C, N, and P stoichiometry for leaf litter of 62 woody species in a subtropical evergreen broadleaved forest.

To understand leaf litter stoichiometry in a subtropical evergreen broadleaved forest, we measured the contents of carbon (C), nitrogen (N) and phosphorus (P) in leaf litters of 62 main woody species in a natural forest of C. kawakamii Nature Reserve in Sanming, Fujian Province. Differences in leaf litter stoichiometry were analyzed across leaf forms (evergreen, deciduous), life forms (tree, semi-tree or shrub), and main families. Additionally, the phylogenetic signal was measured by Blomberg's K to explore the correlation between family level differentiation time and litter stoichiometry. Our results showed that the contents of C, N and P in the litter of 62 woody species were 405.97-512.16, 4.45-27.11, and 0.21-2.53 g·kg-1, respectively. C/N, C/P and N/P were 18.6-106.2, 195.9-2146.8, and 3.5-68.9, respectively. Leaf litter P content of evergreen tree species was significantly lower than that of deciduous tree species, and C/P and N/P of evergreen tree species were significantly higher than those of deciduous tree species. There was no significant difference in C, N content and C/N between the two leaf forms. There was no significant difference in litter stoichiometry among trees, semi-trees and shrubs. Effects of phylogeny on C, N content and C/N in leaf litter was significant, but not on P content, C/P and N/P. Family differentiation time was negatively correlated with leaf litter N content, and positively correlated with C/N. Leaf litter of Fagaceae had high C and N contents, C/P and N/P, and low P content and C/N, with an opposite trend for Sapidaceae. Our findings indicated that litter in subtropical forest had high C, N content and N/P, but low P content, C/N, and C/P, compared with the global scale average value. Litter of tree species in older sequence of evolutionary development had lower N content but higher C/N. There was no difference of leaf litter stoichiometry among life forms. There were significant differences in P content, C/P, and N/P between different leaf forms, with a characteristic of convergence.

[Effects of warming on physicochemical property of Cunninghamia lanceolata branch and leaf litter in subtropical plantation]. / 增温对亚热带杉木枝和叶凋落物理化性质的影响.

At the regional scale, substrate properties are the key factors driving litter decomposition rate. In this study, soil temperature was increased by buried heating cables to explore the impacts of climate warming on the physical and chemical properties in branch and leaf of Cunninghamia lanceolata litter. The results showed that after 5 years of soil warming (4 ℃), the contents of nitrogen (N), phosphorus (P) and water-soluble substance in branch litter increased by 35.2%, 40.8% and 7.6%, while that in leaf litter increased by 41.2%, 45.9% and 5.9%, respectively. The contents of carbon (C), cellulose and C/N in branch litter decreased by 5.1%, 11.6% and 28.8%, and in leaf litter decreased by 5.3%, 11.3% and 33.3%, respectively. Soil warming led to 29.8% increase in specific leaf area (SLA) and 40.7% decrease in tensile strength (LTS) of leaf litter. However, warming did not affect lignin content and pH value in both branch and leaf litter. 13C NMR and infrared spectrum analysis showed that the contents of amino acids, polysaccharides, polyphenols and aliphatic compounds in litter changed significantly after warming. Warming effect differed between litter organs, in that polysaccharides increased significantly only in leaf litter and the increase of amino acids in branch litter was greater than that in leaf litter. Overall, soil warming significantly changed the physical and chemical properties in C. lanceolata branch and leaf litter, which might accelerate the decomposition rate at the initial stage due to the increase of N, P contents and the decrease of LTS, but might decelerate the decomposition rate at the later stage due to an increase of complex polymers content in the litter.

[Effects of forest conversion on litterfall nutrient return and nutrient use efficiency in Mid-subtropical China.] / ä¸­äºšçƒ­å¸¦æ£®æž—è½¬æ¢å¯¹å‡‹è½ç‰©å »åˆ†å½’è¿˜åŠå »åˆ†åˆ©ç”¨æ•ˆçŽ‡çš„å½±å“.

To understand the impacts of mid-subtropical forest conversion on carbon and nutrient cycling, we conducted a 4-year investigation to examine litterfall, nutrient return and nutrient use efficiency of Castanopsis carlesii natural forest, C. carlesii secondary forest and Cunninghamia lanceolata plantation which were transformed from C. carlesii natural forest. The results showed that after C. carlesii natural forest was transformed into C. carlesii secon-dary forest and C. lanceolata plantation, the annual litter production decreased by 29.0% and 45.7%, nitrogen return of litter decreased by 34.0% and 72.7%, and phosphorus return decreased by 38.1% and 56.4%, respectively. The amount of carbon returned from litterfall in C. carlesii natural forest was 25.6% and 44.3% higher than that in C. carlesii secondary forest and C. lanceolata plantation, respectively. For C. lanceolata plantation, C. carlesii secondary forest and C. carlesii natural forest, nitrogen use efficiency of litterfall was 175.4, 94.8 and 92.0 kg·kg-1, respectively, and phosphorus use efficiency of litterfall was 3031.0, 2791.6 and 2537.2 kg·kg-1, respectively. It was concluded that C. lanceolata plantation was more limited by nitrogen compared with C. carlesii natural forest and secondary forest, and the effects of phosphorus limitation had similar effects on the three forests.

Using the entrapped bioprocess as the pretreatment method for the drinking water treatment receiving eutrophic source water.

Control of organic matter, nutrients and disinfection byproduct formation is a major challenge for the drinking water treatment plants on Matsu Islands, Taiwan, receiving source water from the eutrophic reservoirs. A pilot entrapped biomass reactor (EBR) system was installed as the pretreatment process to reduce organic and nitrogen contents into the drinking water treatment plant. The effects of hydraulic retention time (HRT) and combination of preceding physical treatment (ultraviolet and ultrasound) on the treatment performance were further evaluated. The results showed that the EBR system achieved higher than 81%, 35%, 12% and 46% of reduction in chlorophyll a (Chl a), total COD (TCOD), dissolved organic carbon (DOC) and total nitrogen (TN), respectively under varied influent concentrations. The treatment performance was not significantly influenced by HRT and presence/absence of physical pretreatment and the effluent water quality was stable; however, removal efficiencies and removal rates of Chl a, TCOD and DOC showed strong correlation with their influent concentrations. Excitation-emission matrix (EEM) fluorescence spectroscopy identified fulvic-like and humic-like substances as the two major components of dissolved organic matter (DOM) in the reservoir, and decreased intensity of the major peaks in effluent EEM fluorescence spectra suggested the effective removal of DOM without production of additional amount of soluble microbial products in the EBR. Through the treatment by EBR, about 10% of reduction of total trihalomethane formation potential for the effluent could also be achieved. Therefore, the overall results of this study demonstrate that EBR can be a potential pretreatment process for drinking water treatment plants receiving eutrophic source water.

Entrapped biomass for removal of organics and total nitrogen from anaerobic reactor effluents.

Anaerobic processes have been applied to treat low-strength domestic wastewaters with significant energy saving. However, anaerobic process effluents must be further removed of residual organics and total nitrogen before discharge. Reported here are an aerobic entrapped bio-technology (EBT) system and an EBT coupled with activated sludge (EBT + AS) system being tested as a post-anaerobic treatment. Both systems have been operated under aerobic condition to provide organics and total nitrogen removal, achieving COD removal by 74-88% and TN removal by 58-65% at hydraulic retention times of 8-24 h. ΔCOD/ΔNO3 ratios that represent the carbon usage efficiency as electron donors for denitrification were 1.82-1.93 in the EBT and 2.01-2.02 in the EBT + AS systems, with both ratios being lower (i.e. more efficient) than 6 typically required in traditional activated sludge bioreactors. Both systems demonstrate promise for polishing removal of COD and TN.

[Effects of interference intensity on soil respiration and its components in Castanopsis carlesii forest with artificially assisted regeneration in subtropical China]. / å¹²æ‰°å¼ºåº¦å¯¹äºšçƒ­å¸¦ç±³æ§ äººä¿ƒæ›´æ–°æž—åœŸå£¤å‘¼å¸åŠå ¶ç»„åˆ†çš„å½±å“.

The effects of interference intensity on soil respiration (RS) and heterotrophic respiration (RH) were studied in two Castanopsis carlesii forests with artificially assisted regeneration. The results showed that C. carlesii forest decreased the RS and its components with the increasing interfe-rence intensity, particularly decreased its autotrophic respiration (RA, 1.75 t C·hm-2·a-1) by 40% under high interference than under low interference. Compared with C. carlesii forest under low interference, soil organic carbon, fine root biomass, and annual litterfall biomass of C. carlesii forest were significantly reduced under high interference. Soil temperature could explain the seasonal variations of RS, RH, and RA with 84.7%, 68.3% and 5.1% for the C. carlesii forest under low interference, and with 84.4%, 54.6% and 21.7% for the C. carlesii forest under high interference, respectively. The Q10 values of RS, RH and RA in the C. carlesii forest were 1.75, 1.93, 1.27 under low interference, and 2.46, 2.34, 1.65 under high interference, respectively. Carbon storage and soil respiration of forest ecosystem would decrease with the increasing interference intensity, the responses of soil respiration and its components to environmental change were obvious, and forest ecosystem showed vulnerability. It indicated the difficulty of restoring forest ecosystem with high interference during a short term.

Role of Dissolved Organic Matter in Sorption of Perfluorooctanoic Acid to Metal Oxides.

Perfluorooctanoic acid (PFOA) is an important perfluorinated chemical of significant environmental concern. It has been widely found at high concentrations in the environment. We have exposed sediment constituent minerals SiO2, Fe2O3, and Al2O3 to PFOA and humic acid (HA) and studied the adsorption of PFOA by introducing the adsorbates in different orders. The results suggest concurrent sorption of PFOA and HA to the mineral surface or enhanced PFOA sorption when both are introduced to the aqueous phase. However, when PFOA is introduced to the mineral surface that has already been exposed to and extensively coated with HA, little PFOA adsorption occurs, which implies that PFOA released to rivers rich in dissolved organic matter (DOM, i.e. HA) may be immune to sorptive retention by the sediment and be transported downstream unabated. DOM thus can play a significant role in the transport and fate of PFOA in the natural water system.

Photocatalytic mineralization of codeine by UV-A/TiO2--Kinetics, intermediates, and pathways.

This study investigated the photocatalytic degradation of codeine by UV-irradiated TiO2. The degradation kinetics was determined under varied conditions including the TiO2 loading, codeine concentration, and pH. Codeine and several reaction intermediates including morphine were identified and tracked during degradation using HPLC/MS-MS technique, along with TOC and IC measurements. Specifically, removal of 100 µg/L of spike codeine was complete in 3 min by contact with a 0.1 g/L suspension of TiO2 under UV irradiation at pH 7. The degradation kinetics of codeine was first-order with respect to both the catalyst TiO2 and the reactant codeine, with enhanced reaction rates with increasing pH up to pH 9. Mineralization of codeine was possible upon prolonged contact; near complete mineralization of 10 mg/L of codeine was achieved in 90 min with 0.1 g/L TiO2 under irradiation at pH 5, during which the organic nitrogen was converted to NH3-N (74%) and NO3-N (22%). Based on the identified intermediates, two degradation pathways were proposed of which one involved ipso-substitution followed by cleavage of the aromatic ring and another involved repeated hydroxylation of the codeine molecule followed by its fragmentation.

Photocatalytic degradation of methamphetamine by UV/TiO2 - kinetics, intermediates, and products.

Methamphetamine (MAT) is a prescription drug and often a substance of abuse. It is found in WWTP influents and effluents as well as surface waters in many regions, elevating concerns about their potential impact. MAT is not effectively removed by conventional processes of domestic wastewater treatment plants (WWTPs). To contemplate advanced treatment, this study evaluates the feasibility of eliminating MAT by UV-illuminated TiO2, a potential retrofit to existing UV disinfection units. The degradation kinetics and mechanism of MAT by TiO2 under low-wattage UV illumination (9 W with maximum output at 365 nm) were investigated. Experimental parameters were varied including the TiO2 loading, MAT concentration, and pH. During treatment, MAT and its intermediates were tracked by HPLC-MS/MS, along with TOC and IC measurements to determine the mineralization extent. In contact with 0.1 g/L of TiO2 under illumination at pH 7, an entire spike amount of 100 µg/L of MAT was removed from deionized water after 3 min and 76 µg/L of MAT was removed from the secondary wastewater effluent after 30 min. The degradation of MAT followed an apparent first-order kinetics. Near complete mineralization of MAT from 10 mg/L was achieved in 180 min with 0.1 g/L of TiO2 at pH 5, by which the organic nitrogen was converted to NH4(+) and NO3(-). Based on identified intermediates, two degradation pathways were deduced that involved cleavage of the side chain as well as hydroxylation of the MAT compound. The photocatalytic UV/TiO2 process shows promise in arresting the release of MAT and its intermediate derivatives into the water environment.

Deciphering visible light photoreductive conversion of CO2 to formic acid and methanol using waste prepared material.

As gradual increases in atmospheric CO2 and depletion of fossil fuels have raised considerable public concern in recent decades, utilizing the unlimited solar energy to convert CO2 to fuels (e.g., formic acid and methanol) apparently could simultaneously resolve these issues for sustainable development. However, due to the complicated characteristics of CO2 reduction, the mechanism has yet to be disclosed. To clarify the postulated pathway as mentioned in the literature, the technique of electron paramagnetic resonance (ESR) was implemented herein to confirm the mechanism and related pathways of CO2 reduction under visible light using graphene-TiO2 as catalyst. The findings indicated that CO(-•) radicals, as the main intermediates, were first detected herein to react with several hydrogen ions and electrons for the formation of CH3OH. For example, the generation of CO(-•) radicals is possibly the vital rate-controlling step for conversion of CO2 to methanol as hypothesized elsewhere. The kinetics behind the proposed mechanism was also determined in this study. The mechanism and kinetics could provide the in-depth understanding to the pathway of CO2 reduction and disclose system optimization of maximal conversion for further application.

Photocatalytic reduction of carbon dioxide to methanol and formic acid by graphene-TiO2.

UNLABELLED: Graphene-TiO2 was obtained by reduction of graphite oxide by the hydrothermal method. Using photocatalytic activity to reduce carbon dioxide to methanol and formic acid was investigated in this study. The results show that the graphene loading affects the absorption of light in the visible light region. A larger surface area can also improve the catalytic activity. The largest yield of methanol and formic acid, under light of 365 nm, can reach 160 and 150 micromol g(-1), respectively with 8.5% graphene loading. An increase in graphene loading can enhance photocatalytic performance, but too much will also decrease the reduction efficiency by shielding the light from reaching the catalytic surface. The effect of pH was also investigated. The mechanism of the reaction was also discussed in this study. IMPLICATIONS: Graphene-TiO2 hybrids were prepared by the hydrothermal method. Surface area and visible light adsorption increased with the graphene loading. Increased graphene loading improved the methanol and formic acid production. Too much graphene loading will decrease the reduction efficiency. The effect of pH shows that the HCO3- species prefers the formation of formic acid. The mechanism of the reaction was also discussed in this study.

Removal of pharmaceuticals and organic matter from municipal wastewater using two-stage anaerobic fluidized membrane bioreactor.

The aim of present study was to treat municipal wastewater in two-stage anaerobic fluidized membrane bioreactor (AFMBR) (anaerobic fluidized bed reactor (AFBR) followed by AFMBR) using granular activated carbon (GAC) as carrier medium in both stages. Approximately 95% COD removal efficiency could be obtained when the two-stage AFMBR was operated at total HRT of 5h (2h for AFBR and 3h for AFMBR) and influent COD concentration of 250mg/L. About 67% COD and 99% TSS removal efficiency could be achieved by the system treating the effluent from primary clarifier of municipal wastewater treatment plant, at HRT of 1.28h and OLR of 5.65kg COD/m(3)d. The system could also effectively remove twenty detected pharmaceuticals in raw wastewaters with removal efficiency in the range of 86-100% except for diclofenac (78%). No other membrane fouling control was required except scouring effect of GAC for flux of 16LMH.

Improving total nitrogen removal in aeration basin retrofitted with entrapped biomass.

This study presented a method to upgrade existing aeration tanks to remove total nitrogen (TN). Bioplates carrying entrapped biomass were installed in an aeration basin to create anoxic/anaerobic zones where denitrification can proceed. In a reactor that coupled bioplates containing entrapped biomass (equivalent to as high as 7,500 mg/L of biomass) and an activated sludge suspension (at mixed liquor suspended solids of 1,300-2,400 mg/L), nitrification efficiency exceeded 95% for an influent wastewater containing 21-54 mg/L of NH3-N. In all cases amended with alkalinity and with or without added methanol as an electron source, TN removal was between 60 and 70%. The results demonstrated anoxic/oxic or anaerobic/anoxic/oxic processes could be incorporated in a conventional aeration basin, requiring no substantial modifications of the vessel and operation, and thus providing improved treatment in terms of nitrogen removal in the conventional suspended-growth process.

Enhancing total nitrogen removal from wastewater of a science and industrial park using entrapped biomass.

This study employed entrapped biomass technology to augment the conventional activated sludge process with anoxic-oxic (AO)/anaerobic-anoxic-oxic (A20) functions for the removal of total nitrogen (TN) from wastewater of a science and industrial park in Taiwan. The entrapped biomass unit was fabricated in the format of carrier plates on which microbial cells were entrapped. Due to mass transport limitations, anoxic and anaerobic conditions were created within the bioplates that enabled denitrification to occur. The treatment basin incorporated an equivalent amount of 1300-2400mg MLSS/L of activated sludge on the bioplates at packing ratios of 10-30% (volume ratio ofbioplates to basin) operating with the addition of sodium carbonate for alkalinity and methanol for the electron donor. The results showed nearly 90% of ammonia nitrogen being converted to nitrate and 63% of TN removal, in comparison with typically 10% of TN removal in traditional activated sludge process of domestic wastewater plants.

Photocatalytic degradation of malathion by TiO2 and Pt-TiO2 nanotube photocatalyst and kinetic study.

Photocatalytic degradation of malathion, is investigated using Titanium Nanotubes (TNT) and Pt modified TNT (Pt-TNT) photocatalyst in an aqueous solution under 365 nm UV lamp irradiation. The TNT photocatalyst is prepared on pretreated strong alkaline solution via the hydrothermal method. The Pt-TNT was prepared by light deposition. The variations in morphology, formation mechanism, phase structure, and pore structure of TNT and Pt-TNT are characterized using UV-Vis, transmission electron microscopy (TEM), and N2 adsorption/desorption isotherm analyzer, respectively. The effect of the initial malathion concentration, reaction temperature, catalyst loading, solution pH value, irradiation time and Pt loading are studied and the optimized values are obtained. Moreover, the photodegradation performance and kinetics of malathion onto TNT and Pt-TNT are also examined with the aid of model analysis by kinetic data. The results show that under acid conditions, the performance of photocatalysts for treating malathion is high. The time of complete degradation increases with an increase in the initial malathion concentration. The degradation rate decreases with increasing initial malathion concentration. The degradation efficiency can reach 100% under acid conditions for any initial malathion concentration when the reaction time is 70 min. In addition, experimental decoloration kinetics data follow the pseudo-first-order reaction model.

A novel sensor platform matching the improved version of IPMVP option C for measuring energy savings.

It is easy to measure energy consumption with a power meter. However, energy savings cannot be directly computed by the powers measured using existing power meter technologies, since the power consumption only reflects parts of the real energy flows. The International Performance Measurement and Verification Protocol (IPMVP) was proposed by the Efficiency Valuation Organization (EVO) to quantify energy savings using four different methodologies of A, B, C and D. Although energy savings can be estimated following the IPMVP, there are limitations on its practical implementation. Moreover, the data processing methods of the four IPMVP alternatives use multiple sensors (thermometer, hygrometer, Occupant information) and power meter readings to simulate all facilities, in order to determine an energy usage benchmark and the energy savings. This study proposes a simple sensor platform to measure energy savings. Using usually the Electronic Product Code (EPC) global standard, an architecture framework for an information system is constructed that integrates sensors data, power meter readings and occupancy conditions. The proposed sensor platform is used to monitor a building with a newly built vertical garden system (VGS). A VGS shields solar radiation and saves on energy that would be expended on air-conditioning. With this platform, the amount of energy saved in the whole facility is measured and reported in real-time. The data are compared with those obtained from detailed measurement and verification (M&V) processes. The discrepancy is less than 1.565%. Using measurements from the proposed sensor platform, the energy savings for the entire facility are quantified, with a resolution of ±1.2%. The VGS gives an 8.483% daily electricity saving for the building. Thus, the results show that the simple sensor platform proposed by this study is more widely applicable than the four complicated IPMVP alternatives and the VGS is an effective tool in reducing the carbon footprint of a building.

Estimation of phosphorus flux in rivers during flooding.

Reservoirs in Taiwan are inundated with nutrients that result in algal growth, and thus also reservoir eutrophication. Controlling the phosphorus load has always been the most crucial issue for maintaining reservoir water quality. Numerous agricultural activities, especially the production of tea in riparian areas, are conducted in watersheds in Taiwan. Nutrients from such activities, including phosphorus, are typically flushed into rivers during flooding, when over 90% of the yearly total amount of phosphorous enters reservoirs. Excessive or enhanced soil erosion from rainstorms can dramatically increase the river sediment load and the amount of particulate phosphorus flushed into rivers. When flow rates are high, particulate phosphorus is the dominant form of phosphorus, but sediment and discharge measurements are difficult during flooding, which makes estimating phosphorus flux in rivers difficult. This study determines total amounts of phosphorus transport by measuring flood discharge and phosphorous levels during flooding. Changes in particulate phosphorus, dissolved phosphorus, and their adsorption behavior during a 24-h period are analyzed owing to the fact that the time for particulate phosphorus adsorption and desorption approaching equilibrium is about 16 h. Erosion of the reservoir watershed was caused by adsorption and desorption of suspended solids in the river, a process which can be summarily described using the Lagmuir isotherm. A method for estimating the phosphorus flux in the Daiyujay Creek during Typhoon Bilis in 2006 is presented in this study. Both sediment and phosphorus are affected by the drastic discharge during flooding. Water quality data were collected during two flood events, flood in June 9, 2006 and Typhoon Bilis, to show the concentrations of suspended solids and total phosphorus during floods are much higher than normal stages. Therefore, the drastic changes of total phosphorus, particulate phosphorus, and dissolved phosphorus in rivers during flooding should be monitored to evaluate the loading of phosphorus more precisely. The results show that monitoring and controlling phosphorus transport during flooding can help prevent the eutrophication of a reservoir.

Spatially variable deoxygenation in the Danshui River: improvement in model calibration.

A modeling study of the Danshui River, Taiwan, reveals that in-stream BOD deoxygenation rates vary significantly along the river as a result of the highly variable strength of wastewater discharges, which directly reflect the effluent characteristics. A comprehensive field data gathering and lab analysis effort for the study site is presented. Results of the data analyses yielded spatially variable CBOD deoxygenation and nitrification rates, which were incorporated in a model of the river. The model results indicate significant improvement of model calibration, thus enhancing the predictive capability of the model for its use in water quality management. To maximize the benefits of pollution control for the Danshui River system and to achieve the water quality management goal, concurrent reductions of CBOD and ammonia loads, instead of phased reduction of CBOD followed by ammonia reduction, are strongly recommended by the model results.

Improved solubilization of activated sludge by ozonation in pressure cycles.

The generation of a large volume of activated sludge (AS) from wastewater treatment has increasingly become a great burden on the environment. Anaerobic digestion is routinely practiced for excess waste sludge; however, the process retention time is long because of kinetic limitation in the hydrolysis step. We tested the feasibility of applying ozone in pressure cycles to enhance the disintegration and solubilization of AS with the goal to prepare them for digestion using reduced ozone dose and contact time. The AS was subjected to repetitive pressure cycles in a closed vessel in which an ozone gas mixture was compressed into the slurry to reach 1040 kPa in the headspace to be followed by rapid venting. For a returned AS with total COD (tCOD) of 8200 mg L(-1), a dose of 0.01 gO(3)g(-1) total suspended solids (TSS) delivered via 20 pressure cycles within 16 min resulted in a 37-fold increase of the sCOD/tCOD ratio (due to increased soluble COD, i.e. sCOD) and a 25% reduction of TSS, in comparison to a dose of 0.08 gO(3)g(-1) TSS via bubbling contact over 15 min that resulted in a 15-fold increase of the sCOD/tCOD ratio and a 12% reduction of TSS. Sludge solubilization was evidenced by increased dissolved contents of total phosphorous (from 10 to 64 mg L(-1)), total nitrogen (from 14 to 120 mg L(-1)), and protein (from <15 to 39 mg L(-1)) in the sludge suspension after treatment, indicating significant solubilization of AS.

Fate of sulfonamide antibiotics in contact with activated sludge--sorption and biodegradation.

The sorption and biodegradation of three sulfonamide antibiotics, namely sulfamethoxazole (SMX), sulfadimethoxine (SDM), and sulfamonomethoxine (SMM), in an activated sludge system were investigated. Experiments were carried out by contacting 100 µg/L of each sulfonamide compound individually with 2.56 g/L of MLSS at 25±0.5 °C, pH 7.0, and dissolved oxygen of 3.0±0.1 mg/L in a batch reactor over different periods of 2 d and 14 d. All sulfonamides were removed completely over 11-13 d. Sorptive equilibrium was established well within the first few hours, followed by a lag period of 1-3 days before biodegradation was to deplete the antibiotic compounds linearly in the ensuing 10 days. Apparent zeroth-order rate constants were obtained by regression analysis of measured aqueous concentration vs. time profiles to a kinetic model accounting for sorption and biodegradation; they were 8.1, 7.9, and 7.7 µg/L/d for SDM, SMX, and SMM, respectively, at activated sludge concentration of 2.56 g/L. The measured kinetics implied that with typical hydraulic retention time (e.g. 6 h) provided by WWTP the removal of sulfonamide compounds from the wastewater during the activated sludge process would approximate 2 µg/L.