Degradation of phthalate esters and acetaminophen in river sediments using the electrokinetic process integrated with a novel Fenton-like process catalyzed by nanoscale schwertmannite

Phthalates contamination in sediments: A review of sources, influencing factors, benthic toxicity, and removal strategies

Sediments provide habitat and food for benthos, and phthalates (PAEs) have been detected in numerous river and marine sediments as a widely used plastic additive. PAEs in sediments is not only toxic to benthos, but also poses a threat to pelagic fish and human health through the food chain, so it is essential to comprehensively assess the contamination of sediments with PAEs. This paper presents a critical evaluation of PAEs in sediments, which is embodied in the analysis of the sources of PAEs in sediments from multiple perspectives. Biological production is indispensable, while artificial synthesis is the most dominant, thus the focus was on analyzing the industrial and commercial sources of synthetic PAEs. In addition, since the content of PAEs in sediments varies, some factors affecting the content of PAEs in sediments are summarized, such as the properties of PAEs, the properties of plastics, and environmental factors (sediments properties and hydrodynamic conditions). As endocrine disruptors, PAEs can produce toxicity to its direct contacts. Therefore, the effects of PAEs on benthos immunity, endocrinology, reproduction, development, and metabolism were comprehensively analyzed. In addition, we found that reciprocal inhibition and activation of the systems lead to genotoxicity and apoptosis. Finally, the paper discusses the feasible measures to control PAEs in wastewater and leachate from the perspective of source control, and summarizes the in-situ treatment measures for PAEs contamination in sediments. This paper provides a comprehensive review of PAEs contamination in sediments, toxic effects and removal strategies, and provides an important reference for reducing the contamination and toxicity of PAEs to benthos.

Mechanism of simultaneous lead and chromium removal from contaminated wastewater by a schwertmannite-like mineral

In this study, a schwertmannite-like mineral was synthesized for the removal of lead (Pb) and chromium (Cr) from contaminated wastewater. A shaking flask test was performed (150 r/min, 1 h) with FeSO₄·7H₂O, H₂O₂, Na₂SiO₃, and CaCl₂ added for the mineral synthesis reaction. Results show that optimal performance was achieved with the addition of 1.24 g/L FeSO₄·7H₂O, 0.75 g/L H₂O₂, 1.27 g/L Na₂SiO₃, and 0.44 g/L CaCl₂ at a water temperature of 28 °C, with coexisting ion (Na⁺, K⁺, Mg²⁺) concentrations of 1.50 mmol/L and 0.50 mmol/L EDTA as a complexing agent. Under these optimal conditions, maximum Pb and Cr removal rates of 95.08% and 97.99%, respectively, were achieved within the first 1 min of the mineral synthesis reaction, with the synthesis reaction completed by 6 min. The simultaneous removal of Pb and Cr during the schwertmannite-like material synthesis process occurred via electrostatic adsorption and coprecipitation. When the concentration of the complexing agent was increased from 0.75 to 6.03 mmol/L, the Pb removal rate decreased from 71.88 to 35.45%, and the Cr removal rate decreased from 95.13 to 75.07%, showing that Pb and Cr removal exhibited significant levels of inhibition. In contrast, varying reaction temperatures induced no significant differences. The Pb and Cr dissolution rates from Pb/Cr-containing schwertmannite-like minerals were 8.18% and 2.86% after 40 days, respectively. Therefore, the risk of secondary dissolution of heavy metals is small.

A stepwise processing strategy for treating highly acidic wastewater and comprehensive utilization of the products derived from different treating steps

A stepwise processing strategy, including initial neutralization, chemical mineralization, and complete neutralization treating steps, was developed to effectively treat and utilize the highly acidic wastewater derived from titanium dioxide production. Approximately 94.6% of SO₄^2-, 100% of Fe, and most of other metals were recovered to produce white gypsum, schwertmannite, and Fe⁰/Fe₃O₄@biochar (Fe⁰/Fe₃O₄@BC) composite in the corresponding treating steps. The resulting effluent with neutral pH and a small amount of metal ions could be discharged to general sewage treatment plant for further processing. Schwertmannite was applied as a heterogeneous Fenton-like catalyst to stimulate H₂O₂ to produce active radicals for effective degradation and mineralization of methyl orange (MO) in solution. The MO removal of 100% and total organic carbon removal of 91.1% were achieved in schwertmannite/H₂O₂ reaction system, and schwertmannite exhibited good stability and reusability. Fe⁰/Fe₃O₄@BC composite was applied to remove Cr(VI), with the adsorption capacity of 67.74 mg g^-1. The removal of Cr(VI) using Fe⁰/Fe₃O₄@BC composite was a chemisorption process, including the adsorption of Cr(VI), reduction of Cr(VI) to Cr(III), and co-precipitation of Cr(III)/Fe(III) oxides/hydroxides. This stepwise treating strategy is a promising technology for effective treatment of highly acidic industrial wastewater and comprehensive utilization of the related products.

Heterogeneous Fenton catalysts: A review of recent advances

Heterogeneous Fenton catalysts are emerging as excellent materials for applications related to water purification. In this review, recent trends in the synthesis and application of heterogeneous Fenton catalysts for the abatement of organic pollutants and disinfection of microorganisms are discussed. It is noted that as the complexity of cell wall increases, the resistance level towards various disinfectants increases and it requires either harsh conditions or longer exposure time for the complete disinfection. In case of viruses, enveloped viruses (e.g. SARS-CoV-2) are found to be more susceptible to disinfectants than the non-enveloped viruses. The introduction of plasmonic materials with the Fenton catalysts broadens the visible light absorption efficiency of the hybrid material, and incorporation of semiconductor material improves the rate of regeneration of Fe(II) from Fe(III). A special emphasis is given to the use of Fenton catalysts for antibacterial applications. Composite materials of magnetite and ferrites remain a champion in this area because of their easy separation and reuse, owing to their magnetic properties. Iron minerals supported on clay materials, perovskites, carbon materials, zeolites and metal-organic frameworks (MOFs) dramatically increase the catalytic degradation rate of contaminants by providing high surface area, good mechanical stability, and improved electron transfer. Moreover, insights to the zero-valent iron and its capacity to remove a wide range of organic pollutants, heavy metals and bacterial contamination are also discussed. Real world applications and the role of natural organic matter are summarised. Parameter optimisation (e.g. light source, dosage of catalyst, concentration of H2O2 etc.), sustainable models for the reusability or recyclability of the catalyst and the theoretical understanding and mechanistic aspects of the photo-Fenton process are also explained. Additionally, this review summarises the opportunities and future directions of research in the heterogeneous Fenton catalysis.

Arsenic(V) removal behavior of schwertmannite synthesized by KMnO4 rapid oxidation with high adsorption capacity and Fe utilization

Adsorption is a simple and efficient way for arsenic contamination purification in water, with a pressing challenge to find a cheap and efficient adsorbent. As a poorly crystalline Fe(III)-oxyhydroxy sulfate mineral, schwertmannite can be As(V) adsorbent because of its tunnel structure and low cost. However, the schwertmannite synthesized commonly by H₂O₂ rapid oxidation suffers from the low Fe utilization and limited As(V) adsorption capacity. In this research, the schwertmannite is synthesized by KMnO₄. The results show that the Fe utilization can be improved from 40% to 56%, with the As(V) adsorption capacities double times better than those synthesized by H₂O₂ at pH 7 and 2. The As(V) adsorption mechanisms at different pHs and the reason for the improvement of As(V) adsorption capacity are thoroughly investigated. The FTIR and EDS images confirm that As(V) adsorption exchange with SO₄^2- is the dominant mechanism at pH 7 and 2. At pH 11, the As(V) is mainly removed by surface complexation because the surface SO₄^2- is exchanged by OH^-. The intraparticle diffusion model fitting and XPS results further reveal that the tunnel structure built by Fe-SO₄ in the KMnO₄ oxidized schwertmannite is more stable, possibly resulting in the better As(V) adsorption performance.

Low permeability zone remediation of trichloroethene via coupling electrokinetic migration with in situ electrochemical hydrodechlorination

To address the challenge of trichloroethene (TCE) remediation in low permeability zone, an inexpensive Cu-Ni bimetallic cathode was proposed in electrokinetic (EK) remediation system to couple electrokinetic migration with in situ electrochemical hydrodechlorination. Aqueous phase TCE was originally added into the anolyte so that breakthrough curves through the low permeability porous soil compartment could be obtained to better understand TCE migration driven by electroosmosis flow using different cathodes. The Cu-Ni cathode resulted in more TCE migration of 7.64 mg compared to that of 5.99 mg with Ni and 4.22 mg with mixed metal oxide (MMO) cathode, suggesting that the Cu-Ni cathode was capable of driving more TCE flux out of the contaminated soil. With the Cu-Ni cathode, 98.4% of TCE flux that reached the cathode was electrochemically reduced on the cathode, which was much higher than that with MMO cathode (77.9%) or Ni cathode (59.6%). TCE mass that was transported by electroosmosis flow increased from 2.04 to 6.68 mg when the voltage gradient increased from 1 to 4 V cm^-1, with the normalized energy consumption increasing from 0.06 to 0.16 kWh kg^-1 per unit water movement, and from 0.54 to 2.55 kWh g^-1 per unit TCE transport. For TCE that did reach the cathode compartment, > 98% degradation maintained at the Cu-Ni cathode with various voltage gradients. The coupled electrokinetic and electrochemical hydrodechlorination technology appears to be a promising strategy for the remediation of low permeability porous media.

Pilot-scale electro-bioremediation of heavily PAH-contaminated soil from an abandoned coking plant site

This study presents a systematic pilot-scale study on removal of PAHs from the abandoned site of Shenyang former Coking Plant in China (total PAH concentration of 5635.60 mg kg^-1 in soil). Three treatments, including the control treatment (without inoculation and electric field), bioremediation (with inoculation), and the electro-bioremediation (with inoculation and electric field), were conducted with a treatment time of 182 days to assess their PAH-removal efficiency. All the treatments were conducted from May to October under natural conditions. Results show that electro-bioremediation enhanced the removal of total PAHs, especially high-ring (>3 rings) PAHs. At 182 days, the degradation extents of total and 4-6-ring PAHs reached 69.1% and 65.9%, respectively, under electro-bioremediation (29.3% and 44.4% higher, respectively, than those under bioremediation alone). After electro-bioremediation, the total toxicity equivalent concentrations of total PAHs and 4-, 5- and 6-ring PAHs reduced 49.0%, 63.7%, 48.2% and 30.1%, respectively. These results indicate that electro-bioremediation not only effectively removed the PAHs but also reduced the health risks of soil in an abandoned coking plant site. In addition, electro-bioremediation with polarity reversal could maintain uniform soil pH, the degradation extent of PAHs and soil microorganism numbers at all sites. The environmental conditions, such as temperature and rainfall, had little influence on the process of electro-bioremediation. These findings suggest that electro-bioremediation may be applied for field-scale remediation of heavily PAH-contaminated soil in abandoned coking plant sites.

Acetaminophen micropollutant: Historical and current occurrences, toxicity, removal strategies and transformation pathways in different environments

Acetaminophen (ACT) is commonly used as a counter painkiller and nowadays, it is increasingly present in the natural water environment. Although its concentrations are usually at the ppt to ppm levels, ACT can transform into various intermediates depending on the environmental conditions. Due to the complexity of the ACT degradation products and the intermediates, it poses a major challenge for monitoring, detection and to propose adequate treatment technologies. The main objectives of this review study were to assess (i) the occurrences and toxicities, (2) the removal technologies and (3) the transformation pathways and intermediates of ACT in four environmental compartments namely wastewater, surface water, ground water, and soil/sediments. Based on the review, it was observed that the ACT concentrations in wastewater can reach up to several hundreds of ppb. Amongst the different countries, China and the USA showed the highest ACT concentration in wastewater (≤300 μg/L), with a very high detection frequency (81-100%). Concerning surface water, the ACT concentrations were found to be at the ppt level. Some regions in France, Spain, Germany, Korea, USA, and UK comply with the recommended ACT concentration for drinking water (71 ng/L). Notably, ACT can transform and degrade into various metabolites such as aromatic derivatives or organic acids. Some of them (e.g., hydroquinone and benzoquinone) are toxic to human and other life forms. Thus, in water and wastewater treatment plants, tertiary treatment systems such as advanced oxidation, membrane separation, and hybrid processes should be used to remove the toxic metabolites of ACT.

Assessment of Degradation Behavior for Acetylsalicylic Acid Using a Plasma in Liquid Process

Acetylsalicylic acid (ASA) is a pharmacologically active compound. In this study, ASA was decomposed effectively using a plasma in liquid phase process with hydrogen peroxide and TiO2 photocatalyst. Increasing the electrical power conditions (frequency, applied voltage, and pulse width) promoted plasma generation, which increased the rate of ASA decomposition. The added hydrogen peroxide increased the rate of ASA degradation, but injecting an excess decreased the degradation rate due to a scavenger effect. Although there was an initial increase in the decomposition efficiency by the addition of TiO2 powder, the addition of an excessive amount inhibited the generation of plasma and decreased the degradation rate. The simultaneous addition of H2O2 and TiO2 powder resulted in the highest degradation efficiency. We suggest that ASA is converted to salicylic acid through demethylation by hydroxyl radicals and is finally mineralized to carbon dioxide and water via 2,4-dihydroxy benzoic acid and low molecular acids.

Persulfate activation with rice husk-based magnetic biochar for degrading PAEs in marine sediments

Phthalate esters (PAEs) can interfere with the endocrine systems of humans and wildlife. The main objective of this study was to evaluate the suitability of a composite for remediating marine sediments contaminated with PAEs. The composite was synthesized with magnetite nanoparticles (Fe₃O₄) and rice husk biochar (RHB) by using chemical co-precipitation. Fe₃O₄, RHB, and Fe₃O₄-RHB substantially activated sodium persulfate (Na₂S₂O₈, PS) oxidation to form SO₄^-• and thus degrade PAEs in marine sediments in a slurry system. The morphology and structural composition of the magnetic composites were examined using XRD, FTIR, environmental scanning electron microscopy-energy-dispersive X-ray spectrometry, and superconducting quantum interference device. The Fe₃O₄-RHB composites were confirmed to be prepared successfully. The influences of various parameters, including the PS concentration, composite loading, and initial pH, were investigated. The concentration of high-molecular-weight PAEs (HPAEs) in sediment was much higher than that of low-molecular-weight PAEs (LPAEs); di-(2-ethylhexyl) phthalate (DEHP) was an especially salient marker of PAE contamination in sediments. Furthermore, increasing the PS and Fe₃O₄-RHB doses accelerated PAE oxidation at pH 3.0; 83% degradation of PAEs was achieved when the PS and Fe₃O₄-RHB concentrations were increased to 2.3 × 10^-2 mM and 1.67 g/L, respectively. LPAEs such as dibutyl phthalate (DnBP) are easier to degrade than HPAEs such as DEHP, diisononyl phthalate (DINP), and diisodecyl phthalate (DIDP). In addition, possible activation mechanisms of the interactions between S₂O₈^2- and Fe²⁺/Fe³⁺ on the Fe₃O₄ surface, which involve an efficient electron transfer mediator of the RHB oxygen functional groups promoting the generation of SO₄^-• in the Fe₃O₄-RHB/PS system, were clarified. Thus, the Fe₃O₄-RHB/PS oxidation process is expected to be a viable method for remediating PAE-contaminated marine sediment.

Integrated electrokinetic processes for the remediation of phthalate esters in river sediments: A mini-review

Concerning the contamination of phthalate esters (PAEs) in river sediments, this mini-review introduces four recently reported novel "integrated electrokinetic (EK) processes" for the remediation purpose, namely two combined technologies of the EK process and advanced oxidation process (EK-AOP Processes) and two combined technologies of the EK process and biological process (EK-BIO Processes). The following is a comprehensive summary for these remediation processes: (1) the EK process coupled with nano-Fe₃O₄/S₂O₈^2- oxidation process - Test results have shown that nanoscale Fe₃O₄ played a significant role in activating persulfate oxidation. Even a recalcitrant compound like di(2‑ethylhexyl)phthalate (DEHP), its concentration in test sediment was reduced to 1.97 mg kg^-1, far below the regulatory levels set by Taiwan EPA; (2) the EK process integrated with a novel Fenton-like process catalyzed by nanoscale schwertmannite (nano-SHM) - Test results have revealed that simultaneous injection of nano-SHM slurry and H₂O₂ into the anode reservoir and sediment compartment is a good practice. 70-99% in removal efficiency was obtained for various target PAEs; (3) enhanced in situ bioremediation coupled with the EK process for promoting the growth of intrinsic microorganisms by adding H₂O₂ as an oxygen release compound (ORC) - Test results have demonstrated that an intermittent mode of injecting lab-prepared ORC directly into the contaminant zone would be beneficial to the growth of intrinsic microorganisms in test sediment for in situ bioremediation of target PAEs; and (4) coupling of a second-generation ORC (designated 2G-ORC) with the EK-biological process - Test results have proved that 2G-ORC is long-lasting and can be directly utilized as the carbon source and oxygen source for microbial growth resulting in an enhanced biodegradation of PAEs. Except DEHP having a residual concentration of 4 μg kg^-1, all other target PAEs in test sediment were totally removed by this novel combined remediation process.

Degradation of dimethyl phthalate using a liquid phase plasma process with TiO2 photocatalysts

The liquid phase plasma (LPP) method with a TiO₂ photocatalyst and hydrogen peroxide was used to decompose dimethyl phthalate (DMP). As the applied voltage, pulse width, and frequency were increased, the rate of decomposition was increased and the decomposition rate was 63% for 180 min under plasma optimum conditions. The addition of TiO₂ photocatalyst and hydrogen peroxide increased the DMP decomposition reaction rate, but an excess cause a decrease in decomposition rate due to a decrease in conductivity, blocking of ultraviolet light, and scavenger effect. When the TiO₂ photocatalyst and hydrogen peroxide were used together, the decomposition reaction rate of DMP was greatly improved by using LPP single process alone. Also, when all the processes were used at the same time, the decomposition reaction rate was improved to about 2.8 times. DMP undergoes bond cleavage and ultimately decomposes into CO₂ and H₂O via dimethyl 4-hydroxyphthalate and methyl salicylates due to hydroxyl radicals and various active species generated by the LPP reaction.

Schwertmannite: occurrence, properties, synthesis and application in environmental remediation

Schwertmannite is a typical iron-derived mineral, which was originally discovered in acid mine drainings and subsequently synthesized in the laboratory. Increasingly, it is seen as having considerable potential as an adsorbent material, which could be used for environmental remediation (such as the treatment/remediation of arsenic, chromium, antimony, fluoride, and organic contaminants). This study reviews current developments, mainly in the preparation, structure, and water treatment of Schwertmannite. Several key issues are discussed in detail, such as synthetic strategy, the structure-property relationships, potential environmental applications, and related mechanisms. Soil remediation by schwertmannite is compared to water treatment, and its application is further evaluated. Finally, the methodologies for water treatment and soil remediation using schwertmannite are also taken into consideration from an environmental point of view.

Degradation of di (2-ethylhexyl) phthalate in sediment by a surfactant-enhanced Fenton-like process

This is the premier study reporting the remediation of di (2-ethylhexyl) phthalate (DEHP) contaminated sediment by a surfactant-enhanced Fenton-like system. Three widely used non-ionic surfactants were tested, and the order for desorption and solubilization of DEHP was determined as Tween 80 > Triton X-100 > Brij 35. The degradation of DEHP was studied at a near natural pH of 6.0 by two Fenton treatments: (i) Fe³⁺/H₂O₂ and (ii) Fe³⁺/PCA/H₂O₂. Results show that the addition of PCA can significantly enhance DEHP removal from 48.9% to 92.5%. This is consistent with observation that PCA maintained at a relative high level of iron ions, which can catalyze H₂O₂ to generate the reactive hydroxyl radicals (OH). Most of the added Tween 80 and a portion of OM were co-oxidized together with DEHP due to the non-selective nature of OH, which leaded to an increase in DOC content and decreases in sediment pH and total N content. The results provide an efficient and eco-friendly technique for the remediation of DEHP contaminated sediment, and also give insight to its environmental implications.

Electrokinetic-Fenton remediation of organochlorine pesticides from historically polluted soil

Soil contamination by persistent organic pollutants (POPs) poses a great threat to historically polluted soil worldwide. In this study, soils were characterized, and organochlorine pesticides contained in the soils were identified and quantified. Individual electrokinetic (IE), EK-Fenton-coupled technologies (EF), and enhanced EK-Fenton treatment (E-1, E-2, and E-3) were applied to remediate soils contaminated with hexachloro-cyclohexane soprocide (HCH) and dichloro-diphenyl-trichloroethane (DDT). Variation of pH, electrical conductivity, and electroosmotic flow was evaluated during the EK-Fenton process. The IE treatment showed low removal efficiency for HCHs (30.5%) and DDTs (25.9%). In the EF treatment, the highest removal level (60.9%) was obtained for α-HCH, whereas P,P-DDT was the lowest (40.0%). Low solubility of pollutants impeded the HCH and DDT removal. After enhanced EK-Fenton treatment, final removal of pollutants decreased as follows: β-HCH (82.6%) > γ-HCH (81.6%) > α-HCH (81.2%) > δ-HCH (80.0%) > P,P-DDD (73.8%) > P,P-DDE (73.1%) > P,P-DDT (72.6%) > O,P-DDT (71.5%). The results demonstrate that EK-Fenton is a promising technology for POP removal in historically polluted soil.

Ultrasonic-enhanced Fenton-like degradation of bisphenol A using a bio-synthesized schwertmannite catalyst

Schwertmannite (Sch) was synthesized by Acidithiobacillus ferrooxidans and used as Fenton-like catalyst for bisphenol A (BPA) degradation combining with ultrasonic technology (US). Physicochemical characterizations showed that the bio-synthesized Sch particles had a pompon-like morphology with high BET surface area of 92.92m²/g. The degradation reaction showed a two-stage pseudo-first-order kinetic process consisting of an induction period and a followed rapid degradation period. A synergistic effect existed between US and Sch on activating H₂O₂ and the synergy factor was calculated to be 2.32. The catalytic efficiency of the system was mainly affected by pH, Sch dosage and temperature, but less relevant to H₂O₂ concentration. Free OH radicals in the bulk solution were identified to be the dominant oxidant, which were produced by both heterogeneous and homogeneous processes. The promotional effect of US on Fenton-like degradation of BPA can be ascribed to the reasons of (1) increasing the radical generation by ultrasonic cavitation; (2) reducing the apparent activation energies of degradation reaction; (3) accelerating the dissolution of iron and (4) keeping the high surface area of catalyst by continuous surface cleaning. Ecotoxicity tests indicated lower toxicities of intermediates than BPA. In addition, Sch exhibited high reusability in the recycle study.

Effect of the polarity reversal frequency in the electrokinetic-biological remediation of oxyfluorfen polluted soil

This work studies the feasibility of the periodic polarity reversal strategy (PRS) in a combined electrokinetic-biological process for the remediation of clayey soil polluted with a herbicide. Five two-weeks duration electrobioremediation batch experiments were performed in a bench scale set-up using spiked clay soil polluted with oxyfluorfen (20 mg kg^-1) under potentiostatic conditions applying an electric field between the electrodes of 1.0 V cm^-1 (20.0 V) and using PRS with five frequencies (f) ranging from 0 to 6 d^-1. Additionally, two complementary reference tests were done: single bioremediation and single electrokinetic. The microbial consortium used was obtained from an oil refinery wastewater treatment plant and acclimated to oxyfluorfen degradation. Main soil conditions (temperature, pH, moisture and conductivity) were correctly controlled using PRS. On the contrary, the electroosmotic flow clearly decreased as f increased. The uniform soil microbial distribution at the end of the experiments indicated that the microbial activity remained in every parts of the soil after two weeks when applying PRS. Despite the adapted microbial culture was capable of degrade 100% of oxyfluorfen in water, the remediation efficiency in soil in a reference test, without the application of electric current, was negligible. However, under the low voltage gradients and polarity reversal, removal efficiencies between 5% and 15% were obtained, and it suggested that oxyfluorfen had difficulties to interact with the microbial culture or nutrients and that PRS promoted transport of species, which caused a positive influence on remediation. An optimal f value was observed between 2 and 3 d^-1.

Biodegradation of Dimethyl Phthalate by Freshwater Unicellular Cyanobacteria

The biodegradation characteristics of dimethyl phthalate (DMP) by three freshwater unicellular organisms were investigated in this study. The findings revealed that all the organisms were capable of metabolizing DMP; among them, Cyanothece sp. PCC7822 achieved the highest degradation efficiency. Lower concentration of DMP supported the growth of the Cyanobacteria; however, with the increase of DMP concentration growth of Cyanobacteria was inhibited remarkably. Phthalic acid (PA) was detected to be an intermediate degradation product of DMP and accumulated in the culture solution. The optimal initial pH value for the degradation was detected to be 9.0, which mitigated the decrease of pH resulting from the production of PA. The optimum temperature for DMP degradation of the three species of organisms is 30°C. After 72 hours' incubation, no more than 11.8% of the residual of DMP aggregated in Cyanobacteria cells while majority of DMP remained in the medium. Moreover, esterase was induced by DMP and the activity kept increasing during the degradation process. This suggested that esterase could assist in the degradation of DMP.