estriol (E3), and 17α-ethinylestradiol (EE2), are natural and synthetic hormones released into the environment through incomplete sewage discharge. This review focuses on the sources of steroid estrogens in wastewater treatment plants (WWTPs). The mechanisms and fate of steroid estrogens throughout the entire wastewater treatment system are also discussed, and relevant information on regulatory aspects is given. Municipal, pharmaceutical industry, and hospitals are the main sources of steroid estrogens that enter WWTPs. A typical WWTP comprises primary, secondary, and tertiary treatment units. Sorption and biodegradation are the main mechanisms for removal of steroid estrogens from WWTPs. The fate of steroid estrogens in WWTPs depends on the types of wastewater treatment systems. Steroid estrogens in the primary treatment unit are removed by sorption onto primary sludge, followed by sorption onto micro-flocs and biodegradation by microbes in the secondary treatment unit. Tertiary treatment employs nitrification, chlorination, or UV disinfection to improve the quality of the secondary effluent. Activated sludge treatment systems for steroid estrogens exhibit a removal efficiency of up to 100%, which is higher than that of the trickling filter treatment system (up to 75%). Moreover, the removal efficiency of advance treatment systems exceeds 90%. Regulatory aspects related to steroid estrogens are established, especially in the European Union. Japan is the only Asian country that implements a screening program and is actively involved in endocrine disruptor testing and assessment. This review improves our understanding of steroid estrogens in WWTPs, proposes main areas to be improved, and provides current knowledge on steroid estrogens in WWTPs for sustainable development.

Stimulated dissolved organic matter by electrochemical route to produce activity substances for removing of 17α-ethinylestradiol

The influence of the oxidants H2O2, potassium peroxodisulfate, potassium peroxomonosulfate and dissolved organic matter on an electrochemical process for removing traces of 17α-ethinylestradiol was investigated. The electrolytic reactor used a doped Ti anode and a graphite cathode. Under acidic conditions the oxidants and dissolved organic matter significantly promoted 17α-ethinylestradiol's degradation, but under alkaline conditions the effect was slight. The peroxomonosulfate was found to be more effective than the peroxodisulfate, which was more effective than hydrogen peroxide. Up to 90% removal of 17α-ethinylestradiol was achieved when humic acid was present at 0.5mgC·L−1. The degradation rate was reduced obviously as the concentration of humic or fulvic acid increased. The concentration of HO was significantly higher in acidic conditions, which is in line with the degradation performance. HO rather than SO4− was shown to make the main contribution to the electrochemical degradation. Under acidic conditions, this electrochemical technique has good potential technique for the removal of steroid estrogens from water.

Removal of steroid estrogens from municipal wastewater in a pilot scale expanded granular sludge blanket reactor and anaerobic membrane bioreactor

Anaerobic treatment of municipal wastewater offers the prospect of a new paradigm by reducing aeration costs and minimizing sludge production. It has been successfully applied in warm climates, but does not always achieve the desired outcomes in temperate climates at the biochemical oxygen demand (BOD) values of municipal crude wastewater. Recently the concept of ‘fortification' has been proposed to increase organic strength and has been demonstrated at the laboratory and pilot scale treating municipal wastewater at temperatures of 10–17°C. The process treats a proportion of the flow anaerobically by combining it with primary sludge from the residual flow and then polishing it to a high effluent standard aerobically. Energy consumption is reduced as is sludge production. However, no new treatment process is viable if it only addresses the problems of traditional pollutants (suspended solids – SS, BOD, nitrogen – N and phosphorus – P); it must also treat hazardous substances. This study compared three potential municipal anaerobic treatment regimes, crude wastewater in an expanded granular sludge blanket (EGSB) reactor, fortified crude wastewater in an EGSB and crude wastewater in an anaerobic membrane bioreactor. The benefits of fortification were demonstrated for the removal of SS, BOD, N and P. These three systems were further challenged with the removal of steroid estrogens at environmental concentrations from natural indigenous sources. All three systems removed these compounds to a significant degree, confirming that estrogen removal is not restricted to highly aerobic autotrophs, or aerobic heterotrophs, but is also a faculty of anaerobic bacteria.

Evaluating Removal of Steroid Estrogens by a Model Alga as a Possible Sustainability Benefit of Hypothetical Integrated Algae Cultivation and Wastewater Treatment Systems

The wastewater treatment field is increasing its emphasis on energy and resource recovery, while still prioritizing environmental protection. In this vein, there is growing interest in integration of algae cultivation and wastewater as a means to produce bioenergy while also removing dissolved nutrients. This paper assesses algae-mediated removal of estrogenic steroid hormones, which is an important but previously undocumented water quality benefit for municipal and livestock waste treatment facilities, because these entities discharge significant amounts of estrogens and nutrients. Bench-scale experiments were used to investigate apparent removal of four steroid hormones by a model alga, Scenedesmus dimorphus. Removal efficiencies were roughly 85% for 17α-estradiol and estrone and 95% for 17β-estradiol and estriol over eight days. Sorption, direct-photolysis, and algae-mediated biotransformation were evaluated as possible removal mechanisms. Removal was mainly achieved by algae-mediated biotransformation, and a partial mechanism has been proposed based on observed products. A bioassay indicates that removal of the parent estrogens does not always remove estrogenic activity, although estrogenicity associated with 17β-estradiol did decrease slightly. Overall, this study highlights a novel synergy between water and energy sustainability in integrated algae farming and wastewater treatment systems. These systems should be studied further to see if energy production could motivate voluntary removal of currently unregulated emerging contaminants.

Production of a bioflocculant from chromotropic acid waste water and its application in steroid estrogen removal

A novel strain (designated as SW-2) which could convert chromotropic acid into bioflocculants was isolated from chromotropic acid wastewater. Conditions for bioflocculants production were optimized by response surface methodology (RSM) and determined to be inoculum size 7.74%, initial pH 6.9, and CODCr of the chromotropic acid wastewater 425mg/L. The yielded bioflocculant was primarily consisting of polysaccharide and protein. It could maintain its flocculating activity to 0.4% (w/w) kaolin suspensions over pH 3–9 and 20–80°C. In addition, conditions for the removal of estrogens with the bioflocculant were investigated and determined to be bioflocculant dosage 50mg/L, initial pH 3, reaction time 60min, and temperature 45°C. Under these optimal conditions, the removal efficiencies of E1, E2, EE2, and E3 were 87%, 92%, 88% and 96%, respectively. The bioflocculant was shown to offer a promising alternative method of removing estrogens from water in pretreatment applications.

Diagnostic investigation of steroid estrogen removal by activated sludge at varying solids retention time

The impact of solids retention time (SRT) on estrone (E1), 17β-estradiol (E2), estriol (E3) and 17α-ethinylestradiol (EE2) removal in an activated sludge plant (ASP) was examined using a pilot plant to closely control operation. Exsitu analytical methods were simultaneously used to enable discrimination of the dominant mechanisms governing estrogen removal following transitions in SRT from short (3d) to medium (10d) and long (27d) SRTs which broadly represent those encountered at full-scale. Total estrogen (∑EST, i.e., sum of E1, E2, E3 and EE2) removals which account for aqueous and particulate concentrations were 70±8, 95±1 and 93±2% at 3, 10 and 27d SRTs respectively. The improved removal observed following an SRT increase from 3 to 10d was attributable to the augmented biodegradation of the natural estrogens E1 and E2. Interestingly, estrogen biodegradation per bacterial cell increased with SRT. These were 499, 1361 and 1750ng 1012 viable cells−1d−1. This indicated an improved efficiency of the same group or the development of a more responsive group of bacteria. In this study no improvement in absolute ∑EST removal was observed in the ASP when SRT increased from 10 to 27d. However, batch studies identified an augmented biomass sorption capacity for the more hydrophobic estrogens E2 and EE2 at 27d, equivalent to an order of magnitude. The lack of influence on estrogen removal during pilot plant operation can be ascribed to their distribution within activated sludge being under equilibrium. Consequently, lower wastage of excess sludge inherent of long SRT operation counteracts any improvement in sorption.

Removal of steroid estrogens from waste activated sludge using Fenton oxidation: Influencing factors and degradation intermediates

The presence of endocrine disrupting compounds (EDCs) in waste activated sludge (WAS) is raising concerns about their influence on animals and the overall food cycle. Traditional sludge stabilization processes cannot remove EDCs effectively. The main objective of this work was to study the removal of four estrogens (estrone (E1), 17β-estradiol (E2), estriol (E3), and 17α-ethinylestradiol (EE2)) in waste activated sludge treated with Fenton oxidation. The effects of H2O2 dosage, initial pH, reaction time, and Fe(II) to H2O2 molar ratio were investigated. Base on both the removal of estrogens and the solubilization of WAS, the proper reaction conditions were recommended as follows: H2O2 dosage=15.62mmolg−1, initial pH=3, reaction time=60min, Fe(II) to H2O2 molar ratio=0.167. Under these conditions, the removal efficiencies of E1, E2, EE2, and E3 were 70%, 90%, 84% and 98%, respectively; compared with non-Fenton treatment, a 24-fold increase in STOC was achieved, and the extent of solubilization of TSS and VSS was close to 13 and 20%, respectively. The degradation intermediates were detected using GC/MS. Results showed that the phenol structures of targets were mostly oxidized to cyclohexenone moieties and quinone-like structures, which indicated that estrogenic activity was weakened. Pregn-4-ene-3,20-dione and pregn-4-en-20-yn-3-one were observed for the first time. Fenton oxidation was shown to offer a promising alternative method of removing EDCs from sludge in pretreatment applications.