Ze-hua Liu

Removal mechanisms for endocrine disrupting compounds (EDCs) in wastewater treatment - physical means, biodegradation, and chemical advanced oxidation: a review.

Endocrine disrupting compounds (EDCs) are pollutants with estrogenic or androgenic activity at very low concentrations and are emerging as a major concern for water quality. Within the past few decades, more and more target chemicals were monitored as the source of estrogenic or androgenic activity in wastewater, and great endeavors have been done on the removal of EDCs in wastewater. This article reviewed removal of EDCs from three aspects, that is, physical means, biodegradation, and chemical advanced oxidation (CAO).

Urinary excretion rates of natural estrogens and androgens from humans, and their occurrence and fate in the environment: A review

Endocrine disrupting compounds (EDCs) are pollutants with estrogenic or androgenic activities at very low concentrations and are emerging as a major concern for water quality. For sewage of municipal wastewater treatment plants in cities, one of the most important sources of EDCs are natural estrogens and natural androgens (NEAs) excreted from humans. Therefore, estrogenic/androgenic potencies or relative binding affinity of the NEAs were first outlined from different sources, and data of urinary excretion rates of NEAs were summarized. To evaluate their estrogenic activities, their excretion rates of estrogen equivalent (EEQ) or testosterone (T) equivalent (TEQ) were also calculated. Based on our summary, the total excretion rates of EEQ by estrone (E1), 17beta-estradiol (E2), and estriol (E3) only accounted for 66-82% of the total excretion rate of EEQ among four different groups, and the other corresponding natural estrogens contributed 18-34%, which meant that some of the other natural estrogens may also exist in wastewater with high estrogenic activities. Based on the contribution ratio of individual androgens to the total excretion rate of TEQ, five out of 12 natural androgens, T, dihydrotestosterone (DHT), androsterone (AD), 5beta-androstanediol (beta-ADL), and androstenediol (ANL) were evaluated as the priority natural androgens, which may exist in wastewater with high androgenic activities. Published data on occurrence and fate of the NEAs including natural estrogen conjugates in the environment were also summarized here.

A review of phytoestrogens: their occurrence and fate in the environment.

Phytoestrogens are plant compounds with estrogenic activities. Many edible plants, some of which are common in the human diet, are rich in phytoestrogens. Almost all phytoestrogens eaten daily by people were reported partly recovered in urine or feces, which can be regarded as one of the main sources of their occurrence in municipal wastewaters. As they may act as one part of the endocrine disrupting compounds (EDCs) in water systems, some phytoestrogens have been monitored and detected in wastewater and other various environments. It is very difficult to monitor numerous unknown EDCs in complex wastewater samples, and it is helpful if some estimation of target EDCs can be done before monitoring. With this in mind, this review will: (1) summarize estrogenic activities or estrogenic potencies of phytoestrogens by different bioassays; (2) summarize daily urinary excretion rates of phytoestrogens by humans, and compare their urinary excretion rates to that of estrone, which suggests that most phytoestrogens may occur in municipal wastewaters; (3) collect and summarize published data on the occurrence and fate of phytoestrogens in various environments.

Enhanced coagulation of ferric chloride aided by tannic acid for phosphorus removal from wastewater.

Phosphorus removal from wastewater is of great importance. In the present study, ferric chloride was selected as the coagulant, and tannic acid (TA), a natural polymer, as the coagulant aid to develop an effective coagulation process with the emphasis of phosphorus recovery from different types of wastewater. The results showed that TA can accelerate the settling speed by forming flocs with large size, reduce the residual Fe(III) to eliminate the yellow color caused by Fe(III), and slightly increase the phosphorus removal efficiency. The precipitate formed by TA-aided coagulation showed the advantage of releasing phosphorus faster than ferric phosphate, indicating the possibility of phosphorus recovery from wastewater as slow release fertilizer. To further understand the structural characteristics of the precipitate, analytical techniques such as Raman spectroscopy, X-ray photoelectron spectroscopy and matrix-assisted laser desorption ionization-time of flight mass spectrometry were employed. The analytical results indicated that TA-Fe-P complex was formed during the coagulation/flocculation processes. Solid phase in the precipitate consisted of TA-Fe-P complex, Fe-TA complex and/or ferric hydroxyphosphate.

Occurrence, fate and removal of synthetic oral contraceptives (SOCs) in the natural environment: a review.

Synthetic oral contraceptives (SOCs) are a group of compounds with progestagenic and/or androgenic activities, with some also possessing estrogenic activities. Recent research has documented that some of these emerging contaminants have adverse effects on aquatic organisms at very low concentrations. To facilitate the evaluation of their latent risks, published works on their occurrence and fate in the environment are reviewed. Androgenic/progestagenic relative potencies or relative binding affinity of these SOCs as well as their physicochemical properties and toxicity are summarized. Appropriate analytical methods are outlined for various environmental sample types, including methods of sample preparation and limit of detection/quantification (LOD/LOQ). Finally results on their occurrence and fate in wastewater treatment plants (WWTPs) and other environments are critically examined.

Removal of natural estrogens and their conjugates in municipal wastewater treatment plants: A critical review

This article reviews studies focusing on the removal performance of natural estrogens in municipal wastewater treatment plants (WWTPs). Key factors influencing removal include: sludge retention time (SRT), aeration, temperature, mixed liquor suspended solids (MLSS), and substrate concentration. Batch studies show that natural estrogens should biodegrade well; however, batch observations do not always agree with observations from full-scale municipal WWTPs. To explain this discrepancy, deconjugation kinetics of estrogen conjugates in lab-scale studies were examined and compared. Most estrogen conjugates with slow deconjugation rates are unlikely to be easily removed; others could be cleaved in WWTP settings. Nevertheless, some estrogens cleaved from their conjugates may be found in treated effluent, because deconjugation requires several hours or longer, and there is insufficient rest time for the biodegradation of the cleaved natural estrogens in the WWTP. Therefore, WWTP removals of natural estrogens are likely to be underestimated when estrogen conjugates are present in raw wastewater. This review suggests that biodeconjugation of estrogen conjugates should be enhanced to more effectively remove natural estrogens in WWTPs.

Dissolved methane: a hurdle for anaerobic treatment of municipal wastewater.

Wastewater Ze-hua Liu,†,‡,* Hua Yin,†,‡ Zhi Dang,†,‡ and Yu Liu †College of Environment and Energy, South China University of Technology, Guangzhou 510006, China ‡Key Lab Pollution Control & Ecosystem Restoration in Industry Cluster, Ministry of Education, Guangzhou 510006, Guangdong, China Advanced Environmental Biotechnology Center, Nanyang Environment and Water Research Institute, Nanyang Technological University, CleanTech one, Singapore 637141 School of Civil and Environmental Engineering, Nanyang Technological University, Singapore 639798

Influence of co-existed benzo[a]pyrene and copper on the cellular characteristics of Stenotrophomonas maltophilia during biodegradation and transformation.

Microbial remediation has been proposed as a promising technique to remove pollutions, however, its application has been hindered by the lack of understanding the mechanisms involved in contaminants conversion and the influence of pollutants on cellular characteristics. To address this problem, biodegradation and transformation of BaP-Cu(II) by Stenotrophomonas maltophilia, along with interactions of these pollutants with microbial cells through FCM assay were investigated. The results indicated that BaP and Cu(II) were rapidly removed by S. maltophilia on the 1st d, but only less than 10% BaP was broken down due to temporary store in cells, instead of being decomposed immediately. The key ATP enzymes in cells were then activated by BaP to promote bacteria to further decompose BaP. Stimulation of co-existed contaminants strengthened cell membrane permeability and altered cell structure, but a higher esterase activity and DNA in cells of S. maltophilia were still retained.

Profile and removal of endocrine disrupting chemicals by using an ER/AR competitive ligand binding assay and chemical analyses.

An estrogen receptor (ER)/androgen receptor (AR) ligand competitive binding assay (ER/AR-binding assay) and chemical analyses were used to evaluate the endocrine disrupting chemicals (EDCs) behavior of two municipal wastewater treatment plants (WWTPs) (K and S). In the influents, estrone (E1), androsterone (A), androstenedione (AD), BPA (bisphenol A), NP (nonylphenol) and daidzein (DZ) were detected in high amounts with subsequent 24 h-average concentrations of 350, 1000, 29, 1300, 3900, and 5700 ng/L in K-WWTP and of 310, 620, 59, 1600, 2600, and 8400 ng/L in S-WWTP. The estrogenic (androgenic) activity as 17beta-estradiol (E2) equivalents (EEQ) or testosterone (Te) equivalents (TEQ) was consequently 620 ng E2/L (570 ng Te/L) and 580 ng E2/L (800 ng Te/L) for the two WWTPs. The removal efficiencies of the above mentioned sole target chemicals were 51%-100% for K-WWTP and 55.6%-100% for S-WWTP. The removal efficiencies of EEQ were about 73% for both WWTPs, while the removal efficiencies of TEQ were 62.1% for K-WWTP and 98.4% for S-WWTP. In addition, chemical-derived EEQ were about 1.2%-52.4% of those by ER-binding assay for K-WWTP and the corresponding ratios were 1.3%-83.3% for S-WWTP, while chemical derived TEQ were less than 3% of values measured by the AR-binding assay for both WWTPs.

Tea saponin enhanced biodegradation of decabromodiphenyl ether by Brevibacillus brevis.

Decabromodiphenyl ether (BDE209) is a ubiquitous persistent pollutant and has contaminated the environment worldwide. To accelerate BDE209 elimination and reveal the mechanism concerned, the biosurfactant tea saponin enhanced degradation of BDE209 by Brevibacillus brevis was conducted. The results revealed that tea saponin could efficiently increase the solubility of BDE209 in mineral salts medium and improve its biodegradation. The degradation efficiency of 0.5 mg L(-1) BDE209 by 1 g L(-1) biomass with surfactant was up to 55% within 5d. Contact time was a significant factor for BDE209 biodegradation. BDE209 biodegradation was coupled with bioaccumulation, ion release and utilization, and debromination to lower brominated PBDE metabolites. During the biodegradation process, B. brevis metabolically released Na(+), NH4(+), NO2(-) and Cl(-), and utilized the nutrient ions Mg(2+), PO4(3-) and SO4(2-). GC-MS analysis revealed that the structure of BDE209 changed under the action of strain and nonabromodiphenyl ethers (BDE-208, -207 and -206), octabromodiphenyl ethers (BDE-203, -197 and -196) and heptabromodiphenyl ether (BDE-183) were generated by debromination.